Agronomy Journal最新文献

Inefficient fertilizer management and increasing water scarcity are affecting rice yields and thus food security in Central African lowlands. The objective of the study was to determine the effect of biochar and mineral fertilizer application and irrigation regime on paddy rice growth, yield and profitability. A randomized complete block design with a split-split plot arrangement and three replications was used at three field sites and for two consecutive seasons. The main plots consisted of two irrigation regimes, permanent flooding and alternate wetting and drying. Rice (Oryza sativa L.) cultivars TAI and AR2017105 were assigned to subplots. Six fertilization treatments were applied in sub-subplots: control, rice husk biochar or manure-charged biochar, each with and without mineral fertilizer. Alternate wetting and drying did not penalize yield. The combined use of biochar and mineral fertilizer increased paddy rice yield compared to fertilizer alone (+16%) and the control (+85%). The sole application of biochar, with or without manure, did increase yield in the first (+14%) but not in the second season compared to the unfertilized control. In both cropping seasons, the combined use of biochar and mineral fertilizer significantly increased the gross margin of paddy rice farming compared to the sole application of fertilizer. The combined application of biochar and mineral fertilizer under alternate wetting and drying can thus be recommended as a key climate-smart agricultural practice to increase food security and the agronomic profitability of rice cropping in Central African lowlands and comparable rice growing areas worldwide.

The interaction between phosphorus (P) and potassium (K) significantly influences alfalfa (Medicago sativa L.) production. However, our understanding of this interaction in soils with high levels of exchangeable K, calcium (Ca), and magnesium (Mg) remains limited. The interplay between soil P, K, Ca, and Mg, along with harvest timing, can affect the availability and uptake of P and K, leading to varied yield responses. Field research was conducted at the University of Wyoming James C. Hageman Sustainable Agriculture Research and Extension Center at Lingle, WY, to investigate this complex interaction and its impact on alfalfa production from 2019 to 2021. Treatments included (i) 18 selected combinations (kg ha⁻¹) of three levels of P (0, 34, and 67 P₂O₅), three levels of K (0, 168, and 336 K₂O), two levels of Ca (0 and 560 CaO), and two levels of Mg (0 and 56 MgO); and (ii) two harvest schedules (early harvest, late bud to early [10%] bloom; late harvest, 7–10 days after early harvest [∼100% bloom]). Treatments were factorially (18 × 2) arranged in randomized complete blocks with three replications. Under low levels of soil Ca and Mg, the 67 P₂O₅ and 336 K₂O (kg ha⁻¹ year⁻¹) treatment produced the highest early harvest yield responses, while the 34 P₂O₅ and 336 K₂O (kg ha⁻¹ year⁻¹) treatment excelled in late harvest yield. Alfalfa fertilized with 67 P₂O₅ and 336 K₂O (kg ha⁻¹ year⁻¹) consistently achieved significant late harvest yield response in soils with high levels of Ca and Mg, leading to profitable forage production. Similar trends in P and K uptake were observed, indicating that fertilizing alfalfa with P and K can enhance productivity and profits even in soils rich in K, Ca, and Mg levels. In Wyoming and similar regions, we recommend that alfalfa growers and stakeholders consider soil nutritional status—particularly the relative exchangeable levels of K, Ca, and Mg—and harvest timing to develop P and K fertility programs for sustainable production and profitability.

Palmer amaranth (Amaranthus palmeri S. Watson) has evolved resistance to herbicides targeting nine sites of action. Phytoene desaturase-inhibiting herbicides remain among the few sites of action that are still effective in controlling Palmer amaranth. Greenhouse experiments were conducted to evaluate the effectiveness of fluridone and diflufenican in controlling difficult-to-control Palmer amaranth accessions collected in Arkansas from 2016 to 2022, to quantify the response of three accessions that exhibited low sensitivity to both herbicides, and to evaluate the effectiveness of photosystem II inhibitors alone and with fluridone or diflufenican on three accessions. At 14 days after a preemergence application, Palmer amaranth control with fluridone and diflufenican ranged from 42% to 100% and 33% to 99% across 23 accessions, respectively. Three accessions required 10.2 to 26.7 times more fluridone than the susceptible Palmer amaranth standard based on LD₅₀ values (where LD₅₀ is the lethal dose to kill 50% of the population), with less than 50% mortality achieved with a 1x herbicide rate for two of the three accessions. For diflufenican, the LD₅₀ values for the three accessions were 3.9–18.5 times greater than the susceptible standard. An additive response for mortality and biomass reduction resulted from adding fluometuron to fluridone at all rates tested. An additive or sometimes a synergistic response occurred with the combinations of metribuzin plus diflufenican. Overall, fluridone exhibited higher efficacy than diflufenican for most accessions tested. While phytoene desaturase-inhibiting herbicides remain an effective control option for most Palmer amaranth accessions, herbicide mixtures targeting multiple sites of action remain essential for delaying resistance and obtaining effective control of this problematic weed.

Soil microbes are essential for soil nutrient cycling. However, frequent tillage and the use of synthetic agrochemicals can reduce soil microbial diversity and enzyme activity. In this study, the effects of four tillage treatments (mouldboard plough, shallow tine-tillage, no-tillage, and tillage rotation) and two rates of synthetic agrochemicals (standard and reduced, with biostimulants) on soil microbial diversity and enzyme activity were investigated between 2018 and 2020 in a Mediterranean climate zone in South Africa. It was hypothesized that a reduction in tillage frequency and quantity of synthetic agrochemical application would lead to greater microbial diversity and enzyme activity. Soil samples were collected from the 0- to 150-mm layer of a field trial under a dryland crop rotation system. Soil microbial species richness and abundance were assessed using the Shannon–Wiener diversity and evenness indices. The activities of four microbial enzymes—β-glucosidase, acid phosphatase, alkaline phosphatase, and urease—were used to evaluate ecosystem functioning. The combined effects of tillage rotation with a shallow tine implement and the application of biostimulants failed to significantly improve soil microbial diversity, enzyme activity, and crop productivity relative to other treatments. However, the combination did not reduce the wheat (Triticum aestivum) grain yield and quality, and soil biological parameters. Furthermore, the less intensive tillage treatments, ST, NT, and ST-NT-NT-NT, resulted in higher enzyme activity than the mouldboard treatment. Therefore, we suggest that combining non-intensive tillage with reduced synthetic agrochemical use can be a safer, more environmentally friendly alternative to intensive tillage and high agrochemical application in dryland cropping systems.

In northern latitudes, the diversity of the maize (Zea mays L.)–soybean (Glycine max L.) cropping system can be increased by including winter wheat as a rotation crop, providing long-term benefits including improved nutrient availability, nutrient-use efficiency, soil structure, and moisture holding. However, in Ontario, Canada, few farmers have adopted winter wheat (Triticum aestivum L.) due to low profitability. After the wheat harvest, there is a 3-month window with warm days and moist soil, sufficient to grow a short-duration crop. Some millet varieties are short duration. Millets are increasingly valued economically as “ancient grains” for humans, as a nutritious forage, and as effective cover crops due to their fibrous roots and dense foliage. Though millets offer similar long-term benefits to wheat in a rotation, they cannot economically compete with maize or soybean as a summer season crop. We hypothesized that the economic constraints of winter wheat and millets could be overcome by double cropping, specifically by adding a low-input, short-duration millet after winter wheat is harvested. The objective of this study was to evaluate the potential of millets as a post-winter wheat crop in Ontario. Three years of field trials (2020–2022) were conducted in Elora and Essex, Ontario, starting with 81 accessions of five millet crops. Selected accessions of proso millet (Panicum miliaceum L.) produced up to 0.5 t/ha grain yield, whereas foxtail millet [Setaria italica (L.) P. Beav] and barnyard millet (Echinochloa spp.) at Elora, and fonio (Digitaria sp.) in Essex produced up to 0.9–1.6 t/ha dry shoot yield. However, planting date, initial soil moisture, weed management, and fall frost were observed to be critical for millet success.

Intensive dairy production in southern Idaho is associated with the annual application of manure to croplands. However, a one-time heavy application of manure could alternatively be used as a means to improve soil fertility and health for years or even decades, circumventing the need for frequent applications. To determine if this practice would negatively affect soil properties in the short term, we analyzed chemical and biological indicators of soil health for 2 years after dairy manure incorporation. Soil indicators measured were pH, electrical conductivity, extractable nitrogen (N) and phosphorus, total carbon (C) and N, enzyme activities, net N mineralization, soil organic C, soil protein, active C, ammonia oxidation potential, and particulate organic matter. Manure (with and without synthetic fertilizer) was found to significantly affect chemical and biological indicators in both topsoil (0–15 cm) and subsoil (15–30 cm), but the responses were greater in the subsoil. This can be attributed to the fact that manure was incorporated to approximately 30 cm via moldboard plow. All indicators responded positively to manure, except pH, which decreased slightly in the subsoil in the first year after application. Principal component analysis of chemical and biological indicators, across all years and depths, showed that the first two components explained 62% and 8.5% of the variance. While soil indicators were not adversely affected by manure, silage corn (Zea mays L.) yields in year 1 were significantly lower in manured plots, though in year 2, barley grain (Hordeum vulgare L.) yields were statistically similar among manure and fertilizer.

The effect of potassium on dollar spot of annual bluegrass (ABG; Poa annua L. forma reptans (Hausskn.) T. Koyama) and creeping bentgrass (CBG; Agrostis stolonifera L.) is poorly understood. Two field trials were conducted in 2020 and 2021 to determine the effect of K fertilization on dollar spot of ABG and CBG turf grown on a sand mat layer overlying a sandy loam (fine-loamy, mixed, semiactive, and mesic Typic Hapludults) and mowed at 2.8 mm. A 4 × 2 factorial, randomized complete block design evaluated K (potassium sulfate) applied at 0, 3.4, 6.9, and 13.8 kg ha⁻¹ every 2 weeks and N (urea) applied at 4.9 kg ha⁻¹ every 7 or 28 days over 20 weeks. Infection centers were counted over a 2-week period each year after inoculation with Clarireedia jacksonii in mid-September and used to calculate the disease severity. Increasing K fertilization rate consistently increased dollar spot severity on ABG and CBG. Higher N rate either slightly increased or did not affect disease severity on ABG, and either decreased or had no effect on CBG. This is the first study to document the impact of K fertilization on dollar spot severity of ABG turf. Regression analysis indicated that increases in both leaf tissue and mat layer K were associated with greater dollar spot severity on both species. Future research should determine whether the increased dollar spot response to K fertilization occurs at higher antecedent mat layer and leaf tissue K. Additionally, a broader range of N rates may clarify the dollar spot response.

Cover crops in organic cotton systems can offset the carbon loss typically observed in conventional systems. However, their effects on greenhouse gas (GHG) emissions and soil microclimate are poorly understood. Our objective was to investigate the effects of cover crops on soil carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄) emissions and soil moisture and temperature dynamics in organic cotton systems. To achieve this, we used static chamber techniques with soil sensors in a field study near College Station, TX, from 2020 to 2022. Cover crops tested were oat (Avena sativa L.), Austrian winter pea (Pisum sativum L.) (AWP), turnip (Brassica rapa subsp. rapa), a mixture of all three, and a fallow control. In the first year of organic transition (2020), mixed species treatment enhanced CO₂ emission by 39.6%, 34.4%, and 40% than AWP, turnip, and control, respectively. Compared to the control, N₂O emissions were lower in AWP, turnip, and oat treatments by 77%, 57.2%, and 53% in 2020. Weed pressure and drought in 2021 and 2022 neutralized cover crops’ effect on soil GHG emissions. Soils generally acted as net CH₄ sinks, but the uptake did not differ among the treatments. Cover crops depleted soil moisture during their growing period, but surface residues helped retain more moisture during the cotton season. Compared to fallow, mixed species and AWP were observed to reduce soil temperature fluctuations. Therefore, in transitioning, organic systems effects of cover crops on soil GHG emissions can vary depending on weather, weed management, and the cover crop types.

High-throughput phenotyping is an emerging tool that allows access to identify simple and complex traits, accelerating genetic discoveries and selection. Vegetation indices strongly correlate with several economic crop traits, allowing plant breeders to detect variation in breeding populations. Thus, this study used red–green–blue (RGB) vegetation indices to evaluate the influence of the stink bug complex (Euschistus heros, Piezodorus guildinii, Nezara viridula, Dichelops melacanthus, and Edessa meditabunda) on the agronomical traits of soybean (Glycine max) lineages. For instance, two experiments were conducted to assess soybean resistance to the stink bug complex, (1) with and (2) without pesticide control. An unmanned aerial vehicle coupled with an RGB camera acquired aerial photography over the field during the R5 stage. Four vegetation indices and canopy were estimated from the orthomosaic, and the genotypes were evaluated based on agronomical traits. Linear mixed models were used to estimate the variance and significance test of each trait using the likelihood ratio test, and the principal component analysis was performed to verify the multivariate pattern among genotypes. The results showed significant genotypic effects for most traits with high broad-sense heritability for agronomical traits and moderate for vegetation indices. Significant correlations using best linear unbiased predictions were observed among the agronomical traits with the vegetation indices and canopy coverage, which can be used as a tool for the indirect selection of soybean lineages in the breeding pipeline.

USDA National Agricultural Statistics Service pasture and rangeland condition data were used to establish a novel spatiotemporal climatology of condition ratings across the conterminous United States for the May–October grazing season over the 1995–2022 study period. On average, the coverage of grazing land that provides adequate or excess feed underwent a significant reduction during a typical season. Spatially, the southwestern United States exhibited the poorest grazing land conditions on average, with over 20 years below the national mean condition rating. At the national aggregated level, conditions degraded during the 28-year study period, and the most significant trends were observed for grazing lands considered to have poor or very poor condition coverage, which increased. Robustly increasing trends in poor and very poor condition coverage were most apparent across the western half of the United States, which is predominantly rangeland. Meanwhile, the eastern half of the United States, which is mostly pastureland, generally experienced condition improvements. Overall, continued regional climatic changes that may result in increasing temperatures, variable precipitation totals, and subsequent soil moisture declines leading to increased drought instances will continue to impose challenges for grazing land managers. Grazing land condition declines can result in increased feed supply demand and reduced grazing capacity. Should these trends continue, there will be a growing need for flexible livestock, forage, and grazing management strategies in the coming decades to adapt to climate change-induced impacts on water-sensitive ecosystems.