Fallow Control Research Articles

Sprouting and Growth of Garlic (Allium sativum L.) At Green Stage Under Various Nutrients.

Garlic (Allium sativum L.) is a vital crop, yet its growth and sprouting at the green stage can be significantly influenced by nutrient availability, which poses a challenge for optimizing yield and quality. The present research was carried out in 2022–2023 at the Nursery Department of Horticulture, Sindh Agriculture University Tandojam, to assess the sprouting and growth of garlic (Allium sativum L.) at green stage under various nutrients. The experimental trial was carried out in complete randomization (CRD) with three replications. Two varieties, a Chinese and a local (Desi) (Desi) variety, were grown in the pots. Macronutrients used as treatments included N1 (control). N2 = NPK+TE (trace elements) 2 g, L-1. N3 = Calcium Nitrate 0.5g, L-1 and N4 = NPK+TE 2g, L-1 + Calcium Nitrate 0.5g, L-1. The results of the present studies showed a statistically significant difference for treatments and nutrient combinations. Best results for all observations were noted in plants supplied with NPK+TE 2g L-1 that had maximum plant height 55.83 cm, leaves plant-1 6.83, leaf length 47.66 cm, leaf weight 8.96g, plant weight 13.20g, neck thickness 6.55mm, root weight 2.68g, and root depth 19.83cm. Fallow control plant height 41.00cm leaves plant-1 5.00, leaf length 31.00cm, leaves weight 4.73g, plant weight 7.61g, neck thickness 3.51mm, root weight 1.46g and root depth 12.00cm. In between varieties the Chinese had maximum plant height 54.66cm, leaves plant-1 7.00, leaf length 45.00cm, leaves weight 10.04g, plant weight 10.99g, neck thickness 8.26mm, root weight 2.81g and root depth 22.00cm. Based on nutrients, the Chinese variety of garlic performed better growth at the green stage than the local (Desi) variety of garlic. The findings of this study show that nutrient N2 = NPK+TE (Trace Elements) 2g L-1had better results for all parameters, and all results were statistically significant.

Cover crop mixtures do not assemble markedly distinct soil microbiotas as compared to monocultures in a multilocation field experiment

Cover crops are used in cropping systems to enhance ecosystem services, such as soil resilience to erosion or microbial activity. Different cover crops are selected to steer specific processes, but whether cover crop mixtures have an added value over monocultures remains debated. Here, we investigated if cover crop mixtures accumulate soil microbiotas distinct from those of monocultures, potentially leading to more varied microbially-driven soil functions. We performed a field experiment at three locations in the Netherlands, each including nine cover crop monocultures, five- and eight-species mixtures, and a fallow control. After three months, we measured cover crop biomass and profiled soil bacterial, fungal, and arbuscular mycorrhizal fungal communities via amplicon sequencing. The different crop monocultures produced similar biomass across all three locations, and mixtures had average productivity compared to monocultures. The diversity and community structure of soil microbial communities was primarily determined by the geographical location, and then by cover crop treatment at each location. Although the cover crop species affected the soil microbiome differently, cover crop mixtures did neither increase microbial diversity nor the overall community differentiation compared to monocultures. Our results suggest that mixing cover crop species does not significantly influence microbially-driven soil functions, at least in short-term crop rotations.

Winter cover crops and irrigation alter soil microbial community composition in an arid cropping system

Cover cropping is a well-established strategy to improve soil health, especially in arid and semi-arid agricultural systems. Benefits to soil health are often mediated via effects of cover crops on soil microbial community structure, function and diversity, crucial for regulating soil biogeochemical cycles, eventually promoting agricultural sustainability. However, limited water availability is a major constraint for both cover crop growth and soil microbial activity. This study sought to characterize and elucidate the shifts in soil microbial community structure in response to different cover crops and differential irrigation treatments using phospholipid fatty acid (PLFA) profiling in southern New Mexico. We tested five cover crop treatments: Pisum sativum (Australian winter pea), Hordeum vulgare cv. Stockford (barley), Brassica juncea cv. Caliente 199 (brown mustard), a three-way mix, and a fallow control — in combination with irrigation treatments of one, two, or three irrigation applications — in a split-plot design over two years. Zea mays (sweet corn) was grown as the summer cash crop. We collected soil samples just after cover crop planting in the fall of 2018, following second year cover crop termination but during Z. mays growth in June 2020, and after the second season of Z. mays growth in October 2020. Differential irrigation treatments did not lead to consistent patterns of change under any cover crop or irrigation treatment. However, PLFA parameters in cover cropped compared to winter fallow plots tended to decrease under one and three irrigations but increased with two irrigations. Changes were more common for bacterial than for fungal PLFA biomarkers, and more common in B. juncea and H. vulgare cover crops than in P. sativa or the mix. It is important to note that, while cover crop effects were inconsistent, cover cropping did lead to some shifts in PLFA biomarkers, even in the short two-year period of cover cropping.

Winter cover cropping to improve soil health in semiarid, irrigated cropping systems of Central Oregon

AbstractA 1‐year experiment was conducted in Madras, OR, to examine the ability of winter cover crops (CCs) to improve physical, chemical, and biological soil properties over a bare fallow control. Competition for water is frequently seen as an obstacle to cover cropping in semiarid, irrigated systems. Benefits from CCs need to be demonstrated and quantified in regions such as Central Oregon's high desert for growers to make cost/benefit analysis decisions. To support such decisions, the effect of eight winter CC treatments (two brassicas, four legumes, two cereal mixtures) on five agronomic parameters and 39 soil health indicators (0–5 cm) were measured in the spring of 2019 after 8 months of CC growth. We identified four soil indicator response patterns in reference to the fallow: (i) steady improvement over fallow across all CCs (16 indicators, with hairy vetch and turnip being most efficient); (ii) marked improvement over fallow but somewhat constant response among CCs (organic C and N, surface hardness); (iii) negligible change from fallow; and (iv) varied response to CCs including both a deterioration and an improvement of soil health. Overall, 13 soil health indicators and five agronomic parameters responded significantly to CC treatment. CCs generated a stronger response of soil chemical and biological parameters than physical (average 82%, 79%, and 18% improvement over fallow, respectively). Hairy vetch had the greatest positive impact on soil biological and chemical properties but the lowest average impact on physical indicators. Winter CCs do offer soil health benefits in Central Oregon but should not be viewed as a short‐term fix to physical soil deficiencies. Our study provides strong evidence for the general ability of CCs to improve soil health in water‐limited systems. It also demonstrates the need for further studies focused on multiyear rotations, especially related to the improvement of soil physical properties such as soil moisture availability.

Partial substitution of chemical fertilizer by green manure increases succeeding maize yield and annual economic benefit in low‐yield cropland in the Yellow River Delta

AbstractGreen manures (GM) combined with fertilizer reduction is an efficient measure to alleviate the environmental issues caused by the overapplication of chemical fertilizer. However, both the environmental and economic benefits remain unclear in coastal regions that are affected by both soil salinization and climate change. A field experiment was conducted in low‐yield cropland in the Yellow River Delta to explore the effects of green manure rotation combined with fertilizer reduction on the soil environment and economic sustainability. Two GM species, Vicia villosa (HV) and Orychophragmus violaceus (OV), a traditional winter wheat (Wheat), were grown in winter, with a fallow control (Fallow). In the subsequent maize season, three fertilizer rate treatments, a full rate of 600 kg ha−1 compound fertilizer (F100), 85% of the full rate (F85), and 70% of the full rate (F70), were applied in each former treatment. The results indicated that GM return markedly increased soil total N (TN) and P (TP) before the V6 stage of maize (when maize had 6 leaves). The average TN contents of HV and OV increased by 56.9% and 38.5%, respectively, compared with that of Wheat, while the values for TP were 13.6% and 16.9%. Compared with Fallow, the maize yields of HV and OV increased by 25.6% and 13.8%, respectively, while that of Wheat decreased by 9.1%. The average partial fertilizer productivities (PFPs) for HV and OV increased by 25.3% and 14.0% compared with Fallow, while Wheat decreased by 8.9%. The PFPs for F85 and F70 increased by 19.4% and 37.7%, respectively, compared with F100. Reducing the fertilizer rate to 70% in the HV–maize rotation pattern did not reduce but increased the total net profit and rate of return. Thus, HV–maize rotation combined with 30% fertilizer reduction is suggested for sustainable agriculture in this region.

Influence of Soil and Nutrient Management Practices on Crop Productivity and Quality in High Tunnel Organic Leafy Green Production

Despite the growing interest in high tunnel organic vegetable production, limited information is available regarding optimizing nutrient management for organic leafy greens. This 3-year study examined the impacts of cowpea cover crop as well as different organic fertilizers and composts on yield, leaf mineral nutrient content, and phytochemical properties of organic leafy greens produced in high tunnels under Florida sandy soil conditions. The experiment was arranged in a split-split-plot design with three replications. The whole plots consisted of a cowpea (Vigna unguiculata ‘Iron & Clay’) cover crop and a weedy fallow control, with fertilization treatments in the subplots, including preplant application of granular fertilizer vs. weekly injection of liquid fish fertilizer at the same seasonal rates of nitrogen (112 kg/ha), phosphorus (9.8 kg/ha), and potassium (74.4 kg/ha). The sub-subplots included yard waste-based compost (22.4 Mt/ha), cow manure-based compost (22.4 Mt/ha), vermicompost (5.6 Mt/ha), and no compost control. Cowpea was broadcasted (112 kg/ha) in early July or mid-August and terminated 51 to 53 days after seeding. Pac choi (Brassica rapa var. chinensis ‘Mei Qing Choi’) was transplanted in mid-Sep. or mid-Oct. and harvested after 33 to 36 days. Baby spinach (Spinacia oleracea ‘Corvair’) or baby leaf lettuce (Lactuca sativa ‘Outredgeous’) was direct seeded subsequently as a catch crop. Each experimental unit remained in the same location across the 3 years of the study. Cover cropping had little influence on yields, leaf mineral nutrients, ascorbic acid content, total phenolics, and total antioxidant capacity of pac choi and baby spinach/lettuce. Compared with preplant application of the granular organic fertilizer, weekly liquid organic fertigation improved pac choi marketable yield and dry weight by 16.8% and 5.4% on average, respectively, and enhanced leaf nitrogen and phosphorus contents on a dry weight basis. Relative to the no compost control, yard waste compost consistently improved marketable yields of pac choi by 11.6% on average and led to higher yields of the baby spinach/lettuce catch crop in years 1 and 3, suggesting that compost applications may enhance seasonal nutrient availability to better meet crop demand. However, compost application exhibited inconsistent effects on crop mineral nutrient and phytochemical contents across the years, which could be attributed to the different nutrient compositions of the composts applied in each season, as well as the legacy effects from the previous season. Furthermore, the compost benefits may be influenced by the fertilization program as indicated by their interaction effects observed in this study.

Fall/winter cover crop roots change soil hydrology to control the drought status of subsequent season summer maize in Ultisol

Climate change has increased drought frequency, necessitating strategies to reduce water stress, increase water use efficiency, and improve agricultural productivity. The impacts of different fall/winter cover crops on alleviating maize drought in the subsequent season by changing soil water content remain unclear in Ultisol. Our aim was to investigate whether different fall/winter cover crops (taproot and fibrous root) can improve soil water content to attenuate subsequent season maize drought and its underlying mechanism. This research compared four fall/winter cover crops (2 rapeseed cultivars, lucerne and vetiver) and fallow control (no cover crop in winter) to investigate their root traits, root effect on subsequent season soil water content (SWC), soil drought degree (D), maize leaf and root water potential (Ψl, Ψr), maize crop water stress index (CWSI), and maize growth components (aboveground plant and root parameters) in 2019 (a dry year), 2021 (a normal wet year), and 2022 (a severe dry year). The fibrous-rooted vetiver displayed higher average root diameter and higher average root length density, leading to increased SWC (17%, 15%, 15%), and lower D values in all three years. Additionally, it exhibited a more substantial gradient between Ψl, and Ψr and lower CWSI than taproot (rapeseed cultivars and lucerne) and fallow treatment. Furthermore, the cover crop treatments enhanced the gradient between maize Ψl and Ψr to varying degrees in different drought years. Ultimately, the improvement in SWC resulting from cover crop treatments increased maize aboveground growth (plant height, stem diameter, and leaf area) and maize root development, ultimately improving maize yield. This study introduces a new perspective on investigating the role of cover crops in alleviating seasonal drought in subsequent crops, especially by changing soil water properties in the subtropical climate.

Pinpointing the distinctive impacts of ten cover crop species on the resident and active fractions of the soil microbiome

Cover crops are used in agriculture to minimize soil erosion, prevent nutrient leaching and increase soil organic matter content. Cover crops can also be grown to stimulate the soil microbial community to improve soil biological conditions. Despite their widespread use, little is known about the impact of different cover crop species on the composition and activity of the soil microbiome. Here we investigate the effect of distinct cover crop species on the rhizosphere microbiome and characterize both the resident (ribosomal (r)DNA-based) and the potentially active (rRNA-based) fractions of the bacterial, fungal, protist and metazoan communities in the cover crops rhizosphere. We conducted a field experiment using 70-l bottomless containers in which we grew ten monocultures of commonly used cover crop species belonging to five plant families, and an unplanted control treatment (fallow). The total DNA and RNA were extracted from soil and the bacterial, fungal, protistan and metazoan communities were characterized using Illumina MiSeq sequencing. We found that all cover crop species significantly impacted the resident and the potentially active microbial communities in their rhizospheres. Cover crops exerted distinct selection strengths on the native microbial communities. For individual cover crops, the impacts on the resident and the potentially active microbial communities differed while showing similar overall tendencies. Oilseed radish (Brassicaceae) was shown to provoke the strongest microbial shifts, in part attributable to a promotion of the bacterial family Pseudomonadaceae and a repression of Microascaceae in the rhizosphere. Lentil (Fabaceae) induced a widespread stimulation of fungal taxa, including Trichocomaceae and fungal members of the Glomerales order, whereas black oat and hybrid ryegrass (both Poaceae) gave rise to relatively mild changes in the soil microbial communities. Analyses of rRNA-based rhizobiome data revealed that, except for phacelia, all cover crops induced an increase in microbial network complexity as compared to the fallow control. Data presented here provide a broad baseline for the effects of cover crops on four organismal groups, which may facilitate future cover crop selection to advance soil health.

On the legacy of cover crop-specific microbial footprints

Apart from improving the physical and chemical condition of arable soils, cover crops have the potential to boost and activate selected soil microbiota that could contribute to improved nutrient cycling and strengthened disease suppressiveness. However, a main crop can only benefit from cover crop-induced microbial shifts if these persist until the onset of the main growing season. Here, we map the persistence of microbiome changes by cover crops over time. We performed a field experiment on a sandy soil with ten different cover crop monocultures belonging to five plant families, one cover crop mixture and a fallow control. Cover crops were grown for 4.5 months under field conditions in 70-L bottomless containers in a random block design with eight replications. We studied the total (DNA-based) and the potentially active (RNA-based) microbial fractions at the onset of the main growing season, and just after the harvest of the main crop, potato (respectively 3.5 and 10 months after cover crop termination), through MiSeq sequencing. All cover crops tested induced shifts in the soil microbiome that lasted at least until the onset of the main growing season. Cover crop treatments gave rise to species and even cultivar-specific microbial footprints, and - although roughly the same trends were observed - DNA-based microbial shifts were not necessarily paralleled by similar changes at RNA level. We conclude that cover crops have the potential to act as handles to steer the soil microbiome in a way that is supportive of sustainable crop production.

Estimating the Global Influence of Cover Crops on Ecosystem Service Indicators in Croplands With the LPJ‐GUESS Model

AbstractCover crops (CCs) can improve soil nutrient retention and crop production while providing climate change mitigation co‐benefits. However, quantifying these ecosystem services across global agricultural lands remains inadequate. Here, we assess how the use of herbaceous CCs with and without biological nitrogen (N) fixation affects agricultural soil carbon stocks, N leaching, and crop yields, using the dynamic global vegetation model LPJ‐GUESS. The model performance is evaluated with observations from worldwide field trials and modeled output further compared against previously published large‐scale estimates. LPJ‐GUESS broadly captures the enhanced soil carbon, reduced N leaching, and yield changes that are observed in the field. Globally, we found that combining N‐fixing CCs with no‐tillage technique could potentially increase soil carbon levels by 7% (+0.32 Pg C yr−1 in global croplands) while reducing N leaching loss by 41% (−7.3 Tg N yr−1) compared with fallow controls after 36 years of simulation since 2015. This integrated practice is accompanied by a 2% of increase in total crop production (+37 million tonnes yr−1 including wheat, maize, rice, and soybean) in the last decade of the simulation. The identified effects of CCs on crop productivity vary widely among main crop types and N fertilizer applications, with small yield changes found in soybean systems and highly fertilized agricultural soils. Our results demonstrate the possibility of conservation agriculture when targeting long‐term environmental sustainability without compromising crop production in global croplands.

Response of soil organic carbon fractions to cover cropping: A meta-analysis of agroecosystems

Agroecosystems have a large potential for soil carbon (C) sequestration, and cover cropping is one management practice that can enhance soil C while providing other ecological and agronomic benefits. Still, we lack an understanding of the distribution of this added C across soil organic C (SOC) fractions. Two major operational pools make up SOC: easily decomposed, faster-turnover particulate organic C (POC) and slowly decomposed, slower-turnover mineral-associated organic C (MAOC). Though POC is generally more sensitive to environmental change in the short term, recent projections hold that MAOC stocks could face considerable loss in croplands where it is the dominant form of SOC. We used a systematic meta-analysis to determine responses of POC and MAOC concentration and stock to cover cropping and how these responses are influenced by soil, agronomic, and climatic variables. Across 49 studies concentrated in the Americas and Europe, total POC increased by 14.94% and total MAOC increased by 5.56% on average in cover-cropped soils vs. non-cover cropped or fallow control soils, which would effectively reverse or offset projected losses of SOC with climate warming. The effect of cover cropping on POC was greater in soils sampled from 0 to 10 cm vs. 10–30 cm depths and under higher mean annual temperature, but the effect of cover cropping on MAOC was not influenced by either of these factors. The response of POC to cover cropping was significantly positive for certain cover crop growing seasons, cover crop types, and tillage practices in which the MAOC response was not significant, indicating that changes in POC rather than MAOC are responsible for driving the positive response of total SOC to cover cropping. One commonality between POC and MAOC responses to cover cropping was that both dramatically increased with the amount of aboveground C produced by cover crops. Still, POC and MAOC responses to cover cropping were not strongly altered by nitrogen fertilization rate, cover crop diversity, experimental duration, annual precipitation, or baseline soil properties (texture, total organic C, and pH). Our results show that POC is more responsive to cover cropping than MAOC in an average of five years. However, more experimental data are needed to determine how these SOC fractions respond in deeper soil as well as in different geographic regions, climates, and soil orders. Based on our results, we discuss drivers of total and fractional SOC dynamics in agroecosystems and lessons learned from our synthesis of available fractional SOC data.

Double-cropping effects of Brassica carinata and summer crops: II. Effects of winter cropping history on subsequent summer crop production

There is an opportunity for crop farmers in the Southeast United States (SE US) to increase income by producing carinata during the winter following summer crop production. However, a major limitation to the use of carinata as a winter annual in the SE US is the lack of information on double-cropping with summer commodity crops common to the region. Considering that integrating carinata into cropping systems common to the region could impact productivity of those systems, it is critical to quantify the potential effects of carinata on existing cropping systems. To this end, a study was conducted in Jay, Florida for three years to evaluate the effects of winter cropping history (carinata vs. fallow) on the productivity of subsequent summer crops including cotton, peanut, sorghum, and soybean. Treatments (winter carinata vs. winter fallow) were laid out in a randomized complete block design with eight replications. Data were collected on infiltration; plant population; plant canopy height; aboveground biomass; and yield. Infiltration rates, determined within a week of carinata harvest, were affected by winter cropping history, being greater in former carinata plots than former fallow plots. Carinata harvest coincided with the timely planting of cotton and peanut which resulted in these summer crops being sown three to four weeks later than their typical sowing window for the SE US. Winter cropping history (including the winter fallow control) did not influence commodity crop (cotton, peanut, sorghum, and soybean) yields when all summer crops were planted at the same time, as in a double-crop scenario. Regarding the combined productivity of winter (carinata vs. winter fallow) and summer crops, carinata-cotton, carinata-peanut, carinata-sorghum, and carinata-soybean systems were necessarily more productive than their winter fallow counterparts due to no crop production in the fallow during the winter cropping years. Overall, results from this study showed that carinata can successfully replace winter fallow, and can be double-cropped with summer-planted sorghum and soybean with no adverse effect on yield. Double-cropping carinata caused a delay in timely planting of cotton and peanut, and represents a limitation that may hinder its adoption in the SE US until such time a faster-maturing carinata cultivar can be developed.

Reniform Nematode Management Using Winter Crop Rotation and Residue Incorporation Methods in Greenhouse Experiments.

Rotylenchulus reniformis (reniform nematode, RN) is an important pathogen in cotton production. Cultural practices such as crop rotation and biofumigation-management of soil pathogens by biocidal compounds from crop residues-may help manage RN. The objective of this study was to evaluate the efficacy of winter crops for RN management through combinations of rotation and crop residue incorporation in a cotton greenhouse experiment. A total of 10 treatments were evaluated in soil inoculated with RN: three winter crops (carinata, oat, or hairy vetch) grown in rotation with no shoot organic matter (OM) incorporated (1-3), fresh shoot OM incorporated (4-6), or dry shoot OM incorporated (7-9), and a fallow control (10). Roots were re-incorporated in all treatments except fallow. Subsequently, cotton was grown. Oat and fallow were better rotation crops to lower soil RN abundances at winter crop termination than hairy vetch and carinata. After the OM incorporation treatments and cotton growth, oat was generally more effective at managing RN in cotton than carinata or hairy vetch. Within each crop, incorporation treatment generally did not affect RN management. Cotton growth was not consistently affected by the treatments.

A grass–legume cover crop maintains nitrogen inputs and nitrous oxide fluxes from an organic agroecosystem

AbstractLegume cover crops are central to an ecological nutrient management approach that can reduce nitrogen (N) losses from agriculture. Diversifying cropping systems with a legume–grass cover crop mixture could further reduce N losses by increasing soil N assimilation and synchronizing N mineralization with N uptake by the following crop. We established four winter cover crop treatments (crimson clover, cereal rye, clover–rye mixture, and weedy fallow control) in an organic grain agroecosystem that had been managed for 30 years with a legume cover crop as the only external N source. We hypothesized that the legume–grass mixture would provide similar inputs of biologically fixed N2 compared with the sole legume, while reducing N2O emissions during decomposition following tillage. We measured cover crop aboveground biomass C:N and clover N2 fixation, soil inorganic N and N2O fluxes throughout the corn growing season following cover crop tillage, and corn N assimilation at harvest. Even with a reduced clover seeding rate in mixture, the clover and mixture treatments had similar fixed N inputs, litter N and C:N, and no differences in cumulative N2O emissions. During the first peak flux, N2O emissions were 2–5 times higher in clover and mixture relative to rye and fallow, with no differences between clover and mixture. There were no treatment differences at the second N2O peak, which followed the first major rain event. We contextualized these findings by calculating a 6‐year partial N mass balance for this agroecosystem, which was slightly negative (−6.8 ± 0.8 kg N ha−1 year−1) when accounting for historical mean annual N2O emissions and nitrate leaching. Overall, N inputs and harvested N exports were approximately in balance for this legume‐based crop rotation, suggesting that the legacy of ecological nutrient management has promoted efficient N cycling. However, results from our field experiment indicate that short‐term N2O flux rates following cover crop incorporation can be high even for a legume–grass mixture. Additional strategies to reduce soil disturbance are therefore needed to further tighten N cycling in organic grain agroecosystems.

Vegetative buffer strips show limited effectiveness for reducing antibiotic transport in surface runoff.

Vegetative buffer strips (VBS) have been demonstrated to effectively reduce loads of sediment, nutrients, and herbicides in surface runoff, but their effectiveness for reducing veterinary antibiotic (VA) loads in runoff has not been well documented. The objective of this study was to determine the effectiveness of VBS vegetation and width on surface runoff loads of the VAs sulfamethazine (SMZ) and lincomycin (LIN). Experimental design of the plots (1.5×25m) was a two-way factorial with four vegetation treatments (tall fescue [Festuca aruninacea Schreb.]; tall fescue with switchgrass [Panicum virgatum L.] hedge; warm-season native grass mix; and continuous fallow control), and four buffer widths (0, 2, 5, and 9m). Turkey litter spiked with SMZ and LIN was applied to the source area (upper 7m) of each plot, and runoff was collected at each width. Runoff was generated with a rotating boom simulator. Results showed VA loads in runoff at the 0-m sampler ranged from 3.8 to 5.9% of applied, and overall VA transport in runoff was predominately in the dissolved phase (90% for SMZ and 99% for LIN). Among vegetation treatments, only tall fescue significantly reduced loads of SMZ and LIN compared with the control, with load reductions of ∼30% for both VAs. Estimated field-scale reductions in VA loads showed that source-to-buffer area ratios (SBARs) of 10:1 to 20:1 reduced VA loads by only 7 to 16%. Overall, the grass VBS tested here were less effective at reducing SMZ and LIN loads in surface runoff than has been previously demonstrated for sediment, nutrients, and herbicides.

Cereal rye seeding rate does not affect magnitude of weed suppression when planting green within Mid-Atlantic United States

AbstractIn the Mid-Atlantic United States, there is increasing interest in delaying cereal rye termination until after soybean planting (i.e., planting green). Improved understanding of cereal rye seeding rate effects is needed to balance weed and agronomic management goals. We investigated the effects of cereal rye seeding rates on weed control and crop performance when planting green in complementary experiments in two Mid-Atlantic regions. The Pennsylvania experiment was replicated at three site-years and the Delaware experiment at two site-years. In both experiments, population-level weed responses were evaluated across four cereal rye seeding rates: 0, 51, 101, and 135 kg ha−1. The Delaware experiment also implemented a nitrogen treatment factor (0 and 34 kg N ha−1; spring applied). Both experiments showed that integrating cereal rye in the fall significantly improved winter- and summer-annual weed suppression compared with the fallow control, but no differences in total cereal rye biomass production or weed suppression were found among alternative cereal rye seeding rates (51 to 135 kg ha−1). Soybean yield did not differ among treatments in any of the studies. These results show there is no reason to increase cereal rye seeding rates for weed suppression services or to decrease seeding rates for agronomic reasons (i.e., soybean population and yield) when employing planting-green tactics in no-till soybean production within the Mid-Atlantic region of the United States.

Combining reduced tillage and green manures minimized N2O emissions from organic cropping systems in a cool humid climate

Developing and implementing improved management practices are necessary to enhance the sustainability of organic cropping systems. This study examined the effects of various organic cropping systems on soil greenhouse gas (GHG) emissions and crop yields in Québec, Canada. Organic cropping systems combining different: (i) crop sequences (barley [Hordeum vulgare L.]-grain corn [Zea mays L.], soybean [Glycine max (L.) Merr.]-spring wheat [Triticum aestivum L.], and grain corn-soybean), (ii) nitrogen (N) sources (poultry manure [PM] and/or a fall-seeded green manure [GM] or no applied N), and (iii) primary tillage intensities (moldboard plough [MP] or chisel plough [CP]) were compared to a perennial forage (PF) and a bare fallow (BF) control. During the 2019 and 2020 snow-free seasons, nitrous oxide (N2O) and methane (CH4) emissions, soil water content, soil temperature, and mineral N concentrations were monitored periodically on a sandy loam soil. The lowest cumulative N2O emissions were found in CP-GM (0.52 ± 0.11 kg N ha-1 in 2019 and 0.47 ± 0.06 kg N ha-1 in 2020), whereas the highest N2O emissions were found in MP-PM in 2019 (3.55 ± 0.72 kg N ha-1) and BF in 2020 (1.44 ± 0.20 kg N ha-1). For the barley-grain corn sequence, the CP-GM treatment generated N2O emissions that were 40–70 % lower and yields that were 33–51 % lower than the MP-PMGM and CP-PMGM systems, which showed equivalent N2O emissions and yields. Yield-scaled N2O emissions were equivalent for all cropping systems. Peak N2O daily fluxes in the PF occurred shortly after cutting in 2020. During both years, CH4 emissions varied from − 0.65 to + 0.18 kg C ha-1 with no detectable differences among cropping systems. The CP-GM cropping system minimized area-scaled N2O emissions without increasing yield-scaled emissions. However, this was a two-year study on a site that was recently converted from conventional agriculture, so a long-term assessment is still necessary to determine whether the benefits associated with these cropping systems change over time.

Soil bacterial community response to cover crops, cover crop termination, and predicted climate conditions in a dryland cropping system

Soil microbial communities are integral to highly complex soil environments, responding to changes in aboveground plant biodiversity, influencing physical soil structure, driving nutrient cycling, and promoting both plant growth and disease suppression. Cover crops can improve soil health, but little is known about their effects on soil microbial community composition in semiarid cropping systems, which are rapidly becoming warmer and drier due to climate change. This study focused on a wheat-cover crop rotation near Havre, Montana that tested two cover crop mixtures (five species planted early season and seven species planted mid-season) with three different termination methods (chemical, grazed, or hayed and baled) against a fallow control under ambient or induced warmer/drier conditions. Soil samples from the 2018 and 2019 cover crop/fallow phases were collected for bacterial community 16S rRNA gene sequencing. The presence and composition of cover crops affected evenness and community composition. Bacterial communities in the 2018 ambient mid-season cover crops, warmer/drier mid-season cover crops, and ambient early season cover crops had greater richness and diversity than those in the warmer/drier early season cover crops. Soil microbial communities from mid-season cover crops were distinct from the early season cover crops and fallow. No treatments affected bacterial alpha or beta diversity in 2019, which could be attributed to high rainfall. Results indicate that cover crop mixtures including species tolerant to warmer and drier conditions can foster diverse soil bacterial communities compared to fallow soils.

Cover crop monocultures and mixtures affect soil health indicators and crop yield in the southeast United States

AbstractThe southeastern United States has a long history of soil degradation due to intensive agriculture and climatic factors. Conservation management practices such as cover cropping aim to improve soil productivity and restore soil health. Our objectives were to evaluate the performance of cover crops and their short‐term effects on soil health indicators for two southeastern soil types. Cover crop experiments were conducted at the Wiregrass (WREC) and Tennessee Valley (TVREC) Research and Extension Centers in Alabama from 2017 to 2021. Cover crop treatments included winter fallow, monocultures, and two‐ and three‐way mixtures of cereal rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and forage radish (Raphanus sativus L.) preceding a cotton (Gossypium hirsutum L.)–legume {peanut [Arachis hypogaea L.] or soybean [Glycine max (L.) Merr.]} cash crop rotation. At TVREC, aboveground biomass for both rye and clover were greater than radish. All cover crops, except the radish monoculture, increased soil organic carbon (SOC) 19–30% in the top 5 cm at TVREC compared with winter fallow. Similarly, some cover crop treatments increased permanganate oxidizable carbon (POXC) compared with the fallow control. However, this effect was not observed at WREC. Cover crops did not produce many meaningful aggregate stability differences at either location. Treatments containing rye or clover decreased soil strength. by 14–22% at TVREC after 4 yr of cover crop utilization. Short‐term cover crop use improved selected soil health indicators and reversed soil degradation at one location evaluated, but these benefits were dependent on soil type and cover crop selection.

Influence of Leguminous Cover Crops on Soil Chemical and Biological Properties in a No-Till Tropical Fruit Orchard

South Florida’s agricultural soils are traditionally low in organic matter (OM) and high in carbonate rock fragments. These calcareous soils are inherently nutrient-poor and require management for successful crop production. Sunn hemp (SH, Crotalaria juncea) and velvet bean (VB, Mucuna pruriens) are highly productive leguminous cover crops (CCs) that have shown potential to add large quantities of dry biomass to nutrient- and organic-matter-limited systems. This study focuses on intercropping these two CCs with young carambola (Averrhoa carambola) trees. The objective was to test the effectiveness of green manure crops in providing nutrients and supplementing traditional fertilizer regimes with a sustainable soil-building option. Typically, poultry manure (PM) is the standard fertilizer used in organic or sustainable production in the study area. As such, PM treatments and fallow were included for comparison. The treatments were fallow control (F), fallow with PM (FM), sunn hemp (SH), SH with PM (SHM), velvet bean (VB), and VB with PM (VBM). Sunn hemp and VB were grown for two summer growing seasons. At the end of each 90-day growing period, the CCs were terminated and left on the soil surface to decompose in a no-till fashion. The results suggest that SH treatments produced the greatest amount of dry biomass material ranging from 48 to 71% higher than VB over two growing seasons. As a result, SH CCs also accumulated significantly higher amounts of total carbon (TC) and total nitrogen (TN) within their dry biomass that was added to the soil. Sunn hemp, SHM, and FM treatments showed the greatest accumulation of soil OM, TC, and TN. Soil inorganic N (NH₄⁺ + NO3− + NO2) fluctuated throughout the experiment. Our results indicate that generally, VB-treated soils had their highest available N around 2 months post termination, while SH-treated soils exhibited significantly higher N values at CC termination time. Sunn hemp + PM (SHM)treatments had highest soil N availability around 4 months after CC termination. Soil enzyme activity results indicate that at CC termination, SHM exhibited the highest levels of β-1-4- glucosidase and β-N-acetylglucosaminidase among all treatments. Overall, SH, SHM, and FM treatments showed the greatest potential for supplementing soil nutrients and organic matter in a no-till fruit production setting.