Agronomy Journal最新文献

Nitrogen (N) fertilizer recommendations in crops are affected by various factors including environmental and management practices. Effective N management should sustain maize (Zea mays L.) yield while minimizing nitrate (NO₃-N) leaching. This systematic review synthesized 132 peer-reviewed studies to quantify how recommended N rates (RNRs) vary across environmental and management factors, and to evaluate associations between RNRs, yield, and NO₃-N leaching. RNRs were grouped into quartiles derived from the empirical distribution of the study-level RNR values in the review dataset. RNRs were generally higher (>200 kg ha⁻¹) in subtropical and dry climates, in coarse-textured soils, and under irrigation. Yield responses to RNRs tended to be stronger in temperate climates, in coarse-textured soils, with conventional N sources, under split applications, and with irrigation. Studies conducted in semi-humid climates and in fine-textured soils showed weaker and inconsistent associations. NO₃-N leaching increased with RNRs under irrigation-based studies. Apparent increase in NO₃-N leaching in medium-textured soils likely results from residual N accumulation and post-harvest flushing where rainfall is high. These findings should be interpreted cautiously due to uneven study coverage and heterogeneous methods. Several key gaps remain in the evidence base. First, few studies quantify environment-by-management interactions. Second, NO₃-N leaching is rarely measured, and irrigation amount scheduling is often unreported. Third, paired irrigated-rainfed comparisons are uncommon. Finally, criteria for deriving RNR are inconsistent, and geographic coverage is limited. Research priorities include integrated factorial designs across climates and textures, water-accounted paired designs, concurrent residual-N profiling, long-term trials, transparent RNR definitions, and curated open datasets to enable synthesis.

Soil inundation increases anaerobiosis, slows organic matter decomposition, and affects greenhouse gas production from soils. The objective of this study was to evaluate the effects of natural short-duration recurring inundation on CO₂, CH₄, and N₂O emissions, as well as on labile soil permanganate oxidizable carbon and autoclaved-citrate extractable (ACE) protein contents. We assessed two locations in Ohio separately: (1) in the Northwestern location, hayfields prone to high inundation (N-HIH), low inundation (N-LIH), and non-inundated (N-NIH), and (2) in the Southern location, pasture fields prone to inundation (S-IP) or non-inundated (S-NIP) and non-inundated hayfield (S-NIH). Inundation was not controlled or simulated; rather, we evaluated it as a long-term natural effect. We collected greenhouse gas (GHG) samples in spring, early and late summer, and fall of 2021 and 2022. At Northwestern location, N-LIH and N-HIH emitted less CO₂, likely because of lower organic matter oxidation under more intense inundation. This pattern was less evident in the Southern location, where S-NIP and S-IP generally showed similar CO₂ emissions. Both locations acted as CH₄ sinks, and emissions remained largely unaffected by inundation at either location, suggesting that inundation duration and/or intensity were insufficient to maintain anaerobic conditions. Inundation, however, clearly increased N₂O emissions in both locations, especially during the drying period in early and late summer, after the wetter spring seasons, characterizing a progressive response to inundation. We frequently observed the highest N₂O emissions alongside elevated soil ACE protein levels. Natural recurring short-term inundation increased GHG emissions from hayfields and pastures, mainly by increasing N₂O emissions during post-inundation periods.

Wheat (Triticum aestivum L.) remains a major staple crop, which is vulnerable to abiotic and biotic stresses that can be compounded by climate change. This review assesses the projected effects of climate change on wheat production globally with an emphasis on the Canadian Prairies. The review aims to (i) discuss the projected impact of climate change on the Canadian prairie cropping calendar, (ii) assess the potential impacts of climate change on pest dynamics and abiotic stresses, and (iii) discuss beneficial management practices that can be employed to tackle climate change in wheat production systems. Climate change will potentially shift the current Canadian prairie calendar earlier in the year, potentially increasing wheat yields. The impact of climate change on pests is tied to the cropping calendar and the pest involved. Abiotic stresses, except carbon dioxide, will be aggravated. Beneficial management practices, that is, biostimulants, ultra-early seeding, seeding winter wheat, and cultivar mixtures, are potential strategies to stabilize wheat yield and reduce the yield gap under a changing climate. Biostimulants, although effective, have not been extensively tested for their impact on abiotic stresses in the Prairies. Studies on ultra-early warrant further research to address their effectiveness in Northern prairie regions and the challenges encountered by producers. Although growing winter wheat is an option to escape wetter spring conditions, issues with fall establishment and winter survival must be addressed. Despite the extensive global research on varietal mixtures, a knowledge gap exists regarding their benefits in the Canadian prairie context.

The Data Intensive Farm Management (DIFM) project has successfully executed experiments in farmer fields where every spot in the field is part of an experimental plot. What is still unsettled is how best to turn this extensive information into profitable variable rate nitrogen recommendations. This research used Bayesian methods to combine DIFM data with the on-farm experimental data that is used to make regional and state-level recommendations. The goal was to develop site-specific recommendations for corn (Zea mays L.) in a DIFM field. The first step was to estimate yield response using historical data from the maximum return to nitrogen (MRTN) database. The MRTN model allowed parameters to change over time and indicated that increased corn yields were mostly due to increasing yield potential. The second step was to estimate a spatially varying coefficient model using estimates from the first step as informative Bayesian priors. Using 3 years of a single field's on-farm experimental data from the DIFM database, the first 2 years were used to predict the third year. The information from MRTN dominated, which resulted in the predicted spatial variability being small. The method was thus unsuccessful in providing variable rate recommendations. The estimation was also computationally intensive. The conclusion is that less exact methods need to be developed that would have fewer parameters and could be estimated much faster.

In Brazil, most (Zea mays L.) production is in the off-season, following the summer soybean [Glycine max (L.) Merrill] harvest, a period often affected by water scarcity during critical growth stages, which can substantially reduce yields. To address this challenge, foliar nutrient applications can mitigate drought damage if timed correctly. Thus, this study aimed to evaluate the effect of monoammonium phosphate (MAP: 12-61-00) via foliar application at various development stages on maize plant physiology and productivity under water-limited conditions. The research employed a randomized block design with eight treatments and four replicates: a control; MAP applications at V₄, V₆, V₈, R₁, and MAP applied at all stages (MAP-All) (all four stages: V₄ + V_{6 +} V_{8 +} R₁); and two additional treatments supplying nitrogen (N) via urea equivalent to that from MAP: N-V₆ and nitrogen applied at all stages (N-All) (V₄ + V_{6 +} V_{8 +} R₁). Assessments included leaf nutrient content, photosynthetic pigment content, gas exchange parameters, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity, lipid peroxidation, antioxidant enzyme activity, carbohydrate content, and grain yield (GY). The MAP-All treatment demonstrated the most significant positive effects, enhancing the contents of chlorophyll a and b, total chlorophyll, and carotenoids and improving net photosynthesis, stomatal conductance, carboxylation efficiency, and Rubisco activity. This increase in photosynthetic efficiency led to reduced lipid peroxidation and the necessary actions of antioxidant enzymes, leading to greater sugar production in leaves. This resulted in an average increase in GY of 16% compared to the control, equivalent to 884 kg ha⁻¹. The N-All treatment, despite providing a lower dose of N, increased GY by 10% compared to the control, or 408.6 kg ha⁻¹. These findings indicate that foliar MAP applications effectively enhance maize physiological conditions by supplying phosphorus and nitrogen to boost photosynthetic and productive metabolism in off-season maize.

Water scarcity and drought stress pose significant challenges to wheat (Triticum aestivum L. ‘Chamran-2’) production, particularly in arid and semiarid regions. This study, conducted during 2022–2024 in Fars Province, Iran, evaluated integrated nutrient management (INM) strategies under deficit irrigation (DI). A split-plot arrangement within a randomized complete block design was implemented, with four replications. Main plots included full irrigation (FI) and DI applied at noncritical growth stages (tillering, stem elongation, and post-pollination), while subplots comprised four INM treatments: optimal nutrition (control) (ON), biofertilizers with humic acid (BH), foliar sprays of fulvic acid, potassium silicate, and amino acids (F), and a combined F+BH treatment. DI reduced nutrient uptake, photosynthesis, and grain quality, but INM, especially F+BH, mitigated these effects by improving nutrient translocation, osmotic adjustment, and oxidative stress tolerance. The combined F+BH treatment increased chlorophyll a and b by 8.6%, photosynthesis by 7.7%, and stomatal conductance by 13.8%, while reducing proline by 26.2%, indicating stress alleviation. Under DI+F+BH, water use efficiency (WUE) improved by 53.3% compared to FI+ON. Principal component analysis identified calcium, boron, and zinc as key contributors to metabolic efficiency and drought resilience. The DI+F+BH treatment effectively sustained productivity, enhancing physiological traits, grain protein content, and economic returns. DI, combined with F+BH, demonstrated superior WUE and profitability, emphasizing its value as a water-saving strategy in arid regions.

Brazil can expand cultivated areas without deforestation by restoring degraded pastures and optimizing grain production through off-season crops. This study evaluated eight off-season treatments, including fallow, monocrops, and intercropping combinations, and their effects on maize (Zea mays L.) intercropped with guinea grass (Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs ‘Massai’) in a tropical low-altitude region. The millet (Pennisetum glaucum (L.) R. Br.) + guinea grass treatment produced high aboveground biomass, efficient macronutrient accumulation, reduced soil temperature, and increased maize grain yield and guinea grass productivity compared to other treatments. Overall, the use of off-season crops improves degraded pasture renovation, enhances subsequent summer intercropped maize productivity, and represents a promising and sustainable agricultural practice.

Detecting plant nitrogen (N) deficiency is important for enhancing crop yield and nutrient use efficiency. Leaf color, a key indicator of relative pigment expression and crop N status, can be monitored using red, green, and blue (RGB) under-canopy images of maize (Zea mays L.). This study evaluated RGB indices collected from under-canopy images against applied N rates ranging from 0 to 271 kg ha⁻¹ in maize trials conducted in Iowa, Minnesota, and New York (2019–2020). Digital RGB camera images were processed for leaf identification, filtered, and analyzed for RGB band averages. Results showed strong correlations between RGB indices and the applied N rates, especially in indices involving the B band, like (R − B)/(R + B), with R² values up to 0.75 and p < 0.001. Power analysis showed high probabilities of detecting significant effect sizes using rapid multi-image capturing approaches that overcome image-to-image variability. In conclusion, under-canopy imaging can be an inexpensive approach for measuring in-season maize N status, and among the indices tested, (R − B)/(R + B) was the most successful at identifying N stress.

Milk thistle (Silybum marianum L.) is highly valued for its medicinal properties. It is renowned for its capacity to flourish in dry environments, making it an attractive option for farming in areas with scarce water resources. This study aimed to assess how drought stress, foliar potassium sulfate application, and their interaction affect different milk thistle genotypes. Ten different genotypes (nine Iranian and one Hungarian) were assessed under three levels of soil water availability including control, moderate, and severe water stress, with depletion rates of 40%, 60%, and 80% of available water, respectively. Also, two foliar treatments were applied (non-spray and K₂SO₄ spray). Foliar K₂SO₄ application was applied twice, 7 days apart, during the flower bud development stage, using a 2% concentration in both 2020 and 2021. Drought stress adversely affected physiological parameters such as relative leaf water content and photosynthetic efficiency but enhanced antioxidant enzyme activities and osmotic adjustment mechanisms. K₂SO₄ foliar application exhibited dual effects, increasing yield while reducing key bioactive compounds including phenol and flavonoids content of seeds. Genotype-specific responses highlighted varying degrees of tolerance to drought stress and potassium application. Sari exhibited sensitivity to drought, while Isfahan and Hungary genotypes showed tolerance to moderate water stress with potassium foliar spray. Principal component analysis revealed the relationship of traits and genotypes by traits in each moisture condition. The study underscores the complexity of drought response mechanisms and the need for tailored management strategies and genotype selection to ensure resilience and optimize yield in milk thistle cultivation.

Optimizing planting density is crucial for enhancing the yield potential of conventional japonica rice (Oryza sativa L.) by regulating yield components and population characteristics. In a 2-year field study, four conventional japonica rice varieties were evaluated under three planting densities: 16 × 30 cm (20.83 × 10⁴ hills hm⁻²), 12 × 30 cm (27.78 × 10⁴ hills hm⁻²), 10 × 30 cm (33.33 × 10⁴ hills hm⁻²). Super-high-yielding varieties exhibited greater sink capacity and stronger source activity compared with high-yielding varieties. However, differences in population traits such as the top three leaf pattern and panicle architecture were observed due to genetic variation. Increasing planting density improved yield in super-high-yielding varieties primarily by increasing panicle number at maturity. At the same time, higher density stimulated the growth of ineffective tillers, which reduced the productive tiller percentage. This led to a more rapid decline in leaf area during the reproductive stage, lower flag leaf chlorophyll (SPAD) values, restricted overall plant growth, and reductions in plant height as well as the length, width, and angle of the top three leaves. Panicle development was similarly constrained, resulting in shorter panicle length, fewer branch pedicels, and reduced seed-setting rate, 1000-grain weight, and spikelets per panicle. Despite these negative effects, the overall increase in total spikelets compensated for the declines in individual components, leading to net yield enhancement. In conclusion, a moderate increase in planting density for super-high-yielding conventional japonica rice varieties enhances sink capacity and is beneficial for yield improvement.