Discrepancy between the crop yield goal rate and the optimum nitrogen rates for maize production in Mississippi

Abstract

The varying influence of the environment on N supply and demand dictates the need for annually updated fertilizer N recommendations. Currently, crop yield goal (CYG) methods are used by 34 land grant universities, including Mississippi State University, these do not consider environmental variations. This research tested the efficacy of CYG by determining the agronomic optimum N rate (AONR) and the economic optimum N rate for Mississippi corn (Zea mays L.) production. In total, 12 treatments in 2020 and 11 in 2021 were replicated four times over four locations in a randomized complete block design. The optimum N rates were calculated by fitting linear, quadratic, linear plateau, and quadratic plateau models by means of three different goodness of fit measures. Furthermore, differences between the CYG rate calculated from the Mississippi yield goal equation and AONR were compared at different management levels (14 comparisons) (all data combined, both years combined, sites combined by year, and individual sites). Overall, AONR varied from 134 to 301 kg N ha–1 at different management levels. When we compared the AONR to the CYG rate, the CYG rate over‐recommended N in 12 of the 14 possible comparisons, with differences ranging from 69 kg N ha–1 less to 110 kg N ha–1 greater than the AONR. These differences between AONR values highlight variability caused by factors such as the soil, environment, and their interaction with N supply and demand, which are unaccounted for by the CYG method.

Using Data from Uniform Rate Applications for Site-Specific Nitrogen Recommendations

“…It is possible to include them and to rely less on the priors if the level of nitrogen applied varied by year as with on-farm experiments (Hegedus and Maxwell, 2022). The amount of nitrogen applied was expected to be greater than the agronomic optimum for most plots (Oglesby et al, 2023) so the plateau would be the only parameter that could be observed for most plots.…”

Mississippi state and county level yield gap in corn production

“…Lobell et al (2009) and Beza et al (2017) outlined several biophysical factors including nutrient deficiencies, water stress, flooding, planting issues, soil problems, weed pressures, insects, diseases, and lodging, as well as socioeconomic factors such as risk aversion, inexperience, and economic issues. Numerous agronomic strategies exist to improve corn production in Mississippi: substituting crop yield goals (Oglesby et al, 2022) for remote sensing based N management (Dhillon et al, 2020;Sumner et al, 2021), irrigation scheduling using soil moisture sensors (Spencer et al, 2019), crop rotation (Abbas et al, 2012), adopting site-specific optimum plant densities (Williams et al, 2021), proper hybrid selection (Walne & Reddy, 2021;Williams et al, 2020), and optimum planting dates (Williams et al, 2018).…”

Assessing the effect of cultural practices on Mississippi corn production: 2. Grain composition

“…Corn growth depends on various environmental and management factors, and they significantly affect grain quality (Fornah et al, 2020;Sharma et al, 2023;Oglesby et al, 2023). Oil, protein, and starch are the major quality parameters in corn that determine the overall economic and nutritious value of the crop (Hilliard & Daynard, 1974).…”