Effects Of Cover Crops Research Articles

A meta-analysis on cover crop impact on soil water storage, succeeding crop yield, and water-use efficiency

Cover cropping is practiced to enhance soil health and sustain succeeding crop yield; however, the effect of cover crop on soil water storage, succeeding crop yield, and water-use efficiency (WUE) may not be consistent in all regions. A meta-analysis was carried out to evaluate the effect of cover crop on precipitation storage efficiency (PSE, the percent of precipitation that is stored in the soil during the fallow period), soil water storage at succeeding crop planting (SWSP), succeeding crop yield, and WUE from data collected from 117 studies across the world. Cover crop decreased PSE by 33.4% and soil water storage for the whole profile (SWSPT) at soil depth by 13.2%, but increased water storage to a depth of 30 cm (SWSP30) by 6.0% (P < 0.05) compared to no cover crop. Cover crop did not affect succeeding crop yield, but decreased evapotranspiration (ET) by 6.2% and increased WUE by 5.0% (P < 0.05) compared to no cover crop. The effect of cover crop on these parameters varied by soil and climatic conditions of various regions. Leaving cover crop residue at the soil surface or incorporating into the soil reduced PSE, SWSPT, and ET, but increased SWSP30 and WUE compared to residue removal. Maintaining cover crop biomass at 5Mgha−1 and leaving a 20-d interval between cover crop termination and succeeding crop planting, also enhanced PSE and SWSP30. Although cover crop had minimal impact on succeeding crop yield, WUE of succeeding crops can be increased with cover cropping by decreasing evapotranspiration.

Over winter cover crops provide yield benefits for spring barley and maintain soil health in northern Europe

A three-year field experiment investigated the potential yield benefits and soil effects from over winter cover crops in Scotland, U.K. Brassica composition of cover crops significantly increased the grain yield and grain nitrogen (N) concentration of the following spring barley crop. The increased yield with cover crops was outweighed by increased costs and thus without subsidy (Ecological Focus Area) payments there was decreased profitability for the following spring barley crop. Cover crop effects were mostly neutral on soil properties, but surface shear strength was significantly lower than in the stubble control. This indicates that even direct drilling of cover crops will loosen the surface soil. Cover crops varied in their effect on slug populations but in all cases slug numbers were below treatment thresholds. No cover crop effects were detected for total nematode and earthworm abundance or the total soil organic carbon concentration. This study indicates that cover crops can improve cereal production in a region with a short growing season with no negative impact on soil health or the agronomic sustainability.

Cover crop residue moisture content controls diurnal variations in surface residue decomposition

The effect of cover crop (CC) surface residues on water, carbon, and nitrogen cycling in no-till systems depends in part on the water retention properties of decomposing residues and the extent of decomposition. This study (1) examined the effect of decomposition on residue water retention properties; (2) characterized diurnal variations in residue decomposition rates in response to changes in soil-residue-air environmental conditions; and (3) examined the diurnal relationships between cover crop surface residue decomposition and residue environment (moisture and temperature). Maximum gravimetric water content (θg) and characteristic water release curves were determined for red clover (Trifolium pratense L.) and cereal rye (Secale cereale L.) residues collected at 0, 4, 10, and 16 weeks after termination for red clover, and at 2, 5, and 18 weeks for cereal rye. In addition, residue carbon dioxide (CO2-C) flux, along with soil-residue-air environmental conditions, were measured diurnally for red clover at 4, 10, and 16 weeks after termination, and for cereal rye at 5 weeks after termination. Maximum residue θg decreased as decomposition progressed. Cover crop residue decomposition also influenced water release curves such that the water retained at any given water potential (ψresidue) declined with increasing decomposition. These decomposition-associated changes in residue water retention properties were strongly related to residue lignin concentrations. Cover crop surface residue CO2-C flux showed distinct diurnal patterns that were strongly related to ψresidue or residue θg. At a diurnal scale, residue CO2-C flux increased during the nighttime from 18:00 to 06:00 h when residues gain moisture from the atmosphere and soil, and decreased during the daytime from 06:00 to 18:00 h when residues lost moisture via evaporation. Increase in temperature decreased residue CO2-C flux due to moisture limitations. Therefore, CC surface residue decomposition models must address both diurnal changes in ψresidue and the changes in water retention properties as residues decompose.

Improving Soil Quality and Potato Productivity with Manure and High-Residue Cover Crops in Eastern Canada.

Under intensive low residue agricultural systems, such as those involving potato (Solanum tuberosum L.)-based systems, stagnant crop yields and declining soil health and environmental quality are common issues. This study evaluated the effects of pen-pack cow (Bos Taurus) manure application (20 Mg·ha−1) and cover crops on nitrate dynamics and soil N supply capacity, subsequent potato yield, selected soil properties, and soil-borne disease. Eight cover crops were tested and included grasses, legumes, or a mixture of legumes and grasses, with red clover (Trifolium pratense L.) used as a control. Forage pearl millet (Pennisetum glaucum L.) was associated with highest dry matter. On average, red clover had 88% higher total N accumulation than the treatments mixing grasses and legumes, and the former was associated with higher soil nitrate in fall before residue incorporation and overwinter, but this was not translated into increased potato yields. Pearl millet and sorghum sudangrass (Sorghum bicolor × sorghum bicolor var. Sudanese) were associated with lower soil nitrate in comparison to red clover while being associated with higher total potato yield and lower numerical value of root-lesion nematodes (Pratylenchus penetrans), although this was not statistically significant at 5% probability level. Manure incorporation increased total and marketable yield by 28% and 26%, respectively, and increased soil N supply capacity by an average of 44%. Carbon dioxide released after a short incubation as a proxy of soil microbial respiration increased by an average of 27% with manure application. Our study quantified the positive effect of manure application and high-residue cover crops on soil quality and potato yield for the province of Prince Edward Island.

Integrated Management Practices for Establishing Upland Switchgrass Varieties

Establishment of switchgrass (Panicum virgatum L.) is challenging, and failure in establishment may expose growers to considerable economic risk. The objectives of this research were to (i) evaluate whether management practices are variety-specific for the establishment of switchgrass and (ii) assess the effectiveness of cover crops as preceding crops on ‘Shawnee’ switchgrass establishment. Therefore, two studies were conducted at the University of Massachusetts Agricultural Experiment Station in Deerfield, MA, USA, in the 2011–2012 and 2012–2013 growing seasons. In Experiment 1, cover crop treatments (fallow, oat (Avena sativa L.) and rye (Secale cereale L.)) were the main plots, the two seeding methods (no-till drill and a cultipacker seeder (Brillion)) were the sub-plots, and the two varieties (‘Cave-in-Rock’ (CIR) and Shawnee)) were the sub-sub-plots. The second study was conducted using Shawnee switchgrass and involved the three cover crop treatments used in Experiment 1 using a cultipacker seeder with seed firming prior to planting but not afterwards (consistent in both experiments). The results indicated that a combination of oat and no-till resulted in higher tiller density (493%), lower weed biomass (77%), increased switchgrass biomass (SGB) (283%) and SGB to weed biomass (WB) ratio. Compared with Shawnee, CIR planted into a winter-killed oat residue had higher tiller density (93%), lower weed biomass (18%), higher switchgrass yield (128%) and thus a greater SGB:WB ratio (507%). Trends of switchgrass response to management practices, however, were similar between the two varieties, indicating that seed quality rather than management practices could influence switchgrass’s response to management practices. In Experiment 2, Shawnee tiller density was suppressed by rye as the preceding crop, possibly due to late termination of rye. Shawnee switchgrass yields were below 1000 kg ha−1 under all management practices; thus, harvesting should happen in the year following establishment. Future research should focus on comparing no-till drilling with cultipacker seeder with rolling not only before but after seeding to increase seed–soil contact.

Effects of Cover Crop and Tillage Method Combinations on the Microbiological Traits of Spring Wheat (Triticum aestivum L.)

We carried out multivariate characterisation of phenotypic variability in 27 treatments that were combinations of cover crop, tillage method, and year. Canonical variate analysis was employed to observe nine microbiological traits in an experiment established in a split-plot design. Between 2011–2013, a field experiment was conducted on soils classified as Albic Luvisols. The first-order factor was analysis of the effect of sowing a stubble cover crop: (Control: No cover crop sown; cover crop sown after skimming; no tillage: Cover crop sown directly). The second experimental factor involved evaluating the effects of three tillage methods (direct sowing; simplified tillage to a depth of 12–15 cm with a combined cultivator; spring ploughing to a depth of 25 cm) on nine microbiological traits. The year of research was used as a factor to differentiate between the count and activity of soil microorganisms. The traits (moulds and copiotrophic bacteria, and oligotrophic bacteria and actinobacteria) were significantly correlated (positively or negatively) at all five terms. Pearson’s test confirmed the relationships between the physiological groups of soil microorganisms after the application of organic matter, and captured the positive correlation between moulds and copiotrophs at all terms of the study.

Effects of Nitrogen Rate and Cover Crop on Cotton (Gossypium hirsutum L.) Yield and Soil Water Content

The objective of this study was to test the effects of N rates and tillage radish (Raphanus sativus var. longipinnatus) cover crop (TRCC) on soil water and cotton (Gossypium hirsutum L.) yield. In three years of the investigation, the treatments were N rates at 84 kg ha−1 and 140 kg ha−1 with and without TRCC. Soil water contents were measured using soil water sensors. Results showed that cotton yield was not significantly (p &gt; 0.05) influenced by TRCC. Compared to N rate at 84 kg ha−1, 140 kg N ha−1 increased lint yield by 2.0%, 7.4%, 18.4% in 2017, 2018, and 2019, respectively, but the increase was significant only in 2019 (p &lt; 0.02). Interactions between TRCC and nitrogen rate on yield were significant (p &lt; 0.03) only in 2017. TRCC increased soil water infiltration capacity, resulting in higher soil water content. Use of TRCC did not affect the cotton yield, which could be due to the high inputs of water and high rates of N neutralizing the positive contributions to the cotton growth expected from the TRCC. Sub-optimum winter temperatures hampered the establishment and subsequent growth of TRCC, which also possibly contributed to its minimum impacts on cotton crop performance in the following season.

First-year cover crop effects on the physical and hydraulic properties of the surface layer in a loamy soil

Soil degradation is a global problem, threating its conservation and affecting agronomic production. No-tillage (NT) is the main management system for soil conservation world-wide. However, in Argentina, simplification of the crop sequence with high proportion of soybean under NT is a very common practice, leading to soil physical constrains. Crop sequence intensification through the inclusion of cover crops has been reported as an effective tool in the long-term for the enhancement of ecosystems services, improving NT performance. The objective of this work was to follow the evolution of the structural pore domain in the surface layer during the first year after the incorporation of cover crop (cover fallow of barley (Hordeum vulgare L.) and vetch (Vicia sp. L.), CF), as compared with bare fallow (BF), under NT management in a field experiment located in the Argentinean Depressed Pampas Region. Mini-infiltration and evaporation experiments were conducted in undisturbed soil samples (0−5 cm depth) in the laboratory in order to determine the pore size distribution (PoSD) and hydraulic conductivity (K (h)) functions in three different dates (after cover crop seeding, after maize seeding and before maize harvest) in order to follow the changes in soil pore functioning during the first year of cover cropping management. Changes in the soil pore functioning were observed in the short-term after the first cover crop cycle, showing the time-dependence of the hydraulic soil properties. These changes were mainly observed during the maize cycle. Under CF an increment of structural porosity (PS) was observed at the end of the maize crop cycle, while during the fallow period this variable remained relatively constant. K (h) and structural porosity connectivity (Cw) showed a rapid increment under BF during the fallow period, while under CF the increase was more gradual, which could be related to pore clogging and roots decay cycles. From the obtained results, we found that the introduction of cover crops under NT promotes the increment of a secondary pore system related to structural soil porosity during the first year and enhances the unsaturated hydraulic conductivity and pore connectivity, especially at the end of the summer crop cycle. Our results highlight the importance of including cover crops into the crop rotation to improve the structural porosity and its connectivity. As well, the results show the necessity of including the short-term changes in the study of soil hydraulics properties.

Effect of Cover Crop, Slurry Application with Different Loads and Tire Inflation Pressures on Tire Track Depth, Soil Penetration Resistance and Maize Yield

Agricultural soils can be affected in their ecological functions by in-field traffic of agricultural machinery. A three-factorial research design was carried out in a field experiment to test the effect of slurry tanker filling level (filled, half-filled, empty), tire inflation pressure of the slurry tanker (high: 300 kPa, low: 100 kPa), and ground covering (+cover crop, −cover crop) on tire track and soil penetration resistance (averaged, 0–20 cm, 21–40 cm) after application on the fields in spring. Additionally, the effect on grain yield of the subsequent culture was considered. The total weight of the tractor slurry tanker combination was 16,470 kg (empty), 25,940 kg (half-filled), and 34,620 kg (filled). The low tire inflation pressure of the slurry tanker increased the mean tire–soil contact area by 75% (filled), 38% (half-filled), and 16% (empty tanker). The results obtained show a significant effect of tire inflation pressure and ground covering on the measured parameters. The tire inflation pressure reduction effect on track depth was highest in the filled slurry tanker (−17.8%). With increasing wheel load, the effect of reduced tire inflation pressure on soil penetration resistance (0–20 cm) increased. In the subsoil (21–40 cm), the effect of tire inflation pressure was much lower, indicating that a reduction of tire inflation pressure preserves the upper layers rather than the lower ones. Furthermore, cover crops are linked to a higher degree of soil deformation after traffic with the tractor–slurry combination due to their loosening effect on the topsoil. Tire tracks were 15.0% deeper in the cover crop field than in the field without a cover crop. It is assumed that cover crop mixtures with different types of root mass can influence the mitigation of soil compaction in an ameliorative way.

The Effect of Summer Cover Crops and Strawberry Cultivars on the Twospotted Spider Mite, Tetranychus urticae (Acari: Tetranychidae) and the Predatory Mite, Neoseiulus californicus (Acari: Phytoseidae) in Organic Strawberry Production Systems in Florida.

The twospotted spider mite, Tetranychus urticae (Koch) (Acari: Tetranychidae), is a key pest of strawberries and many other crops worldwide. Cover cropping, selecting tolerant or resistant cultivars, and biological control are important strategies of an organic management plan. In this study, we examined the effect of summer cover crops and strawberry cultivars on populations of T. urticae and a commercially available predatory mite, Neoseiulus californicus McGregor (Acari: Phytoseiidae), commonly used for T. urticae management in Florida. In the 2013-2014 season, four cover crops and eight strawberry cultivars were screened at the research station and on a commercial organic strawberry farm. The following season, the most promising cover crops (sunn hemp and hairy indigo) and cultivars, 'Sensation', 'Strawberry Festival', and 'Winterstar' were tested at the research station and on two small organic farms. In the 2016-2017, 2017-2018, and 2018-2019 seasons, a 4-way mix of cover crops was compared to sunn hemp and hairy indigo. In 2016-2017, 'Florida Radiance' was added to the three previously selected cultivars. 'Florida Beauty' replaced 'Strawberry Festival' in 2017-2018 and 2018-2019, and 'Florida Brilliance' replaced 'Winterstar' in 2018-2019. The effects of summer cover crops on both T. urticae and N. californicus were minimal. 'Florida Brilliance', 'Florida Radiance', 'Sensation', 'Strawberry Festival', and 'Winterstar' had lower T. urticae populations and higher yields in most seasons at most locations. The establishment and abundance of N. californicus was similar on these cultivars and was generally higher where T. urticae populations were higher. Implications for organic strawberry production in Florida are discussed.

Benefits of increased cover crop diversity for predators and biological pest control depend on the landscape context

Abstract Increasing plant diversity in agricultural systems is a promising way to balance food production and biodiversity conservation. Biological pest control, a crucial ecosystem service delivered by natural enemies, could particularly benefit from increased plant diversity at the local scale. Such positive effects however often depend on the landscape context that shapes the pool of natural enemy species available and their ability to colonize newly created habitats. However, how the landscape context modulates the local effect of plant diversity on natural enemies and pest control services remains unclear. Here, we manipulated the diversity of cover crops (2 versus 20 plant species) in nine pairs of vineyards located along a landscape gradient ranging from 20 to 60% of semi‐natural habitats. We sampled natural enemy communities in the soil and foliage and measured the predation rate of an important moth pest in European vineyards (Lobesia botrana). Diverse cover crops enhanced the abundance of natural enemies by 140% across the experiment, but without changing their taxonomic richness and composition. We further found a distance‐decay effect of cover crops on natural enemy abundance across cover crop types. The landscape context remarkably modulated the effects of local plant diversity on natural enemy abundance and predation rates. While predation rates were on average similar in the low and high cover crop diversity treatments across the experiment, diverse cover crops had higher positive effects on predation and natural enemies in simple (&lt;50% semi‐natural habitats) than complex landscapes. Predation rates increased from 11 to 42% in the high compared with low cover crop diversity treatments in simple landscapes. Synthesis and applications: Our study demonstrates the benefits of increasing plant diversity at the local scale to enhance the abundance of natural enemies as well as the level of biological pest control services in vineyard agroecosystems. Diverse cover crops mostly benefit natural enemies and biological pest control in simplified landscapes, highlighting that the success of local agroecological practices in improving biodiversity and ecosystem services depends on the landscape context. Thus, we suggest that a strategic spatial arrangement of agricultural practices increasing local plant diversity is necessary to maximize beneficial effects on biodiversity and ecosystem services.

Cover crop species and mycorrhizal colonization on soil phosphorus dynamics

Phosphorus (P) plays an important role in the physiological plant processes; however, in tropical soils, P is one of the most limiting nutrients for crop yield due to its low mobility, determined by the adsorption of this element to the soil. To enhance P-use and P-acquisition efficiency, this research aimed to evaluate the effect of cover crops and mycorrhizal colonization on changing soil P fractions, both organic and inorganic. A complete randomized block design was adopted in a field experiment, with four replications using four cover crops: i) pigeon pea (Cajanus cajan); ii) crotalaria (Crotalaria juncea); iii) millet (Pennisetum glaucum); iv) brachiaria (Brachiaria ruziziensis) and v) fallow, as control. The arbuscular mycorrhizal fungus colonization, the fungal spore density, soil P fractionation, and N, P, and K uptake were assessed. Our results show that cover crops affected the soil P cycling in deeper soil layers. Cover crops may increase arbuscular mycorrhizal inoculum potential for the succeeding crop in rotation or intercropping, when used as a green manure.

Climate change and cover crop effects on water use efficiency of a corn-soybean rotation system

Climate change led to increased temperature and variable rainfall, which may pose great threats to both agricultural productions and environmental impacts. In this study, we aim to explore how changing climate and its extremes in the 20th and 21st-century influence system water use efficiency (sWUE) of a corn-soybean cropping rotation in a humid sub-tropic environment, and how much can cover crops mitigate these impacts. Different from the traditional yield-focused water use efficiency (WUE), sWUE addresses both production and environmental quality goals by considering grain yields and all major system water losses (evapotranspiration, runoff, and drainage). A calibrated crop simulation model, Root Zone Water Quality Model version 2 (RZWQM2), was applied to simulate grain yields and all major system water losses. The model was forced by daily climate data from in situ observations during 1956–2015 and 10 downscaled and bias corrected General Circulation Model (GCMs) projections under the representative concentration pathways (RCP) 4.5 and 8.5 scenarios during 2020–2079. The results showed that, under the historical baseline and the future RCP4.5 and RCP8.5 scenarios, due to the growth of cover crops, the sWUE for corn were improved by 1.7%, 2.6% and 2.3%, respectively (p-value < 0.001), and for soybean by 0.7% (p = 0.06), 1.0% (p-value < 0.001) and 0.9% (p-value < 0.001). Soil evaporation, as the largest source of water loss from the cropping system, was significantly decreased by 1.7%, 2.6% and 2.3% during the corn growing season, and by 0.7%, 1.0% and 0.9% during the soybean growing season. The annual drainage was decreased by 38 mm, 53 mm and 67 mm, under the baseline, RCP4.5 and RCP8.5, respectively. With the incorporation of wheat cover crops, the correlations of temperature or precipitation extremes with grain yields and major water losses were mostly decreased, suggesting that growing cover crop is an effective means to mitigate the impact of climate extremes on sWUE of a corn-soybean cropping.

Cover Crop Impacts on Water Dynamics and Yields in Dryland Wheat Systems on the Colorado Plateau

On the semiarid Colorado Plateau, dryland farmers are challenged by degraded soils and unreliable precipitation. While cover crops have been shown to support soil fertility, control erosion, and enhance soil water capture, they also use limited soil water and, thus, may impact cash crop productivity in dryland systems. Most literature on cover crops comes from relatively humid climates, where yield penalties due to cover crops may be less pronounced. Two field trials were conducted in Southwestern Colorado to assess the short-term viability of cover crops in dryland systems in this region. The effect of cover crops on subsequent winter wheat (Triticum aestivum L.) yield ranged from a decrease of 78% to an increase of 13%, depending on the amount of cover crop biomass produced in the previous year. Cover crop biomass was inversely correlated with soil nitrate levels and soil water storage at wheat planting, which decreased by 0.39 mg kg−1 and 10 mm, respectively, per 1000 kg ha−1 of cover crop biomass produced. Less available soil water and immobilized N therefore appeared to contribute to wheat yield reductions. These impacts are particularly important for semiarid environments, where decomposition of residue is water-limited and soil water recharge depends on unpredictable precipitation patterns.

Perennial cover crop biomass contributes to regulating soil P availability more than rhizosphere P-mobilizing capacity in rubber-based agroforestry systems

Cover crops used in agroforestry systems (AFS) are generally perceived to improve soil quality, but mechanisms underlying phosphorus (P) cycling in complex rhizosphere system are less clear, because the impacts of incorporated crops are often determined by inclusion time, residue management and species. We quantified 7-year cumulative effects of perennial legume cover crop–Flemingia macrophylla on rhizosphere P cycling and availability during the dry and wet seasons in young and mature rubber-based AFS (i.e., YAFS and MAFS) in tropical China by analyzing cover crop biomass and P content, as well as net rhizosphere changes in P-mobilizing capacity (pH, organic acids and phosphatase activity) and P fractions. Compared to their monoculture counterparts, YAFS enhanced plant biomass and P stock in both seasons, whereas MAFS exhibited an opposite trend, except for increased biomass and P stock of floor litter in the dry season. Moreover, YAFS had a greater effect on net rhizosphere properties by reducing pH and increasing organic acids concentrations and acid phosphatase activity, but MAFS hardly alter them. However, these changes had little effect on net rhizosphere P fractions in both seasons, except the contribution of calcium–P to increasing P availability to a certain extent. Net rhizosphere organic P and microbial biomass P in YAFS were enhanced in both seasons by abundant residue returns from cover crop. Net rhizosphere available P surplus occurred in YAFS in the dry season and maintained balance in the wet season, but it almost reached a deficit in MAFS in both seasons. These results suggest that rhizosphere P cycling was more improved by cover crop in YAFS than MAFS, and biomass of cover crop residue contributed to regulating rhizosphere P cycling and availability more than rhizosphere P-mobilizing capacity. Our study highlights the importance of residue management of permanent cover crops on rhizosphere P cycling and availability in AFS with different ages.

Effects of Weed Management Treatments and Cover Crops as Winter Plating on Weed Population and Yield of Two Cultivars of Tomato

علفهای هرز یکی از عمده­ترین عوامل کاهنده در تولید گوجه فرنگی محسوب می­شوند. گیاهان پوششی از طریق چندین خصوصیت مانع جوانه­زنی و کاهش سبز شدن و استقرار علف­های هرز می­شوند. هدف از این مطالعه ارزیابی کنترل علف­های هرز با استفاده از گونه­های مختلف پوششی زمستانه در تولید گوجه فرنگی بود. این آزمایش به صورت اسپلیت پلات در قالب طرح بلوک­های کامل تصادفی با سه تکرار در مزرعه صبوری واقع در مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی خراسان رضوی در سال زراعی 97-1396 انجام شد. عامل اصلی شامل چهار گیاه پوششی زمستانه ]خلر (Lathyrus sativus)، ماشک گل خوشه­ای (Vicia villosa)، شنبلیله (Trigonella foenum-graecum) و چاودار (Secale cereale)[، آبیاری (خاک­ورزی بدون گیاه پوششی) و شاهد (خاک­ورزی بدون آبیاری پاییزه) و عامل فرعی دو رقم گوجه فرنگی (8320 و 6515 از شرکت فلات) بود. گیاهان پوششی زمستانه در بهار به خاک برگردانیده شدند. صفات مورد مطالعه شامل تراکم نسبی، تراکم و وزن خشک علفهای هرز در واحد سطح (در سه مرحله شامل 30 روز پس کاشت، 50 روز پس از کاشت و پیش از برداشت) و تعداد و عملکرد میوه و شاخص بریکس گوجه فرنگی در سه چین بود. نتایج نشان داد که دامنه کنترل گونه­های علف­ هرز در بین گونه­های پوششی زمستانه مختلف بود. کمترین تراکم و وزن خشک علف­های هرز برای ماشک گل خوشه­ای و چاودار مشاهده شد و بیشترین میزان به شاهد اختصاص داشت. ماشک گل خوشه­ای و چاودار گونه­های آللوپاتیکی با کارایی بالاتری در کنترل علف­های هرز دو لپه در مقایسه با گونه­های تک لپه هستند. اثر ساده و متقابل گیاهان پوششی زمستانه و رقم بر تعداد میوه و عملکرد میوه و شاخص بریکس گوجه فرنگی معنی­دار بود. بالاترین عملکرد در چین­های اول، دوم و سوم در تیمار ماشک گل­خوشه­ای (به ترتیب با 98/5760، 2896 و 51/1563 گرم بر مترمربع) به دست آمد و کمترین میزان به شاهد (به ترتیب با 32/4156، 65/1742 و 90/600 گرم بر مترمربع) اختصاص داشت. عملکرد کل رقم 6515 نسبت به رقم 8320 برابر با 15 درصد بالاتر بود. بیشترین و کمترین تعداد میوه در چین­های اول، دوم و سوم به ترتیب برای تیمار ماشک گل­خوشه­ای (به ترتیب با 31/75، 87/37 و 38/22 میوه بر مترمربع) و شاهد (به ترتیب با 33/54، 78/22 و 85/8 میوه بر مترمربع) مشاهده شد. شاخص بریکس رقم 8320 بالاتر از رقم 6515 بود. به طور کلی جمعیت علف هرز یکساله، دو ساله و چند ساله تحت تأثیر گونه­های پوششی زمستانه قرار گرفتند. نتایج این مطالعه نشان می­دهد که گونه­های پوششی زمستانه می­تواند به طور مؤثری در مدیریت تلفیقی علف­های هرز برای کاهش آلودگی علف­های هرز در تولید گوجه فرنگی مدنظر قرار گیرند.

Winter cover crops and no-till promote soil macrofauna communities in irrigated, Mediterranean cropland in California, USA

Cover crops and reduced tillage are two elements of conservation agriculture with potential to support larger and more diverse soil biological communities. Soil macrofauna can be indicators of soil quality and can regulate multiple soil functions, but their response to cover crop adoption in temperate regions is not well studied. We evaluated soil macrofauna communities and related soil quality metrics in response to a 16-year winter cover crop and tillage trial located in the San Joaquin Valley of California, USA. The most abundant taxa were Coleoptera (beetles) and Lumbricidae (earthworms), with average densities ranging between 5 and 318 beetles m−2 and 65–480 earthworms m−2 depending on sample date and treatments. Overall macrofauna abundance increased by 93% with the addition of cover crops in rotation, and 50% with the elimination of tillage. Taxonomic richness increased by 48% with cover crops in treatments managed without tillage, though there was no effect of cover crops under standard tillage. Macrofauna abundance was positively related to total soil carbon, water infiltration, and soil aggregate stability. Macrofauna community composition was best explained by soil carbon, water stable aggregate fraction, and cover crop usage. Agricultural management practices that foster soil biological communities may support biodiversity and improve environmental outcomes critical for sustainable food production.

Pelleted biosolids and cover crop effects on major Southern row crops

Pelleted biosolids (PBS) can be used as a low-cost nutrient source alternative to conventional fertilizers for row crop production. A field study was conducted on a Marietta loam at the Plant Science Center at Mississippi State to determine the response of row crops to PBS relative to poultry litter (PL) and inorganic fertilizer N in the presence/absence of cover crop residues. Fertilization treatments included PBS and PL at agronomic rate, PBS as one-time single application at the high rate, inorganic fertilizer N, and unfertilized control. At agronomic rate, PBS and PL relative to inorganic fertilizer had similar effects on corn (Zea mays L.) grain and cotton (Gossypium hirsutum L.) yields N and P utilizations. However, in 2019, corn grain yield and grain N uptake with PBS were less by 31% and 55% as compared to inorganic fertilizer, respectively. Pelleted biosolids and PL had similar residual effects on soybean (Glycine max L.) grain yield and grain N and P uptakes. Averaged across fertilization treatments, the presence of winter wheat (Triticum aestivum L.) cover crop residue significantly increased seed cotton yield by 7% as compared to winter fallow. One-time single application of PBS at the high rate resulted in significant NO3–N concentration below 30 cm and substantial P accumulations at the top 15 cm soil depth. At the agronomic rate, PBS can be considered as an alternative effective fertilizer for row crop productions.

Effect of winter cover crops on soil nutrients in two row-cropped watersheds in Indiana.

The midwestern United States is a highly productive agricultural region, and extended crop-free periods in winter/spring can result in nitrogen (N) and phosphorus (P) losses to waterways that degrade downstream water quality. Planting winter cover crops can improve soil health while reducing nutrient leaching from farm fields during the fallow period. In this study, we used linear mixed effects models and multivariate statistics to determine the effect of cover crops on soil nutrients by comparing fields with cover crops (n=9) versus those without (n=6) in two Indiana agricultural watersheds: the Shatto Ditch Watershed, which had>60% of croppable acres in winter cover crops, and the Kirkpatrick Ditch Watershed, which had ∼20%. We found that cover crops decreased soil nitrate-N by>50% and that the magnitude of reduction was related to the amount of cover crop biomass. In contrast, cover crops had variable effects on water extractable P and Mehlich III soil test P. Finally, cover crop biomass significantly increased soil N mineralization and nitrification rates, demonstrating that cover crops have the potential to supply bioavailable N to cash crop after termination. Our study showed that widespread implementation of winter cover crops holds considerable promise for reducing nutrient loss and improving soil health. The degree to which these results are generalizable across other systems depends on factors such as climate, soil characteristics, and past and current agronomic practices.

How do nitrogen fertilization and cover crop influence soil C-N stocks and subsequent yields of sugarcane?

Sugarcane production for biorenewables demands substantial inputs of nitrogen (N) fertilizer that can lead to environmental consequences, and no clear effect has been reported on soil organic carbon (SOC) and N stocks. The use of a previous legume crops cultivation to add N to soil is a promising strategy to reduce the dependence in synthetic N fertilizer, having an international appeal for sustainable production of bioenergy crops. This study investigates a four-year impact of N fertilization on SOC and N stocks and sugarcane ratoon yields in a sandy and clayey soils, while considering the effects of a legume cover crop cultivated during the renovation period on decreasing N fertilizer requirements. Treatments with N fertilizer rates were arranged in a randomized block design after plant-cane harvest: 60, 120, 180 kg N ha−1 and control (without N) in two paired areas previously managed with Crotalaria spectabilis and bare fallow. Soil samples for SOC and N stocks were quantified at the beginning of the trial, and measured again along with microbiological attributes after four consecutive years, while sugarcane yield was assessed annually. SOC and N stocks were unaffected by N fertilizer rates, whereas the cultivation of cover crop increased soil N storage and microbial biomass carbon. There was limited responsiveness of sugarcane ratoons to additional N supplied by inorganic fertilizer under cover crop, whereas positive responses occurred under bare fallow. Considering the average of four-harvest yields, cover crop increased sugarcane yield by 9 % (5 Mg ha−1) at sandy soil and 15 % (16 Mg ha−1) at clayey soil relative to bare fallow. Cover crop provided an annual N fertilizer replacement of 9 and 15 kg ha−1 in the sandy and clayey soils. The long-lasting historical effect of cover crop in increasing sugarcane yield per area without the need for extra N from fertilizer opens a new possibility to increase the sustainability and alleviate associated greenhouse gas emissions of sugarcane fields by allowing savings in synthetic N fertilizer.