Agrosystems, Geosciences & Environment最新文献

Teff [Eragrostis tef (Zucc.) Trotter] grass has gained popularity in the United States as an emergency summer forage for livestock due to its drought tolerance and rapid growth habit. An alternative forage would benefit Texas Rolling Plains growers due to the summer forage shortage caused by drought conditions. However, among the teff research conducted in the United States, there is great variability in the forage yields and nutritive values depending on the amount of nitrogen and available water. The objective of the study was to evaluate forage productivity and nutritive value of teff in the Texas Rolling Plains under irrigated and dryland conditions with two nitrogen rates and application timings. Nitrogen fertilizer treatments included single applications of either 50 or 100 lb a⁻¹ applied at planting and a split application of either 50 or 100 lb a⁻¹ applied both at planting and after the first harvest. No differences were observed among nitrogen rates and application methods in the irrigated trial (5286 lb a⁻¹). The split application of 100 lb a⁻¹ produced the greatest total yield in the dryland trial (3096 lb a⁻¹) with no yield advantage of 100 lb N a⁻¹ over 50 lb N a⁻¹ at the first cutting. Forage nutritive values were similar to the warm-season forage species utilized in the region. This study showed that teff can be an alternative forage species in the region. Future research will include planting dates, nitrogen application timing, cutting height, and the interaction of these factors on yield and nutritive values of teff.

Field application of beef cattle feedlot runoff may transport manure-borne microbes and antibiotic resistant bacteria to agricultural soils eventually impacting deeper soils and groundwater. To evaluate this potential, total soil, antibiotic resistance (AR), and fecal indicator bacteria (Escherichia coli and Enterococcus) and the presence/abundance of AR genes were examined to a depth of 1.8 m in an agricultural field receiving long-term application of feedlot runoff and compared to a nearby pasture receiving no runoff. While plate counts of total soil bacteria and cefotaxime-resistant, erythromycin-resistant, and tetracycline-resistant bacteria decreased with depth on both fields (p < 0.001) by an average 2-log₁₀ colony forming unit g⁻¹ to 1.8-m depth, field differences were only observed with greater abundances of total soil and erythromycin-resistant bacteria (p ≤ 0.026) in the runoff-amended versus control field soils. Soil bacterial and fecal indicator bacterial isolates evaluated phenotypically for resistance to 12 antibiotics varied in range and sensitivity. Using a culture-independent approach, erm(C) and tet(Q) were detected using polymerase chain reaction in 31% and 58% of runoff-field samples throughout the soil profile. Detection of erm(C) and tet(Q) in the control field soil profile was less frequent (0% and 11%, respectively). Two other genes, erm(A) and tet(X) were not detected in any soil samples. Based upon these results, long-term applications of beef cattle feedlot runoff may increase the total abundance of microorganisms in the surface and shallow soil, but the relative enrichment of AR was dependent upon the type of resistance evaluated and, more specifically, the genes targeted for analysis.

Cover crops have been promoted for increasing soil organic matter, which is critically low in many mid-Southern US row crop production fields. This study was conducted to inform adaptive management in the early transition period of conservation adoption. Temporal change in soil chemistry was investigated with a split-field experiment conducted over a 3-year period in Mississippi corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotational cropping systems that newly implemented winter cover crops and simultaneously reduced tillage. Relative to the untreated (i.e., winter fallow and multiple tillage passes) half of each study field, the chemical soil properties of the treated (i.e., winter cover crop and reduced tillage) half of each study field were not significantly different at the 0.05 significance level. This was true for soil organic matter, all macronutrients, pH, cation exchange capacity, base saturations, and micronutrients, with the exception of iron. Given these results, it is unlikely that growers adopting cover crops while reducing tillage will be able to accumulate significant soil organic matter in the early transition period.

Applying high carbon (C) additive to cattle pens and land application of the resultant manure mix offers a potential strategy for optimizing manure and soil management while mitigating environmental concerns. An experiment was conducted in western Nebraska from 2019 to 2022 to evaluate the effect of adding coal char (∼290 g C kg⁻¹ by wt.) on feedlot manure's properties and stability and the interacting effect of manure-char on crop yields in a corn (Zea mays L.)–dry bean (Phaseolus vulgaris L.)–corn rotation. Treatments in the crop field included manure from pens with or without char (each at 34 and 68 Mg ha⁻¹; low and high rate), urea at 100% recommended nitrogen (N) rate with or without 45 Mg char ha⁻¹, and a control. Applying char to pens kept them drier following snowfall events. The high surface area and cation exchange capacity of char improved soil and manure nutrient retention. The 100% urea-N plus char treatment had a greater corn yield than the low-rate char–manure mix or high-rate manure in 2020. In 2021, there was a trend for higher bean yields with the high char–manure rate treatment than the control. In 2022, all the fertilized treatments had greater grain yields than the control. A one-time high-rate char–manure mix or manure application could replace 314 kg N ha⁻¹ and 90 kg P₂O₅ ha⁻¹ over 2 years without any yield penalty. This study underscores the synergy between char and manure or chemical fertilizers to improve nutrient balance and supply, ultimately enhancing crop production.

Drought is a major factor affecting coffee production, and different genotypes exhibit varying degrees of resistance to drought stress. We examined root traits and biomasses of drought-resistant (74110, Angafa, Bultum, Chala, and Gawe) and drought-sensitive (75227, Koti, Melko CH2, Menasibu, and Mokah) Coffea arabica varieties at seedling stage under contrasting watering regimes (water stressed and well watered) for 30 days followed by 15 days of recovery to identify the association between drought resistance and root traits and dry matter partitioning, and the impact of drought stress on growth performance of arabica coffee varieties. We used a split-plot design with three blocks, where watering regime was the whole-plot factor and variety was the subplot factor. During water-stress and recovery periods, the interaction effect between watering regime and variety significantly affected root traits and dry matter partitioning, while the watering-regime main effect affected biomass. We observed a higher (1) tap root diameter (0.34 cm), lateral root number (80.7), and root volume (4.7 cm⁻³) for 74110; (2) lateral root number (79.3), specific root length (24.8 cm g⁻¹), and root-mass ratio (0.41 g g⁻¹) for Bultum; and (3) root length density (3.3–5.2 cm cm⁻³), root angle (42.6°–47.8°), root-mass ratio (0.40–0.42 g g⁻¹), and root-shoot ratio (0.67–0.72 g g⁻¹) for Angafa, Chala, and Gawe under water-stressed condition. During both study periods, biomasses were much lower under water-stressed than under well-watered condition. The findings show the association between drought resistance and root traits and dry matter partitioning, and the impact of drought stress on growth performance of young arabica coffee.

To improve cover crops such as peas (Pisum sativum), as rotational partners, intraspecific variation for cover cropping traits such as nutrient mobilization, carbon deposition, and beneficial microbial recruitment must be identified. The majority of research on cover crops has focused on interspecies comparisons for cover cropping variation with minimal research investigating intraspecies variation. To address if variation of cover cropping traits is present within a cover cropping species, we grew 15 diverse accessions (four modern cultivars, three landraces, and eight wild accessions) of pea in a certified organic setting. We measured various cover cropping traits, such as nutrient mobilization, soil organic matter deposition, and microbial recruitment, and quantified the effect of pea accession on the growth and yield of a subsequently planted crop of corn (Zea mays). We discovered that the domestication history of pea has a significant impact on soil properties. Specifically, domesticated peas (modern cultivars and landraces) had higher average plant–soil feedback values for amounts of nitrogen, carbon, and manganese compared to wild peas. Additionally, no variation for prokaryotic recruitment (α- and β-diversity) was observed within pea; however, we did observe significant variation for fungal recruitment (α- and β-diversity) due to domestication and accession. Our results demonstrate that there is variation present in peas, and likely all crops, that can be selected to improve them as rotational partners to ultimately boost crop yields in sustainable agroecosystems.

Potassium (K) is an essential macronutrient involved in many physiological and biochemical functions that affect a plant's susceptibility to disease. These processes include stomatal regulation, enzyme activation, and solute transport, each of which is often discussed through the lens of either plant nutrition or plant disease control. However, the interaction between these stresses and the resulting physiological and agronomic impact is an important consideration when managing a cropping system as a whole and is scarcely addressed in the literature. Therefore, a review of the literature was focused on the interaction of K nutrition and the resulting impact on plant disease control. Nutrient management, especially K, can manipulate these essential plant processes to provide the host plant with either an advantage or disadvantage in disease susceptibility, depending on the pathogen and the situation. Numerous studies have been conducted investigating the individual pathogen and host relationships, concluding that the majority of bacterial and fungal diseases decreased with increasing K nutrition, while viral diseases and nematode infections had inconsistent responses to K nutrition. These differences in the response of disease to K nutrition complicate generalizations across species and environments. Similarly, the impact of K on plant growth is affected by the concentration of each nutrient and its ratio with other nutrients. Therefore, a review of the major physiological processes that depend on plant K nutrition is discussed below with the resulting impact on plant disease control.

Black oat (Avena strigosa Schreb.) might be an attractive forage species in the northeastern United States, since it is generally more heat tolerant and disease resistant than other cool-season grasses. Black oat is currently recommended for fall and winter production in USDA Plant Hardiness ones 8b–10a, which is beyond the northeastern United States (Zones 2a–6a). The objective was to evaluate 10 black oat breeding lines (referred to as “UF1” through “UF10”) for forage accumulation, crude protein (CP), neutral detergent fiber (aNDF), acid detergent fiber (ADF), and in vitro digestible organic matter (IVDOM) concentrations. The experiment was carried out in April–July 2022 in Pennsylvania Furnace, PA. Triticale (× Triticosecale Wittmack cv. TriCal 342) and Legend 567 oat (Avena sativa L.) were included as controls, as well as Haden oat and Gunner triticale, as regionally recommended cultivars. The forage accumulation within the black oat germplasm ranged from 364 to 864 lb dry matter (DM) acre⁻¹, observed in UF7 and UF9, respectively, during the first harvest. During the second harvest, forage accumulation within black oat ranged from 1048 to 1408 lb DM acre⁻¹, from UF8 and UF1, respectively. Crude protein concentrations ranged from 16% to 23% across all black oats, with no differences found within the germplasm. The IVDOM concentrations averaged 78% across all treatments during the first harvest and decreased to 66% during the second harvest. Overall, this study showed that black oat merits further evaluation as forage species in the northeastern United States, but further studies are required to address management of the species.

The production of canola (Brassica napus L.) in the United States is low, whereas the demand is high. Most US canola research is centered in the Midwest, with minimal to no research in Southern states including Mississippi. Therefore, a study was conducted in Mississippi to assess the feasibility of canola as a double crop with soybean (Glycine max L.) rotation and determine its optimum nitrogen (N) requirement. After canola was harvested, soybean was planted within the same experimental plots. In total, six N treatments (0 [control], 34, 67, 101, 135, and 168 kg N ha⁻¹) were applied to canola and replicated four times across all site-years in a randomized complete block design. The application of N increased seed yield, aboveground biomass, and N content compared to the control in canola. Across all site-years, the highest seed yield was 1726 kg ha⁻¹ at 168 kg N ha⁻¹. Moreover, N uptake, plant height, and test weight were highest at 135 kg N ha⁻¹, which were 76%, 21%, and 44% greater than control, respectively. Oil content and seed weight were inversely related to N rates indicating dilution with increased N. Overall, 141 kg N ha⁻¹ was found to be the agronomic optimum nitrogen rate, and no further supplementation was deemed necessary to maximize canola yield in Mississippi. Additionally, the following soybean crop benefitted from the N applied to canola and produced greater yields. This study establishes that canola has the potential for double cropping without adversely affecting subsequent soybean yield, provided optimum N rates are applied.

Abiotic stress conditions caused by increasing anthropogenic activities over the years necessitate using marginal waters in agricultural irrigation and pose a risk to public health by causing salt stress and heavy metal pollution in the soil. The study exposed rocket (Eruca sativa L.), cress (Lepidium sativum L.), and parsley (Petroselinum crispum Mill.) plants to heavy metals (Zn, Cu, Ni, Pb, Cd, and Cr at rates of 300, 140, 75, 300, 3, and 100 mg kg⁻¹, respectively) and salt stress (3, 6, and 9 dS m⁻¹). Both stress conditions affected plant growth negatively. Biomass losses reaching 88% occurred in the rocket, which was determined to be more sensitive to salt stress than heavy metal stress. In parsley, on the other hand, it was determined that the above-ground organs were more affected by salt stress, but the negative effect of heavy metal stress on the roots was higher than salt stress. In cress, the cultivars produced different responses to stress factors. The Zeybek cultivar was more affected by salt stress, and Bahargülü was more affected by heavy metal stress. In general, an increase in macro- and micronutrients was found under stress conditions. In addition, it was determined that the plants were hyper-accumulative in terms of lead absorption and were sorted as cress > parsley > rocket in terms of metal uptake. According to these findings, these plants should be grown taking into account the lead values in the soil, and consumers should be aware that they are a group of vegetables that accumulate lead.