Cover Crop Termination Date Effects on Greenhouse Gas Fluxes in Rainfed and Irrigated No-till Corn.

Cover crops (CC) can increase SOC and scavenging of N, particularly when CC are grown for longer periods. This increased storage of C and N with increased CC growing time could alter gaseous emissions of C and N (CO₂, N₂O, and CH₄) and related soil properties. Thus, the objective of this research was to assess soil greenhouse gas fluxes, and related soil properties of temperature, water content, soil aggregation, and air-filled porosity changes throughout the year under no CC and early or late terminated CC in rainfed and irrigated no-till continuous corn beginning after three years of CC. Soil gas fluxes, temperature, and water content were monitored biweekly from March through May and monthly from June through February. Soil porosity and soil aggregation were determined seasonally on soil samples from 0 to 5 cm depth. Both early and late terminated CC did not affect N₂O or CH₄ fluxes. Early terminated CC increased CO₂ fluxes less than late termination, likely due to influences of plant respiration. Soil water content was less under late terminated CC compared to no CC; however, soil aggregation increased under late terminated CC compared to control. A comparison of cumulative CO₂ fluxes with CC biomass showed that these two parameters are similar in C level, which suggests CO₂ fluxes from the soil did not increase under CC. Overall, it appears that while CC may improve some soil properties, greenhouse gases are generally not affected by CC.