Winter wheat yield and nitrous oxide emissions in response to cowpea-based green manure and nitrogen fertilization

Abstract

The aim of this study was to compare the effects of cowpea green manure and inorganic nitrogen (N) fertilizers on yields of winter wheat and soil emissions of nitrous oxide (N2O). The comparisons included cowpea grown solely as green manure where all biomass was terminated at maturity by tillage, summer fallow treatments with 90 kg N ha−1 as urea (90-N), and no fertilization (control) at planting of winter wheat. Fluxes of N2O were measured by closed chamber methods after soil incorporation of cowpea in autumn (October–November) and harvesting of winter wheat in summer (June–August). Growth and yields of winter wheat and N concentrations in grain and straw were also measured. Cowpea produced 9.5 Mg ha−1 shoot biomass with 253 kg N ha−1 at termination. Although soil moisture was favorable for denitrification after soil incorporation of cowpea biomass, low concentrations of soil mineral N restricted emissions of N2O from cowpea treatment. However, increased concentrations of soil mineral N and large rainfall-induced emissions were recorded from the cowpea treatment during summer. Growth of winter wheat, yield, and grain N concentrations were lowest in response to cowpea treatment and highest in 90-N treatment. In conclusion, late terminated cowpea may reduce yield of winter wheat and increase emissions of N2O outside of wheat growing seasons due to poor synchronization of N mineralization from cowpea biomass with N-demand of winter wheat.

Influence of Tillage Systems, and Forms and Rates of Nitrogen Fertilizers on CO2 and N2O Fluxes from Winter Wheat Cultivation in Oklahoma

“…Alternatively, early-terminated legumes with less structural components can mineralize rapidly after termination, and the mineralized nutrients may be more efficiently transferred to winter wheat. However, if proper synchronization between N mineralization from green manures and uptake by the recipient crop is not achieved, yields of winter wheat may decrease and emissions of N 2 O increase outside the growth period of winter wheat [18].…”

Soil N2O emissions following termination of grass pea and oat cover crop residues with different maturity levels

“…Additionally, results from the variable importance matrix suggested soil EC to be the second most important soil variable for predicting N 2 O emissions after soil NH þ 4 , and correlations between N 2 O emissions and soil EC were significant (R = 0.70). Stable soil EC after rainfall events noted at the end of this study might be due to uptake of minerals in decomposing biomass and NH þ 4 by finger millet (Kandel et al, 2019a(Kandel et al, , 2019b.…”

“…Although legume-based cover crops can biologically fix atmospheric nitrogen (N), non-legume cover crops can also increase the soil N pool by scavenging N and decreasing N loss through leaching and gaseous emissions (White et al, 2017). Regardless of type of cover crops, their successful use as source of N for the following crops depends on synchronization of N mineralization from decomposing plant tissues and demand of the following recipient crops (Myers et al, 1994;Kandel et al, 2019aKandel et al, , 2019b. While rapid decomposition and mineralization of biomass immediately after termination may risk N loss prior to establishment of following crop, slow mineralization rates may hinder N transfer to following cash crops (Kumar and Goh, 1999;Kandel et al, 2018Kandel et al, , 2019b.…”

“…Regardless of type of cover crops, their successful use as source of N for the following crops depends on synchronization of N mineralization from decomposing plant tissues and demand of the following recipient crops (Myers et al, 1994;Kandel et al, 2019aKandel et al, , 2019b. While rapid decomposition and mineralization of biomass immediately after termination may risk N loss prior to establishment of following crop, slow mineralization rates may hinder N transfer to following cash crops (Kumar and Goh, 1999;Kandel et al, 2018Kandel et al, , 2019b. Additionally, if N in cover crop residue mineralizes outside the growing season of the recipient crops, it is prone to loss from the soil (Kandel et al, 2019b).…”

“…While rapid decomposition and mineralization of biomass immediately after termination may risk N loss prior to establishment of following crop, slow mineralization rates may hinder N transfer to following cash crops (Kumar and Goh, 1999;Kandel et al, 2018Kandel et al, , 2019b. Additionally, if N in cover crop residue mineralizes outside the growing season of the recipient crops, it is prone to loss from the soil (Kandel et al, 2019b).…”