Table 1.
Experimental treatments in the three experiments.
Fertilizer blend ratios are expressed according to nitrogen supply. The numbers in the treatment codes refers to the blend ratio expressed in % dry matter. No fertilizers were added for the negative control experiment. The species Arthrospira platensis and Rhodobacter sphaeroides were used for respectively the microalga (MA) and purple non-sulfur bacteria (PNSB) fertilizers. Two ryegrass pot trials were performed with either individual (a) or microbial fertilizer blends (b). AHB: aerobic heterotrophic bacteria; SF2: conventional organic fertilizer.
Table 2.
NPK content of fertilizers: Conventional organic fertilizer SF2, aerobic heterotrophic bacteria (AHB), Arthrospira platensis as microalga (MA) and Rhodobacter sphaeroides as purple non-sulfur bacteria (PNSB).
Fig 1.
Schematic overview of the experimental setup of the pot trial with tomato.
Fig 2.
Nitrogen mineralization and nitrification: Profiles of total ammoniacal nitrogen, nitrate nitrogen and pH.
(A) organic growing medium without fertilizer (different primary y-axis), (B) conventional organic fertilizer SF2, (C) aerobic heterotrophic bacteria (AHB), (D) microalga (MA), (E) purple non-sulfur bacterium (PNSB), (F) 85% AHB and 15% MA, (G) 85% AHB and 15% PNSB and (H) 85% AHB, 12.5% MA and 12.5% PNSB. All individual or fertilizers blends were supplied at 352 mg-N L-1. Error bars represent the standard deviations. Significant differences among treatments are indicated per sampling point by letter code for ammonia nitrogen, nitrate nitrogen and pH, resp. in italic, bold and grey.
Fig 3.
Perennial ryegrass: Cumulative aboveground dry matter (DM) yield.
A non-fertilized negative control (Neg control) was compared to a conventional organic fertilizer (SF2) and three microbial fertilizers, i.e. aerobic heterotrophic bacteria (AHB), microalga (MA) and purple non-sulfur bacteria (PNSB) individually or in blends (according to nitrogen supply). Significant differences among treatments are indicated by letter code per sampling point, while error bars represent the standard deviation.
Table 3.
Pot trial with tomato: Total plant length (mean ± standard deviation per treatment).
A non-fertilized negative control (Neg control) was compared to a conventional organic fertilizer (SF2) and three microbial fertilizers, i.e. aerobic heterotrophic bacteria (AHB), microalga (MA) and purple non-sulfur bacteria (PNSB), individually or in blends (according to nitrogen supply).
Fig 4.
Pot trial with tomato: Alternaria leaf spot (mean ± standard deviation) for a selection of treatments.
A conventional organic fertilizer (SF2) was compared to three microbial fertilizers, i.e. aerobic heterotrophic bacteria (AHB), microalga (MA) and purple non-sulfur bacterium (PNSB) individually or in blends (according to nitrogen supply). Significant differences among these treatments are indicated by letter code.
Table 4.
Pot trial with tomato: Leaf greenness index (LGI) after 94 days, tomato yield and disease index upon infection with powdery mildew (mean ± standard deviation per treatment).
A non-fertilized negative control (Neg control) was compared to a conventional organic fertilizer (SF2) and three microbial fertilizers, i.e. aerobic heterotrophic bacteria (AHB), microalga (MA) and purple non-sulfur bacteria (PNSB), individually or in blends (according to nitrogen supply).