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Management of Soil Nitrogen through the use of Organic Amendments for Cereal Crop Production

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Title: Management of Soil Nitrogen through the use of Organic Amendments for Cereal Crop Production
Author: Woodley, Alexander
Department: School of Environmental Sciences
Program: Environmental Sciences
Advisor: Voroney, Paul
Abstract: The diversity of organic amendments currently being approved for use in certified organic farming has outpaced the fundamental research on their nutrient properties, including nitrogen (N) availability, crop N-use efficiency and effects on soil N dynamics. This understanding is essential for implementing best management practices (BMP) that address the economic and environmental risks associated with their usage in organic cereal production. The goal of the research was to develop scientifically-based BMPs that maximize the N use efficiency of organic amendments in organic cereal crop production. Field trials examined grain yield response to amendment applications, and their impact on residual soil N. A laboratory incubation study with a range of organic amendments was conducted to measure organic carbon (C) and N mineralization rates to guide prediction of N release for field studies. Mineralization of composted amendments was lower than that of fresh manures. Field trials showed positive grain yield response to applications of turkey litter compost (TLC) for cereal crops including oat (Avena sativa), spelt (Triticum spelta), corn (Zea mays), wheat (Tritictum aestivum) and rye (Secale cereale). Crop yield response to TLC was lower than that fresh poultry litter (PL) due to its lower N availability. There was no evidence of a carryover effect in the second year after application of either TLC or PL. Incorporation of red clover which had been underseeded to winter wheat increased a following corn crop yield by 16% over a control treatment without red clover. In two field trials comparing TLC applied in the fall vs spring on spelt and rye crops showed higher grain N concentrations in the spring applied treatments. It is recommended that TLC be applied in spring as the potential for overwinter N losses through leaching is an unnecessary risk. Modest applications of TLC should be incorporated into an integrated N management system coupled with crop rotations to enhance N availability for high N requirement crops. The use of green manures is recommended as a third component in organic farming management to ensure adequate N supplies.
Date: 2015-03
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