https://orcid.org/0000-0002-7028-4809
Figures
Abstract
The expansion of brewery factories with huge production potential of brewery sludge in Ethiopia presents a significant opportunity to enhance sustainable soil and crop productivity. Hence, this field experiment was conducted in North Mecha district, Northwestern Ethiopia, to improve the yield and nnitrogen use efficiency of maize by applying brewery sludge (BS), blended nitrogen, phosphorous and sulfur (NPS) fertilizers alone and in combination. Six treatments (T1: control, T2: 100% recommended dose of blended nitrogen, phosphorous, sulfur (RDNPS (100 kg NPS ha-1)); T3: 75% RDNPS + 25% recommended dose of brewery sludge (RDBS); T4: 50% RDNPS + 50% RDBS; T5: 25% RDNPS + 75% RDBS; T6: 100% RDBS (10 t BS ha-1) were laid out in a Randomized Complete Block Design (RCBD) with three replications. The results revealed that both single and combined fertilizer applications resulted in higher production, nitrogen uptake, and efficiency as compared to no fertilizer application. Notably, the combined application of 75% RDBS with 25% RDNPS produced the highest above-ground biomass yield (23161.9 kg ha-1), grain yield (10620.6 kg ha-1), stover yield (12541.3 kg ha-1), harvest index (45.85%), nitrogen concentration in grain (1.71%) and stover (1.00%), as well as grain (181.72 kg ha-1), stover (124.17 kg ha-1), and total (305.89 kg ha-1) nitrogen uptake. Furthermore, the combined application of 75% RDBS with 25% RDNPS produced the highest grain yield (10620.6 kg ha-1), net benefit (170987.97 Ethiopian Birr (ETB) ha-1), and an acceptable marginal rate of return (MRR) (12613.93%) for maize production in the region. Hence, the study reveals that using BS and blended NPS at precise ratios can improve maize productivity in the North Mecha district. However, as the experiment was carried out only in one location for one cropping season, further studies at different locations for several years or seasons should be conducted to come up with strong and reliable recommendations.
Citation: Assefa F, Mengist Y, Yigermal H, Nakachew K (2025) From brewery waste to agricultural wealth: Enhancing nitrogen use efficiency and productivity of maize through brewery sludge and blended NPS fertilizer in North Mecha District, Northwestern Ethiopia. PLoS One 20(5): e0319958. https://doi.org/10.1371/journal.pone.0319958
Editor: Paulo H. Pagliari, University of Minnesota, UNITED STATES OF AMERICA
Received: May 28, 2024; Accepted: February 10, 2025; Published: May 8, 2025
Copyright: © 2025 Assefa et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are included in the paper and its Supporting Information files.
Funding: The author(s) received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist
Introduction
Maize (Zea mays) is one of the major cereal crops grown in Ethiopia with high yield potentials of 15.8 t ha-1 compared to other major cereal crops grown in the country [1]. However, its current national average yield is less than four t ha-1 due to several production constraints [2–5]. The most significant limiting factors affecting its productivity were declining soil fertility and low nutrient use efficiency [5–9], poor agronomic practices [10], limited use of inputs, poor seed quality, disease and insect pests [11].
Among the aforementioned constraints, declining soil fertility is the major biophysical and manageable abiotic stress limiting maize productivity and food self-sufficiency under increasing population pressure [5,7,12–15]. Unbalanced and continuous application of limited chemical fertilizers such as Diammonium phosphate (DAP: 18% N and 46% P2O5) and Urea (46% N) over an extended period is a primary factor contributing to the decline in soil fertility which leads to low nutrient (N) use efficiency, nutrient response, and maize performance in Ethiopia [16]. This practice, both in terms of quantity and type, can worsen the depletion of essential macronutrients like K, Mg, Ca, S and micronutrients like B, Zn, Cu that are not adequately provided by chemical fertilizers and thereby lead to chemical soil degradation [17–23]. Due to the impact of imbalanced nutrient supply on plant nutrient uptake and utilization, crop yield is reduced [16]. Therefore, it is crucial to apply the right nutrient source at the recommended rate, at the right time during the growing season, and with the right application methods (referred to as the 4R’s) to optimize crop nutrient use efficiency [24,25]. However, 30–40% of Ethiopian farmers often find it expensive to use the recommended rates, leading them to apply lower recommended rates (37–40 kg ha-1 (NPS + Urea)) [26], which resulted in low nutrient use efficiency and crop yield. Consequently, addressing this issue has become a top priority and a significant national concern, prompting various initiatives to counteract the adverse effects of chemical farming. Because continual application of chemical fertilizers can lead to changes in soil pH, acidification, and soil compaction, ultimately reducing organic and humus content and beneficial organisms, increasing leaching of nutrients (N), hindering plant growth, and potentially contributing to greenhouse gas emissions [27]. As a result, the utilization of organic fertilizers has emerged as a viable solution for integrating nutrient supply systems in agriculture to efficiently utilize applied nutrients and increase crop productivity [28].
Hence, in Ethiopia, there is an expansion of brewery factories with the production potential of substantial amounts of sludge, which can be utilized as an organic soil amendment for sustainable crop production. As the sludge is also an environmentally friendly, renewable source of nutrients for crops with almost no toxic effects [29,30], it can be directly applied to soil to amend and restore its fertility [31]. It is also more effective than traditional organic fertilizer, as it contains 20–30% more nutrients than commonly used organic fertilizer [32] and reduces the application of chemical fertilizers by 40–50% [29]. Studies have demonstrated that the application of BS can significantly increase crop yield, improve soil fertility by enhancing physical and chemical properties of soil, beneficial microorganisms and serve as a valuable source of nutrients like nitrogen, phosphorus, potassium and other micronutrients [33–35]. Moreover, in Ethiopia, there is limited research on the utilization of brewery sludge as an organic soil amendment. Nonetheless, its application to agricultural land has been found to have a positive impact on soil pH, electrical conductivity, and the overall productivity of crops like sorghum [36], haricot bean [37], wheat [35], potato [38], and maize [39] compared to chemical fertilizers. However, its sole application is also limited by a slow release of nutrients, low nutrient content and high labor demand for preparation and transportation [40]. Thus, soil fertility can be effectively restored and crop productivity enhanced by implementing the concept of integrated soil fertility management [41]. The combined use of organic and inorganic nutrient sources also helps to maintain high nutrient use efficiency, soil and crop productivity [42,43]. In light of this, an important area of research in the North Mecha district was the use of BS in combination with chemical fertilizers to enhance nitrogen use efficiency and maize production sustainably.
Materials and methods
Description of the study area
A field experiment was conducted during the main cropping season from June to December 2021 in Kudmi village, found within the North Mecha district, at the research and technology demonstration and transfer site of the College of Agriculture and Environmental Sciences, Bahir Dar University. The topography of the experimental area is a gentle slope, and the area is located at 11° 20′ N to 11° 25′ N latitude and 37° 05′ E to 37° 09′ E longitude with an altitude of 1960 m above sea level [44]. According to the Bahir Dar Meteorology Station report (unpublished), the area receives an annual mean rainfall of approximately 1395 mm. The daily mean minimum and maximum temperatures of the area are 12.8 and 27°C, respectively. Crop-livestock mixed farming is the dominant production system in the district. The main crops cultivated are maize, finger millet, teff, barley, pulses and oil crops.
Description of the experimental material
The Bako Hybrid (BH)-661 maize (Zea mays) variety was used as a test crop in the study as previously used in the same research by Assefa et al [45].The BH-661 variety has high productivity (average 12 t ha-1) and extensive average coverage in Ethiopia, particularly in the Amhara region [46]. As shown below in Table 1, Blended NPS fertilizer containing 19% N, 38% P2O5 (16.59% P), 7% S and BS that used malt barely as a raw material for beer production, containing 4.23% N, 0.176% P, 0.377 mg/g Zn, 0.0043 mg/g Cd, 0.091 mg/g Cr, 0.054 mg/g Cu and 0.017 mg/g Ni [49] collected from the Dashen brewery company located at Gondar was used as the experimental material.
Experimental treatments, design and procedures
Six treatments were imposed in the experiment, which was carried out using a randomized complete block design (RCBD) with three replications. Standard recommendation rates were followed for fertilizer rates, 100 kg blended NPS ha-1 fertilizer and 10 t BS ha-1 [45]. The treatments were T1: control, T2: 100% RDNPS; T3: 75% RDNPS + 25% RDBS; T4: 50% RDNPS + 50% RDBS; T5: 25% RDNPS + 75% RDBS; T6: 100% RDBS (Table 1). The land was prepared with oxen/animal-drawn plowing and hand tools and subsequently leveled and smoothed by human labor using hand tools. As per the design and treatments, the experimental field was then manually subdivided into blocks and plots based on the design and treatments. Then, BS was applied three weeks before sowing to favor the nutrient break down and blended NPS fertilizer was applied during sowing to ready for crops at a depth of 20 cm. The gross land area of the experiment was 13.25 m × 23.5 m (311.375 m2) and a gross plot size of 3.75 m × 3 m (11.25 m2). A 1.0 m wide-open path separated the adjacent blocks, and a 0.5 m wide path separated plots within a block from one another. Using a random table number, the experimental treatments were assigned to the experimental plots in each block. As a result, there were five rows totaling 3 m in length, with 10 plants per row and 50 plants per plot. To avoid possible border effects, the net plot size (harvestable area) was 2.25 m × 2.4 m (5.4 m2) (i.e., the middle 3 rows from each plot) by excluding the guard rows of each plot horizontally and a 0.3 m row segment from both ends of the plot vertically. All the remaining necessary agronomic practices and crop management activities were subsequently performed uniformly.
The study involved standard agricultural practices and did not include any invasive methods or the collection of all the data on maize, no additional permits were required from governmental or regulatory bodies.
Data collection and measurements
Soil data.
Prior to sowing, soil samples were taken from the entire experimental field at a depth of 0–20 cm in a diagonal pattern using a soil auger following plowing. The samples were combined and thoroughly mixed to create a composite sample weighing one kilogram, which was then air-dried and ground to pass through a 2 mm sieve for analysis of specific soil physicochemical properties, including particle size distribution, soil pH, total nitrogen, available phosphorous and cation exchange capacity (CEC). Particle distribution in the soil was assessed using the hydrometer method as developed by Ref [50]. Soil pH was measured potentiometrically in a 1:2.5 soil-water suspension as described in Ref [51]. Total nitrogen was assessed via the micro-Kjeldahl method as Ref [52], organic carbon via the wet digestion method as outlined in Ref [53], and available phosphorus following Olsen [54]. CEC was determined from NH4OAc-saturated samples using the micro-Kjeldahl procedure [55].
Crop data.
Aboveground dry biomass yield (AGDBY) was determined by weighing the whole aboveground plant parts from the net plot area after complete oven-drying at 105˚C for 24 h. Grain yield was determined from the net harvestable area sampled for AGDBY determination; the yield was adjusted to 12.5% moisture content, and the result converted to kg ha-1.
where MC = grain moisture content. Stover yield was measured by taking the weight of the straw harvested from the net plot area of each plot and converting it to kilograms per hectare after sun drying the straw. Harvest index (HI): The HI was calculated as the ratio of grain yield to total aboveground dry biomass yield multiplied by 100 at harvest from the indicated treatments [56].
For plant tissue analysis at maturity, representative non-border maize plant samples were randomly collected from each plot, separated into grain and straw, and stored in paper bags. The grain and straw samples from each treatment were oven-dried at 70°C to a constant weight, ground using a stainless steel grinder, re-dried at 60°C, and ashed in a muffle furnace at 550°C for eight hours. The dried samples were milled, and the N contents of the grain and straw samples were determined using the micro-Kjeldahl method as outlined by the American Association of Cereal Chemists (AACC) [57].
The following N-efficiency parameters were calculated for each treatment following [58]:
- Nitrogen uptake was calculated by multiplying the grain and straw yield (kg ha − 1) by the nitrogen concentration (%) of each treatment as follows:
- Agronomic nitrogen use efficiency (ANUE, kg kg − 1) is the economic production obtained per unit of nitrogen applied. According to [59],
where Gf is the grain yield of the fertilized plot, Gu is the grain yield in the unfertilized plot and qNa is the quantity of N applied.
- Physiological nitrogen use efficiency (PNUE, kg kg-1) is the biological production per unit of nitrogen absorbed. It was calculated using the formula;
adopted from [60], where Byf is the biological yield (grain plus straw) of the fertilized plot (kg), Byu is the biological yield of the unfertilized plot (kg), Nf is the total N uptake of the fertilized plot (kg), and Nu is the total N uptake of the unfertilized plot (kg).
- Agro-physiological nitrogen use efficiency (APNUE, kg kg-1) is a measure of how efficiently the plant converts the applied nitrogen into increased biomass or yield.
where Gf is the grain yield of the fertilized plot (kg), Gu is the grain yield of the unfertilized plot (kg), Nf is the total N uptake of the fertilized plot (kg), and Nu is the total N uptake of the unfertilized plot (kg).
- Apparent recovery efficiency of nitrogen (AREN, %) is the quantity of nitrogen absorbed per unit of nitrogen applied.
adopted from [61], where Nf is the total N uptake of the fertilized plot (kg), and Nu is the total N uptake of the unfertilized plot (kg)and qNa is the quantity of N applied (kg).
- Nitrogen use efficiency (NUE, kg kg-1) measures the overall efficiency of nitrogen use by the plant [62].
Where Byf is the biological yield (grain plus straw) of the fertilized plot (kg), Byu is the biological yield of the unfertilized plot (kg) and qNa is the quantity of N applied (kg).
- The nitrogen harvest index (NHI, %) was determined as the ratio of nitrogen uptake by grain to nitrogen uptake by grain plus straw multiplied by 100, as described by [58].
Statistical data analysis
The data collected in this experiment were collected following standardized protocols and the analysis was carried out using the SAS version 9.0 software computer program’s general linear model (GLM) procedure [63]. As described in Montgomery [64], the residuals were examined to verify the normal distribution and homogeneous variance model assumptions on the error terms for each response variable. Because the six treatment combinations were randomized within each block, the independence assumption was valid. When a treatment effect was significant, multiple means comparisons were performed at the 5% level of significance using the least significant difference (Fisher’s LSD) method to generate letter groupings.
Partial budget analysis
A partial budget analysis was conducted to assess the economic viability of different treatments involving brewery sludge and blended NPS fertilizer. The analysis included partial budgeting, dominance analysis, and marginal analysis techniques. Partial budgeting and marginal analysis were employed to evaluate the economic aspects of the data collected. Partial budgeting serves as a tool to organize experimental data and provide insights into the costs and benefits associated with various treatment options. Meanwhile, marginal analysis is utilized to compare variable costs with the net benefits in order to determine the most cost-effective technology for recommendations derived from the experiment. Market prices for maize were obtained from local market rates in Ethiopian Birr (ETB) per kilogram at harvest time. Fixed prices for blended NPS fertilizer, BS as well as their transportation and application costs, were considered during the time of sowing.
The average partial budget for the six treatments was calculated based on income and expenses related to variable costs (Table 7). Net benefits were determined by subtracting total variable costs from gross field benefits, which were calculated by multiplying the farm price of the crop for each treatment. Variable costs excluded expenses for other agronomic practices like seed, land preparation, sowing, weeding, farm maintenance, and harvesting, as these costs were consistent across all treatments. The sum of variable costs was deducted from gross field benefits to obtain net benefits. The average yield was adjusted downwards by 10% to account for differences between experimental field conditions and expected yields under farmers’ practices within the same treatments. Based on the results of the dominance analysis, treatments were chosen in increasing order of total variable costs. For each pair of ranked treatments, the percent marginal rate of return (MRR) was calculated. The MRR (%) between any pair of non-dominated treatments was the return per unit of investment in fertilizer. It was calculated by dividing the change in net benefit by the change in variable costs. Analysis of the marginal rate of return (MRR) was carried out for non-dominated treatments, and the MRRs were compared to the minimum acceptable rate of return (MARR) of 100% to determine the optimum treatment [65].
Results and discussion
Physicochemical properties of soil and brewery sludge
The findings from the analysis of the soil and brewery sludge are detailed in Table 2. The soil analysis revealed that the Kudmi soil belongs to the clay textural class and has a high cation exchange capacity of 30 cmol (+)/kg. The pH of the soil in the study area was 5.32, which is moderately acidic with moderate total nitrogen (0.28%), available phosphorus (0.398 mmol/L [67] and organic matter (2.42%) [68]. The BS exhibited a high pH value of 6.69, suggesting the potential to raise the low soil pH of 5.32 to slightly acidic upon application (Table 2). Furthermore, the available phosphorus (AP) and total nitrogen (TN) content of BS was higher than that of the soil, as the sludge involves the use of grains and other organic materials rich in nutrients such as phosphorus and nitrogen. Additionally, its cation exchange capacity (CEC) value was higher than that of the soil, likely due to its highly porous structure with a large surface area, providing more sites for cation exchange to occur [70]. This increased surface area allows for greater interaction between the BS and soil particles, leading to higher CEC values [71].
Maize yield and yield component parameters
Aboveground dry biomass yield.
The co-application of BS and blended NPS fertilizer had a highly significant (P < 0.001) effect on the aboveground dry biomass yield of maize. The combined application of 25% RDNPS + 75% RDBS resulted in the highest aboveground dry biomass yield (20791.5 kg ha-1), an increase of 48.96% compared with that of the control treatment (Table 3). An increase in aboveground dry biomass yield could result from the overall improvement in vegetative growth as a result of the combined application of BS and blended NPS fertilizers. Furthermore, the increase in the aboveground dry biomass yield of maize from plots fertilized with combined BS and blended NPS fertilizer could be attributed to the plants receiving a proper and balanced supply of nutrients throughout the growth period. The observed similarity in values between the control treatment and 100% RDNPS may indicate that nitrogen application rates were insufficient to elicit significant differences, suggesting that environmental factors and soil type could have influenced nitrogen uptake and maize yield outcomes [72]. These findings are in accordance with those of Fashaho [73], who reported that the combined application of 10 t ha-1 bioslurry with 90 kg ha-1 mineral N increased the aboveground dry biomass yield of maize by 3.3 times compared with that in the control treatment. Similarly, a study on bioslurry and chemical fertilizer found that a combination of 25% bioslurry and 75% RDNPS fertilizer produced the highest (24.40 t ha-1) maize biomass yields in Hawassa, Ethiopia [74]. These findings were also consistent with those of [75], who reported that combining organic and mineral fertilizers increased grain weight, grain and straw yield and biological yield. Similarly, [76] reported that the combined application of inorganic and organic fertilizers resulted in greater total dry matter in maize than did the application of either fertilizer source alone.
Grain yield.
The grain yield of maize was significantly affected (P < 0.001) by the combined application of BS and NPS fertilizer. The highest grain yield (10620.6 kg ha-1) was recorded in the combined application of 25% RDNPS + 75% RDBS, with an increase of 73.2% compared with that in the control (untreated) treatment (Table 3). This increased grain yield of maize might be due to sufficient nutrient retention and availability for crops, increased kernels per ear and thousand kernels weight, all of which resulted in improved maize yield [77]. This increase in maize grain yield may also be due to synergistic effects of nutrient interactions that improve soil structure [78,79], water holding capacity [80], microbial activity, as well as the fertilizer nutrient utilization rate of soil [81]. Consistent with the results of this study, [73] also reported that the application of 10 t ha-1 bioslurry along with 90 kg ha-1 mineral N increased the grain yield by 3.08 times over that in the control treatment. In agreement with these findings, the combined application of 4 t FYM with 75/60 kg N/P ha-1 is an inexpensive and beneficial combination for increasing hybrid maize (BH140) production in the West Hararghe zone of Eastern Ethiopia [82]. Tuyishime [83] also reported an increase in maize grain yield in northern Rwanda by combining 10 t ha-1 bioslurry and 50 kg ha-1 urea.
Stover yield.
Analysis of variance indicated that the stover yield of maize was high significantly (P < 0.01) affected by the combined application of BS and blended NPS fertilizer. The highest stover yield of maize (10171 kg ha-1) was recorded in plots treated with 25% RDNPS + 75% RDBS, whereas the lowest (7825 kg ha-1) was from the untreated (control) plot. This might be due to the role of BS in improving soil structure, water retention and nutrient availability. The organic matter in the sludge enhances soil fertility, microbial activity and nutrient cycling, supporting better maize growth and stover production. In agreement with our finding, Tsehay et al [74] found and reported that the combined application of 25% bio-slurry and 75% chemical fertilizer resulted in the highest stover yield of maize (11.5 t ha − 1), followed by 50% bio-slurry and 50% chemical fertilizer and 100% bio-slurry, which are 11.3 and 10.17 t ha − 1, respectively. The lowest stover yield (8.43 t ha − 1) was recorded in the control group. Similarly, Tukur and Kesarwani [84] and Yigermal et al [85] reported that an application of 5 t ha − 1 of the poultry manure with 50% RDF (50 N + 30 P + 20 K + 10 Z kg ha − 1) produced the highest (13.843 t ha − 1) stover yield, whereas an application of 100% RDF (100 N + 60 P + 40 K + 20 Z kg ha − 1) produced the lowest (8.321 t ha − 1) stover yield.
Harvest index.
Analysis of variance indicated that the harvest index was high significantly affected (P < 0.01) by the combined application of BS and blended NPS fertilizers. The highest harvest index (51.09%) was recorded in the application of the 25% RDNPS + 75% RDBS treatment, which was significantly at par with the application of the rest combinations ratio of RDBS with RDNPS, whereas the lowest (43.73%) was recorded in the untreated or control treatment, followed by the sole RDNPS application (Table 3). These differences could be attributed to the increased availability and uptake of essential nutrients from the applied BS and blended NPS fertilizers and sink to the grain yield of maize. Sole application of RDNPS also yielded lower results, indicating that the synergistic effect of combining organic and inorganic fertilizers is crucial for maximizing maize productivity [45]. In agreement with the findings of this study, those of Muhmood et al [86] revealed that the addition of 0.6 t ha-1 bio slurry with 50% recommended N had the highest (16%) harvesting index of okra, whereas the lowest (11.9%) was from the control treatment. Similarly, Fashaho [73] reported that the highest harvest index (35.1%) of maize was recorded after the application of 10 t ha-1 bio slurry fertilizer in combination with 30 kg ha-1 mineral nitrogen fertilizer, while the lowest was recorded after the sole application of 15 t ha-1 bio slurry organic fertilizer at high altitudes in the Gicumbi district, northwestern Rwanda. The results of this study, however, contradict the findings of Ahmad et al [87], who reported that the integrated application of organic, inorganic and biofertilizers had a non-significant effect on the harvest index of maize in low-fertile soil.
Grain and stover nitrogen concentration of maize
Percentage of Nitrogen concentration in Grain.
Grain nitrogen concentration was significantly (P < 0.05) affected by the combined application of BS and blended NPS fertilizer as soil fertility amendments. The highest (1.71%) grain nitrogen concentration percentage was found following the application of 25% RDNPS + 75% RDBS, whereas the lowest (1.32%) was from the untreated treatment (Table 4). The grain N concentration progressively improved as the amount of BS increased and the amount of blended NPS fertilizer decreased. This is related to the fate of nitrogen from blended NPS fertilizer, which leaches. However, the combination of blended NPS fertilizer and BS may affect nitrogen release dynamics in the soil because blended NPS fertilizer is a readily available source of nitrogen, but BS can behave as a slow-release source over time. This combination has the ability to provide a consistent supply of nitrogen to crops, resulting in higher nitrogen concentrations. In agreement with this study, Hossaen et al [88] reported that lower N concentration on grain of rice was found with a ratio of 75% urea: 25% organic sources, while maximum N concentration was obtained with 25% urea: 75% organic sources. According to Yigermal et al [85], the maximum total N after each crop harvest was also found in the treatment where organic fertilizers were applied, integrated with low mineral N sources fertilizer. Similarly, the maximum (1.43%) N concentration in grain maize was found in the treatment receiving 75% N from mineral sources and the remaining 25% from FYM, followed by 1.39% in the treatment receiving N in a 50:50 ratio [89].
Percentage of nitrogen concentration in stover.
Stover nitrogen concentration was highly and significantly (P < 0.01) affected by the combined application of BS and blended NPS fertilizer. The highest (1.00%) stover nitrogen concentration percentage was found with the application of 25% RDNPS + 75% RDBS, whereas the lowest (0.62%) was recorded in the control treatment (Table 4). This might be due to the combination of blended NPS fertilizer and BS providing a balanced and readily available supply of nitrogen to the plants, leading to increased nitrogen uptake and accumulation in the stover [90]. In harmony with this finding, Rehim et al [91] found that the highest (0.59%) N concentration in straw of wheat was recorded with the combined application of 75% urea + 25% FYM, while the lowest (0.29%) was found with no/any fertilizer application. Similarly, Amanullah et al [92] and Shah and Ahmad [93] also reported that the highest nitrogen concentration in wheat straw was recorded in the combined application of organic manure and mineral fertilizer.
Grain, stover and total nitrogen uptake of maize
Grain nitrogen uptake.
The combined application of BS and blended NPS fertilizer had a very highly significant (P < 0.001) effect on maize grain nitrogen uptake. The application of 25% RDNPS + 75% RDBS resulted in the highest (181.72 kg ha-1) grain nitrogen uptake, whereas the untreated plot had the lowest (81.65 kg ha-1) (Table 5). This might be due to the improvement of soil fertility and biological activity with BS, which in turn affects nitrogen availability for crops as reported by [94,95]. The present results are consistent with Khan et al [89] the maximum N uptake of 49.72 kg ha-1 was obtained in treatment receiving 75% N from urea and 25% from FYM.
Stover nitrogen uptake.
The analysis of variance (ANOVA) revealed that the stover nitrogen uptake of maize was high significantly (P < 0.01) affected by the combined application of organic BS and blended NPS fertilizers. The highest nitrogen uptake (102.28 kg ha-1) in stover of maize was recorded with the application of 25% RDNPS + 75% RDBS, whereas the untreated plots had the lowest (48.70 kg ha-1) nitrogen uptake by stover of maize, as shown in Table 5 below. This might be due to the combined application of BS and blended NPS fertilizer, which enhances soil pH and organic matter, leading to better nutrient retention and availability to the crop [96]. In agreement to this study Baradhan et al [97], conducted a field experiment in the Experimental Farm of Annamalai University and reported that the combined application of 100% recommended dose of inorganic fertilizer (RDF) with 2.5 t ha-1 poultry manure resulted in the highest nitrogen availability and uptake by maize crop.
Total nitrogen uptake.
The ANOVA revealed that the stover nitrogen uptake of maize was very highly and significantly (P < 0.001) affected by the combined application of organic BS and blended NPS fertilizers. The highest total nitrogen uptake(284 kg ha-1) of maize was recorded with the application of 25% RDNPS + 75% RDBS, whereas the untreated plots had the lowest (130.53 kg ha-1) total nitrogen uptake by maize as shown in Table 5 below. Similar to this result, Khan et al [89] reported that the application of 25% FYM + 75% N resulted in the highest total nitrogen uptake and the lowest was recorded from the untreated plot of maize crop. Our result is in corroborated the findings of Dunjana et al [98], Negassa et al [99] and Rusinamhodzi et al [100], those stated that the integrated application of organic and mineral fertilizers at appropriate rates can be an effective approach to improve maize N uptake.
Nutrient use efficiency
Nutrient Use Efficiency (NUE) can be greatly influenced by the management of fertilizers, soil, and irrigation [101]. With a rising need for fertilizer nutrients to support global food demands, the limited availability of fertilizer resources and concerns about their environmental impacts have heightened. Consequently, there is a growing emphasis on enhancing NUE without compromising crop productivity. It measures how effectively crops absorb and utilize nutrients to achieve optimal yields. As such, the NUE concept encompasses three key plant processes: nutrient uptake, assimilation, and utilization [102,103]. It can be also characterized using several indices [104].
Agronomical nitrogen use efficiency.
Agronomic nitrogen use efficiency (ANUE) is a metric that includes yield potential of an applied fertilizer and relates directly to economic return [105]. According to the results of ANOVA, the combined application of BS and blended NPS fertilizer had not statistically significant (P > 0.05) effect on the ANUE of maize. However, the highest ANUE (13.94 kg kg-1) was recorded with the application of 25% RDNPS + 75% RDBS followed by the application of 100% RDNPS (13.73 kg kg-1), whereas the lowest ANUE (3.88 kg kg-1) was obtained from the application of 100% RDBS (S1 Fig). The highest agronomic nitrogen use efficiency observed could be attributed to the synergistic effects, balanced nutrient composition, and enhanced soil health resulting from the combined use of BS and blended NPS fertilizer. These results are in line with those of El-Syed et al [106] compost with inorganic NPK did not show any significant effect on ANUE compared to adding inorganic NPK alone. In the same way, Asaye et al [107], reported that the integrated application of vermicompost with blended NPS fertilizer resulted in a higher ANUE of maize than the application of sole blended NPS fertilizer. Similarly, Dorsey [108] and Ramesh [109] concluded that the combined application of vermicompost with urea fertilizer produced higher agronomic nitrogen use efficiency of the wheat crop.
Physiological nitrogen use efficiency.
Physiological nitrogen use efficiency (PNUE) represents the fraction of plant acquired N that is converted to grain yield. The ANOVA revealed that PNUE of maize was significantly (P < 0.05) affected by the combined application of BS and blended NPS fertilizer. The highest PNUE (66.71 kg kg-1) was recorded with the sole application of 100% RDNPS, whereas the lowest PNUE (27.69 kg kg-1) was obtained with the combined application of 75% RDNPS with 25% RDBS as shown below in S1 Fig. This result may be due to the application of 100% RDNPS, which likely provided the maize plants with optimal levels of readily available nitrogen, phosphorus and sulfur, which are essential nutrients for plant growth and development. In agreement with this finding, Bekalo [110] reported that application of the recommended dose of NP fertilizer increased PNUE between 39.6 and 60.6% against the combined application of NP fertilizer with FYM and sole FYM in potato crops. However, our result was in contrast with those of Agegnehu et al [7] who reported that the application of biochar + 23 kg N ha-1 resulted in the highest physiological nitrogen use efficiency of 33 kg kg-1 N at Holetta and 48 kg kg-1 N at Robgebeya.
Agro-physiological nitrogen use efficiency.
According to the ANOVA, the combined application of BS and blended NPS fertilizer had a non-significant (P > 0.05) effect on the agro-physiological nitrogen use efficiency (APNUE) of maize. However, the highest APNUE (37.78 kg kg-1) was found with the sole application of 100% RDNPS, whereas the lowest APNUE (25.46 kg kg-1) was recorded from the combined application of 75% RDNPS + 25% BS (S1 Fig). This result might be due to the nutrient balance, enhanced nutrient interactions, organic matter content and slow release of nutrients, which leads to higher APNUE maize. In line with the report of this study, Fazily et al [111] conducted research at the Agronomy Research Farm of Haryana Agricultural University under irrigation and reported that the highest APNUE (54.17 kg kg-1) of maize was recorded under the application of 25% RDN + 75% FYM followed by 50% RDN + 50% FYM (50.70 kg kg-1), whereas the lowest APNUE (47.54 kg kg-1) was observed with the application of 100% RDN + 25% FYM in comparing the combined application of chemical fertilizer with farm manure only.
Apparent recovery efficiency of nitrogen.
Analysis of data showed that the apparent recovery efficiency of nitrogen (AREN) of maize was significantly (P < 0.05) affected by the combined application of BS and blended NPS fertilizer (S1 Fig). The highest AREN (47.67%) was found with the combined application of 25% RDNPS + 75% RDBS followed and statistically at par with the combined application of 75%RDNPS + 25%RDBS (46.53%), whereas the lowest AREN (12.69%) was found in plots treated with only 100% RDBS. This could be due to the combined application of BS and blended NPS, which may enhance nutrient availability, promote microbial activity, and improve soil structure, leading to higher AREN. Our result was in consistent with those of Agegnehu et al [7] those reported that the AREN responded significantly to biochar with N fertilizer.
Utilization efficiency of nitrogen.
The utilization efficiency of nitrogen (UEN) for a cereal crop depends on its ability to acquire nitrogen from the available supply and how effectively it utilizes nitrogen to produce grain [7,112,113]. In most cases, annual crops only take up nitrogen from the soil at optimal fertilizer rates for a period of 8–12 weeks, leading to a mismatch between nitrogen availability and crop demand, which contributes significantly to nitrogen losses [114]. The result of this study indicated that the combined application of BS and NPS fertilizer did not have a significant effect (P > 0.05) on the nitrogen utilization efficiency of maize. However, the highest UEN (21.22%) was observed when 25% RDNPS with 75% RDBS was applied, while the lowest UEN (4.16%) was recorded with the sole application of 100% RDBS (10 t ha-1 BS), as shown in Table 6. This discrepancy may be due to the tendency of nitrogen in organic amendments to undergo immobilization, resulting in plants recovering limited amounts of nitrogen from these amendments in the short term [7]. However, split applications of urea, particularly three-way splits (one-fourth at sowing, one-half at vegetative stages, and one-fourth at tasseling) compared to single applications, enhance the UEN of maize [72,115].
Nitrogen harvest index.
Nitrogen harvest index (NHI) indicates the level of efficiency of plants to use acquired nitrogen for grain formation. A high NHI indicates efficient utilization of nitrogen. The analysis results of this study showed that NHI was not significantly (P > 0.05) affected by the combined application of BS and blended NPS fertilizer. This might be due to the brewery sludge not having provided sufficient readily available nitrogen to enhance the NHI, as its organic matter content can lead to slower nitrogen release compared to synthetic fertilizers [116].
This result is in line with Agegnehu [117], who found and report that NHI of barley was not significantly affected by the application of organic amendments and chemical nitrogen fertilizer at Holotta, Ethiopia.
Partial budget analysis
According to the manual for the economic analysis of International Maize and Wheat Improvement Centre (CIMMYT [65]), combined applications of 75% RDBS with 25% RDNPS fertilizer rates resulted in the highest net benefit of 170987.97 ETB ha-1 with the most acceptable MRR (12613.93%), followed by the sole application of 100% recommended brewery sludge (10 t ha-1) resulted in a net benefit of 125230.94 ETB ha-1 with 3681.77% MRR whereas the lowest from the control (Table 7). As a result, this treatment combination was the most recommended and cost-effective for maize production. This implies that using the best organic and inorganic fertilizers is critical for improving soil fertility and crop productivity. The result was in line with Jinwei and Lianren [118] and Lingaraju et al [119] that a combined application of organic manure and inorganic fertilizer produced a high net benefit income and cost-benefit ratio compared with the sole application of either organic or inorganic fertilizer on maize crops.
Conclusion and recommendations
The results of a field experiment conducted in the North Mecha district of Northwestern Ethiopia show that using both BS and blended NPS fertilizers, either alone or in combination, has considerable potential to increase maize output in the research area. The results clearly show that the application of 25% RDNPS with 75% RDBS fertilizer ratios led to the maximum maize above-ground biological yield, grain yield, nitrogen uptake and overall nitrogen use efficiency when compared to sole chemical fertilizer applications or no fertilizer use. The study emphasizes the need to address soil fertility issues in Ethiopia through targeted fertilizer applications to boost maize productivity. Farmers in the North Mecha district can use the determined optimal fertilizer combination as a realistic and successful technique to maximize maize yields and economic returns. However, further research is required to fine-tune the rates and application methods of BS, NPS and their combination in order to achieve long-term agronomic gains in maize production. Long-term success in increasing maize yield in the region will depend on continuous monitoring and adaptation of fertilizer techniques depending on local soil conditions and crop requirements.
Supporting information
S1 Fig. Nitrogen use efficiency indices of maize as affected by sole and integrated brewery sludge and blended NPS fertilizer.
https://doi.org/10.1371/journal.pone.0319958.s001
(DOCX)
Acknowledgments
We extend our appreciation to Bahir Dar University for generously providing an unreserved plot of land at the Kudmi research site for the experimentation. These contributions were invaluable to the successful execution of the research project.
References
- 1. Belachew K, Yehuala N, Maina H, Dersseh W, Zeleke B, Stoddard FL. Yield gaps of major cereal and grain legume crops in Ethiopia: a review. Agronomy. 2022;12(10):2528.
- 2. Assefa F, Ayalew D. Status and control measures of fall armyworm (Spodoptera frugiperda) infestations in maize fields in Ethiopia: a review. Cogent Food Agric. 2019;5(1):1641902.
- 3. Abate T, Shiferaw B, Menkir A, Wegary D, Kebede Y, Tesfaye K, et al. Factors that transformed maize productivity in Ethiopia. Food Secur. 2015;7:965–81.
- 4.
Abdulkadir B, Kassa S, Desalegn T, Tadesse K, Haileselassie M, Fana G, et al. Crop response to fertilizer application in Ethiopia: a review. In: Tamene L, Amede T, Kihara J, Tibebe D, Schulz S, editors; 2017.
- 5. Amare T, Erkihun A, Zerfu B, Asmare W, Selamyihun K, Beamlaku A, et al. Yield-limiting plant nutrients for maize production in northwest Ethiopia. Exp Agric. 2022;58(1):e5.
- 6.
IFPRI. Fertilizer and soil fertility potential in Ethiopia, constraints and opportunities for enhancing the system, sustainable solution for enduring hunger and poverty. Washington (DC); 2010.
- 7. Agegnehu G, Nelson PN, Bird MI. The effects of biochar, compost and their mixture and nitrogen fertilizer on yield and nitrogen use efficiency of barley grown on a Nitisol in the highlands of Ethiopia. Sci Total Environ. 2016;569–570:869–79. pmid:27288288
- 8.
Amare T, Bazie Z, Alemu E, Wubet A, Agumas B, Muche M, et al. Crops response to the balanced nutrient application in Northwestern Ethiopia, vol. 17. Amhara Agricultural Research Institute (Arari); 2018.
- 9. Kebede D, Ketema M. Why do smallholder farmers apply inorganic fertilizers below the recommended rates. Empirical evidence from potato production in eastern Ethiopia. Adv Crop Sci Technol. 2017;5(2):265.
- 10. Hirpa K, Bulto T. Effects of different termite management practices on maize production in Assosa district, Benishangul Gumuz Region, Western Ethiopia. J Biol Agric Healthc. 2016;6:23.
- 11.
Abera W. Genetic diversity, stability, and combining ability of maize genotypes for grain yield and resistance to NCLB in the mid-altitude sub-humid agro-ecologies of Ethiopia. University of KwaZulu-Natal Republic of South Africa; 2013.
- 12. Bosede AJ. Economic assessment of fertilizer use and integrated practices for environmental sustainability and agricultural productivity in Sudan savannah zone, Nigeria. Afr J Agric Res. 2010;5(5):338–43.
- 13. Chianu JN, Chianu JN, Mairura F. Mineral fertilizers in the farming systems of sub-Saharan Africa. A review. Agron Sustain Dev. 2012;32(2):545–66.
- 14. Mafongoya P, Bationo A, Kihara J, Waswa BS. Appropriate technologies to replenish soil fertility in southern Africa. Nutr Cycl Agroecosys. 2006;76(2–3):137–51.
- 15. Waddington SR, Li X, Dixon J, Hyman G, De Vicente MC. Getting the focus right: production constraints for six major food crops in Asian and African farming systems. Food Secur. 2010;2(1):27–48.
- 16. Bado VB, Bationo A. Integrated management of soil fertility and land resources in Sub-Saharan Africa: involving local communities. Adv Agron. 2018;150:1–33.
- 17. Asgelil D, Taye B, Yesuf A. The status of micro-nutrients in Nitisols, Vertisols, Cambisols and Fluvisols in major Maize, Wheat, Teff and Citrus growing areas of Ethiopia. Proc Agric Res Fund. 2007:77–96.
- 18. Bindraban PS, Dimkpa C, Nagarajan L, Roy A, Rabbinge R. Revisiting fertilisers and fertilisation strategies for improved nutrient uptake by plants. Biol Fertil Soils. 2015;51(8):897–911.
- 19. Kihara J, Nziguheba G, Zingore S, Coulibaly A, Esilaba A, Kabambe V, et al. Understanding variability in crop response to fertilizer and amendments in sub-Saharan Africa. Agric Ecosyst Environ. 2016;229:1–12. pmid:27489394
- 20. Mtangadura TJ, Mtambanengwe F, Nezomba H, Rurinda J, Mapfumo P. Why organic resources and current fertilizer formulations in Southern Africa cannot sustain maize productivity: Evidence from a long-term experiment in Zimbabwe. PLoS One. 2017;12(8):e0182840. pmid:28797062
- 21. Roobroeck D, Palm CA, Nziguheba G, Weil R, Vanlauwe B. Assessing and understanding non-responsiveness of maize and soybean to fertilizer applications in African smallholder farms. Agric Ecosyst Environ. 2021;305:107165. pmid:33390635
- 22. ten Berge HFM, Hijbeek R, van Loon MP, Rurinda J, Tesfaye K, Zingore S, et al. Maize crop nutrient input requirements for food security in sub-Saharan Africa. Glob Food Secur. 2019;23:9–21.
- 23. van der Velde M, Folberth C, Balkovič J, Ciais P, Fritz S, Janssens IA, et al. African crop yield reductions due to increasingly unbalanced Nitrogen and Phosphorus consumption. Glob Chang Biol. 2014;20(4):1278–88. pmid:24470387
- 24. Chathurika JAS, Indraratne SP, Dandeniya WS. Site specific fertilizer recommendations for maize (Zea mays L.) grown in reddish brown earth and reddish brown latasolic soils. Trop Agric Res. 2015;25(3):287.
- 25. Ferguson RB, Hergert GW, Schepers JS, Gotway CA, Cahoon JE, Peterson TA. Site‐specific nitrogen management of irrigated maize. Soil Science Soc of Amer J. 2002;66(2):544–53.
- 26.
Spielman DJ, Kelemwork D, Alemu D. Seed, fertilizer, and agricultural extension in Ethiopia. In: Food and agriculture in Ethiopia: progress and policy challenges, vol. 74; 2011. 84 p.
- 27.
Pahalvi HN, Rafiya L, Rashid S, Nisar B, Kamili AN, Chemical fertilizers and their impact on soil health. In: Microbiota and biofertilizers, vol 2: ecofriendly tools for reclamation of degraded soil environs; 2021. p. 1–20.
- 28. Faheed FA, Abdel Fattah Z. Effect of Chlorella vulgaris as bio-fertilizer on growth parameters and metabolic aspects of lettuce plant. J Agric Soc Sci (Pakistan). 2008;4(4):165–9.
- 29.
Islam. Use of bioslurry as organic fertilizer in Bangladesh agriculture. International Workshop on the Use of Bioslurry Domestic Biogas Programme; Bangkok, Thailand; 2006.
- 30. Islam SMER, Rahman MM, Oh DH, Ra CS. The effects of biogas slurry on the production and quality of maize fodder. Turk J Agric For. 2010;34(1):91–9.
- 31.
Bejiga A. Fertilizing potential of brewery wastewater sludge for cultivation of lettuce and tomato on planosol and vertisol soils, in Alemnesh Bejiga 2019. Fertilizing potential of brewery wastewater sludge for cultivation of lettuce and tomato on planosol and vertisol soils. Msc Thesis, Addis Abeba University, Addis Abeba, Ethiopia; 2019.
- 32.
Mwanga KE. Effects of bio-slurry and farm yard manure on soil amelioration and chinese cabbage (Brassica Rapa Var. Chinensis) yields in Njombe region, Tanzania. Morogoro,Tanzania: Sokoine University of Agriculture; 2016.
- 33. Engida T, Mekonnen A, Wu JM, Xu D, Wu ZB. Review paper on beverage agro-industrial wastewater treatment plant bio-sludge for fertilizer potential in Ethiopa. Appl Ecol Environ Res. 2020;18(1):33–57.
- 34. Alayu E, Leta S, Aragaw T. Characterization of the physicochemical and biological properties of Kombolcha brewery wastewater treatment plant bio-solid in relative to agricultural uses. Adv Recycl Waste Manag. 2018;3(1):1–7.
- 35. Jebesa WT, Astatkie T, Zerfu A, Kenea HD, Abamecha N, Shumuye M, et al. Impact of brewery sludge application on heavy metal build-up, translocation, growth and yield of bread wheat (Triticum aestivum L.) crop in Northern Ethiopia. Heliyon. 2024;10(11).
- 36. Daba N, Alemu A, Mohammed M. Impact of brewery waste sludge on sorghum (Sorghum bicolor L. Moench) productivity and soil fertility in Harari Regional State, Eastern Ethiopia. Turk J Agric-Food Sci Technol. 2017;5(4):366–72.
- 37. Ahmed A, Muktar Mohammed M, Merga B. Effects of brewery waste sludge on haricot bean (Phaseolus vulgaris L.) productivity and soil fertility. Cogent Food Agric. 2019;5(1):1667729.
- 38. Mohammed M, Merga B, Ahmed A. Effects of brewery waste sludge on potato (Solanum tuberosum L.) productivity and soil fertility. Cogent Food Agric. 2019;5(1):1707053.
- 39. Merga B, Mohammed M, Ahmed A, Wakgari M. The application of brewery sludge for maize production. Ethiop J Sci Sustain Dev. 2020;8(1).
- 40.
Verma BC, Pramanik P, Bhaduri D. Organic fertilizers for sustainable soil and environmental management. In: Meena RS, editor. Nutrient dynamics for sustainable crop production. Singapore: Springer; 2020. p. 289–313.
- 41.
Antil RS, Raj D. Integrated nutrient management for sustainable crop production and improving soil health. In: Meena , editor. Nutrient dynamics for sustainable crop production. Singapore: Springer; 2020. p. 67–101.
- 42. Singh J, Kaur J, Mehta D, Narwal R. Long-term effects of nutrient management on soil health and crop productivity under rice-wheat cropping system. Indian J Fertilisers. 2012;8(8):28–48.
- 43. Singh Brar B, Singh J, Singh G, Kaur G. Effects of long term application of inorganic and organic fertilizers on soil organic carbon and physical properties in maize–wheat rotation. Agronomy. 2015;5(2):220–38.
- 44.
Mengstie FA. Assessment of adoption behavior of soil and water conservation practices in the Koga watershed, highlands of Ethiopia. Citeseer; 2009.
- 45. Assefa F, Gebremedhin Z, Alem T. Data on the effects of brewery sludge and blended NPS fertilizer rates on yield and yield components of maize (Zea Mays L.) in North Mecha District, Northwestern Ethiopia. Data Brief. 2023;51:109707. pmid:37965600
- 46. Bassa D, Goa Y. On farm evaluation of improved maize (Zea mays L) varieties for yield and adaptation in highland of Alicho, Silti and Analemo districts of Southern Ethiopia. Int J Res Stud Sci Eng Technol. 2017;4(2):18–22.
- 47.
Canadian Council of the Ministers of the Environment (CCME). Guidelines for compost quality. In: M.o.P.W.a.G.S. Canada, editor. Cat. No. PN1341., no limits in use; 2005.
- 48.
United States Environmental Protection Agency (USEPA). A plain English guide to the EPA part 503 biosolids rule. US Environmental Protection Agency, Office of Wastewater Management, Municipal Technology Branch; 1994.
- 49.
Goshe M. Analysis of some selected parameters of dashen brewery sewage sludge for agricultural productivity. Gondar, Ethiopia: University of Gondar; 2020.
- 50. Bouyoucos GJ. A recalibration of the hydrometer method for making mechanical analysis of soils. Agron J. 1951;43(9):434–8.
- 51.
Sahlemedhin S, Taye B, Procedures for soil and plant analysis. Technical paper 74, National soil research center. Addis Ababa: Ethiopian Agricultural Research Organization; 2000.
- 52.
Jackson ML. Soil chemical analysis, vol. 498. Englewood Cliffs (NJ): Prentice Hall Inc.; 1958. p. 183–204.
- 53. Walkley A, Black I. An examination of the Degtjareff method for determining soil organic matter, and a proposed modification of the chromic acid titration method. Soil Sci. 1934;37(1):29–38.
- 54.
Olsen SR. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. US Department of Agriculture; 1954.
- 55.
Rhoades JD. Cation exchange capacity. In: Methods of soil analysis: part 2 chemical and microbiological properties, vol. 9; 1982. p. 149–57.
- 56. Donald C, Hamblin J. The biological yield and harvest index of cereals as agronomic and plant breeding criteria. Adv Agron. 1976;28:361–405.
- 57. Rehman A, Nawaz S, Alghamdi HA, Alrumman S, Yan W, Nawaz MZ. Effects of manure-based biochar on uptake of nutrients and water holding capacity of different types of soils. Case Stud Chem Environ Eng. 2020;2:100036.
- 58.
Fageria NK. Nitrogen management in crop production. CRC Press; 2014.
- 59.
Dobermann A. Nutrient use efficiency—measurement and management. In: Krauss A, Isherwood K, Heffer P, editors. Fertilizer best management practices: general principles, strategy for their adoption and voluntary initiatives versus regulations, vol. 1442. Agronomy & Horticulture -- Faculty Publications; 2007. p. 1–28.
- 60. Fageria NK, Baligar VC. Enhancing nitrogen use efficiency in crop plants. Adv Agron. 2005;88:97–185.
- 61. Raun WR, Johnson GV. Improving nitrogen use efficiency for cereal production. Agron J. 1999;91(3):357–63.
- 62. Tilman D, Cassman KG, Matson PA, Naylor R, Polasky S. Agricultural sustainability and intensive production practices. Nature. 2002;418(6898):671–7. pmid:12167873
- 63.
SAS. SAS 9.4 output delivery system: user’s guide. SAS Institute; 2014.
- 64.
Montgomery , Douglas C. Introduction to statistical quality control. John Wiley & Sons; 2020.
- 65.
CIMMYT. From agronomic data to farmer recommendations: an economics training manual. CIMMYT; 1988.
- 66.
USDA. Module 3-USDA textural classification. Study guide. Washington (DC): United States Department of Agriculture; 1987. p. 1–48.
- 67.
Tadesse T, Haque I, Aduayi EA. Soil, plant, water, fertilizer, animal manure and compost analysis manual; 1991.
- 68.
Landon JR. Booker tropical soil manual: a handbook for soil survey and agricultural land evaluation in the tropics and subtropics. Routledge; 2014.
- 69.
Hazelton P, Murphy B, Interpreting soil test results: What do all the numbers mean? CSIRO Publishing; 2016.
- 70. Alayu E, Leta S. Brewery sludge quality, agronomic importance and its short-term residual effect on soil properties. Int J Environ Sci Technol. 2020;17(4):2337–48.
- 71. Kharel G, Sacko O, Feng X, Morris JR, Phillips CL, Trippe K, et al. Biochar surface oxygenation by ozonization for super high cation exchange capacity. ACS Sustain Chem Eng. 2019;7(19):16410–8.
- 72. Davies B, Coulter JA, Pagliari PH. Timing and rate of nitrogen fertilization influence maize yield and nitrogen use efficiency. PLoS One. 2020;15(5):e0233674. pmid:32469984
- 73.
Fashaho A. Evaluation of soil properties and response of maize (Zea Mays L.) to bioslurry and mineral fertilizers in terraced acrisols and lixisols of Rwanda. Njoro, Kenya: Egerton University; 2020.
- 74. Kebede T, Keneni YG, Senbeta AF, Sime G. Effect of bioslurry and chemical fertilizer on the agronomic performances of maize. Heliyon. 2023;9(1):e13000. pmid:36711291
- 75. Achieng J, Ouma G, Odhiambo G, Muyekho F. Effect of farmyard manure and inorganic fertilizers on maize production on Alfisols and Ultisols in Kakamega, western Kenya. ABJNA. 2010;1(4):430–9.
- 76. Kibunja CN, Mwaura F, Mugendi D. Long-term land management effects on soil properties and microbial populations in a maize-bean rotation at Kabete, Kenya. Afr J Agric Res. 2010;5(2):108–13.
- 77. Mohammadi G, Rostami Ajirloo A, Ghobadi M, Najaphy A. Effects of non-chemical and chemical fertilizers on potato (Solanum tuberosum L.) yield and quality. J Med Plants Res. 2013;7(1):36–42.
- 78. Yang W, Li C, Wang S, Zhou B, Mao Y, Rensing C, et al. Influence of biochar and biochar-based fertilizer on yield, quality of tea and microbial community in an acid tea orchard soil. Appl Soil Ecol. 2021;166:104005.
- 79. Zhou Z, Gao T, Zhu Q, Yan T, Li D, Xue J, et al. Increases in bacterial community network complexity induced by biochar-based fertilizer amendments to karst calcareous soil. Geoderma. 2019;337:691–700.
- 80. Chew J, Zhu L, Nielsen S, Graber E, Mitchell DRG, Horvat J, et al. Biochar-based fertilizer: Supercharging root membrane potential and biomass yield of rice. Sci Total Environ. 2020;713:136431. pmid:31958720
- 81. Shi W, Ju Y, Bian R, Li L, Joseph S, Mitchell DRG, et al. Biochar bound urea boosts plant growth and reduces nitrogen leaching. Sci Total Environ. 2020;701:134424. pmid:31726412
- 82. Bekeko Z. Evaluation of enriched farmyard manure and inorganic fertilizers profitability in hybrid maize (BH‐140) production at west Hararghe zone, eastern Ethiopia. J Genet Environ Resour Conserv. 2014;2(1):83–9.
- 83.
Tuyishime O. Effect of bioslurry and inorganic-N fertilizers on soil properties and improvement of maize productivity in Musanze District, Rwanda. Nairobi, Kenya: Kenyatta University; 2012.
- 84. Tukur A, Kesarwani A. Effect of integrated nutrient management on growth and yield parameters of maize (Zea mays L.) as well as soil physico-chemical properties. J Sci Tech Res. 2017;1(2):1–6.
- 85. Yigermal H, Kelemu N, Assefa F. Effects of integrated nutrient application on phenological, vegetative growth and yield-related parameters of maize in Ethiopia: a review. Cogent Food Agric. 2019;5(1):1567998.
- 86. Muhmood A, Javid S, Ahmad Z, Majeed A, Rafique R. Integrated use of bioslurry and chemical fertilizers for vegetable production. Pak J Agric Sci. 2014;51(3):565–70.
- 87. Ahmad Z, Shah F, Khan S, Ali W, Malik W. Maize yield and soil properties as influenced by integrated use of organic, inorganic and bio-fertilizers in a low fertility soil. Soil Environ. 2013;32(2):121–9.
- 88. Hossaen M, Shamsuddoha A, Paul A, Bhuiyan M, Zobaer A. Efficacy of different organic manures and inorganic fertilizer on the yield and yield attributes of boro rice. Agriculturists. 2011;9(1–2):117–25.
- 89. Khan A, Shah SA, Haroon H, Ibadullah I, Azeem I, Khan K. et al. Effect of organic and inorganic sources of nitrogen on maize yield, nitrogen uptake and soil fertility. J Agron Plant Breed. 2017;13(2):101–10.
- 90. Rajendran S, Sundaram L. Degradation of heavy metal contaminated soil using plant growth promoting rhizobacteria (PGPR): assess their remediation potential and growth influence of Vigna radiata. Int J Agric Technol. 2020;16(2):365–76.
- 91. Rehim A, Khan M, Imran M, Bashir MA, Ul-Allah S, Khan MN, et al. Integrated use of farm manure and synthetic nitrogen fertilizer improves nitrogen use efficiency, yield and grain quality in wheat. Ital J Agron. 2020;15(1):29–34.
- 92. Amanullah H, Ullah MS, Elshikh MS, Alwahibi J, Alkahtani AM, . Nitrogen contents in soil, grains, and straw of hybrid rice differ when applied with different organic nitrogen sources. Agriculture. 2020;10(9):386.
- 93. Shah Z, Ahmad MI. Effect of integrated use of farm yard manure and urea on yield and nitrogen uptake of wheat. J Agric Biol Sci. 2006;1(1):60–5.
- 94. Amanullah A, Inamullah X. Dry matter partitioning and harvest index differ in rice genotypes with variable rates of phosphorus and zinc nutrition. Rice Sci. 2016;23(2):78–87.
- 95.
Jan A, Shah Z, Khan MJ, Parmar B, Fahad S. Organic carbon sources and nitrogen management improve biomass of hybrid rice (Oryza sativa L.) under nitrogen deficient condition. In: Advances in rice research for abiotic stress tolerance. Elsevier; 2019. p. 447–67.
- 96. Teressa D, Kibret K, Dechasa N, Wogi L. Soil properties and nutrient uptake of maize (Zea mays) as influenced by mixed manure and blended inorganic fertilizer in Haramaya district, eastern Ethiopia. Heliyon. 2024;10(16):e04234.
- 97. Baradhan G, Saranya M, Kumar S, Rex Immanuel R, Rao G. Effect of integration of chemical fertilizers with organic manures on growth, yield and nutrient uptake in hybrid maize (Zea mays L.). Crop Res. 2022;57(5 and 6):325–9.
- 98. Dunjana N, Nyamugafata P, Shumba A, Nyamangara J, Zingore S. Effects of cattle manure on selected soil physical properties of smallholder farms on two soils of Murewa, Zimbabwe. Soil Use Manag. 2012;28(2):221–8.
- 99. Negassa W, Gebrekidan H, Friesen D. Integrated use of farmyard manure and NP fertilizers for maize on farmers’ fields. JARTS. 2005;106(2):131–41.
- 100. Rusinamhodzi L, Corbeels M, Zingore S, Nyamangara J, Giller KE. Pushing the envelope? Maize production intensification and the role of cattle manure in recovery of degraded soils in smallholder farming areas of Zimbabwe. Field Crops Res. 2013;147:40–53.
- 101.
Panhwar QA, Ali A, Naher UA, Memon MY. Fertilizer management strategies for enhancing nutrient use efficiency and sustainable wheat production. In: Organic farming. Elsevier; 2019. p. 17–39.
- 102.
González-Fontes A, Navarro-Gochicoa MT, Ceacero CJ, Herrera-Rodríguez MB, Camacho-Cristóbal JJ, Rexach J. Understanding calcium transport and signaling, and its use efficiency in vascular plants. In: Plant macronutrient use efficiency; Elsevier; 2017. p. 165–80.
- 103.
Brouder SM, Volenec JJ. Nutrition of plants in a changing climate. In: Marschner’s mineral nutrition of plants. Elsevier; 2023. p. 723–50.
- 104.
Sarkar D, Baishya LK. Nutrient use efficiency. In: Naeem M, Ansari AA, Gill SS, editors. Essential plant nutrients: uptake, use efficiency, and management. Cham: Springer; 2017. p. 119–46.
- 105. Bhunia S, Bhowmik A, Mallick R, Mukherjee J. Agronomic efficiency of animal-derived organic fertilizers and their effects on biology and fertility of soil: a review. Agronomy. 2021;11(5):823.
- 106. El-Syed NM, Helmy AM, Fouda SE, Nabil MM, Abdullah TA, Alhag SK, et al. Biochar with organic and inorganic fertilizers improves defenses, nitrogen use efficiency, and yield of maize plants subjected to water deficit in an alkaline soil. Sustainability. 2023;15(16):12223.
- 107. Asaye Z, Kim D-G, Yimer F, Prost K, Obsa O, Tadesse M, et al. Effects of combined application of compost and mineral fertilizer on soil carbon and nutrient content, yield, and agronomic nitrogen use efficiency in maize-potato cropping systems in southern Ethiopia. Land. 2022;11(6):784.
- 108.
Dorsey ND. Nitrogen use efficiency and nitrogen response of wheat varieties commonly grown in the Great Plains, USA, Kansas State University; 2014.
- 109. Ramesh S. Grain yield, nutrient uptake and nitrogen use efficiency as influenced by different sources of vermicompost and fertilizer nitrogen in rice. J Pharmacogn Phytochem. 2018;7(5):52–5.
- 110.
Bekalo TG. Potato productivity, nutrient use efficiency and soil chemical property as influenced by organic and inorganic amendments in Arbegona district, southern Ethiopia. MSc Thesis, Hawassa University College of Agriculture; 2017.
- 111. Fazily T, Thakral SK, Dhaka AK, Sharma MK, Effect of integrated nutrient management on fertilizer use efficiency in wheat (Triticum aestivum l.) under irrigated condition. Int J Adv Agric Sci Technol. 2020;7:1–9.
- 112. Bingham IJ, Karley AJ, White PJ, Thomas WTB, Russell JR. Analysis of improvements in nitrogen use efficiency associated with 75 years of spring barley breeding. Eur J Agron. 2012;42:49–58.
- 113. Huggins D, Pan W. Key indicators for assessing nitrogen use efficiency in cereal-based agroecosystems. J Crop Prod. 2003;8(1–2):157–85.
- 114. Robertson GP, Vitousek PM. Nitrogen in agriculture: balancing the cost of an essential resource. Annu Rev Environ Resour. 2009;34:97–125.
- 115. Mosisa W, Dechassa N, Kibret K, Zeleke H, Bekeko Z. Effects of timing and nitrogen fertilizer application rates on maize yield components and yield in eastern Ethiopia. Agrosyst Geosci Environ. 2022;5(4):e20322.
- 116. Sisay A, Garomsa T, Legesse L. Effects of brewery beer bio-sludge and liquid biofertilizer on performance of the malt barley yield, grain quality and soil fertility at Arsi and West Arsi Zone, 2017 Ethiopia. Int J Agric Anim Prod (IJAAP). 2022:2799–0907.
- 117.
Agegnehu G. Biochar, compost and biochar-compost: Effects on crop performance, soil quality and greenhouse gas emissions in tropical agricultural soils. James Cook University; 2017.
- 118. Zhao J, Zhou L. Combined application of organic and inorganic fertilizers on black soil fertility and maize yield. J Northeast Agric Univ. 2011;18(2):24–9.
- 119. Lingaraju BS, Parameshwarappa KG, Hulihalli UK, Basavaraja B. Effect of organics on productivity and economic feasibility in maize-bengalgram cropping system. Indian J Agric Res. 2010;44(3):211–5.