Assessment of long-term effects of different nitrogen and tillage management practices on irrigated corn yields and nitrogen uptake

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

Submitted to: Soil and Water Conservation Society Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2019
Publication Date: 7/28/2019
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. 2019. Assessment of long-term effects of different nitrogen and tillage management practices on irrigated corn yields and nitrogen uptake. Soil and Water Conservation Society Proceedings.

Interpretive Summary: Corn is the most nitrogen-fertilized crop in the USA, and management practices such as nitrogen fertilizer rates and tillage intensity affect grain yields and nitrogen uptake. Since 2001 we have been studying the long-term effects of nitrogen fertilizer and tillage management practices on irrigated corn yields and nitrogen uptake in a Fort Collins clay loam soil at the Colorado State University Agricultural Research, Development and Education Center (ARDEC) near Fort Collins, Colorado. Several nitrogen rates were used for irrigated no-till (NT), conventional tillage (CT) and strip-till (ST) corn. Biomass production was monitored by collecting samples at about 146 days after planting (DAP) to determine corn grain, cob, stalk and total aboveground biomass. Corn harvest grain yields were determined by harvesting 15 m of row at about 173 DAP. Nitrogen analyses were conducted for all plant compartments. We used a linear-plus-plateau model, defined by a classic switching regression type of function, to assess the effects of nitrogen rates on NT, ST and CT systems. For this study, the R-NLS function was used to solve this nonlinear fixed-effects regression model. Results were also checked with the MATLAB ® FITNLM function for robustness. Results presented will include fitting the linear-plus-plateau model to determine the minimum nitrogen level to reach the plateau yield of grain and/or other biomass compartments as well as nitrogen uptake and nitrogen use efficiencies.

Technical Abstract: Corn is the most nitrogen-fertilized crop in the USA, and management practices such as nitrogen fertilizer rates and tillage intensity affect grain yields and nitrogen uptake. Since 2001 we have been studying the long-term effects of nitrogen fertilizer and tillage management practices on irrigated corn yields and nitrogen uptake in a Fort Collins clay loam soil at the Colorado State University Agricultural Research, Development and Education Center (ARDEC) near Fort Collins, Colorado. Several nitrogen rates were used for irrigated no-till (NT), conventional tillage (CT) and strip-till (ST) corn. Biomass production was monitored by collecting samples at about 146 days after planting (DAP) to determine corn grain, cob, stalk and total aboveground biomass. Corn harvest grain yields were determined by harvesting 15 m of row at about 173 DAP. Nitrogen analyses were conducted for all plant compartments. We used a linear-plus-plateau model, defined by a classic switching regression type of function, to assess the effects of nitrogen rates on NT, ST and CT systems. For this study, the R-NLS function was used to solve this nonlinear fixed-effects regression model. Results were also checked with the MATLAB ® FITNLM function for robustness. Results presented will include fitting the linear-plus-plateau model to determine the minimum nitrogen level to reach the plateau yield of grain and/or other biomass compartments as well as nitrogen uptake and nitrogen use efficiencies.