Assessment of long-term effects of tillage and nitrogen management practices on irrigated corn yields and nitrogen use efficiencies

Authors: Delgado, Jorge; Halvorson, Ardell; VILLACIS-AVEIGA, ALEXIS - Virginia Polytechnic Institution & State University; Del Grosso, Stephen - Steve; Stewart, Catherine; Manter, Daniel; ALWANG, JEFFREY - Virginia Polytechnic Institution & State University; Floyd, Bradley; D Adamo, Robert; MINER, GRACE - Colorado State University

Submitted to: Proceedings of Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/10/2020
Publication Date: 3/10/2020
Citation: Delgado, J.A., Halvorson, A.D., Villacis-Aveiga, A., Del Grosso, S.J., Stewart, C.E., Manter, D.K., Alwang, J., Floyd, B.A., D'Adamo, R.E., Miner, G. 2020. Assessment of long-term effects of tillage and nitrogen management practices on irrigated corn yields and nitrogen use efficiencies. In: Schlegel, A.J., editors. Proceedings of Great Plains Soil Fertility Conference, March 10-11, 2020, Denver, Colorado. p. 14-18.

Interpretive Summary: Corn is one of the most fertilized crops in the USA and there remains a need to continue improving nitrogen management practices to increase nitrogen use efficiencies (Ribaudo et al. 2011). The Northern Plains region ranks second-highest out of ten U.S. regions in total farmland receiving nitrogen fertilizer applications, and third-highest in tonnage of nitrogen fertilizer application (Ribaudo et al. 2011). More recently, Nehring and Mosheim (2019) reported that in farms in the United States, the nitrogen recovery efficiency for corn increased from 73 percent in 1996 to 81 percent in 2010. However, several publications have reported on how the nutrient losses from farms areas are impacting air and water quality and having potential impacts on human health (International Joint Commission. 2013; Monchamp et al. 2014; Smith et al 2018; Temkin et al. 2019). Although nitrogen use efficiencies have been reported to be increasing, there remains a need to assess how management factors such as tillage and nitrogen rates impact nitrogen use efficiencies, and in particular there is a need to conduct long-term studies that can be used to conduct nitrogen budgets. Our goal is to present details from our analysis of long-term tillage studies that we have been conducting, and preliminary results from the 2001 to 2017 period will be presented. These long-term research results suggest that even with no tillage, there are significant losses of nitrogen to the environment. The data suggest that the losses of nitrogen from tillage systems is higher than those from no-tillage systems. We are currently working on several nitrogen balance assessments and papers to verify this current hypothesis. The results from 2006 to 2017 suggest that no-till and strip tillage both recover over 100% of the total nitrogen fertilizer applied if we just consider the total aboveground nitrogen uptake versus the nitrogen fertilized applied. However, since the non-fertilized control plots assess the background nitrogen (N) sources and they averaged a total uptake of 77 kg N/ha, then the fertilizer nitrogen uptake for no-till and strip tillage is estimated to be about 116 kg N/ha (193 – 77 kg N/ha). This suggests that we are losing at least about 37 kg N/ha of the applied N fertilizer (nitrogen use efficiency of 74%). It also supports the conclusion that any nitrogen fertilizer applied over 165 kg N/ha will be lost. The losses from the system could be much higher since a significant amount of the nitrogen uptake is also returned to the soil with the crop residue. The percentage of recovery of the nitrogen fertilizer with the grain compartment is lower (125 kg N/ha – 48 kg N/ha = 77 kg N/ha removed/157 kg N/ha = NUE of 49%). A detailed analysis will be presented.

Technical Abstract: Corn grain yields and nitrogen uptake are affected by management factors such as tillage intensity and nitrogen rates. Additional data about the long-term effects of tillage and nitrogen rates on yields and nitrogen use efficiencies of irrigated corn are needed. We are presenting preliminary results from a 17-year study about the effects of these management practices on irrigated corn yields and nitrogen uptake in a Fort Collins clay loam soil at Colorado State University’s Agricultural Research, Development and Education Center (ARDEC) near Fort Collins, Colorado. We monitored the effects of different nitrogen rates on irrigated corn under no-till (NT), conventional tillage (CT) and strip-tillage (ST). Corn grain, cob, stalk and total aboveground biomass were measured at about 146 days after planting (DAP), harvest grain yields were measured at about 173 DAP, and nitrogen content was measured for all crop components. The effects of nitrogen rates on NT, ST and CT systems were studied with a linear-plus-plateau model, which is defined by a classic switching regression type of function. This long-term research suggests that ST and NT are recovering about 75% of the nitrogen fertilizer that is being applied into the system and that any nitrogen that is applied over a rate of 165 kg N/ha will be lost. However, the nitrogen losses could potentially be higher as the recovery of the nitrogen with the grain component is much lower (close to 50%). Details of preliminary results on how tillage intensity has affected yields, nitrogen dynamics, and recovery use efficiencies will be presented.