Cover crop and crop residue removal effects on temporal dynamics of soil carbon and nitrogen in a temperate, humid climate

Responses of leached nitrogen concentrations and soil health to winter rye cover crop under no-till corn-soybean rotation in the northern Great Plains

Winter rye (Secale cereale L.) is an important cover crop (CC) in the northern Great Plains (NGP), yet concerns over its establishment under the variable weather conditions of this region are an important limitation for its widespread adoption. This study evaluated the impacts of no-till corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation with winter rye CC established in 2017 on (a) water quality (nitrate-N [NO3 - -N], ammonia-N [NH4 + -N], and total nitrogen [TN]) and (b) soil health parameters at the 0-to-15-cm depth. Data showed that rye CC biomass was 251 kg ha-1 in 2018, 1,213 kg ha-1 in 2019, and 147 kg ha-1 in 2020, coinciding with contrasting growing degree days for rye CC (i.e., 1,458, 2,042, and 794, respectively), as a consequence of variable weather conditions. Water quality was not affected for the periods when rye growth was <300 kg ha-1 . In the season when rye CC had greater biomass (1,213 kg ha-1 ), significant reductions in leached NO3 - -N (19-20%) and TN (8.5-16%) concentrations were observed due to greater N uptake by rye CC (18.8 kg N ha-1 ). Rye CC showed significantly (p ≤ .05) higher microbially active carbon ( ∼13%) and water-extractable organic N(∼11%) than the control treatment. Nonsignificant impacts on soil health indicators due to rye CC showed that the study duration (3 yr) may not be sufficient to see the beneficial impacts of CCs on soils. However, significant reductions in leached NO3 - -N and TN concentrations for one (2019) out of three study years suggest that rye with optimal growth has the potential of reducing N leaching and enhancing soil health for the NGP region.

Influence of cover crops at the four spheres: A review of ecosystem services, potential barriers, and future directions for North America

Cover crops have been studied for over a century, but the recognition of a complex interaction of cover crop on the Earth's biosphere, lithosphere, hydrosphere, and atmosphere is relatively recent. Furthermore, previously published cover crop research has largely focused on evaluating cover crop impacts on subsequent crop yield. Understanding the cover crop-induced benefits on soil organic carbon (SOC) sequestration, nitrous oxide (N₂O) emissions, wind and water erosion, weed control, and soil microbial communities has gained considerable attention in the last few decades, which is crucial to make progress towards developing sustainable agricultural production systems. New research is continuously published to gain a comprehensive understanding of the multiple ecosystem services provided by cover crops. Here, in this review, we aimed to (a) summarize current knowledge related to cover crop impacts on agroecosystem functioning and explore the potential mechanisms responsible for those effects, and (b) identify the key factors limiting the adoption of cover crops into agroecosystems and the conspicuous knowledge gaps in cover crop research. Overall, the review results suggest that cover crops increased subsequent crop yield, increased SOC storage, increased weed suppression, mitigated N₂O emissions, reduced wind and water erosion, suppressed plant pathogens, and increased soil microbial activity and wildlife biodiversity. However, the magnitude of benefits observed with cover crops varied with cover crop type, location, and the duration of cover cropping. Notably, cover crop termination methods, designing crop rotations to fit cover crops, additional costs associated with cover crop integration, and uncertainty related to economic returns with cover crops are some of the major barriers limiting the adoption of cover crops into production systems, particularly in North America. In addition to long-term effects, future research on cover crop agronomy, breeding cover crop cultivars, and interactive effects of cover crops with other sustainable land management practices is needed.

Different leafy vegetable cropping systems regulate growth, photosynthesis, and PSII functioning in mono-cropped eggplant by altering chemical properties and upregulating the antioxidant system

Continuous cropping of eggplant threatened regional ecological sustainability by facilitating replanting problems under mono-cropping conditions. Therefore, alternative agronomic and management practices are required to improve crop productivity at low environmental cost for the development of sustainable agricultural systems in different regions. This study examined changes in soil chemical properties, eggplant photosynthesis, and antioxidant functioning in five different vegetable cropping systems over a 2-year period., 2017 and 2018. The results showed that welsh onion-eggplant (WOE), celery-eggplant (CE), non-heading Chinese cabbage-eggplant (NCCE), and leafy lettuce-eggplant (LLE) rotation systems significantly impacted growth, biomass accumulation, and yield than fallow-eggplant (FE). In addition, various leafy vegetable cropping systems, WOE, CE, NCCE, and LLT induced significant increases in soil organic matter (SOM), available nutrients (N, P, and K), and eggplant growth by affecting the photosynthesis and related gas exchange parameters with much evident effect due to CE and NCCE. Moreover, eggplant raised with different leafy vegetable rotation systems showed higher activity of antioxidant enzymes, resulting in lower accumulation of hydrogen peroxide and hence reduced oxidative damage to membranes. In addition, fresh and dry plant biomass was significantly increased due to crop rotation with leafy vegetables. Therefore, we concluded that leafy vegetable crop rotation is a beneficial management practice to improve the growth and yield of eggplant.

Cover crop-driven shifts in soil microbial communities could modulate early tomato biomass via plant-soil feedbacks

Sustainable agricultural practices such as cover crops (CCs) and residue retention are increasingly applied to counteract detrimental consequences on natural resources. Since agriculture affects soil properties partly via microbial communities, it is critical to understand how these respond to different management practices. Our study analyzed five CC treatments (oat, rye, radish, rye-radish mixture and no-CC) and two crop residue managements (retention/R+ or removal/R-) in an 8-year diverse horticultural crop rotation trial from ON, Canada. CC effects were small but stronger than those of residue management. Radish-based CCs tended to be the most beneficial for both microbial abundance and richness, yet detrimental for fungal evenness. CC species, in particular radish, also shaped fungal and, to a lesser extent, prokaryotic community composition. Crop residues modulated CC effects on bacterial abundance and fungal evenness (i.e., more sensitive in R- than R+), as well as microbial taxa. Several microbial structure features (e.g., composition, taxa within Actinobacteria, Firmicutes and Ascomycota), some affected by CCs, were correlated with early biomass production of the following tomato crop. Our study suggests that, whereas mid-term CC effects were small, they need to be better understood as they could be influencing cash crop productivity via plant-soil feedbacks.