Cover Crop Termination Research Articles

Cover Crop Termination Methods and Custom Residue Manager Effects on Collard Production

Producers are looking for more sustainable methods of producing fresh vegetables. No-till systems that use cover crops to keep the soil surface covered can increase sustainability by reducing soil erosion, reducing weed pressure, and retaining soil moisture compared to bare soil cropping systems. Cover crop termination methods along with planting equipment modifications required to work in high residue planting systems are often areas of interest to farmers prior to adopting no-till systems. The objectives of this experiment are to compare the effects of two different cover crops, iron clay pea (Vigna unguiculata L.), and pearl millet (Pennisetum glaucum L.), using three different termination methods (rolled/crimped, mowed, and mowed + incorporated via tillage) and two no-till transplanter configurations (with and without residue manager) on soil properties and collard (Brassica oleracea L. var. viridis) yield. Results show that biomass production for pearl millet was greater, with a three-season average of 8461 kg ha−1 compared to 6465 kg ha−1 for iron clay pea. Rolled cover crops under drier weather conditions retained more volumetric soil moisture compared to other methods for both cover crops. Increases in total soil carbon and nitrogen concentration in the top 15 cm ranged from 8 to 11% and 23 to 35%, respectively. Collards grown in an iron clay pea cover crop produced greater weight and height per plant for all growing seasons compared to those grown in pearl millet. Collard yield was affected by cover crop type as reported with iron clay peas ranging from 2881–13,168 kg ha−1 compared to lower yield for the pearl millet cover crop with a range of 1354–8943 kg ha−1. Overall, both cover crops showed the ability to improve soil health by increasing total soil carbon, but collard production was better in the iron clay pea cover crop.

Recurring Rolling/Crimping Effects on Termination Effectiveness of Iron Clay Pea and Pearl Millet Warm-Season Cover Crops

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.

Enhancing winter rye termination by mixing glyphosate with other herbicides using water or UAN as the carrier

AbstractHerbicides are often used to terminate cover crops. Producers would like to use herbicides that work quickly, are effective, and do not increase the risk of selecting herbicide-resistant weeds. Eight experiments were conducted to determine whether mixing glyphosate (900 g a.e. ha−1) with rimsulfuron (15 g a.i. ha−1), mesotrione (100 g a.i. ha−1), or rimsulfuron + mesotrione enhances winter rye control and to ascertain whether using urea ammonium nitrate (UAN) as the herbicide carrier improves and accelerates herbicide efficacy. Winter rye control was assessed 1, 2, 3, and 4 wk after application (WAA) and biomass was measured 4 WAA. The addition of rimsulfuron, mesotrione, or rimsulfuron + mesotrione to glyphosate did not enhance winter rye control. Similarly, using UAN as the herbicide carrier did not improve or accelerate herbicide efficacy. Glyphosate alone provided the greatest level of winter rye control. The addition of rimsulfuron, mesotrione, or rimsulfuron + mesotrione to glyphosate did not increase the level or speed of control. However, mixing glyphosate with rimsulfuron, mesotrione, or rimsulfuron + mesotrione adds other modes of action without compromising winter rye control.

Increasing rye cover crop biomass production after corn residue removal to balance economics and soil health

Low or variable cover crop (CC) biomass production could limit CC benefits. Longer CC growing periods via late termination could increase CC benefits, especially under limited crop residue return. We studied whether early (2–3 wk before planting)- or late (at planting)-terminated winter rye (Secale cereale L.) CC maintains soil properties, crop yields, and farm income under 0%, 25%, 50%, 75%, and 100% corn (Zea mays L.) residue removal in rainfed and irrigated no-till in the U.S. Great Plains after 6 yr. Early-terminated CCs produced < 1 Mg ha-1 of biomass while late-terminated CCs averaged 1.6 Mg ha-1 at the rainfed site and 3.0 Mg ha-1 at the irrigated site. At the rainfed site, CC termination date did not affect soils, but ≥ 75% residue removal reduced soil organic matter (OM) fraction concentrations and 100% reduced mean weight diameter of water-stable aggregates (MWD) in the 0–5 cm depth. At the irrigated site, late-terminated CC increased MWD by 0.22 mm and OM concentration by 5.1 g kg-1 compared with no CC. At the same site, 100% residue removal reduced microbial biomass, while ≥ 50% removal reduced OM concentration by 7.6 g kg-1, available water, and MWD by 0.75 mm relative to no removal. Cover crops only partially offset the adverse effects of residue removal if biomass production was 3 Mg ha-1 yr-1. Corn yield was generally unaffected. High residue removal rates offset CC-induced reduction in net income. Overall, late-terminated CC partially maintains soil health indicators following residue removal and minimally impacts crop yields and economics.

Cereal rye residue management tactics influence interrow and intrarow weed recruitment dynamics in field corn when planting green

AbstractDelaying cover crop termination until cash crop planting (i.e., planting green) is an emerging no-till practice. Improved management recommendations are needed for optimizing weed suppression benefits while minimizing other pest, fertility, and crop management risks when planting green in corn production systems. In a 2-yr field experiment, we evaluated the interaction between cereal rye residue management tactics (standing residue, roll-crimping, roll-crimping with row cleaners) and herbicide programs (1-pass preemergence [PRE], 2-pass postemergence [POST]) when planting green on weed recruitment spatial patterns and corn performance compared to standard termination (14 d preplant [DPP]) and ryelage harvest (14 DPP) practices. In a 2-yr on-farm experiment, we evaluated corn performance in response to the same residue management tactics. Cereal rye biomass production varied significantly across years in on-station experiments, with average (4.9 Mg ha−1) and anomalous (9.9 Mg ha−1) levels observed in 2020 and 2021, respectively. In 2020, planting green with an integrated roll-crimper/row cleaner system resulted in greater intrarow weed density compared with planting green into standing cereal rye. Interrow weed density was lower when roll-crimping was employed compared to early termination (14 DPP). Planting green into standing cereal rye resulted in greater mean corn height (V5 stage) compared to other treatments, but corn population and yield did not differ. In 2021, few differences in weed recruitment patterns were observed, but corn population and yield were significantly lower in planting green treatments compared to early termination. In both years, late-season weed biomass was lower in two-pass POST programs compared to one-pass PRE programs. On-farm trials showed that planting green into standing residue increases corn height and can reduce corn populations, which may lead to reduce yields. Our results suggest that management recommendations for optimizing herbicide application timing should consider intrarow and interrow weed recruitment dynamics associated with residue management tactics needed to optimize corn performance.

Determining cardinal temperatures for eight cover crop species

AbstractGrowing degree days (GDD) is a tool to predict plant growth and can be adapted for use in any plant species, including cover crops. A limitation of the GDD calculation is accurate temperature parameters used to predict plant development. For most cover crop species, the cardinal temperatures are not well defined in the literature, leading to a less accurate calculation of GDD. The objective of this study was to determine the cardinal temperatures of eight cover crop species, including Austrian winter pea (Pisum sativum), balansa clover (Trifolium michelianum), barley (Hordeum vulgare), black‐seeded oats (Avena sativa), common vetch (Vicia sativa), cereal rye (Secale cereale), crimson clover (Trifolium incarnatum), and hairy vetch (Vicia villosa), using a growth chamber experiment. Seven different temperature regimes from 4 to 34°C were implemented, and the number of leaves was counted from day 0 to 21. As a result, the data were regressed to estimate the cardinal temperatures for each species. The results of this research identified base (2), optimum (3), and maximum (8) temperatures for cover crops that were not previously reported. Five cardinal temperatures determined in this study were different from what was previously recorded; base and optimum temperatures were −4.5 and 24.8°C for cereal rye, 3.9 and 26.6°C for crimson clover, and the base temperature was 3.4°C for balansa clover. The successful identification of these cardinal temperatures for cover crops will allow the development of plant growth and biomass prediction models to aid in cover crop termination decision support tools.

The effects of cereal rye cover crop seeding rate, termination timing, and herbicide inputs on weed control and soybean yield

AbstractGrowers have been experimenting with cover crop termination timings to maximize weed suppression and potentially reduce herbicide inputs in soybean [Glycine max (L.) Merr.]. A field study was replicated three times from 2018 through 2021 in South Charleston, OH, to evaluate different management strategies involving a cereal rye (Secale cereale L.) cover crop. The objectives were to determine the effects of cereal rye seeding rate (0, 50, and 100 kg ha−1), management program (preplant, postplant, and delayed), and soybean residual herbicide (flumioxazin + chlorimuron ethyl and no herbicide) on cover crop, weed, and soybean parameters. The preplant program consisted of cereal rye terminated 7 d before planting (DBP) + a postemergence application. The postplant program consisted of cereal rye terminated 7 d after planting (DAP) + a postemergence application. In the delayed program, saflufenacil was applied in April and cereal rye was terminated 21 DAP, and there was no postemergence application. Giant foxtail (Setaria faberi Herrm.) density was reduced by the presence of cereal rye, averaged over other factors, regardless of seeding rate. Cereal rye seeding rate did not affect giant ragweed (Ambrosia trifida L.) density. The delayed management program was generally associated with the lowest weed density, but weed density was often similar in the postplant program. Setaria faberi density was lower in treatments that included a residual herbicide. Residual soybean herbicide use did not affect density of A. trifida. Terminating cereal rye after soybean planting resulted in increased soybean yield in 2019 and reduced yield in 2020, compared with preplant rye termination. These data suggest that adjusting the cereal rye management program may have a greater effect on weed suppression than adjustments to seeding rate. Delaying termination of cereal rye can aid in the suppression of weeds, but a comprehensive herbicide program was necessary to provide adequate (&gt;85%) weed control.

Optimizing organic no‐till planted soybean with cover crop selection and termination timing

AbstractResearch is needed to develop and optimize agroecological practices that can replace unsustainable managementand increase agricultural diversification. Field experiments were conducted in Maryland and New York to assess the effect of cover crop cultivar selection and cover crop termination soybean [Glycine max (L.) Merr.] planting (roll‐plant) date on cover crop growth stage, biomass, and reseeding; weed biomass; and soybean density and yield in organically managed no‐till planted soybean production. Twelve winter cereal cultivars—four each for barley (Hordeum vulgare L.), cereal rye (Secale cereale L.), and triticale (× Triticosecale Wittm. ex A. Camus.)—were seeded at equivalent densities and terminated at four roll‐plant dates. Although many cover crop cultivars had not yet reached the recommended growth stage for adequate termination (anthesis) at the earlier roll‐plant dates, greater soybean yields and similar cover crop reseeding, compared with later dates, were observed. Weed biomass was low across treatments despite cover crop biomass production below the recommended threshold of 8 Mg ha−1. When pooled over cultivars, triticale performed as well as cereal rye in terms of biomass production, weed suppression, and soybean yield. Within each species, differences in weed biomass and soybean yield were observed among cultivars, but inconsistent across site‐years. Results from this research also show that planting soybean before cover crop anthesis can help maximize yield. Farmers can improve management in cover crop‐based no‐till planted soybean by selecting regionally adapted winter cereal species and cultivars that perform well across a range of outcomes, rather than focusing exclusively on biomass production.

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.

Cover Crop Residues Decomposition and Nutrient Releases in a Sandy Ultisols of U.S. Coastal Plain: Impacts of Termination Timing

ABSTRACT One benefit of cover cropping is nutrient provision, which can be optimized by management practices to synchronize nutrient releases from residue decomposition with the demands of subsequent cash crops. In the present study, we investigated how termination timing affects the decomposition of cereal rye (Secale cereale L.) residues and the release of associated nutrients. Field experiments were conducted in 2019 and 2020 in typical Ultisols of the Southeastern U.S. with soybean (Glycine max L.) and corn (Zea mays L.) rotation. Cover crops were drill-seeded and terminated 1-, 2-, 3- and 4-week before cash crop planting. Litter bag method and a two-parameter exponential decaying model were applied to estimate residue decomposition and nutrient releases. In 2019, cover crop biomass production ranged from 5757 to 6520 kg ha−1, which was not affected by termination timing. In contrast, cover crop biomass increased when delaying termination by 1 week in 2020. Cover crop provided up to 82 kg nitrogen (N) ha−1, 15 kg phosphorous (P) ha−1, and 89 kg potassium (K) ha−1 in 2019. As expected, terminating cover crops at 1-week intervals resulted in different decomposition rates but imposed inconsistent effects on N, P, and K releases. There was no difference in N, P, and K content in cash crops. However, cover cropping resulted in higher corn yields than control plots when terminated at 4-week before corn planting. The results suggested that cover crops can have significant nutrient benefits in the tested soils and climatic conditions, but optimal management is the key to realizing the potential.

Cover cropping impacts on soil water and carbon in dryland cropping system.

Incorporating cover crops into the rotation is a practice applied across many parts of the globe to enhance soil biological activities. In dryland farming, where crop production is highly dependent on rainfall and soil water storage, cover cropping can affect soil water, yet its effects on soil hydrological and biological health require further investigation. The objective of this study was to evaluate the effect of different timing of summer sorghum cover crop termination on soil water, total and labile organic carbon, arbuscular mycorrhizal fungi and their mediating effects on wheat yield. Through on-farm trial, soil characteristics along with wheat biomass, yield and grain quality were monitored. In comparison with the control (fallow), the early terminated cover crop was the most effective at retaining greater soil water at wheat sowing by 1~4% in 0-45cm soil profile. An increase in water use efficiency, yield and grain protein by 10%, 12% and 5% was observed under early termination. Under late terminated summer cover crop, there was 7% soil water depletion at wheat planting which resulted in 61% decline in yield. However, late-terminated cover crop achieved the greatest gain in soil total and particulate organic carbon by 17% and 72% and arbuscular mycorrhizal fungal Group A and B concentration by 356% and 251%. Summer cover crop incorporation resulted in a rapid gain in labile organic carbon, which constituted hotspots for arbuscular mycorrhizal fungi growth, conversely, fungal activities increased labile organic carbon availability. The combined effect of increased soil water at sowing and over the growing season, organic carbon, and microbial activities contributed to greater yield. The findings suggest that summer cover cropping with timely termination can have implications in managing soil water at sowing time and enhancing soil water storage during the season, soil carbon, and facilitating microbial activities while enhancing productivity in the dryland cropping system.

Above and belowground litter decomposition of cover crops grazed at different intensities

AbstractGrazing cover crops may increase land‐use efficiency while promoting sustainability. We investigated how grazing intensity affects cover crop litter quantity, quality, decomposition, and cotton (Gossypium hirsutum L.) N uptake. Cover crops were a mixture of rye (Secale cereale L.) and oat (Avena sativa L.) managed as follows: no grazing +34 kg N ha−1 (NG34), no grazing +90 kg N ha−1 (NG90), heavy grazing (HG), moderate grazing (MG), and light grazing (LG). Grazed treatments received 90 kg N ha−1. After cover crop termination, above‐ and belowground litter was collected and incubated in situ for 0, 4, 8, 16, 32, 64, and 128 days, with cotton plants sampled on the same days to estimate N recovery and synchrony between N release from litter and uptake by cotton. By Day 128, only 13% of initial NG34 aboveground biomass had disappeared, whereas 42% of HG disappeared. Nitrogen retained in aboveground litter of HG was less than NG90 (27 vs. 60 kg N ha−1), and aboveground final N stock (at Day 128) of HG was less than NG90 and LG (16, 47, and 41 kg N ha−1, respectively). Belowground litter contributed 98 kg N ha−1 versus 46 for aboveground. Belowground N disappearance from litter bags was greater from NG90 than NG34 (39 vs. 21 kg N ha−1). Cotton N uptake by Day 128 was similar across treatments (191 kg N ha−1). Grazing cover crops impact aboveground litter quantity, quality, and decomposition rates, and belowground litter plays an important role on the N cycling.

Short-Term Effects of Cover Crops on Soil Physical, Chemical, and Biological Properties in the Southeastern Argentinean Pampas

ABSTRACT Cover crop (CC) inclusion in cropping sequences could ameliorate negative effects of continuous agriculture on soil properties. The use of CC as a sustainable management tool can reverse the soil degradation process and improve soil health in the short term. The present study evaluated soil properties following short-term cover cropping in on-farm conditions. Three strip-trial experiments were conducted. Treatments were: i) oat (Avena sativa), ii) vetch (Vicia villosa), and iii) control (without CC). Prior to CC chemical termination, shoot and root dry matter (DM) and DM nitrogen accumulation in CC shoot (Nac) were determined. After CC termination, we determined: soil bulk density (BD), penetration resistance (PR), infiltration (INF), aggregate stability, total and particulate organic carbon (POC), organic nitrogen, nitrogen mineralized in anaerobic incubation (Nan) and soil glomalin. On average across sites, grater shoot, and root DM were determined in oat than vetch, while Nac was greater in vetch. The POC and Nan increased by CC inclusion mainly in 0–5 cm soil depth. Improvements of over 50% in INF (0–20 cm) and 8% in BD (0–5 cm) were determined in CC treatments compared to control. The effects of CC on some soil parameters depended on the previous management practices (i.e. tillage system, crop sequences). In the short-term, CC inclusion improves some soil properties, depending on their sensibility to management practices.

Cover crop termination options and application of remote sensing for evaluating termination efficiency.

Efficient termination of cover crops is an important component of cover crop management. Information on termination efficiency can help in devising management plans but estimating herbicide efficacy is a tedious task and potential remote sensing technologies and vegetative indices (VIs) have not been explored for this purpose. This study was designed to evaluate potential herbicide options for the termination of wheat (Triticum aestivum L.), cereal rye (Secale cereale L.), hairy vetch (Vicia villosa Roth.), and rapeseed (Brassica napus L.), and to correlate different VIs with visible termination efficiency. Nine herbicides and one roller-crimping treatment were applied to each cover crop. Among different herbicides used, glyphosate, glyphosate + glufosinate, paraquat, and paraquat + metribuzin provided more than 95% termination for both wheat and cereal rye 28 days after treatment (DAT). For hairy vetch, 2,4-D + glufosinate and glyphosate + glufosinate, resulted in 99 and 98% termination efficiency, respectively, followed by 2,4-D + glyphosate and paraquat with 92% termination efficiency 28 DAT. No herbicide provided more than 90% termination of rapeseed and highest control was provided by paraquat (86%), 2,4-D + glufosinate (85%), and 2,4-D + glyphosate (85%). Roller-crimping (without herbicide application) did not provide effective termination of any cover crop with 41, 61, 49, and 43% termination for wheat, cereal rye, hairy vetch, and rapeseed, respectively. Among the VIs, Green Leaf Index had the highest Pearson correlation coefficient for wheat (r = -0.786, p = <0.0001) and cereal rye (r = -0.804, p = <0.0001) with visible termination efficiency rating. Whereas for rapeseed, the Normalized Difference Vegetation Index (NDVI) had the highest correlation coefficient (r = -0.655, p = <0.0001). The study highlighted the need for tankmixing 2,4-D or glufosinate with glyphosate for termination instead of blanket application of glyphosate alone for all crops including rapeseed and other broadleaf cover crops.

Simulated effects of cover crops with no-tillage on soil and crop productivity in rainfed semi-arid cotton production systems

Cover cropping and no-tillage (NT) practices are promoted for soil health and environmental benefits. However, producing enough quantity of biomass to meet expected benefits can be a challenge in semi-arid cropping systems where water resources are limited, and producers have lingering questions regarding cover crop selection, termination timings, water use, and their subsequent effect on cash crop. The objective of this study was to assess the impacts of cover crops with NT on soil and crop productivity in a rainfed, continuous cotton (Gossypium hirsutum L.) system using the Denitrification Decomposition (DNDC) model. Treatments included: (a) conventional till (CT); (b) NT, and NT with the following cover crops: (c) Austrian winter pea (Pisum sativum L.) (Pea); (d) crimson clover (Trifolium incarnatum L.) (Clover); (e) hairy vetch (Vicia villosa L.) (Vetch); (f) a multi-species mixture (Mixture); and (g) winter wheat (Triticum aestivum L.) (Wheat). The DNDC model adequately simulated the seed cotton yield and cover crop biomass during calibration (root mean square error (RMSE) = 200 and 398 kg ha−1, respectively) and validation (RMSE = 277 and 270 kg ha−1, respectively). Stocks of soil organic carbon (SOC) and total nitrogen (TN) were simulated with Nash–Sutcliffe efficiency (NSE) of 0.91 and 0.78 during calibration, and with NSE of 0.88 and 0.75, respectively during validation. Long-term simulations revealed: (1) Vetch and Pea produced greater biomass and hence highest SOC and TN contents, which was followed by Mixture, Wheat, and Clover; (2) cotton yield in cover crop treatments was no different to that in non-cover crop treatments when cover crop was terminated about six weeks prior to cotton planting; (3) later termination of cover crops can result in greater cotton yield loss due to soil water depletion by cover crops. Overall, this study highlights the potential of conservation practices, such as cover crops and NT to improve soil health without significant loss in cotton yields.

Evaluating the impact of at-plant termination of a cereal rye cover crop with different corn planting dates on arthropod activity.

Greater cover crop biomass is expected to result in a favorable microhabitat for beneficial arthropods. Natural Resources Conservation Service (NRCS) cover crop termination guidelines are based on the cash crop planting date. Therefore, a delay in cash crop planting could result in greater cover crop biomass. However, studies on delays in cash crop planting and greater cover crop biomass have led to a decrease in cash crop yield. Thus, a field study was conducted in eastern Nebraska over two years to evaluate the impact of early and late corn planting dates with at-plant cover crop terminations on pest potential, beneficial arthropod activity, and agronomic parameters. To measure arthropod activity and pests in the system, pitfall traps, and corn injury assessments were performed during the early stages of corn development. A total of 11,054 and 43,078 arthropods were collected in 2020 and 2021, respectively. The results have shown no impact of the corn planting dates with at-plant cover crop termination on arthropods but identified that cereal rye cover crop supports greater Araneae activity while its alternative prey varied when compared to the no-cover treatment. Significant yield penalties were observed when cover crop was used regardless of the corn planting dates. Pest pressure was not significant in any year, however, future research using cereal rye and different cover crop species should be used in this system with an artificial infestation of a pest to be able to evaluate the trade-offs between possible cash crop yield reductions and potential biological control of pests.

Delayed cover-crop termination and reduced herbicide inputs produce trade-offs in soybean phase of US Northeast forage-grain rotation

AbstractRegion- and system-specific research is needed to understand the viability of delayed cover-crop termination (i.e., planting green) as an integrated weed management (IWM) tactic in no-till soybean. In a 3-yr field experiment, we evaluated the potential for planting green to facilitate elimination of soil-applied, preemergence residual herbicides within a soybean phase of a 6-yr grain–forage cropping systems experiment in Pennsylvania. This IWM tactic was contrasted with a Standard treatment, which included 14 to 21 d pre-plant termination of cereal rye and a two-pass herbicide program with preemergence herbicides. A 63% increase in cereal rye biomass production was observed within the IWM treatment in 2019, but only a 22% and 33% increase in 2020 and 2021, respectively. In 2020, significantly lower volumetric water content (%VWC) was observed within the IWM treatment in dates closest to planting and greater %VWC at multiple dates in June and July compared to the Standard treatment. No differences occurred in soybean populations, but soybean biomass at the V4 growth stage was reduced in the Standard treatment compared to the IWM treatment, which we attribute to injury from preemergence applications. The Standard treatment resulted in greater soybean yield (2,590 kg ha–1) than the IWM treatment (1,870 kg ha–1) in 2020, but yields were similar in other years. The IWM treatment resulted in 58% fewer herbicide inputs, as measured by the number of active ingredients applied, compared to the Standard over the 3-yr study. Yet, peak weed biomass did not differ between treatments. However, the IWM treatment resulted in greater total horseweed density and the number of horseweed plants that exceeded recommended size-based height thresholds (10 cm) compared to the Standard treatment just prior to postemergence applications (35–42 d after planting) in 2020 and 2021, underscoring the importance of integrating surface mulch residues with effective herbicide sites of action.

Winter cover crop impact on soil health in Texas Rolling Plains dryland cotton

AbstractThe Rolling Plains of Texas are historically semi‐arid with sporadic, high intensity storms followed by periods of long drought. Fallow management is a common practice intended to store soil water, but leaves the bare soil exposed to erosive forces that can diminish the soil productivity. Cover crops in no‐till (NT) agriculture have been proposed to increase soil health under environments with low precipitation as an alternative to fallow management. This study evaluated multiple treatments in a dryland cotton system including: (1) conventional tillage (CT); (2) NT; and NT with the following cover crops: (3) wheat; (4) Austrian winter pea; (5) crimson clover; (6) hairy vetch; and (7) mixed species cover. Soil samples were collected at 0, 3, and 6 weeks after cover crop termination and analyzed for soil organic carbon, total nitrogen, inorganic N, water‐extractable organic carbon, water‐extractable organic nitrogen, carbon mineralization, and phospholipid fatty acid analysis. For all parameters tested, there was no significant difference between CT and NT at any date or depth, so the addition of cover crops to NT cotton systems might be needed in order to enhance NT in regard to soil function. The multi‐species mixed treatment was predicted to perform the best out of the cover crop treatments due to its combined benefits from grasses and legumes. However, the single‐species Austrian winter pea treatment had 24% and 28% higher soil carbon and nitrogen than no‐till without a cover crop, and can be a useful alternative to fallow management under these dryland agriculture conditions.

How Much Impact Has the Cover Crop Mulch in Mitigating Soil Compaction?—A Field Study in North Italy

Soil compaction was largely studied in different scenarios with laboratory and field scale experiments, with various soil conditions and traffic intensities. However, a detailed analysis to better understand the protective role of plant residues or cover crop mulch is still required. A field test was conducted in Northeast Italy aiming to fill this gap. Rye was chosen as a winter cover crop, and growth on a controlled traffic random block experimental field. Four different cover crop mulch treatments were compared to study the effects of root systems: roller crimper, flail mower, bare soil control and harvested biomass control. Four different traffic intensities were used to evaluate the multiple passages with 0, 1, 3, 5 traffic events. During traffic events, the mean normal stress was measured. Penetration resistance was then evaluated after trafficking and soil samples were collected. The obtained results showed a 19.3% cone index increase in bare soil compared to flail mower treatment after the first traffic event, while low differences were found in harvested biomass bulk density during the first and third traffic events. Moreover, mean normal stress increased 16.5% on harvested biomass treatment compared to the flail mower. These findings highlight that the cover crop maintains a lower soil penetration resistance during compaction events, helping the subsequent field operations. Furthermore, roller crimper and flail mower cover crop termination impact soil bearing capacity differently due to different soil moisture content. However, the results showed a low contribution of cover crop mulch on mitigating soil compaction effects during the experiment.

Cover crop termination timings and methods effect on cotton (Gossypium hirsutum L.) development and yield

AbstractCover crops have been promoted for use in agricultural systems due to both environmental and economic opportunities. Cotton (Gossypium hirsutum L.) growers in West Tennessee faced challenges in 2015 and 2016 with cover crop termination management which resulted in failed cotton stands. The objective of this experiment was to determine effects of cover crop termination timing and method on cotton emergence, development, and yield. Field experiments were conducted from 2018 to 2020 in both small plot and on‐farm scenarios across West Tennessee. Cover crop termination timings consisted of an at‐planting termination, 3 weeks prior to planting, and both a broadcast and furrow‐strip termination 6 weeks prior to planting. The cover crop termination methods consisted of chemical termination, mechanical termination, and chemical + mechanical termination. At‐planting termination reduced emergence by 25% and delayed maturity of 65% of the stand relative to a 6‐week broadcast termination. Mechanical termination reduced emergence by 26% and delayed maturity of 26% of the stand relative to the chemical and chemical plus mechanical termination treatments. Thrips injury ratings were greater in cotton following a chemical + mechanical termination of the cover crop. Damage from three‐cornered alfalfa hoppers (Sissistilus festinus) was less prevalent in cotton following cover crops terminated 6 weeks prior to planting in a broadcast method compared to other timings. While early season effects were observed, end‐of‐season yield differences were not noted. Still, producers in short season environments should be aware of the higher level of risk associated with at‐planting terminations or terminations.