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Title: Nitrogen fertilizer effects on irrigated conventional tillage corn yields and soil carbon and nitrogen pools

Author
item JANTALIA, CLAUDIA - Embrapa
item Halvorson, Ardell

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2011
Publication Date: 3/23/2011
Citation: Jantalia, C.P., Halvorson, A.D. 2011. Nitrogen fertilizer effects on irrigated conventional tillage corn yields and soil carbon and nitrogen pools. Agronomy Journal. 103:871-878.

Interpretive Summary: This 10 year study investigated how N fertilization under irrigated, conventional plow tillage (CT) management impacts corn grain and stover production, stover characteristics, and aboveground crop biomass, and soil quality parameters of a clay loam soil, including total soil C (TSC), soil particulate organic matter (POM), soil organic C (SOC), and total soil N (TSN) stocks in the 0-7.6, 0-15.2, and 0-30.4 cm soil depths. Nitrogen fertilization significantly increased corn grain, stalks, cob and stover yields as well as C and N content of the biomass. The C:N ratios of stalks and stover decreased with increasing N rate, but cob C:N ratios did not change. Increasing N rate increased TSN concentration in 0-7.6 and 7.6-15.2 cm depths and decreased C:N ratio in all soil layers between 1999 and 2008. We found no significant change in SOC and POM-C stocks under increasing N fertilizer addition after 10 years despite higher stover yields, and stover C and N returned to the soil at harvest with increasing N rate. The lack of C storage with increasing C inputs suggests that decomposition processes dominate the SOC stocks. Removal of stover as a cellulosic feedstock for ethanol production would likely result in SOC loss and deterioration of soil quality and productivity with time under an irrigated, CT continuous corn production system in the semi-arid central Great Plains of the USA as returning all stover only maintained SOC.

Technical Abstract: Conventional plow tillage (CT) is a common soil management practice under irrigated continuous corn (Zea mays L.) in the semiarid central Great Plains that requires a relatively high nitrogen (N) fertilizer rate to optimize grain yield and economic returns. This study investigated how four rates of N input (0, 67, 101, and 224 kg N ha) under irrigated CT management affects aboveground corn production, stover characteristics and crop biomass. We also examined soil quality parameters under these treatments, including total soil C (TSC) and soil particulate organic matter (POM), soil organic C (SOC) and total soil N (TSN) stocks in the 0-7.6, 0-15.2, and 0-30.4 cm soil depths of a clay loam soil. Nitrogen fertilization significantly increased corn grain, stalks, cob and stover yields as well as C and N content of the biomass. The C:N ratios of stalks and stover decreased with increasing N rate, but cob C:N ratios did not change. Increasing N rate increased TSN concentration in 0-7.6 and 7.6-15.2 cm depths and decreased C:N ratio in all soil layers between 1999 and 2008. We found no significant change in SOC and POM-C stocks under increasing N fertilizer addition after 10 years of irrigated, CT continuous corn despite higher stover yields, and the stover C and N returned to the soil after harvest with increasing N rate. The lack of C storage with increasing C inputs suggests that decomposition processes dominate the SOC stocks.