Agrosystems, Geosciences & Environment最新文献

With declining of the Ogallala Aquifer in the Central High Plains, cotton (Gossypium hirsutum L.) has emerged as a low-water-demanding alternative to corn (Zea mays). However, cotton harvest leaves minimal cover on the soil surface following harvest due to application of harvest aids. Planting cover crops following cotton harvest is not always viable as it often leaves insufficient time for establishing covers due to cold and dry conditions in the region. Seeding cover crops in standing cotton may be a viable option; however, the effect of harvest aids on these covers remains unknown. This study evaluates the response of cover crops winter pea (Pisum sativum), triticale (Triticosecale rimpaui Wittm), hairy vetch (Vicia villosa), black oats (Avena sativa), crimson clover (Trifolium incarnatum), and rapeseed (Brassica napus L.) to different cotton harvest aids (DFT-6EC and AIM). The crops were grown in pots in climate-controlled chambers and green cover was measured weekly using Canopeo application. The crops were sprayed with harvest aids 42 days after planting. The green cover was reduced in all crops by at least 45% within 2 weeks after spraying for both harvest aids when compared to check pots, with winter pea losing 100% of green cover. The average harvest biomass was reduced by 45% and 52% in pots sprayed with AIM and DFT as compared to check pots, respectively. These results show that cover crops are susceptible to cotton harvest aids and will need adequate time to produce biomass before harvest aid application if interseeded in cotton crops.

Cover cropping is an important management practice that can benefit the cash crop and the environment. Plant species, weather, and cover crop termination influence biomass production and N fixation potential. This study was conducted to determine optimal termination dates for production systems in Arkansas based on growing degree days (GDD) for eight different cover crop species: Austrian winter pea (AWP) (Pisum sativum), balansa clover (Trifolium michelianum), barley (Hordeum vulgare), black-seeded oats (Avena sativa), common vetch (Vicia sativa var. Cahaba), cereal rye (Secale cereale), crimson clover (Trifolium incarnatum), and hairy vetch (Vicia villosa). Field studies were conducted at three research stations in Arkansas to provide differences in climate and rate of GDD accumulation. An area of 0.17 m² was harvested for aboveground biomass and total N uptake randomly within each experimental unit every 2 weeks, starting on February 15. Aboveground biomass accumulation and N content were regressed as a function of GDD for each cover crop treatment. At the Rohwer site, AWP, for example, accumulated an average of 3643 kg ha⁻¹ of biomass and 107 kg N ha⁻¹ at termination, whereas 30 days before termination, the average was 1868 kg ha⁻¹ of biomass and 69 kg N ha⁻¹. The growth rate increased dramatically closer to termination due to warmer temperatures, which allowed for rapid GDD and aboveground biomass accumulation. These results suggest that termination dates can be identified using previous and forecasted weather data.

Soil fertility depletion, particularly nitrogen and phosphorus, is a major constraint to wheat (Triticum aestivum L.) productivity in Ethiopia, influencing crop yields and food security. A field experiment was conducted to determine the optimum nitrogen and phosphorus rates for wheat yield, nutrient uptake, nutrient use efficiency, and economic returns in Wadla District, North Wollo, Ethiopia. The experiment was arranged in a factorial randomized complete block design with three replications. The treatment consisted of 46, 92, 138, and 184 kg ha⁻¹ N levels and 23, 46, 69, and 92 kg ha⁻¹ P₂O₅ levels. Yield and yield component parameters, as well as a plant sample, were collected. The collected data were analyzed using Statistical Application Software in a mixed model. The results showed that the nutrient levels significantly influenced yield, yield components, nutrient uptake, nutrient use efficiency, and economic returns. The maximum biological grain (3840.0 kg ha⁻¹) and biomass (7910 kg ha⁻¹) yields were recorded at 138 kg N ha⁻¹ with 92 kg P₂O₅ ha⁻¹. The highest performance, in terms of economically yield-related parameters, was recorded with the combined application of 138 kg N ha⁻¹ and 69 kg P₂O₅ ha⁻¹, resulting in biomass and grain yields of 7800 and 3770 kg ha⁻¹, respectively. Total nitrogen uptake was high for 138 kg N ha⁻¹ (82.52 kg N ha⁻¹), while phosphorus uptake was high for 69 kg P₂O₅ ha⁻¹ (18.42 kg P ha⁻¹), with uptake efficiency decreasing at higher rates. The nutrient use efficiency parameter also reached its highest values at the lowest to moderate N and P levels. Partial budget analysis indicates that the applications of 138 kg N ha⁻¹ with 69 kg P₂O₅ ha⁻¹ gave the highest net benefit of 258,954.2 ETB ha⁻¹, with a marginal return of 5825.3%. Therefore, the application of 138 kg N ha⁻¹ and 69 kg P₂O₅ ha⁻¹ is recommended for maximizing wheat yield, economic returns, and enhancing nutrient uptake and nutrient efficiency in Wadla and similar agro-ecological areas. Further research should be done on the long-term residual effect of P and nutrient efficiency through regular soil testing and monitoring to enhance nutrient uptake while minimizing environmental footprints.

Soil health is critical to sustain crop productivity and ecosystem functions. However, assessing soil health remains challenging due to variability in soil types, management practices, and climatic conditions. The objective of this study is to compare selected soil health indicators between croplands and undisturbed reference sites across a gradient of soil and climatic conditions in Nebraska. Four paired sites were selected from Cropland Reference Ecological Units representing distinct soil textures and precipitation regimes in Major Land Resource Areas (MLRAs) 106 and 67A. Soil samples were analyzed for organic matter (OM), β-glucosidase (BG) and phosphomonoesterase (PME), inorganic phosphorus (P), pH, bulk density (BD), and microbial community components (fungal-to-bacterial ratio and total fungal biomass). Reference sites with higher precipitation and finer soil textures had greater OM, BG, and PME and lower pH than those with low precipitation and coarse soils. Croplands at sites with manuring and no-till recorded lower OM depletion from reference site levels (28%) than sites with continued conventional tillage (31%–54%), underscoring the benefits of low-intensity land preparation and organic amendments. Croplands had lower PME activity than reference sites, suggesting that crop production entirely depends on P input to meet crop P requirements. A manured cropland had a higher BD than the reference site, illustrating the overall impact of management on soil health, which would have been otherwise overlooked had it not been compared against reference sites. Such comparisons between croplands and reference sites with regional consideration also help establish site-specific soil health targets.

The Mississippi River Basin has been extensively altered with levees, channelization, and agricultural land conversion. Much of the disturbed land was historically bottomland hardwood forests (BHF) and wetlands. As knowledge about sediment and nutrient nonpoint pollution has expanded, several wetland restoration and water quality monitoring programs have been developed through the United States Department of Agriculture Natural Resources and Conservation (e.g., the Agricultural Conservation Easement Program, Environmental Quality Incentive Program, and Edge-of-Field (EOF) Water Quality Monitoring Activity). Traditional water quality monitoring includes the use of pressure transducers, piezometers, and grab samples. The EOF water quality monitoring system generally focuses on agricultural inputs and uses non-contact measurement sensors. EOF monitoring stations include a flume, water sampler, and an ultrasonic level sensor. This system can monitor water quality in most flow conditions; however, BHF wetlands have more complex flow requiring a modification of the standard EOF station. By using a laser Doppler velocimeter (e.g., LaserFlow, Teledyne ISCO) in place of the flume and ultrasonic sensor, stage and velocity can be calculated in bidirectional flow at various speeds and levels. Nonetheless, more research is required into alternative instrumentation in complex heterogeneous hydrology found in BHFs.

Digital soil mapping (DSM) provides a low-cost approach for characterizing the spatial variation in soil properties, which contributes to inconsistent productivity. This study utilized random forest (RF) models to facilitate the DSM of apparent soil electrical conductivity (EC_a), cation exchange capacity (CEC), and soil organic matter (SOM) in agricultural fields across the Lower Mississippi Alluvial Valley based on a bare soil composite of Landsat 9 multispectral imagery and digital elevation models. Model data were collected during nongrowing seasons from 2019 through 2024. Field data included EC_a of the upper 0.5 m of soil from agricultural fields (n = 347) and soil-test-estimated values for CEC and SOM collected on a ∼0.4-ha (1-acre) grid from the upper 0- to 15-cm depth (n = 14,349). The RF model utilized a stratified K-fold cross-validation with fivefolds. Stratification by farm was used to ensure each fold in the cross-validation process contained a representative distribution of data drawn from all farm locations. Data were divided into an 80/20 split for training and testing purposes. Models had moderate accuracy (R² = 0.45, 0.74, and 0.72 for EC_a, CEC, and SOM) with moderate predictability (ratio of performance to deviation = 1.35, 1.95, and 1.91 for EC_a, CEC, and SOM). The contrasting performance between the CEC and SOM models with the EC_a model is likely due to the dynamic nature of soil properties, which is more pronounced in EC_a. Accordingly, models could have benefitted from covariates such as soil moisture and climatic factors or higher spectral resolution imagery, such as hyperspectral.

Cover crops play a significant role in improving and maintaining good soil quality. However, there are often some agronomic and cost challenges associated with successfully establishing cover crops. In Northeastern regions of the United States, abiotic stressors such as cold affect and high costs limit uptake of the practice. Using two field trials, a high tunnel study, and laboratory methods, we investigated the possibility of growing improved winter peas (Pisum sativum L.) as a cash cover crop in Northeastern regions of the United States. Results of the field trial showed no significant variance in winter survival between the winter pea genotypes tested. The genotypes tested include cold-hardy cultivars traditionally cultivated for forage and improved winter pea breeding lines selected for edible traits. In two field trial seasons of 2021/2022 and 2022/2023, all genotypes reached their reproductive stage in the first week of June when seeded the previous year around the end of September in Vermont. Our results show that although peas are a viable overwinter crop allowing potential double cropping. However, the mid-June maturity date for dry or fresh pea harvest conflicts with spring planting of cash crops on many Vermont and Northeastern farms, greatly limiting the potential of double cropping to increase winter cover cropping uptake. Consequently, some reported barriers to winter cover crop adoption in the far Northeast, such as high seed cost and time constraints, cannot easily be solved by double cropping.

Pastoral grasslands in New Zealand's mountainous landscapes contribute substantially to a primarily agricultural national economy. This landscape supports mosaics of regenerating indigenous biodiversity among more productive naturalized exotic herbage, each raising fundamental ecological, agronomic, and environmental concerns. Our objective was to investigate whether increased or lesser attention to native plant assemblages in these vegetation mosaics significantly influences soil carbon (C) stocks. At mid-altitudes below the original tree line, we compared paired plots of regenerating successional endemic myrtaceous woody shrub communities (Kunzea ericoides, kānuka) with exotic pasture at comparable slopes and aspects. We also investigated native snow tussock grass communities, the dominant vegetation at higher altitudes bordering the original tree line. Soils beneath kānuka had significantly higher C concentrations, C stocks, and carbon:nitrogen (N) ratios than adjacent areas of pasture. Soil C stocks were 15.43% higher under kānuka than under adjacent pasture. The bases of snow tussocks were frequently raised 10–20 cm above the surrounding inter-tussock land surface with a sparse vegetation cover that provides pathways for stock, making them more susceptible to soil erosion. Soil directly beneath the snow tussocks had significantly higher C, nitrogen, and phosphorus (P) in comparison with adjacent inter-tussock spaces. Soil C stocks were 38.7% higher under snow tussock than in the adjacent inter-tussock spaces. Our findings indicate that maintaining and enhancing endemic woody shrub and snow tussock assemblages is beneficial to productive and sustainable pasturage, while also playing a significant role in biodiversity conservation and climate change mitigation.