Agrosystems, Geosciences & Environment最新文献

Zinc (Zn) fertilization of hard red and soft white winter wheat (Triticum aestivum L.) is uncommon in the low precipitation zone of the inland Pacific Northwest. It is uncommon because there have been no indications of deficiency. Soil test data, however, show Zn levels have been declining over time. We conducted a four-site-year experiment to evaluate effects of fertilization on early-season tissue Zn concentration (TZC), dry matter accumulation (DMA), Zn uptake (ZNU), the grain test weight (TWT), protein content (PRO), and yield (YLD) of two regionally adapted cultivars. Planting occurred late in September or early in October. Zinc fertilizer, placed with the seed while planting, was applied at rates of 0 and 5 kg Zn ha⁻¹. Application of 5 kg Zn ha⁻¹ increased TZC and ZNU at one of two sites. There were corresponding trends of increased DMA and improved YLD. Response to fertilization occurred on a relatively shallow soil that had a diethylenetriamine-pentaacidic acid–extractable Zn test level of 0.3 mg kg⁻¹.

Since the adoption of national rules for organic agriculture in the United States, there has been a continued interest in meeting crop nitrogen (N) needs using animal manure. However, a lack of consistent information on the N supplying potential of manure creates uncertainty for farmers and often leads to overapplication, which can negatively impact both crop productivity and environmental sustainability. We investigated short-term N mineralization and microbial biomass carbon (MBC) and nitrogen (MBN) following dairy manure (DM) and its compost (DMC) application to organic annual forage production system. N mineralization was determined based on the change in mineral N during a ≤75-day in-field soil core-resin bag incubation. DM and DMC application rates were targeted to supply 123 and 56 kg potentially plant-available nitrogen (PAN) ha⁻¹ in the first and second year of application, respectively. Net N mineralization exhibited a range of 42–277 kg N ha⁻¹ in Year 1 and 31–54 kg N ha⁻¹ in Year 2 across amendment treatments and increased over the course of incubation duration in both years. The proportion of total N added that was mineralized in Year 1 was greater from DM than DMC (≤35% vs. ≤7%, respectively), suggesting the inability of DMC to supply optimal levels of N to annual forages in the first crop season. In Year 2, net N mineralization did not differ between DM and DMC, but was significantly less in the unamended control than both amendments. MBC and MBN were more influenced by seasonality and soil sampling depth than by organic amendments.

A sorghum sudangrass (SSG) cover crop grown after a cash crop could take up residual nitrogen (N) before it is lost. As in-field monitoring of SSG properties is laborious, predicting biomass and N concentrations with spectral sensors could be useful. At two sites in Live Oak, Florida, we evaluated the response of SSG to residual N from previous N fertilization and the performance of handheld and satellite sensors in estimating SSG properties. We quantified aboveground biomass, plant N, leaf greenness (NDVI), net potential N mineralization (PNM), and soil permanganate oxidizable carbon (POXC). Residual N did not affect SSG properties, PNM was highest at the highest N input rate in one site, and soil POXC was correlated with SSG properties (biomass and plant N). NDVI measured from a handheld sensor better predicted SSG properties than satellite imagery in these small plots, suggesting a greater potential to be a useful management tool.

In the last four decades, the Jiangsu province, like the rest of China, has undergone rapid economic development coupled with a rapid increase in environmental pollution. Freshwater ecosystems have been particularly affected. In Lake Tai, China's third-largest freshwater lake by volume, water quality has been severely reduced. There is a renewed interest in establishing riparian buffer strips in China as a conservation practice for mitigating agricultural non-point source pollution. To study the effect of riparian buffers on phosphorus attenuation, eight 50 m × 20 m plots were established between a rice farm and the shore of Lake Tai in China, with the 20 m width facing the lake shore. They were planted with hybrid poplar (Populus deltoides × euramericana), hybrid cypress (Taxodium ascendens × mucronatum), or a mixture of both at densities of 2 m × 3 m, 2 m × 5 m, or 5 m × 5 m, while one plot was left as a control. Samples collected from soil, tree leaves, and groundwater during 2014–2018 were analyzed for multiple forms of phosphorus. Results indicated that riparian buffer width and time (year) were the most significant factors of phosphorus attenuation on all plots. Tree density had a minor effect, with medium density being the most effective, and we found negligible differences among hybrid tree species on attenuating phosphorus. Farmers should use densely vegetated buffer strips at least 15 m wide to ensure a significant reduction in nutrient runoff. Species selection should be based on market value and ecological benefits.

The value of glyphosate to growers practicing minimum or no-till farming has been primarily a function of three factors: broad-spectrum weed control, little to no carryover effect, and cost effectiveness. A 2-year field study was conducted in 2021 and 2022 at the University of Idaho Research and Extension Centers at Kimberly and Aberdeen, ID, to evaluate the efficacy of alternative pre-plant burndown herbicide treatments as compared to glyphosate treatment, the industry standard in small grain production systems. Herbicide cost comparison and crop injury observation were also conducted. Most herbicide treatments provided $�\ge$90% control of the predominant weed species at 3 weeks after herbicide application. At least six different herbicide treatments had an equivalent cost to that of glyphosate at $26.50 ha⁻¹. No observable damage from herbicide treatments was observed and crop yield was not affected by the treatments. These factors indicate that there are alternatives to pre-plant burndown herbicides that are equally effective as glyphosate. With combinations of herbicides, each having a different site of action, weed control can be achieved while simultaneously reducing the risk of herbicide resistance.

Little information is available on optimizing the number of nitrogen (N) splits based on nitrate (NO₃-N) leaching and maize yield in sandy soils. To address this gap, we evaluated the impact of multiple N splits (2-, 3-, 4-, and 5-N splits) on NO₃-N leaching and maize (Zea mays L.) grain yield in irrigated loamy sand soil at a producer site in the Bazile Groundwater Management Area of Northeast Nebraska. Porous suction cup lysimeters were installed at a depth of 120 cm to collect pore water samples from 23 leaching events in 2021, a dry year. Increasing the number of N-splits did not affect the pore-water NO₃-N concentration; however, it was 169%, 152%, 150%, and 129% higher in 2-, 3-, 4-, and 5-N split treatments compared to control, that is, without N application. Though the 2-, 3-, 4-, and 5-N splits had 110%, 71%, 120%, and 91% higher area-based NO₃-N leaching than the control, less deep percolation and more evapotranspiration in control led to no significant differences in area-based NO₃-N leaching among all treatments. All N-splits resulted in higher maize yield, nitrogen use efficiency, plant N uptake, harvest index, and aboveground biomass than control; however, the number of N-splits did not affect these parameters. The inclusion of environmental cost reduced the return to nitrogen by 92–143 $ ha⁻¹ across all N-split treatments but did not significantly affect the differences among the splits. Overall, the results indicate that increasing the number of N-splits does not provide agronomic, economic, and environmental benefits in irrigated maize fields during a dry year.

California produces many key agricultural products in the United States. Current geospatial agricultural datasets are limited in mapping accuracy, spatial context, or observation period. This study uses machine learning and high-resolution imagery to produce a time series of crop maps to assess crop type trends and patterns across central California from 2005 to 2020. National Agriculture Imagery Program and Landsat imagery were used to classify nine crop types that are common in the study region: grain crops, field crops, rice, citrus and subtropical, deciduous fruit and nut, vineyard, berry and vegetable, pasture, and fallow/young perennial crop types. To create labeled data, we sampled 1253 fields and manually identified crop types for each examined year using high-resolution imagery and Landsat normalized difference vegetation index time series. We applied a random forest machine learning algorithm in Google Earth Engine. Results show that the mean overall classification accuracy of the nine-class map was 93.1%, with individual accuracies ranging from 99.3% (rice) to 89.5% (fallow/young perennial). Mann–Kendall trend tests showed significant (p < 0.05) declines in field crop and pasture area during the study period, while deciduous fruit and nut, citrus and subtropical, and fallow/young perennial crop types experienced significant increases. At an aggregate level, there was a general shift from annual crop types to perennial crop types. These data provide a 16-year time span of spatially explicit crop type classifications, trends, and patterns in central California that can be used to aid managers and decision makers for resource planning or hazard mitigation.

Understanding the trade-offs between improving turfgrass performance and seed production capacity would improve acceptance and accelerate the release of new perennial ryegrass (Lolium perenne L.) cultivars. An experiment was designed to measure the turfgrass quality, seed yield, and component traits among 20 perennial ryegrass entries grown in turfgrass and seed production swards at two locations in Minnesota, a seed production region of the United States. Turfgrass quality scores, when averaged across collection dates, were not strongly correlated with seed yield at either location. However, data from several individual turfgrass quality rating dates were moderately correlated with seed yield at both locations (p < 0.100). Within the dates that correlated with seed yield, turfgrass component traits were regressed against quality scores. Crown rust severity, color, and density were important in the first year, and winter injury and texture were important in the second year. Plots with more fertile tillers were associated with higher seed yield and lower turfgrass quality (p < 0.050), but there was no relationship between entries in the two growing environments for fertile tiller production (p > 0.250). Entries that exhibited a faster vertical growth rate in turfgrass swards tended to mature earlier in seed plots, a trait that was correlated with higher seed yield (p < 0.001). However, the vertical turfgrass growth rate was not directly correlated with seed yield (p > 0.800). Few tradeoffs between the growing environments were found under the growing conditions and germplasm employed.

Upland cotton (Gossypium hirsutum) production is important for the economy of the Texas High Plains (THP). This region of Texas is semi-arid and regularly experiences harsh weather conditions that can be difficult to predict. Some years, a cold front will pass through the area before local cotton crops have reached maturity and there are concerns that fiber maturation stops after these cold weather events. In 2020, fiber samples were collected at two locations on the THP (representing northern and southern cotton producing regions) before, during, and after a cold front (<10°C) moved through the area in September, which is a critical period for fiber maturation. Single boll samples were taken at New Deal, TX (representing a southern location) in the first position from nodes 5, 8, and 11. At Etter, TX (representing a northern location), 30-boll bulk samples were taken from first position bolls on nodes 5, 8, and 11. Advanced fiber information system testing determined the fiber quality of single boll samples. Lint weight in both locations continued to increase despite the cool temperatures. At New Deal, upper quartile length, length, short fiber content, seed coat neps, fineness, and maturity all saw significant improvements from before to after the cold front. This indicates that the bolls continued developing after exposure to cool temperatures on the THP.

Interseeding annual warm-season forages into perennial cool-season grasses may increase herbage mass and quality. Yet, methods to do so successfully remain elusive. From 2020 to 2022, we conducted an experiment that evaluated herbage mass responses to sod suppression after interseeding sorghum × sudangrass [Sorghum bicolor (L.) Moench × S. bicolor (L.) Moench ssp. drummondii (Nees ex Steud.) de Wet & Harlan] in three N-fertilized and three mixed-legume smooth bromegrass (Bromus inermis Leyss.) pastures. Sod suppression treatments included glyphosate [N-(phosphonomethyl) glycine] applications of 0, 0.55, 1.10, 1.65, and 2.20 kg ha⁻¹ on pastures that were heavily grazed in two rotational stocking periods in spring and an additional 0 kg ha⁻¹ glyphosate control where herbage was stockpiled throughout spring, mowed, and removed before interseeding sorghum × sudangrass. In herbage samples collected 8 weeks after treatment, perennial grass mass showed exponential decay responses as glyphosate rate increased, while sorghum × sudangrass, weedy grass, and total herbage mass showed logistic growth responses. Sorghum × sudangrass reached a high of 2316 kg ha⁻¹ as glyphosate rate increased to 1.65 kg ha⁻¹ while weedy grass mass continued to increase as glyphosate rate increased to 2.20 kg ha⁻¹. Reduced perennial grass mass in herbage samples collected the next spring indicated the presence of a tradeoff between increasing summer herbage now and reducing next spring herbage later with glyphosate application after interseeding sorghum × sudangrass. We concluded practitioners should not use glyphosate for sod suppression before interseeding warm-season annual forages into perennial cool-season grass pastures.