Agricultural & Environmental Letters最新文献

Resin-extractable phosphate (PO₄-P) is a widespread sink-based measure of soil bioavailable phosphorus (P) used in biogeochemistry and soil fertility. However, acid elution of P may hydrolyze organic P and thus compromise measurement of PO₄-P. We evaluated sodium bicarbonate (NaHCO₃) as an alternative to sulfuric acid (H₂SO₄) for PO₄-P elution. We found 0.5 M NaHCO₃ achieved ≈100% PO₄-P recovery at higher initial PO₄-P concentrations (20 and 30 mg P/L), compared to 95%–98% with 0.25 M H₂SO₄. For 24 soil samples representing all 12 USDA soil orders, NaHCO₃ elution yielded 9.6% higher resin extractable PO₄-P than H₂SO₄. Additionally, the PO₄-P remaining in water extract after resin removal (H₂O_re-PO₄) was consistently quantifiable, and constituted up to 46% of total extractable PO₄-P. These results demonstrate (i) NaHCO₃ is a more effective eluent for resin extractable P than H₂SO₄, and (ii) H₂O_re-PO₄ should be quantified when measuring resin extractable P.

This study aimed to estimate mixed-species cover crop (CC) biomass and nutrient contents using remote sensing, as ground-based measurements are time-consuming and costly. Eleven CC treatments with varying grass-legume proportions (GLP) were sampled, and nutrient contents were determined along with multispectral imagery captured during the first and fourth weeks of March and the fourth week of April 2023. Biomass N (R² = 0.46–0.60) and K% (R² = 0.41—0.71) decreased with increasing GLP. The chlorophyll absorption ratio index and the normalized difference vegetation index closely followed the biomass nutrients N, P, and K combined yield (Bio_NPK) trend. Machine learning algorithms random forest (RF) and partial least square (PLS) regression were better for biomass (R² = 0.74 with RF) and N% (R² = 0.72 with PLS) prediction compared to the Bio_NPK prediction. These results are crucial for scientists to devise appropriate analysis approaches for estimating the benefits of mixed-species CC.

Soybean (Glycine max) is the most important protein crop being produced globally. Sulfur is essential for enhancing its nutritional quality, particularly by increasing S-containing amino acids. Gypsum, which provides calcium and sulfur, and cover crops, which improve soil health and indirectly affect nutrient dynamics, are promising management practices for enhancing soybean nutrient content. A 5-year study across three US. locations evaluated the effects of surface-applied gypsum and cover crops of cereal rye (Secale cereale) on continuous soybean production. The objective was to evaluate the soybean nutrient composition affected by these practices across various soil types and climatic conditions. Findings revealed consistent increases in soybean sulfur content with gypsum application, regardless of cover crop use. Responses of other elements were site-dependent. In the case of cover crops, significant changes in element composition were observed mainly at the Ohio site.

Particulate organic matter may be an important component feeding soil microbial activity. This study described population-level statistics of particulate organic carbon (C) and nitrogen (N) in predominately Ultisols across 181 farms throughout North Carolina, Virginia, and Georgia. Soil profiles were sampled under conventional-till cropland (n = 186), no-till cropland (n = 127), grassland (n = 322), and woodland (n = 171). Particulate organic C (g C kg⁻¹ soil) varied from 2.0 to 18.0 (5% to 95% distribution) at 0- to 10-cm depth, 0.4 to 3.9 at 10- to 30-cm depth, and 0.1 to 1.9 at 30- to 60-cm depth. As a proportion of total N, particulate organic N was 0.26 ± 0.10, 0.12 ± 0.09, and 0.08 ± 0.08 kg kg⁻¹ at 0- to 10-, 10- to 30-, and 30- to 60-cm depths, respectively. Particulate organic C was most dramatically affected at 0- to 10-cm depth, following the order: conventional-till cropland < no-till cropland < grassland < woodland. Particulate organic N followed a similar order, except there was no difference between grassland and woodland. Particulate organic matter brings vitality to soil along a trajectory toward greater organic matter.

Healthy soil supports the global carbon cycle, the water cycle, and many nutrient cycles to stabilize ecosystems. We take these processes for granted, and yet, disruptions to these cycles would be devastating if soils became defunct and plants could not photosynthesize. As with the health of the human body to which we rely on to carry out our daily lives, so too does the health of soil give essential life to our world. Strong corollaries exist between the functioning of the human body and the soil body. This essay explores these two bodies through simile. Just as we wish others good health, so too should each of us (and society) wish a world with excellent soil health. A foundational pathway laid by strong science, but pitched to engage more of the public in this effort to foster better soil health might be through non-traditional impressionistic storylines.

In situ soil respiration is driven by annual patterns of temperature and soil moisture, but what about extracellular enzyme activities responsible for depolymerizing soil organic matter? We conducted biweekly measurements of potential soil β-glucosidase activities during a 4-month period from March soil thawing through July in annually cropped field plots in eastern South Dakota. Our objective was to determine the best sampling time to resolve the effects of crop rotational diversity on soil microbial activities. Potential β-glucosidase activities were elevated immediately following soil thaw, peaked in May, and declined to their lowest value in mid-summer. Temperature and precipitation had no value in predicting enzyme activities; however, enzyme activities were affected by crop rotational diversity and responded to current crop and previous crop. These findings are pertinent to the use of soil extracellular enzymes in soil health assessments and as indicators of microbial substrate preference with implications for soil carbon stabilization.