Agrosystems, Geosciences & Environment最新文献

Hemp (Cannabis sativa L.) was re-legalized as an agricultural crop through the USDA 2018 Farm Bill, but cropping guidelines remain limited, especially for floral hemp grown for cannabinoid extraction. In this study, the response of direct-seeded, field-grown autoflower and full-season hemp cultivars to varying rates of applied irrigation was compared over multiple years in a semi-arid environment. Measurements included floral and total biomass, cannabinoid concentration, and cannabinoid yield. The primary flower size did not vary much regardless of irrigation amount, even for plants grown with no supplemental irrigation. As irrigation increased from very low levels up to 100% of the location's potential evapotranspiration (PEt) and beyond, leaf and stem biomass continued to increase as the plants also got taller. Secondary and tertiary flower biomass increased with irrigation, but only up to about 80% of PEt. Above that amount, floral biomass typically plateaued for both autoflower and full-season types. Floral cannabinoid concentrations did not vary much regardless of irrigation amount. Irrigating at rates greater than about 80% of PEt does not generally increase cannabinoid yield. In contrast, under very dry conditions hemp can grow, reach maturity, and produce some flowers and associated cannabinoid yield even when receiving little or no rainfall or irrigation. Thus, growing hemp with low, moderate, or no irrigation in a semi-arid climate may be economically feasible (despite the lower yield) in certain situations, depending on costs of irrigation water, other crop management decisions, and market valuation of end products.

Management practices that increase soil organic carbon (SOC) and nitrogen (N) stocks improve soil health, crop productivity, and agricultural sustainability. Irrigation is crucial in mitigating the effect of sporadic droughts on agricultural productivity in the southeastern Coastal Plains of the United States and is well-recognized for improving SOC and N accrual under semiarid conditions. However, our understanding of its impact on SOC and N storage in sandy soils under humid climates is limited. Our objective was to quantify the differences in SOC and N storage between irrigated and rainfed management in a humid agroecosystem. We sampled four typical southeastern Coastal Plains soils in the United States: Bonneau (BnA), Dunbar (Dn), Norfolk (NkA), and Noboco (NcA), all of which are loamy sand, both in irrigated and rainfed areas of the same experimental field. We found no significant difference in soil respiration (as 3day-CO₂-C), microbial biomass carbon (MBC), hot water-extractable carbon (HWEC), inorganic N, and labile organic nitrogen (LON) between irrigated and rainfed conditions. In addition, we found no difference in SOC and N stocks under the irrigated versus rainfed scenario. Our results indicated that 29 years of supplemental irrigation had no significant impact on soil C and N fractions or SOC and N storage compared to rainfed conditions under continuous long-term conservation tillage.

Eucalyptus trees (ETs) cover approximately 20 million ha globally, with Brazil leading at 5.6 million ha. In Africa, ET plantations span around 1.5 million ha, primarily in South Africa and Ethiopia. In Ethiopia, ET plays a key role in agroforestry, covering 506,000 ha, which represents 90% of all planted trees in the form of woodlots. These woodlots, particularly in the Akaki River catchment, are essential for local livelihoods, providing timber, fuelwood, and construction materials. However, while the socioeconomic benefits and ecological effects of ET are well-documented, the spatial distribution of ET across Ethiopia remains underexplored. Furthermore, previous studies have examined machine learning (ML) algorithms and vegetation indices (VIs) separately for identifying tree species, but limited research has compared these methods for mapping specific land features, such as ET distribution. This study aims to address this gap by comparing ML algorithms, including artificial neural networks (ANN), random forest (RF), and support vector machines (SVM), with VIs like the normalized difference vegetation index (NDVI), green optimized soil adjusted vegetation index, green chlorophyll index, and modified soil adjusted vegetation index to map the spatial distribution of Eucalyptus globulus Labill. woodlots using Sentinel-2 imagery. Our results show that RF outperformed other ML techniques with 96.3% overall accuracy (OA) and a 0.93 kappa coefficient (K), while ANN and SVM attained 88.7% and 81.7% OA, respectively. Among the VIs, NDVI was the most reliable, with an OA of 90.7% and a K of 0.887. We conclude that ML algorithms provide a more robust method for mapping specific land features like ET distribution than VIs. Future research should investigate the effects of ET on ecosystem services, incorporating socioeconomic data and advanced ML techniques, such as deep learning, to enhance mapping accuracy.

Tree cultivation provides food, raw materials, carbon sequestration, and many other ecosystem services. Developing innovative approaches for tree analysis to help optimize their management is crucial. Cherry trees provide numerous health and economic benefits, with Michigan home to 75% of the cherry trees grown in the United States. In this study, we investigated the coarse root architecture of tart cherry trees using non-invasive imaging techniques to reconstruct their spatial distribution and extent. Roots from matured orchards in Michigan were imaged using ground-penetrating radar (GPR) with an 800 MHz antenna. The processed radiograms were analyzed using MALA Vision software, through which a three-dimensional cube was generated. Depth slices extracted from this cube were subsequently analyzed using convolutional neural networks—a novel approach employed to identify and extract root patterns from the imaging data. A nondestructive, controlled root experiment was conducted to validate and assess the detection capabilities of the GPR frequency employed. The findings from this experiment informed the image interpretation process used to reconstruct root geometry. Results indicated that the GPR could detect and reconstruct coarse roots with diameters as small as 4.3 cm. To establish an allometric relationship between root systems and canopy size, an unmanned aerial vehicle was utilized to estimate tree canopy dimensions. Comparative analysis revealed that the lateral extent of coarse roots was approximately 1.2 times larger than the canopy area. Finally, a separate experiment involving root proxies was developed to create a predictive model for root biomass, achieving an accuracy of 95%.

The authors studied the efficacy of six objective-based, reduced tillage cover cropping systems with or without livestock grazing to induce changes in soil condition and soil health on a fine sandy loam during the organic transition phase in the northern Great Plains. A randomized complete block design with a split-plot arrangement and four replicates was used in an experiment conducted at the USDA-ARS Northern Great Plains Research Laboratory, Mandan, ND. Main-plot factors were grazing versus no grazing, while six cover crop mixtures (soil building cover crop mix, pollinator cover crop mix, weed suppression cover crop mix, multipurpose cover crop mix, annual crop rotation, or perennial forage biculture) were the split-plot factors. Soil parameters were analyzed at the beginning and end of the 3-year organic transition period from 0- to 10-cm and 10- to 30-cm depth samples. No cover crop mixtures or grazing effect was observed on wet aggregate stability. However, wet aggregate stability decreased in all treatments after 3 years of organic transition. In general, soil pH decreased with the transition to organic systems. Soil organic C increased in both the grazed and ungrazed perennial forage biculture treatments and the ungrazed soil building, annual crop rotation, and multipurpose cover crop mixes. Soil total N increased under the grazed annual crop rotation. Aggregated soil quality index values did not vary between cover cropping systems after organic transition. Outcomes from this study provided useful insight into perennial and cover crop effects on key chemical and physical properties of soil known to influence crop productivity in semi-arid regions.

Inadequate soil water for timely crop establishment in dryland agricultural production systems of the inland Pacific Northwest is a key limiting factor in crop production. It is important to identify management practices that reduce soil water evaporation in the long fallow season prior to seeding wheat (Triticum aestivum L.) in the fall. In a 2-year study, we assessed the impacts of four residue management approaches (conventional stubble height, high stubble left standing, high stubble mowed in spring, and residue removed) in conjunction with two row orientations (north-south vs. east-west) at low and intermediate precipitation dryland agriculture sites. Soil cores to a 120-cm depth were collected at the beginning and end of each fallow season. Near-surface microclimate data (relative humidity, air temperature, soil temperature, and windspeed) were collected. Taller stubble had significantly lower windspeed compared to short residue heights. Higher soil temperatures were observed where residue was removed, but higher air temperatures were observed in high stubble. Differences in snow capture were noted during one snowfall event with high winds. Row orientation demonstrated little impact on any of the parameters. No statistically significant (p < 0.05) differences were found between treatments in wheat yield, fallow soil water storage, or reference evapotranspiration. The results of this study suggest that while residue management can have effects on microclimate, it did not lead to differences in soil water storage or wheat yield in a climate where little precipitation is received for the last 3 months of the fallow season.

Cover crops are touted for improving soil health, reducing nutrient losses to ground and surface waters, and providing soil protection between cash-crop growing seasons. While they may improve cash crop yield stability and resilience in the long term, cover crops incur seed, planting, termination, and labor costs to farmers while providing little to no short-term revenue. Short growing seasons and harsh winters in many regions make cover crop establishment difficult, resulting in persistent questions about their conservation efficacy and economic feasibility. Row crop farmers with livestock may graze cover crops to defray feed costs, but this increases the importance of cover crop establishment and biomass accumulation. We worked with four farmers in south-central Wisconsin to assess short-term ecological and economic dimensions of rotational grazing of cover crops and to demonstrate “real world” risks in Wisconsin row crop systems. Rotational grazing of cover crops in row crop operations did not appear to impact sensitive soil health indicators, but it did positively affect each farmer's bottom line in the project's first year. In the project's second year, cover crops did not establish well, and only one farmer had a positive economic benefit from grazing cover crops. Nonetheless, all four farmers are determined to plant and graze cover crops in future years. They reported not being discouraged by the “failures” but instead excited for the opportunity.

Palmer amaranth (Amaranthus palmeri S. Watson) is classified as a noxious weed in Minnesota, necessitating its eradication within the state. Manure from livestock fed contaminated feed was identified as a major pathway for the introduction of Palmer amaranth in Minnesota. Black soldier fly larvae (Hermetia illucens L.) (BSFL) are known to feed on organic materials and have been extensively studied for improving manure management. However, little is known about their effect on the fate of weed seeds. Laboratory experiments assessed the effect of BSFL on the fate of Palmer amaranth seeds in dairy manure over a 10-day incubation period. The addition of BSFL during incubation reduced manure weight by 42% compared to a nontreated control. The presence of Palmer amaranth seeds in dairy manure did not impact the biomass accumulation of BSFL during incubation. Palmer amaranth seed recovery from dairy manure was 67%, with no additional reduction observed in the presence of BSFL. Germination of recovered Palmer amaranth seeds dropped to 22% in manure treatments, compared to 64% in a non-manure control seed lot, with no further reduction noted with the addition of BSFL. Overall, mixing Palmer amaranth seeds in manure reduced their emergence to 14%, which could be attributed to the reduction in both seed recovery and germination. However, the addition of BSFL to manure did not affect the number of seeds recovered or their germination.

Bambara groundnut (BG) (Vigna subterranean L. verdc) is a highly nutritious and economically important leguminous crop of African origin that forms symbiotic relationships with nitrogen-fixing rhizobia, but it has a low yield. Currently, there is a paucity of information on effective rhizobium inoculant (to improve the yield) for BG, which are cheaper and safer alternatives to chemical fertilizers. Indigenous rhizobia strains were trapped from 54 farm soils collected at three Nigerian states (Niger, Kaduna, and Kano). Six selected rhizobium strains (Bradyrhizobium spp.) were identified using 16S rDNA sequencing, applied as an inoculant in a field experiment using a completely randomized block design, and compared with USDA110 strain (Bradyrhizobium japonicum), urea fertilizer, and uninoculated plants on two selected BG varieties (TVSU1248 and TVSU 631). Nutrient utilization and nitrogen fixation in plants were determined at 6 weeks, while leaf chlorophyll was determined fortnightly. Seed yield was determined at maturity. The strains increased the %nitrogen (1.33 ± 0.10–≥1.37 ± 0.05), %phosphorous (0.48 ± 0.02–≥0.51 ± 0.02), %nitrogen fixed (21.07 ± 2.38–≥61.30 ± 6.13), nodulation (72.50 ± 21.075–154.00 ± 23.79), and leaf chlorophyll, which was ≥49.74 ± 1.47 mg/L, ≥51.82 ± 1.86 mg/L, and ≥49.65 ± 1.56 mg/L at second, fourth, and sixth weeks after planting, respectively, and the yield of BG (from an average of 398.6 to 1454.725 kg/ha). Seed yield was highest (1869.85 ± 273.68 kg/ha) in BG variety TVSU1248 using BN5 strain. Indigenous Bambara-symbiotic strains significantly increased the seed yields and plant nutrients, showing their potential use as an inoculant to improve the yield of BG.

Grassland management significantly influences soil organic carbon (SOC) and nutrient fluxes. This study investigated the effects of five distinct grassland management types on SOC, nitrogen (N), and phosphorus (P) in Ethiopia's Central Rift Valley. We collected soil samples from random grazing natural grasslands (random grazed); periodically mowed and grazed natural grasslands (mowed-grazed); cultivated, fertilized, and mowed grasslands (cultivated-mowed); periodically mowed area closure natural grasslands (mowed-closed); and protected native forest grasslands (protected forest). We analyzed SOC, labile and stable C fractions, total N, total P, and soil aggregate indices using standard methods, also calculating the C management index and stability ratio. Our findings reveal significant variations (p < 0.01) in SOC fractions across management types. Protected forest grasslands exhibited the highest labile C (1.41%), while random grazed grasslands showed the lowest (0.39%). For stable C, mowed-closed grasslands had the highest (0.92%) and random grazed the lowest (0.23%). Total N ranged from 1.18% in protected forest and cultivated-mowed to 0.04% in random grazed, with total P highest in cultivated-mowed soils. SOC, total N, and total P levels also varied significantly (p < 0.05) with soil depth. The highest total SOC was observed in protected forest, followed by mowed-closed, cultivated-mowed, mowed-grazed, and random grazed. Overall, grassland management practices that minimize soil disturbance, such as protected forest and mowed-closed, proved most effective in enhancing SOC storage and total N content. This study underscores the critical importance of implementing sustainable grassland management to maximize C sequestration in the region.