Relating four-day soil respiration to corn nitrogen fertilizer needs across 49 U.S. Midwest fields

Authors: BEAN, GREGORY - Soil Health Institute; Kitchen, Newell; Veum, Kristen; CAMBERATO, JAMES - Purdue University; FERGUSON, RICHARD - University Of Nebraska; FERNANDEZ, FABIAN - University Of Minnesota; FRANZEN, DAVID - North Dakota State University; LABOSKI, CARRIE - University Of Wisconsin; NAFZIGER, EMERSON - University Of Illinois; SAWYER, JOHN - Iowa State University; YOST, MATT - Utah State University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2020
Publication Date: 5/19/2020
Citation: Bean, G.M., Kitchen, N.R., Veum, K.S., Camberato, J.J., Ferguson, R.B., Fernandez, F.G., Franzen, D.W., Laboski, C.A., Nafziger, E.D., Sawyer, J.E., Yost, M.A. 2020. Relating four-day soil respiration to corn nitrogen fertilizer needs across 49 U.S. Midwest fields. Soil Science Society of America Journal. 84(4):1195-1208. https://doi.org/10.1002/saj2.20091.
DOI: https://doi.org/10.1002/saj2.20091

Interpretive Summary: Soil microbes drive biological processes that further mediate soil chemical and physical processes necessary for plants to sustain growth, including the release of plant available nutrients. Soil respiration has been proposed as one universal indicator capable of representing plant nutrient availability and to potentially inform fertilizer management decisions. The purpose of this research was to test the idea of using soil respiration for making profitable nitrogen (N) management decisions in corn. Trials were conducted at 49 sites in eight Midwest US states from 2014 to 2016 using a standard set of protocols. Across all years soil respiration was moderately related to the economically optimum N rate (EONR) (r^2 = 0.21). However, when analyzed by year, soil respiration was strongly related to EONR for only 2016 (r^2 = 0.50), and poorly related for the first two years (r^2 < 0.20). These results illustrate the wide range of outcomes in soil respiration as influenced by growing-season weather and the problematic nature of its use alone as a universal indicator for prescribing N fertilization rates. This research supports other research that suggests tools that don't rely on the the weather and soil interactions that vary over different growing seasons. These results will help advance the concepts of using soil biological tests as an aid but not as a stand alone tool for N fertilizer recommendations, and in the end will result in more reliable tools to help producers more profitability manage N fertilizer in corn.

Technical Abstract: Soil microbes drive biological processes that further mediate chemical and physical processes necessary for plants to sustain growth, including the decomposition of organic matter, the release of plant available nutrients, and the manipulation of soil structure as examples. Soil respiration has been proposed as one universal indicator capable of representing these functions, and to potentially inform crop and soil management decisions. Research is needed to test the premise that soil respiration is helpful for profitable N management decisions in corn (Zea Mays L). The objective of this research was to evaluate the relationship of soil respiration to corn grain yield response to fertilizer N. A total of 49 N response trials were conducted across eight states over three growing seasons (2014 – 2016). The 4-day Comprehensive Assessment of Soil Health (CASH) soil respiration method was used to quantify soil respiration. Averaged over all sites N fertilization did not impact soil respiration, but at four sites soil respiration decreased as N fertilizer rate applied at-planting increased. Across all years soil respiration moderately related to the economically optimum N rate (EONR) (r^2 = 0.21). However, when analyzed by year, soil respiration was strongly related to EONR for 2016 (r^2 = 0.50) and poorly related for the first two years (r^2 < 0.20). These results illustrate the wide range of outcomes in soil respiration as influenced by growing-season weather and the problematic nature of its use alone as a universal indicator for prescribing N fertilization rates.