Search Results (21)

Chickpea is a highly weed-prone crop with limited herbicide options and high labor demands, raising the following question: Can fall-planted legume–cereal cover crops (CCs) improve soil properties while reducing herbicide use and manual weeding pressure? To explore this, we evaluated the effect of fall-planted winter rye (WR) alone in 2021 and mixed with hairy vetch (HV) in 2022 and 2023 at Randolph farm in Petersburg, Virginia. The objectives were two-fold: (a) to examine the effect of CCs on soil properties using monthly growth dynamics and biomass harvested from fifteen 0.25 m²-quadrants and (b) to evaluate the efficiency of five termination methods: (1) green manure (GM); (2) GM plus pre-emergence herbicide (GMH); (3) burn (BOH); (4) crimp mulch (CRM); and (5) mow-mulch (MW) in suppressing weeds in chickpea fields. Weed distribution, particularly nutsedge, was patchy and dominant on the eastern side. Growth dynamics followed an exponential growth rate in fall 2022 (R² ≥ 0.994, p < 0.0002) and a three-parameter sigmoidal curve in 2023 (R² ≥ 0.972, p < 0.0047). Biomass averaged 55.8 and 96.9 t/ha for 2022 and 2023, respectively. GMH consistently outperformed GM in weed suppression, though GM was not significantly different from no-till systems by the season’s end. Kabuli-type chickpeas under GMH had significantly higher yields than desi types. Pooled data fitted well to a three-parametric logistic curve, predicting half-time to 50% weed coverage at 35 (MM), 38 (CRM), 40 (BOH), 46 (GM), and 53 (GMH) days. Relapses of CCs were consistent in no-till systems, especially BOH and MW. Although soil properties improved, CCs alone did not significantly suppress weed. Full article

A two-year field trial (2021–2023) was conducted to evaluate the impacts of cover crop (CC) inclusion (cereal rye, crimson clover, mixtures of cereal rye and crimson clover, and fallow control) and nitrogen (N) fertilization (0, 22, 45, 90, 135, and 180 kg N ha⁻¹) in cotton production in sandy soils. Cover crops were planted in October and terminated two weeks before cotton planting in May. The N was applied in split applications. Cover crop aboveground biomass was collected, oven dried, and weighed, and then used for C and N analyses. Soils were sampled at CC termination and analyzed for biogeochemical properties. Cotton lint yields and agronomic nutrient use efficiency (aNUE) were estimated. The CC mixtures provided higher organic C and N inputs as residue returns than individual species. Integrating CCs had limited impacts on measured soil properties. Integrating CCs resulted in positive, neutral, and adverse effects on lint yield and aNUE depending on species and growing seasons. Applying N at 22 kg ha⁻¹ increased lint yields in 2022, while higher rates did not improve the yields further. Similar patterns of impacts were observed at the N rate of 45 kg ha⁻¹ in 2023. The results indicated that integrating CC mixtures can favor long-term C and N sequestration in sandy soils. However, optimal management is essential to realize their benefits. Relevant research to better understand the decomposition of their residues would be beneficial in improving the management of desirable outcomes. Full article

By improving soil properties, cover crops can reduce wind erosion and sand damage to emerging cotton (Gossypium hirsutum L.) plants. However, on the Texas High Plains, questions regarding cover crop water use and management factors that affect cotton lint yield are common and limit conservation adoption by regional producers. Studies were conducted near Lamesa, TX, USA, in 2017–2020 to evaluate cover crop species selection, seeding rate, and termination timing on cover crop biomass production and cotton yield in conventional and no-tillage systems. The no-till systems included two cover crop species, rye (Secale cereale L.) and wheat (Triticum aestivum L.) and were compared to a conventional tillage system. The cover crops were planted at two seeding rates, 34 and 68 kg ha⁻¹, and each plot was split into two termination timings: optimum, six to eight weeks prior to the planting of cotton, and late, which was two weeks after the optimum termination. Herbage mass was greater in the rye than the wheat cover crop in three of the four years tested, while the 68 kg ha⁻¹ seeding rate was greater than the low seeding rate in only one of four years for both rye and wheat. The later termination timing produced more herbage mass than the optimum in all four years. Treatments did not affect cotton plant populations and had a variable effect on yield. In general, cover crop biomass production did not reduce lint production compared to the conventional system. Full article

Sunn hemp (Crotalaria juncea L.), a warm season leguminous cover crop, is commonly used in rotation with organic strawberry production in Florida’s subtropical environment. This study was conducted to explore the impacts of sunn hemp on growth and yield performance of the subsequent organic strawberry crop in sandy soils, taking into consideration the nutrient contribution from soil incorporation of sunn hemp biomass. Sunn hemp was seeded during the summer off-season and terminated before flowering, three weeks prior to the fall planting of two strawberry cultivars (‘Strawberry Festival’ and ‘Camino Real’). With sunn hemp residues incorporated into the soil, two application rates of nitrogen (N) through pre-plant organic fertilization for the strawberry season were used, including N at a rate of 84 kg/ha, without consideration of the N credit from sunn hemp, and N at a rate of 19.8 kg/ha, with consideration of the estimated N credit from sunn hemp. A summer fallow without cover crop and with a pre-plant organic fertilizer application at the N rate of 84 kg/ha was included as the control. Overall, the sunn hemp incorporation at three weeks after termination did not benefit the strawberry plant growth or fruit yield in this study, with rather low levels of soilborne pathogen and nematode infestations. Both sunn hemp treatments exhibited a significantly lower level of total soil N compared to the summer fallow plots at the end of the strawberry season. The reduction in the pre-plant N fertilization resulted in lower above-ground plant dry weight and accumulation of N, phosphorus (P), and potassium (K) at the end of the strawberry season, along with fewer leaves and smaller crowns of the strawberry plants during the early season. Both sunn hemp treatments decreased early fruit yields, while the sunn hemp treatment with the reduced N fertilization also led to a significant reduction in the total fruit number and weight, although no significant differences in the whole-season marketable fruit yield were observed among the nutrient management treatments. Overall, ‘Strawberry Festival’ yielded higher than ‘Camino Real’, but the effects of nutrient management did not vary with the strawberry cultivars. Further studies are needed to enhance organic strawberry nutrient management involving rotational cover crops. Full article

Summer cover crop utilization by no-till vegetable farms is essential for continuous soil protection, especially in the southern United States where intense storms are likely to occur in hot and humid summer months. A field experiment was conducted at the National Soil Dynamics Laboratory in Auburn, AL, USA, between the summers of 2015 and 2017 to determine the effectiveness of an experimental roller/crimper in mechanically terminating summer cover crops. Iron clay peas (Vigna unguiculata, L.) planted on a sandy loam and pearl millet (Penninsetum glaucum, L.) planted on clay soil were selected to determine termination rate effectiveness in single, double, and triple rolling/crimping over the same area. Overall, termination rates for both cover crops were higher for rolling three times (71%) compared to rolling once (55%) or twice (63%). However, cover crop termination was inhibited due to rainfalls on the experimental area during the three-week evaluation period. In 2016, drought conditions and high temperatures (32.6 °C) caused biomass reduction, especially for pearl millet, of over 31% to 39% compared to 2017 and 2015. Rolling provided higher soil-water conservation compared with the non-rolled control due the cover crop mulch layer blocking sunlight, keeping the soil surface cooler and preventing water evaporation. Recurrent rolling did not cause soil compaction above the 2.0 MPa level that inhibits root growth, but changes in soil strength were dependent on the soil moisture content. Full article

Cover cropping is vital for soil health. Timing and method of termination are major factors influencing the agroecological benefits of cover crops. Delay in the termination of cover crops results in greater biomass production. Likewise, incorporation of cover crops during termination often speeds residue mineralization compared to no-till systems. We used four termination strategies for a late-terminated winter rye–legume mix (in tilled and no-till systems) and four N application rates in the succeeding sweet corn crop to examine how cover crop termination affected N response in sweet corn as well as the independent effects of N application rate and cover crop termination method. The experiment was conducted using a randomized complete block design with four replications. Increasing N fertilization up to 144 kg N ha⁻¹ promoted yield and quality in sweet corn as well as summer weed growth. The cover crop termination method did not affect sweet corn response to N fertilizer. This suggests that when rye is terminated late in the spring before planting cash crops, the incorporation of its residues may not greatly affect the soil N dynamics. This indicates that decisions to incorporate rye residues may be taken by farmers with an eye mainly towards management issues such as weed control, environmental impacts, and soil health. Full article

The use of roller crimpers to terminate plants and obtain a natural mulch before cash crop establishment has been identified as a valid and sustainable approach to control weeds. Several enhancements have been evaluated to improve and speed up plant termination to avoid delays in cash crop planting and consequent yield losses, which can occur with standard roller crimpers. In the present study, a new prototype machine provided with a roller crimper and an undercutting blade, allowing it to simultaneously crimp plant stems and cut root systems, has been designed, realized, and tested. The aim of the research was therefore to evaluate the effectiveness of the prototype for plant termination and to compare it with a commercial roller crimper. The termination was performed on a spontaneous vegetation cover (weeds). A monophasic exponential decay model to evaluate the weed termination rate over time was performed. The fitted model showed that the prototype is able to achieve a greater and faster weed devitalization compared to the commercial roller crimper, with a lower plateau (0.23 vs. 5.35 % of greenness of plant material, respectively) and higher constant of decay (1.45 vs. 0.39 day⁻¹, respectively). Further studies are needed to evaluate the prototype’s effectiveness in relation to different soil textures, moisture conditions, and amounts of plant biomass to manage, to further improve the machine and extend its use in a broad range of situations, including cover crop termination. Full article

Cover crops could provide environmental benefits in spring-grain systems through diversification, reduced nitrate leaching, and carbon sequestration. However, few farmers apply the technique, partly as they believe the cover crops will compete with the main crop and cause yield losses. Cover crops can either be sown together with the grain (undersown) or in autumn and establish after grain harvest. The current study uses a mixed-method approach combining field trials, interviews, and literature synthesis. The field trials focused on perennial ryegrass (Lolium perenne L.), Italian ryegrass (Lolium multiflorum Lam.), and meadow fescue (Festuca pratensis L.) that were undersown with 15 kg ha⁻¹ but with different seeding dates in spring wheat and barley. The interviews focused on gathering practical experiences from farmers in Norway and the literature synthesis gathered results from other studies. For carbon sequestration, nine studies were judged relevant for our target climate and included in our synthesis. They showed a median value at 264 kg C ha⁻¹ year⁻¹. In our field trials, 300–900 kg DM ha⁻¹ year⁻¹ was produced, with Italian ryegrass sown at the same date as the grain on top. Our trials showed no significant grain yield reduction due to the use of cover crops. However, our synthesis of the literature showed a 5–10% yield reduction with Italian ryegrass that was sown at the same time as the grain. One- or two-weeks delay in the sowing of Italian ryegrass, or reduced seeding rates, could reduce the problem. The interviews showed that farmers do not prefer undersown species, especially not perennial species, as they have experienced that such species may come up again in the following years and cause a weed problem. We recommend farmers to use cover crops and for undersowing, we recommend Italian ryegrass that is sown one or two weeks after the grain. Perennial ryegrass can also be recommended, as long as the growth is properly terminated. Full article

A no-till experiment was conducted in Auburn, AL U.S.A. to evaluate the effectiveness of an experimental two-stage roller/crimper in reoccurring rolling over the same area planted with a cereal rye/crimson clover cover crop mix and its influence on bush bean yield. Cover crop termination was much greater with rolling/crimping when compared to the non-rolled (untreated) control. During the three growing seasons, rolling three times had significantly higher termination rates compared to all other treatments, exceeding 90% in 2020. These results suggest that there may be an advantage to rolling/crimping three times so that planting of the cash crop could potentially be performed one week earlier, under favorable soil moisture conditions. However, for growing seasons 2018 and 2020 at three weeks after rolling, there were no differences between rolling treatments. In 2019, rolling three times over the same cover crop area was the only treatment that achieved above 90% termination rate indicating a clear advantage of recurring rolling/crimping in 2019. Rolling/crimping proved to be effective as yield was significantly higher compared to not rolled when averaged over all three growing seasons. This is possible due to the difficulty in planting into a standing cover crop which could have negative effects on seed to soil contact, but more importantly explained with the slight soil moisture advantage given to the rolled plots over the standing cover crop plots. Thus, optimum soil moisture when planting beans is key for successful germination and good main crop stand. Full article

In a no-till system, there are many different methods available for terminating cover crops. Mechanical termination, utilizing rolling and crimping technology, is one method that injures the plant without cutting the stems. Another popular and commercially available method is mowing, but this can cause problems with cover crop re-growth and loose residue interfering with the planter during cash crop planting. A field experiment was conducted over three growing seasons in northern Alabama to determine the effects of different cover crops and termination methods on cantaloupe yield in a no-till system. Crimson clover, cereal rye, and hairy vetch cover crops were terminated using two different roller-crimpers, including a two-stage roller-crimper for four-wheel tractors and a powered roller-crimper for a two-wheel walk-behind tractor. Cover crop termination rates were evaluated one, two, and three weeks after termination. Three weeks after rolling, a higher termination rate was found for flail mowing (92%) compared to lower termination rates for a two-stage roller (86%) and powered roller-crimper (85%), while the control termination rate was only 49%. There were no significant differences in cantaloupe yield among the rolling treatments, which averaged 38,666 kg ha⁻¹. However, yields were higher for cereal rye and hairy vetch cover crops (41,785 kg ha⁻¹ and 42,000 kg ha⁻¹) compared to crimson clover (32,213 kg ha⁻¹). Full article

A decrease in water resources, as well as changing environmental conditions, calls for efficient irrigation-water management in cotton-production systems. Cotton (Gossypium sp.) is an important cash crop in many countries, and it is used more than any other fiber in the world. With water shortages occurring more frequently nowadays, researchers have developed many approaches for irrigation-water management to optimize yield and water-use efficiency. This review covers different irrigation methods and their effects on cotton yield. The review first considers the cotton crop coefficient (Kc) and shows that the FAO-56 values are not appropriate for all regions, hence local Kc values need to be determined. Second, cotton water use and evapotranspiration are reviewed. Cotton is sensitive to limited water, especially during the flowering stage, and irrigation scheduling should match the crop evapotranspiration. Water use depends upon location, climatic conditions, and irrigation methods and regimes. Third, cotton water-use efficiency is reviewed, and it varies widely depending upon location, irrigation method, and cotton variety. Fourth, the effect of different irrigation methods on cotton yield and yield components is reviewed. Although yields and physiological measurements, such as photosynthetic rate, usually decrease with water stress for most crops, cotton has proven to be drought resistant and deficit irrigation can serve as an effective management practice. Fifth, the effect of plant density on cotton yield and yield components is reviewed. Yield is decreased at high and low plant populations, and an optimum population must be determined for each location. Finally, the timing of irrigation termination (IT) is reviewed. Early IT can conserve water but may not result in maximum yields, while late IT can induce yield losses due to increased damage from pests. Extra water applied with late IT may adversely affect the yield and its quality and eventually compromise the profitability of the cotton production system. The optimum time for IT needs to be determined for each geographic location. The review compiles water-management studies dealing with cotton production in different parts of the world, and it provides information for sustainable cotton production. Full article

Sorghum/sorghum–sudangrass hybrids (SSgH) have been used as a cover crop to improve soil health by adding soil organic matter, enhancing microbial activities, and suppressing soil-borne pathogens in various cropping systems. A series of SSgH were screened for (1) allelopathic suppression and (2) improvement of soil edaphic factors and soil microbial profile against plant-parasitic nematode (PPNs). The allelopathic potential of SSgH against PPNs is hypothesized to vary by variety and age. In two greenhouse bioassays, ‘NX-D-61′ sorghum and the ‘Latte’ SSgH amendment provided the most suppressive allelopathic effect against the female formation of Meloidogyne incognita on mustard green seedlings when using 1-, 2-, or 3-month-old SSgH tissue, though most varieties showed a decrease in allelopathic effect as SSgH mature. A field trial was conducted where seven SSgH varieties were grown for 2.5 months and terminated using a flail mower, and eggplant was planted in a no-till system. Multivariate analysis of measured parameters revealed that increase in soil moisture, microbial biomass, respiration rate, nematode enrichment index, and sorghum biomass were negatively related to the initial abundance of PPNs and the root-gall index at 5 months after planting eggplant in a no-till system. These results suggested that improvement of soil health by SSgH could lead to suppression of PPN infection. Full article

In drill-seeded, delay-flooded organic rice production, reliable predictions of N supply from cover crop (CC) residues to subsequent rice are still a challenge. An incubation was conducted to determine the effects of CC types (clover, ryegrass, clover and ryegrass mixtures, and fallow), residue application rates (0, 0.6, 1.2, 1.8, and 2.4%) and incubation time on soil CO₂ evolution and N mineralization and availability. The cumulative CO₂ evolution linearly increased with increasing residue rate. Compared to the control, adding CCs residue significantly increased the cumulative CO₂ emission, which was greatest in soils with clover or mixtures of clover and ryegrass, followed by fallow, and lowest in soils with ryegrass. The modeling results indicated clover had the greatest initial C and N mineralization rates and the shortest half-lives. A temporary decrease in soil mineral N caused by immobilization occurred at the initial incubation stage in all treatments. However, the trend reversed progressively, with the clover treatment requiring the shortest time to meet the crossover point. The results suggested clover was the optimal CC type, 0.6% was the optimal residue rate, and a minimum of 27 days between CC termination and rice planting was required to maximize mineral N supply for organic rice. Full article

Rollers/crimpers have been used to terminate cover crops typically with supplemental herbicide application to speed-up termination. Due to environmental concerns, there is a need to reduce herbicide use. In the Southern USA, the cash crop is typically planted three weeks after a rolled cover crop reaches more than 90% kill rate which eliminates competition with the cash crop for water and nutrients. A three-year replicated field experiment was initiated in the fall of 2014 to determine the effects of recurring rolling by experimental rollers/crimpers in terminating a cereal rye cover crop in central Alabama and how multiple rolling affected soil strength. Experimental 2-stage (one smooth drum and one crimping drum), 4-stage (one smooth drum and three crimping drums), spiral, and smooth rollers were tested to roll rye 1, 2, and 3 times (conducted at the same day). A smooth roller with mounted spray boom applying glyphosate rolling once was also evaluated, and untreated rye was the control. Rye was terminated at the milk growth stage and was evaluated one, two and three weeks after rolling. At one week after rolling, the highest rye kill rate was obtained with rolling three times by the 4-stage (96%), 2-stage (92%), spiral roller (81%); rolling once by the smooth roller with glyphosate (94%) compared to the untreated rye at 37%. At two weeks after rolling no differences among rollers were found (91% to 98%); the untreated rye was 54%. Similarly, at three weeks after rolling no differences were detected among rollers (99% to 100%); the untreated rye was 86%. Rolling 2 or 3 times compared with rolling one time did not cause soil compaction. However, at the 15 cm depth cone index (CI) did exceed 2 MPa (a critical value of root penetration restriction); although this CI increase was solely related to decrease in gravimetric soil moisture content (GMC). In addition, over three growing seasons, the seed cotton yield was not affected by rolling treatments with the average yield of 3601 kg ha⁻¹ (1512 kg ha⁻¹ of cotton lint). Full article

The cotton bollworm Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) is an important pest of many crops that has developed resistance to almost all groups of insecticides used for its management. Insecticide resistance was often related to Transposable Element (TE) insertions near specific genes. In the present study, we deeply retrieve and annotate TEs in the H. armigera genome using the Pipeline to Retrieve and Annotate Transposable Elements, PiRATE. The results have shown that the TE library consists of 8521 sequences representing 236,132 TE copies, including 3133 Full-Length Copies (FLC), covering 12.86% of the H. armigera genome. These TEs were classified as 46.71% Class I and 53.29% Class II elements. Among Class I elements, Short and Long Interspersed Nuclear Elements (SINEs and LINEs) are the main families, representing 21.13% and 19.49% of the total TEs, respectively. Long Terminal Repeat (LTR) and Dictyostelium transposable element (DIRS) are less represented, with 5.55% and 0.53%, respectively. Class II elements are mainly Miniature Inverted Transposable Elements (MITEs) (49.11%), then Terminal Inverted Repeats (TIRs) (4.09%). Superfamilies of Class II elements, i.e., Transib, P elements, CACTA, Mutator, PIF-harbinger, Helitron, Maverick, Crypton and Merlin, were less represented, accounting for only 1.96% of total TEs. In addition, we highlighted TE insertions in insecticide resistance genes and we successfully identified nine TE insertions belonging to RTE, R2, CACTA, Mariner and hAT superfamilies. These insertions are hosted in genes encoding cytochrome P450 (CyP450), glutathione S-transferase (GST), and ATP-binding cassette (ABC) transporter belonging to the G and C1 family members. These insertions could therefore be involved in insecticide resistance observed in this pest. Full article