Agricultural & Environmental Letters最新文献

Soil health practices can improve soil conditions and provide ecosystem services, but increased risk of phosphorus (P) loss can be an unintended consequence. We investigated conservation tillage and cover crops effects on soil P stratification, P accumulation at depth, and soil aggregation for sandy Coastal Plain soils from the Mid-Atlantic United States soil cores from 10 agricultural fields with 0–15 years of conservation tillage or cover cropping were analyzed for Mehlich-3 P and dry aggregate stability. We found no evidence that conservation tillage or cover cropping caused P stratification or accumulation in study fields that were already enriched with P prior to soil health implementation. Annual particulate, dissolved runoff, and leachate P loads decreased when estimated using the North Carolina Phosphorus Loss Assessment Tool assuming no-till and cover crops (soil health) compared to conventional till and winter fallow (conventional). We suggest that soil health practices are unlikely to exacerbate P losses from high P Coastal Plain soils beyond their initial risk profile.

Few studies have addressed whether in-field practices to reduce nitrate-nitrogen (NO₃-N) leaching might increase nitrous oxide (N₂O) emissions, which could undermine attempts to mitigate agricultural N pollution. Over a 3-year period, we assessed the impacts of N application timing and cereal rye (Secale cereale L.) cover crop on subsurface drainage NO₃-N leaching and N₂O emissions to quantify changes in total N loss and corresponding social and environmental damage costs under continuous corn (Zea mays L.). While NO₃-N losses were reduced by 37% with the combination of in-season split N application and cereal rye cover crop relative to pre-season N application, soil N₂O emissions increased by 26%, highlighting a tradeoff between N loss pathways. As a result, total N losses and social and environmental damage costs from each system were not different. These results demonstrate the importance of addressing agricultural N pollution using a holistic framework accounting for the environmental and social risks of both NO₃-N losses and N₂O emissions.

Raman spectroscopy (RS) is a vibrational spectroscopy. This work reported the RS spectral characteristics of fiber and seed of six cotton (Gossypium sp.) genotypes differing in fiber length. While the RS spectra of fiber samples were dominated by the cellulose-related peaks, the spectra of cottonseed samples were featured by the bands related to oil, protein, carbohydrate, and lignin components. Principal component analysis (PCA) revealed that the first two principal components (PCs) accounted for >87% of the total variation of the two types of samples. The PC1 versus PC2 plot classified the six fiber samples into three groups, but their cottonseeds into four groups. This experimental evidence implied the possibility of RS combined with PCA for rapid fiber phenotyping of cotton as well as for evaluating cottonseed nutrient information.

Soil health can differ across cropping systems because of variation in edaphic and management factors. We evaluated how biological indicators of soil health (soil organic matter [SOM], permanganate oxidizable carbon [POXC], mineralizable carbon [MinC], autoclaved-citrate-extractable [ACE] protein, and potentially mineralizable nitrogen [PMN]) compared across four common Wisconsin cropping systems: grazed cool-season pastures, forage-based rotations that included perennial legumes or grasses, annual rotations receiving manure, and annual rotations receiving synthetic fertilizers. Biological indicators of soil health were up to 195% greater in pastures than other cropping systems. MinC, POXC and PMN were 10%–90% greater in forage-based rotations than annual cropping systems, but only MinC and POXC were greater in annual systems with manure compared to those without manure by 35% and 7%, respectively. Perennial vegetation and livestock integration offer the greatest potential to increase biological indicators of soil health in agricultural lands.

To better understand cover crop benefits and receive nitrogen scavenging credits for cover cropping, farmers need simple and robust methods of predicting cover crop biomass production. A new regulation focused on improving nitrogen management on over 200,000 ha of irrigated land in the central coast of California motivated us to evaluate if the shoot length of rye (Secale cereale L., ‘Merced’) and triticale (× Triticosecale Wittmack, ‘Pacheco’) could predict shoot biomass. Field samples for rye (n = 162) and triticale (n = 126) were collected at various developmental growth stages from organic and conventional vegetable farms and planting date trials, across multiple soil types, planting times, row spacings, and plant densities. Main shoot length was well-correlated with oven-dry shoot biomass for rye (r² = 0.87) and triticale (r² = 0.88). This provides farms in California and beyond with a simple, robust method to estimate cover crop shoot biomass.

Biochar is used as a soil amendment for improving soil health. Biochar is known to possess high adsorption capacity for nutrient ions, especially toward NH₄⁺. However, there is limited information regarding the direct binding mechanisms of NH₄⁺ on biochar. Although few infrared spectroscopic studies were conducted by characterizing the biochar solid phase, no research was reported, in which the adsorption mechanism was deciphered in the presence of water. Here we report NH₄⁺ adsorption mechanism on pinewood biochar using in situ attenuated total reflectance Fourier transform infrared spectroscopy. The results indicated that NH₄⁺ adsorbed strongly on pinewood biochar at pH 8.5 and less at pH 5.5 as revealed by infrared band shifts and symmetry change. Macroscopic adsorption envelope corroborated the spectroscopic finding by resulting in higher adsorption capacity with increasing pH.

Infrastructure installation (e.g., pipelines) disturbs soils, often resulting in increased soil compaction (bulk density [Bd] and penetration resistance [PR]). The relationship of PR to Bd, gravimetric water content (Θg), and a suite of other properties were determined on seven topsoils to provide a model and database for reclamation specialists to use when assessing disturbed soils. Penetration resistance had a strong linear association with Bd, but higher Θg reduced the range of PR as Bd increased. Step-wise regression identified Bd, Θg, texture, clay speciation, and organic matter as significant factors to predict PR. The model predicts PR from <1 to 8 MPa and closely match measured values. Soil Bd and Θg contributed to 84% of the model's explained variation in predicting PR. This study provides a tool for reclamation specialists that aids in understanding the risks associated with disturbances and highlights the importance of keeping Θg low during installation of pipelines.

The first compilation of nutrient export coefficients for specific land uses in the United States was completed in 1980. Building off that effort, the “Measured Annual Nutrient loads from AGricultural Environments” (MANAGE) database was developed in 2006 to summarize annual field-scale nitrogen (N) and phosphorus (P) runoff data from agricultural land uses. It also presents descriptive data such as land use, tillage, conservation practices, soil type, soil test P, slope, and fertilizer formulation, rate, and application method, along with runoff, precipitation, and soil erosion. Here, we update MANAGE to facilitate regional analyses, adding 27 studies and Level II ecoregion delineations for each of the 94 studies such that data are now available from 11 of the 50 North American Level II ecoregions, representing the major U.S. agricultural regions. This contemporary data repository is freely available from USDA Ag Data Commons to support scientific analyses, model evaluations, and management and policy decisions.