Effect of Cover Crop Type and Application Rate on Soil Nitrogen Mineralization and Availability in Organic Rice Production

Abstract

In drill-seeded, delay-flooded organic rice production, reliable predictions of N supply from cover crop (CC) residues to subsequent rice are still a challenge. An incubation was conducted to determine the effects of CC types (clover, ryegrass, clover and ryegrass mixtures, and fallow), residue application rates (0, 0.6, 1.2, 1.8, and 2.4%) and incubation time on soil CO2 evolution and N mineralization and availability. The cumulative CO2 evolution linearly increased with increasing residue rate. Compared to the control, adding CCs residue significantly increased the cumulative CO2 emission, which was greatest in soils with clover or mixtures of clover and ryegrass, followed by fallow, and lowest in soils with ryegrass. The modeling results indicated clover had the greatest initial C and N mineralization rates and the shortest half-lives. A temporary decrease in soil mineral N caused by immobilization occurred at the initial incubation stage in all treatments. However, the trend reversed progressively, with the clover treatment requiring the shortest time to meet the crossover point. The results suggested clover was the optimal CC type, 0.6% was the optimal residue rate, and a minimum of 27 days between CC termination and rice planting was required to maximize mineral N supply for organic rice.

Changes over time in organic matter dynamics and copper solubility in a vineyard soil after incorporation of cover crop residues: Insights from a batch experiment

“…The second stage extended from day 3 to day 60 and was characterized by a shift in the resource-use strategy to target decaying more structural compounds, as indicated by the gradual decrease in C mineralization rates. This second stage is in agreement with that reported in several other studies showing that the rapid increase in CO2 fluxes after CC incorporation was quickly followed by a slowing down of mineralization rates (Lynch et al, 2016;Ghimire et al, 2017;De Notaris et al, 2020;Li et al, 2021). This is usually due to the fact that microbial communities produce more enzymes to acquire energy and nutrients from the organic residues (Fig.…”

Switchgrass cropping systems affect soil carbon and nitrogen and microbial diversity and activity on marginal lands

“…Soil microorganisms are the key players in decomposing organic matter to mineral forms that are available to crops (Kaschuk et al, 2010; Li et al, 2021), which was also supported by the significant correlations between microbial biomass (MBC and MBN) with enzyme activities, microbial diversity, and plant height in this study (Table 3, Table S2). Soil MBC and MBN contents were highly correlated, and their responses to cropping system, N rate, year, and location are consistent (Tables 2 and 3).…”

“…Soil microbial biomass under monocropping of switchgrass, especially MBN, was lower than those in the restored prairie and the undisturbed control systems with diverse plant species (Figure 3a,e), which indicates that plant diversity might be an important factor impacting soil MBC and MBN. This result is supported by Li et al (2021), who evaluated soil MBC and MBN under different cover crop mixtures and reported that soil with more diverse species of cover crops had greater MBC and MBN contents. Compared with the first year, the average MBC and MBN decreased in the second and third years, which is interesting because DOC and TDN increased in the second and third years (Figures 1c,g and 3c,g).…”

Cover Crops for Sustainable Cropping Systems: A Review

“…On the other hand, the phytomass characterized by a high C/N ratio (e.g., Graminaceae) with a high lignin content will persist in the soil for a longer time, improving physical characteristics and increasing element exchange capacity (Figure 5) [87]. However, the use of these species must be carefully evaluated concerning the amount of soil nitrogen available for the main crop, to avoid competition between the associated crops or unavailability of the element for the cash crops that will follow [111]. The use of cover crops through improved soil macroaggregate architecture provides diverse microhabitats for soil micro and macro fauna (Table 2).…”