|Rotz, Clarence - Al|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2010
Publication Date: 1/1/2011
Citation: Schmidt, J.P., Sripada, R.P., Beegle, D.B., Rotz, C.A., Hong, N. 2011. Within-field variability in optimum nitrogen rate for corn linked to soil moisture variability. Soil Science Society of America Journal. 75:306-316. Interpretive Summary: Improving nitrogen (N) fertilizer use efficiency for corn (Zea mays L.), which is usually less than 50%, depends on a better understanding of the mechanisms that contribute to within-field spatial variability in N availability and demand (thus optimum N rate). Our objective was to determine whether economic optimum N rate (EONR) for corn was related to within-field variability in soil water content changes during the growing season. The EONR for corn was determined at each of ten locations along a hillslope in central Pennsylvania (2005 to 2007), while soil water content (Wp, 0-90 cm) was determined weekly between mid June to August. During the drier growing seasons of 2005 and 2007, greater EONR corresponded with greater soil water availability. During a wetter season in 2006, in-season changes in soil water content were not related to EONR. Incorporating landscape / hydrology and in-season weather modeling to develop spatially variable N fertilizer recommendations should increase overall N use efficiencies for corn, reducing the adverse environmental impacts of N fertilizer.
Technical Abstract: Understanding the interaction between yield response to N and other growth-limiting factors is essential to improving spatially dependent N fertilizer applications. Our objective was to evaluate the impact of soil water content variability on the economic optimum N rate (EONR) for corn (Zea mays L.). Corn grain yield response to N was determined at each of ten locations along a hillslope in central Pennsylvania (2005 to 2007). Soil water content (Wp, 0-90 cm) was also determined at each location approximately weekly between mid June to August. Mean EONR (n = 10) was 117, 140, and 169 kg N per ha in 2005 to 2007, respectively, while the range in EONR among locations each year was 47 to 194, 118 to 187, and 98 to 224 kg N per ha, respectively. The mean Wp (n = 10) was between 15 to 25 cm in 2005, 23 to 37 cm in 2006, and 21 to 27 cm in 2007. While there was a greater temporal change in the mean Wp in 2006, greater temporal variability was observed among locations during the drier growing seasons of 2005 and 2007. The EONR in 2005 and 2007 was strongly related (r2 = 0.74 and 0.71, respectively) to the change in Wp at each location, as determined during a defining drying / wetting cycle in June and July. During the relatively wetter 2006 growing season EONR was not related to changes in Wp. Increasing water availability during drier growing seasons increased EONR.