Soil Fertility Information
A corn-soybean rotation is used on a significant acreage in the Midsouth. It is well-known that nitrogen [N] fertilizer is required by corn, and is applied to only corn in this rotation since soybean “fixes” atmospheric N that is subsequently used by it in lieu of N from fertilizers.
Results from research that was conducted in Minnesota during the 2014-2016 growing seasons are reported in an article titled “Nitrous oxide emissions from soybean in response to drained and undrained soils and previous corn nitrogen management”. Pertinent points from that research follow.
• The objective of the study was to quantify the effect on agronomic parameters and nitrous oxide [N2O] emissions during the soybean year of the rotation that result from application of N fertilizer to the previous corn crop in the rotation. [N2O is a significant greenhouse gas.]
• Soils at the research site were poorly drained to somewhat poorly drained clay loams.
• Urea was the N fertilizer form that was broadcast-applied to corn. According to information in the article titled “Management of nitrogen fertilizer to reduce N2O emissions from field crops”, a urea form of N can reduce N2O emissions compared to those from anhydrous ammonia.
• Results from the research reported in the article are: 1) the largest contribution to N2O emissions is linked to N fertilizer in the year of its application; 2) adding adequate drainage can enhance N2O mitigation during years with high precipitation; 3) N management during the corn year of the rotation did not influence soybean seed yield, N removal, or N2O emissions during the soybean phase; and 4) N2O emissions during the corn year may have been increased by the decomposition of the previous year’s soybean residue.
It is likely that the above information gleaned from a corn-soybean rotation will also apply to a rice-soybean rotation that is commonly used in the Midsouth, especially where furrow vs. flood irrigation is used for the rice crop.
A Southeast FarmPress article titled “Finding optimal rates for chicken litter and yields” by John Hart cites ongoing research that is being conducted by a Clemson Univ. team to determine optimal litter application rates for sustainable crop production and soil health enhancement in the southeastern U.S. The team is conducting the research at 11 [2023] and 9 [2024] on-farm sites in South Carolina with the goal of determining site-specific optimal application rates of chicken litter across diverse farming conditions and site characteristics. To ensure consistency in the research, litter from a single source is being used. The findings from this research thus far indicate that the rate of poultry litter application will likely depend on: 1) whether or not a crop is irrigated; 2) the crop rotation system that may be used; 3) the tillage system that is used; and 4) whether or not a legume cover crop precedes corn. Finally and most importantly, economically optimum rates of litter application varied considerably among sites due to field-to-field differences. Thus, a one-rate-fits-all approach for poultry litter application to crop sites is not feasible.
As concern about climate change increases, soybean producers must become increasingly cognizant of the production practices [e.g. tillage system, crop rotation, fallow vs. cover crops in the off-season] they use, and how those practices may need changing to help mitigate known contributors to atmospheric and environmental degradation.
Composed by Larry G. Heatherly, Nov. 2024, larryh91746@gmail.com