Date of Award

1-4-2016

Document Type

Thesis and Dissertation

Degree Name

Master of Science (MS)

Department

Department of Agriculture

First Advisor

Shalamar Armstrong

Abstract

The pairing of cover crops with spring application of nitrogen has shown improved nitrogen efficiency in corn production systems. However, studies have shown that only 50% of central Illinois farmers practice spring application of nitrogen. Furthermore, the literature demonstrates that in years with above average rainfall, fall applied N management systems are more susceptible to N loading relative to spring systems. Therefore, the objective of this research was to determine the efficacy of winter cover crops to impact the distribution of soil inorganic N following fall applied anhydrous ammonium. The experimental site is located at the Illinois State University Research and Teaching Farm in Lexington, IL. The treatments consisted of a control, daikon radish, cereal rye and a cereal rye/daikon radish mixture. All treatments received a fall application of 200 kg N ha-1 in the form of anhydrous ammonia. Soil samples were collected in the spring at four separate depths and were analyzed for inorganic N. At the 0-5cm depth, we determined that tillage radish resulted in 18% greater soil NO3- relative to the control. In the environmental depth of 20-80cm, we observed that fall applying N into a living cover crop resulted in 35% (cereal rye) and 22% (daikon radish) less soil NO3- when compared to the control. In 2014 and 2015, each treatment was further divided into three nitrogen rate subplots: 200, 145 and 90 kg N ha-1. However, no obvious trend within the rate applied (90, 145 and 200 kg ha-1) was observed. After four consecutive years of established cover crops, corn uptake and yield data was collected. On average the addition of daikon radish at 200 kg N ha-1 increased total crop uptake by 20%; while the inclusion of cereal rye despite application rate significantly (P= 0.0021) increased total N at R6. Consequently, sampling at harvest (2014) demonstrated the capacity of the cover crops (cereal rye, P= 0.0323) despite rate to increase the crop yielding potential 3-6%. Over a four year period, winter cover crops reduced nitrate leaching and stabilized a greater concentration of soil NO3- in the agronomic depths following fall applied N, relative to the control. The results of this study also suggest that cover crop inclusion into a fall applied system has the potential to advance nitrogen use efficiency, yield and profitability.

Comments

Imported from ProQuest Deppe_ilstu_0092N_10666.pdf

Page Count

165

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