Agricultural & Environmental Letters最新文献

Rising concentration of surface O₃ threatens crop production and food security. To improve the evaluation and develop efficient adaptations, it is essential to study the effects of acute O₃ pollution. We adopted this study by open-top chamber (OTC) method and found that the fumigation of elevated O₃ (NF40) for short (tillering and jointing, heading and ripening) and long periods during rice growth reduced the grain yield by 17, 19 and 25%, respectively, showing that both of the acute and chronic O₃ pollution reduce rice production. Moreover, in comparison with the plants under chronic O₃ pollution, grain yield was increased when O₃ was removed at different stages: 32% increment at tillering and jointing and 34% increment at heading and ripening. These results suggest a possibility to recover the yield loss in rice under O₃ pollution.

Soil aggregate stability is widely considered an indicator of soil health. However, there is a lack of test procedure standardization for this soil property. Presently, air-drying and manual grinding are commonly used in preparing samples for testing, which are time-consuming and labor intensive. This study evaluated oven-drying (65 °C) aggregates and processing by either disk or flail mechanical grinders as a way to improve efficiency of conducting aggregate stability analysis as compared with air drying and manual grinding. Surface soil samples were collected from forest, grassland, no-till, and cultivated areas across 22 fields in Oklahoma with textures ranging from sandy loam to clay loam. The stable fractions of oven-dried samples were highly correlated to the results of the analysis that used air-drying. The stable fractions of mechanically ground samples were also highly correlated with manually ground samples. Oven-drying in combination with either of the grinding methods is a suitable way of improving the efficiency of soil aggregate stability analysis.

Continuous corn (Zea mays L.) yield increases are required to promote economic development and support a larger population. Reducing the existing yield gaps is a potential strategy to accomplish this goal. The objective of this study was to evaluate yield trends, and gaps at different production levels in Mississippi using data from 2012 to 2021. Production levels considered were Mississippi yield contest (Yc), Mississippi State University hybrid testing trials under irrigation (Yp) and dryland (Yw), and actual yield (Ya) from USDA National Agricultural Statistics Service. Since 2012, Yc, Yp, and Ya are stagnant, and Yw has a nonsignificant positive trend. Averaged over 10 yr, a yield gap of 5.6 Mg ha⁻¹ between Yc and Ya, 4.1 Mg ha⁻¹ between Yp and Ya, and 2.0 Mg ha⁻¹ between Yw and Ya were noted at state level. Existing yield gap underlines current production limitations and necessitates adoption of improved agronomic practices.

Core Ideas

Agriculture faces a dilemma with nitrogen (N)—it is often the most necessary external input to optimize production, several generations of farmers became accustomed to its relatively inexpensive cost, and it contributes to widespread pollution due to numerous loss pathways to the environment. However, standard N fertilizer recommendations have not accounted well enough for a key source via mineralizable soil N. Soil-test biological activity (STBA) is strongly associated with mineralizable soil N, both of which become surface-enriched with conservation agricultural management using soil health principles. A series of field experiments assessed the contribution of mineralizable soil N to the N supply needed to optimize corn (Zea mays L.) grain and fall-stockpiled tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] production. This essay synthesizes how STBA along with cost-to-value threshold can be used to modify the N fertilizer factor to optimize economic return and avoid environmental degradation.

Adjacent fields with contrasting histories present an opportunity to evaluate the legacy of management on soil health (SH) and grain productivity. In 2011, two fields transitioned to no-till grain production. During the previous 25 yr, one was pasture (pasture-to-grain; PTG), whereas the other was annually tilled for grain cropping (long-term grain; LTG). The study objectives were to contrast these two fields relative to SH and productivity. Yield data was collected from 2011 to 2021 and SH sampled in 2021. The PTG out-yielded LTG each year, with an average 46% yield increase. 2021 SH metrics demonstrated similar trends, with PTG 62% higher than LTG. Contrasting across fields (2020–2021), SH metrics were related to yield (r² = .46–.78), but these relationships weakened when assessed within each field. These findings affirm SH indicators are sensitive to the legacy of management and are meaningful indicators of productivity across sites but less informative for within-field variability.

To examine the role of dam impoundment in elevating the levels of soil-associated phosphorus (P) and trace elements in reservoir hydro-fluctuation belts (RHB), soil samples in RHB and adjacent uplands (non-flooded area, NFA) in the Three Gorges Reservoir, China, were collected and analyzed. Concentrations of available P, copper (Cu), chromium (Cr), and zinc (Zn) were found to be higher in RHB than in NFA (p < .05), whereas organic carbon was comparable in RHB and NFA (p > .05). The elevated levels of Cu, Cr, and Zn in RHB were probably associated the repeated drying–rewetting cycles created by the dam impoundment. The 95th percentile of the single-factor pollution index and geo-accumulation index in RHB were 1.29 and −0.21 for Zn, 3.21 and 1.15 for Cu and 3.37 and 1.17 for Cr. Elevated pollution potential of soil-associated Zn, Cu, and Cr existed in RHB of the Three Gorges Reservoir.

Core Ideas

Assessing the success of cover crops (CCs) as a way to promote soil health at the farm scale remains a challenge. At four on-farm CC experiments in Nebraska, we quantified soil health relative to a reference soil. We examined physical, chemical, and biological properties in near-surface soil. Cover crops reduced the soil health gap between bare (no-CC) and reference soil in the short (3-yr) timescale, but the magnitude of responses depended on cropland management history and ecological dynamics of reference site plant communities. Increases in soil health relative to reference soils showed some relationship to increases in soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) yields. Clear discrimination of reference from bare soils was most influenced by organic matter and infiltration measurements conducted under the highest sampling intensity. Framing soil metrics relative to reference soils and ensuring appropriate sampling intensity are important to quantify the effects of CC on farm landscapes.

Tractor guidance (TG) improve environmental gains relative to nonprecision technologies; however, studies evaluating how tractor operator experience for nonguidance comparisons affect gains are nonexistent. This study explores spatial relationships of overlaps and gaps with operator experience level (0–1, 2–3, 6+ yr) during fertilizer and herbicide applications based on terrain attributes. Tractor paths recorded by global navigation satellite systems were used to create overlap polygons. Results illustrate operator experience level is critical for better efficiency gains estimation (for non-TG comparisons). Operators with 6+ yr of experience reduced overlap by 7.7 and 20.6% compared with operators with 2–3 and 0–1 yr of experience, respectively. New operators had consistently higher overlap across all slope (<0.5, 0.5–1, 1–2, 2–5, 5–9, and 9–15%) and roughness classes (<0.1, 0.1–0.2, 0.2–0.3, 0.3–0.5, 0.5–0.7, 0.7–1 and >1). A low interpersonal reliability value of 0.02–0.03 indicates operator experience is crucial to estimate TG efficiency gains and consistent drivers experience levels are needed when evaluating economic and environmental gains from TG.

Pollinator declines have driven research and increased monitoring efforts. Within North Dakota, USA, our research group initiated research in 2015 on pollinator conservation and management. We synthesized results across five projects, producing 12 publications and providing baseline data on pollinator diversity and rangeland management to improve conservation efforts while land-sharing with livestock. We detected 76 species of butterflies and ∼318 bee species. Butterfly diversity and relative abundance were driven by floral resources and less exotic plant invasions, with a positive relationship between flowers and pollinators. Invasive forbs were visited by pollinators, primarily honey bees. We also found management influenced vegetation characteristics within pastures, but landscape context was important for determining the specific outcome. Although pollinator abundance did not distinctly respond to management, diversity was affected by regime and grazer type. Using fire and grazing may benefit flowers to support pollinators. Our research will help guide rangeland management decisions that promote land sharing and benefit pollinator conservation efforts.

Core Ideas

Soil organic carbon (C) and nitrogen (N) accumulation contributes to improved soil health condition, particularly after a history of tillage-intensive land use. Soil-test biological activity (STBA) is an active fraction of organic matter that is responsive to conservation management. This essay summarizes the need, concept, and method of calculating root-zone enrichment of STBA and other organic C and N fractions on private farms. Calculation of root-zone enrichment separates the pedogenic influence on organic matter content from that of contemporary management. This separation is particularly important when attempting to determine STBA or soil organic C stock change in response to management across variable landscapes. Reasonable farm-level estimates of STBA and stocks of soil organic C and N can be obtained from one to two dozen sampling sites on farms with differences in land use, a process that could help propel in-depth assessments of soil health condition and C stock change.