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Answers to frequently asked questions

Posted by asdavis1 on 16 Nov 2012 at 17:57 GMT

Dear readers,

Thank you for the many good questions you have asked about this study, both on the PLOS ONE website, and via email. Below is a link to a FAQ site set up by the Leopold Center at Iowa State University to provide the answers to these and other questions about the Marsden farm study.



Adam Davis

No competing interests declared.

RE: Answers to frequently asked questions

AMMcGuire replied to asdavis1 on 30 Sep 2015 at 18:47 GMT

In your 2015 results on the linked page, you state
"Soil health improves. Soil managed with the longer rotations (3- and 4-year vs. 2-year) has more particulate organic matter carbon, more microbial biomass, and greater ability to release nitrogen from organic matter."

However, I think this is misleading, as I would think it is the manure applications that have a much greater effect on soil health than length of rotation, yet this is not mentioned at all. Do you have evidence that it is the length of rotation rather than the manure that is improving soil health?

No competing interests declared.

RE: RE: Answers to frequently asked questions

asdavis1 replied to AMMcGuire on 01 Oct 2015 at 14:30 GMT

Thank you for your comment. You are correct, that with the management protocols for this experiment, we can't separate manure effects from extended rotation effects. We do not make this claim in our PLOS ONE piece. In related work, Marriott & Wander (2006) found that manure + legume effects on organic matter in conventional and organic farming systems didn't differ from legume alone effects. Increases in potentially mineralizable N in amended systems may be strongly affected by manuring (Spargo et al., 2011).

Marriott, E. E., and M. M. Wander. 2006. Total and labile soil organic matter in organic and conventional farming systems. Soil Science Society of America Journal 70:950-959.

Spargo, J. T., M. A. Cavigelli, S. B. Mirsky, J. E. Maul, and J. J. Meisinger. 2011. Mineralizable soil nitrogen and labile soil organic matter in diverse long-term cropping systems. Nutrient Cycling in Agroecosystems 90:253-266.

No competing interests declared.