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

Abstract

Cultivation of winter wheat under reduced tillage systems is increasing in the U.S. Southern Great Plains. Likewise, there is revived interest for including summer legumes in monocultures of winter wheat as green sources of nitrogen (N). This study investigated the influence of tillage systems (no- and conventional tillage), and source and rates of N fertilizer (0, 45 and 90 kg N ha−1 yr−1 in inorganic N fertilizer, and cowpea as green manure) on emissions of carbon dioxide (CO2) and nitrous oxide (N2O) from winter wheat cultivation. The study was conducted within a long-term field experiment initiated in 2011, at upland and bottomland sites near El Reno, Oklahoma during the 2016–2017 growing season of winter wheat. The experiment was conducted site-wise as split-plots in a completely randomized design, with N treatment as main plots and tillage system as subplots. Thus, there were a total of eight treatment combinations with three replicated plots (4 m × 10 m) in each combination in both sites. Net ecosystem exchange (NEE) of CO2 was measured by a closed chamber connected to an infra-red gas analyzer, and fluxes were partitioned to gross primary production (GPP) and ecosystem respiration (ER). Heterotrophic soil respiration (SR) was measured on bare soil spots. Fluxes of N2O were measured with an opaque closed chamber system with a portable gas analyzer. Dynamics of canopy CO2 fluxes (NEE, GPP and ER) were similar between tillage systems, while canopy CO2 fluxes increased with rate of N fertilization. Canopy CO2 fluxes from cowpea and an unfertilized control were similar, and the lowest, due to poor growth of winter wheat compared to the N fertilized treatments. Fluxes of N2O approximated zero from all treatments throughout the study and no response of N fertilizer or tillage system was seen. In conclusion, the results from this study indicated that canopy fluxes of CO2 from winter wheat are controlled by forms and rates of N fertilizers rather than tillage systems.

Conservation tillage increases corn and soybean water productivity across the Ohio River Basin

“…In Southern Illinois, Kapusta et al (1996) also observed no difference in corn yield among CT, NT, and RT on a silt loam soil after 20 years under each tillage treatment. Moreover, similar GPP for wheat between CT and NT systems was recently reported in the inland Pacific Northwest region with a Mediterranean climate (Chi et al, 2016) and in the Southern Great Plains with a humid subtropical climate (Kandel et al, 2020) using the eddy covariance method.…”

Cover cropping and conservation tillage improve soil health in the southeastern United States

“…More active fractions of organic C and N, enzyme activities, and associated microbial properties have been shown sensitive to tillage management in the region, including studies in the Central Rolling Prairies MLRA in Oklahoma (Kandel et al., 2020), in the Southern High Plains in Texas (Burke et al., 2019), in the Mississippi Blackland Prairie MLRA (Adeli et al., 2019), in the Southern Mississippi River Alluvium MLRA (Locke et al., 2013; Tyler, 2019), in the Southern Piedmont MLRA in Georgia (Franzluebbers & Stuedemann, 2015), in the Southern Blue Ridge MLRA in North Carolina (Wang et al., 2017), at multiple long‐term research station locations in North Carolina (Roper et al., 2017), and in multiple on‐farm fields in North Carolina (Franzluebbers, 2021). Curiously, in an earthworm preference study, a manure worm ( Eisenia fetida ) had no preference for soil under NT or with tillage when taken from a 4‐yr study in the Southern Mississippi River Alluvium in Arkansas (Bouldin et al., 2016).…”

Optimized nitrogen fertilizer application strategies under supplementary irrigation improved winter wheat (Triticum aestivum L.) yield and grain protein yield

“…Rajinder et al (2017) showed that split applications of nitrogen fertilizer may help to meet the nitrogen demand via soil supply and to enhance crop yield, grain quality, and fertilizer use efficiency. For this reason, appropriate split nitrogen applications are the most critical component of nitrogen fertilizer management ( Kandel, Gowda & Northup, 2020 ; Li et al, 2021 ). Previous studies have shown that pre-jointing nitrogen accumulation increased with an increase in the basal nitrogen rate, while post-jointing nitrogen accumulation increased with the increase in the topdressing nitrogen rate at a total fertilizer application rate of 210 kg/ha ( Shi et al, 2012 ).…”