Agrosystems, Geosciences & Environment最新文献

Winter cover crops (CCs) have the potential to reduce phosphorus (P) loss by temporarily fixing P into CC biomass. A field experiment with no-tillage (NT) and conventional tillage (CT) was used to study the ability of different CC species planted after corn (Zea mays L.) and soybean (Glycine max L.) harvests to reduce the P availability in soil solution. The effect of three crop rotations (corn–no CC–soybean–no CC [C–S], corn–cereal rye (Secale cereale)–soybean–hairy vetch (Vicia villosa) [C–R–S–HV], corn–cereal rye–soybean–oats (Avena sativa)+ radish (Raphanus sativus L.) [C–R–S–OR]) and two tillage (NT and CT) treatments was determined on soil available P and soil solution P content through pan (A horizon) and tension (100-cm depth) cup lysimeters. The experiment was set up as a randomized complete block design with tillage as a split factor with three replicates. Over the study period, incorporating hairy vetch in C–R–S–HV rotation reduced the Mehlich-3 P content in soil by 26%–29% compared to the C–S and C–R–S–OR rotation. Both CC rotations (C–R–S–HV and C–R–S–OR) were effective in reducing dissolved reactive P (DRP) concentration in pan and tension cup lysimeters compared to the C–S in both CT and NT systems. However, these results varied with CC species grown and seasonal variability in precipitation. A significantly lower DRP load with crop rotation and tillage treatments was observed mainly during the CC growing season. During the study period, crop rotations with reduced labile soil P content and DRP loss were ranked in an order of C–R–S–HV > C–R–S–OR > C–S. Overall, this study showed that CCs have the potential in both CT and NT systems to significantly reduce P in soil and soil solution, and these effects are resilient to a wide range of precipitation conditions.

The viability of modern horticulture heavily relies on adopting sustainable practices. Understanding soil spatial variability on heavy clay soils and its impact on young trees is crucial to design suitable soil and water management strategies that guarantee the sustainability of orchards. The objective of this study was to assess in an orchard with heavy clay soils of the Riverine Plain, NSW, the impact of soil spatial variability on the development of young almond (Prunus dulcis (Mill.) D. A. Webb) trees and evaluate the use of remote and proximal sensing tools for identifying threatening factors for the sustainability of the crop. Soil and aerial surveys were used to assess the soil and crop spatial variability in an 8.3-ha irrigation block. The site was divided into five areas based on apparent electrical conductivity (EC_a) measurements where soil samples were collected. Tree growth, soil, and plant water status were monitored in two contrasting areas in EC_a. In the first year of study, a significant and positive correlation was found between EC_a and percentage of ground canopy cover. Soil analysis and soil moisture monitoring revealed that high values of exchangeable sodium percentage, which are indicative of sodic soils prone to dispersion, and limited water infiltration were the cause of the reduced tree growth in areas with low EC_a. The impact of soil spatial variability on tree growth decreased in the second growing season due to weather and water management factors that influenced soil water content. This study showcases the usefulness of remote and proximal sensing in assessing potential soil-spatial-related issues in newly established orchards as well as the impact soil spatial variability can have on tree development in the first years after planting.

Biological nitrogen fixation by rhizobia bacteria plays a pivotal role in sustainable agriculture by converting atmospheric nitrogen into a form that plants can assimilate, thereby reducing the need for synthetic fertilizers. This process can be dramatically reduced by various abiotic stressors. Native rhizobia strains, which are naturally occurring, may be better adapted to the local soil and climatic conditions, making them more resilient to stress factors such as drought, salinity, temperature extremes, and pH variations compared to commercial strains that may have been developed in and for different environments. This study aimed to compare the efficacy of native rhizobia species with a commercial inoculant and uninoculated controls in maintaining nitrogen fixation under induced stress by delayed planting in field peas over two growing seasons (2021 and 2022) in central South Dakota. Our findings indicate that native rhizobia, while not outperforming the commercial inoculant, demonstrated competitive nitrogen fixation capacities. Overall, total nitrogen fixation was not statistically different between a commercial inoculant and native rhizobia formulations. Planting date emerged as a significant factor influencing nitrogen fixation, with later planting substantially reducing overall effectiveness. These results highlight the potential of native rhizobia as an alternative to commercial inoculants and underscore the need for increased screening throughput and improved methods to assess rhizobia efficacy and nodule competition in field settings.

Microplastics (MPs), formed from the physical breakdown of larger plastics, have been found across a variety of ecosystems. Much research has been done on the effects of MPs in aquatic ecosystems, but fewer studies have explored their effects in terrestrial environments, particularly in agroecosystems where modern practices contribute strongly to MP soil pollution (e.g., plasticulture, fertilization with contaminated biosolids, and composts). Aquatic pharmaceutical contamination is also considered an emerging pollutant threat. Naproxen, a commonly used drug, has been found in wastewater and natural freshwater bodies globally. Thus, crops may be exposed to multiple pollutants simultaneously through soil and water inputs. Our research provides insight into the individual and interactive effects of soil MP pollution intensity and exposure to naproxen-contaminated water on growth and development of Lactuca sativa (lettuce). Soil abiotic factors (pH, electrical conductivity, and rates of soil moisture loss) are also reported. We found that 7% polyester MP-contaminated soil significantly reduced total aboveground biomass and coarse root biomass, while both 0.03% and 7% polyester MP-contaminated soil significantly reduced leaf count and average leaf size. However, 1 mg/L naproxen had no effect on plant growth or development, and there were no interactive effects of naproxen with MPs. MPs also significantly increased rates of soil moisture loss, but we found no effects of MPs or naproxen on soil pH or electrical conductivity. Predicted global increases in soil MP contamination levels will potentially have negative consequences for food systems.

Remote sensing tools, along with Global Navigation Satellite System cattle collars and digital soil maps, may help elucidate spatiotemporal relationships among soils, terrain, forages, and animals. However, standard computational procedures preclude systems-level evaluations across this continuum due to data inoperability and processing limitations. Deep learning, a subset of neural network, may elucidate efficiency of livestock production and linkages within the livestock-grazing environment. Consequently, we applied deep learning to environmental remote sensing data to (1) develop predictive models for yield and forage nutrition based on vegetation indices and (2) at a pixel-level (per 55 m²), identify how grazing is linked to soil properties, forage growth and nutrition, and terrain attributes in silvopasture and pasture-only systems. Remotely sensed data rapidly and non-destructively estimated herbage mass and nutritive value for enhanced net and primary productivity management in livestock and grazing systems. Cattle grazed big bluestem (Andropogon gerardii ‘Vitman’) with 182% greater frequency than orchardgrass (Dactylis glomerata L.) in the pasture-only system. Real-time estimates of vegetative bands may assist in predicting grazing pressure for more efficient pasture resource management. Cattle grazing followed distinct soil-landscape patterns, namely reduced cattle grazing preference occurred in areas of water accumulation, which highlights linkages among terrain, soil-water movement, soil properties, forage nutrition, and animal grazing response spatially and temporally. Results from this study could be scaled up to improve grazing management among the largest land-use category in the United States, that is, grasslands, which would allow for sustainable intensification of forage-based livestock production to meet growing demands for environmentally responsible protein.

Increasing soybean [Glycine max L. (Merrill)] productivity relies heavily on optimizing crop geometry, encompassing both inter- and intra-row spacing. This crucial agronomic practice directly impacts the productivity of soybean crops, making it vital for farmers to consider soybean maturity group when determining optimal crop geometry. Hence, the study was conducted to determine the effect of inter- and intra-row spacing on yield and yield components of soybean varieties and to determine appropriate plant spacing for each maturity group of soybean varieties to achieve a high yield of soybean in the study area. Two soybean varieties from each maturity group, four inter-row spacing (30, 40, 50, and 60 cm), and two intra-row spacing (5 and 10 cm) were arranged in factorial combinations in randomized complete block design with three replications. The results showed that days to flowering, days to maturity, plant height, number of seeds/pod, number of pods/plant, and 100-seed weight were significantly influenced by the main effect of varieties, inter- and intra-row spacing for each maturity group of soybean varieties. The highest grain yield was recorded from narrow inter-row spacing for early and medium maturity groups regardless of intra-row spacing while the highest grain yield was obtained from 50-cm inter-row spacing for late maturing groups. Thus, it can be concluded that 40-cm inter-row spacing is recommended for early and medium soybean varieties, while 50-cm inter-row spacing is recommended for late-maturing soybean varieties for western parts of Oromia and similar agroecologies.

Adoption of dicamba-tolerant soybeans contributed to widespread reports of chemical trespassing on adjacent, sensitive soybeans. Reports of the impact of dicamba on sensitive soybeans (Glycine max L.) have been well documented; however, the potential for dicamba carryover into harvested beans from sensitive plants has largely been overlooked. Field trials in central Missouri focused on assessing the injury and yield response of sensitive soybeans to concentrations of dicamba as low as 0.25% of the use rate (10 µL L⁻¹ dicamba). In both 2018 and 2019, dicamba-sensitive soybeans were planted in conventional row spacing and treated with 10–300 µL L⁻¹ dicamba at both V3 and R1 soybeans. Dicamba symptoms were visible in less than 7 days after application (DAA); significant injury was observed at 10 µL L⁻¹ and persisted through the duration of the study (28 DAA). Injury levels reached almost 50% with 300 µL L⁻¹ dicamba. Step-wise increases in soybean yield losses occurred with increasing dicamba concentrations and reached 50% with 300 µL L⁻¹ dicamba. Yield losses were up to 10% greater for R1 versus V3 soybeans treated with the same dicamba concentration. Dicamba residues in bean tissue ranged from 0.72 to 0.81 mg kg⁻¹ for 150 to 300 µL L⁻¹ dicamba, and residues were similar for beans at both V3 and R1. Dicamba persisted in beans harvested up to 122 days after plant exposure to dicamba. Although dicamba residues were within limits established by the EPA (10 mg kg⁻¹), residues exceeded that allowed in marketed, organic soybeans (0.5 mg kg⁻¹).

Purple nutsedge (Cyperus rotundus L.) poses a significant challenge to Florida tomato (Solanum lycopersicum L.) producers due to its ability to puncture plastic mulch, resilient tubers, and rapid rhizome proliferation. Preemergence herbicides effectively suppress purple nutsedge in tomatoes under plastic mulch. Although the impact of co-application of herbicides with fertilizers has been studied in row crops, its potential in vegetable plasticulture systems remains unexplored. This study aimed to evaluate the effectiveness and crop safety of the preemergence herbicide S-metolachlor, both as a standalone treatment and in combination with a fertilizer enhancer or chelated iron in tomato plasticulture. Field trials at the University of Florida's Southwest Florida Research and Education Center, Immokalee, FL, involved applying S-metolachlor at the recommended rate of 1 kg a.i. ha⁻¹ on raised beds before installing plastic mulch. The herbicide was applied as a blanket spray alone, mixed with fertilizer enhancer, and coated on chelated iron fertilizer. Results indicate that using S-metolachlor alone effectively reduced purple nutsedge density compared to the nontreated control in both trials I and II. Combining S-metolachlor with fertilizer enhancer or chelated iron resulted in a >30% and 57% reduction in purple nutsedge density, respectively, compared to the nontreated control in trial II. These treatments did not adversely impact chlorophyll content or crop yield (p > 0.05) compared to the nontreated control. Notably, tomato yield significantly (p < 0.05) decreased with increased purple nutsedge density at 4, 8, and 12 weeks after transplanting. Overall, the results from both trials suggest that using S-metolachlor is an effective approach to reduce purple nutsedge infestation in plastic-mulched raised beds without negatively impacting tomato health and productivity.

Biofertilizers can be better alternatives to chemical fertilizers to enhance plant nutrition and productivity as they improve the soil fertility and crop productivity in an eco-friendly and cost-effective manner. A pot experiment was conducted between December 2018 and March 2019 in southern Ethiopia to evaluate the combined inoculation of arbuscular mycorrhizal fungi (AMF) and Meso-rhizobium (MR) on biomass yield, nutrient uptake, and moisture stress tolerance of chickpea (Cicer arietinum L.) (variety: Habru). The experiment was executed as a factorial arrangement using a completely randomized design with three replications. The treatments were control (non-fertilized), sole AM fungi inoculation, AM fungi inoculation with phosphorus fertilizer (20 kg P ha⁻¹) and MR, and sole inorganic fertilizers (20 kg P;10 kg N ha⁻¹) at four different moisture levels (optimum throughout the growing season, stressed at vegetative, flowering, and seed filling stages). The results demonstrated that biomass yields were limited by moisture stress, especially at vegetative and flowering stages of chickpea. Sole and co-application of AMF with MR and inorganic P increased biomass yields on average by 19%, 39%, and 33% under water stress conditions, respectively, compared to the non-inoculated control. The application of AMF with MR and inorganic P also significantly increased nodulation, AMF colonization, and nutrient uptake, but these effects were dependent on soil moisture status. In conclusion, there are potential advantages to be gained from sole and combined AMF application with rhizobium to improve growth and productivity of chickpea through enhanced nutrient and water uptake, though the results of this pot experiment should be validated through field trials.

Field trials were conducted in 2021 and 2022 to evaluate the effects of planting date (mid-March, mid-April, and mid-May) on 11 fiber hemp (Cannabis sativa L. <0.3% total tetrahydrocannabinol) varieties. Trials were conducted in Goldsboro, Kinston, and Salisbury, NC. Each location followed a split-plot randomized complete block design with at least three blocks where planting date was the main-plot and variety the sub-plot. Varieties investigated originated from China and Australia (2021 only). Data collection included flowering time, end of season stand counts, stem height, diameter, and final retted dry straw yield. We found differences among the varieties investigated in both years; however, no distinct trend was observed across years. All varieties investigated flowered at the end of August and beginning of September, allowing for a long growing season and ability to produce abundant biomass. In general, the Chinese genetics yielded higher stem biomass compared to previously reported European genetics. Stem thickness was >7.5 mm, which is generally considered the maximum width for textile-grade fiber production. To achieve thinner stems from the varieties investigated, harvesting prior to male-flower initiation may be required. The crop experienced temperatures below freezing in both years with no signs of damage. Taken together, farmers seeking to plant fiber hemp in North Carolina have a wide planting window from mid-March to mid-May using these Chinese varieties.