Double-cropped Soybean Research Articles

A comparative analysis of soil organic carbon stock and soil aggregation in two crop sequences in the Rolling Pampa (Argentina)

Understanding how farming practices affect soil organic carbon (SOC) accumulation is essential for sustainable agriculture. Agronomic decisions, such as crop sequence, significantly influence various soil properties. However, the overall benefits of crop rotation on soil structure and SOC storage remain uncertain. We compared the effects of soybean (Glycine max L.) monocropping with a three-year crop rotation comprising wheat (Triticum aestivum L.)/soybean double crop, maize (Zea mays L.), and soybean on the vertical distribution of SOC up to one metre depth. Additionally, we examined carbon accumulation as particulate organic matter-carbon (POM-C), soil aggregation, and structural stability in the topsoil. Compared to monocropping, crop rotation increased SOC concentrations (19 vs. 16 gC kg soil⁻¹), stock (12 vs. 10.7 MgC ha⁻¹), and POM-C content (6 vs. 3.2 gC kg soil⁻¹) in the first 5 cm of soil. At 20–65 cm depth, rotation showed a marginal increment of SOC stock with respect to soybean monocropping. The increased surface SOC content in the rotation positively affected the POM-C content and macro-aggregation. However, soil structural stability showed a tendency to be higher in the monocropping, especially at a depth of 5–20 cm. Overall, crop rotation demonstrated potential for enhanced carbon sequestration in temperate agroecosystems within three years, despite not significantly improving soil structural stability.

Profitability of foliar fungicides in double crop soybean under low-disease environments

Double-crop soybean production involves planting soybean (Glycine max) directly following winter wheat (Triticum aestivum) harvest. Frogeye leaf spot (FLS), caused by Cercospora sojina, is an important late-season foliar disease affecting soybean fields in the United States. In some instances, foliar fungicides have been used in double-crop soybean production with little to no FLS present, raising questions on the profitability of these applications. This study analyzed yield data from 25 fungicide trials across five states (Illinois, Indiana, Kentucky, Missouri, and Tennessee) conducted under low FLS pressure, from 2008 to 2021, on double-crop soybean. Fungicide classes evaluated in the trials included quinone outside inhibitors (QoI), demethylation inhibitors (DMI), and methyl benzimidazole carbamates (MBC) applied alone, and mixtures of chemistry classes that included DMI+succinate dehydrogenase inhibitor (SDHI), MBC+DMI, QoI+DMI, and QoI+DMI+SDHI. A network meta-analytic model estimated yield differences between fungicide-treated and nontreated plots, which ranged from -28 to 72 kg/ha among the fungicide treatments. Negative yield response values were estimated for the single fungicide classes MBC (-15.7 kg/ha) and QoI (-28.4 kg/ha). Yield difference as high as 72.8 kg/ha was estimated only for DMI+SDHI. Economic analyses indicated that, due to the lower yield responses, probabilities of breaking even were lower than 50% for all fungicide treatments, regardless of the fungicide cost or soybean sale price. Therefore, the low yield responses associated with foliar fungicides in low-disease environments linked to the higher risk of not offsetting the costs, suggest that growers should consider disease risk prior to making the fungicide application.

Corn and Soybean Production – 2022 Summary

Soybean and corn varieties were tested in replicated field trials at the Southeast Research and Extension Center in Parsons through the Kansas State University variety testing program. In total, nine corn varieties and three maturity checks were tested. Fourteen full season and ten double-cropped soybean varieties were tested, with three maturity checks. Additionally, sorghum and sunflower varieties were tested. The 2022 summer crop growing season was challenging. High temperatures and low rainfall reduced crop production. Crop production was severely impacted by the hot, dry conditions, both across the state and in the cultivar trials at Parsons. No yield results are available for the variety tests from Parsons.

Effects of Tillage System, Sowing Date, and Weather Course on Yield of Double-Crop Soybeans Cultivated in Drained Paddy Fields

In temperate monsoon areas, major constraints of soybean production in drained paddy fields are excess soil water during monsoon seasons. To further understand how agronomic practices and weather course affect the yield of soybeans, we conducted field experiments at Gwangju, Korea (35°10′ N, 126°53′ E) over three years (2018–2020). Double-crop soybeans were grown at two tillage systems (TS) [rotary tillage (RT), deep plowing followed by rotary tillage (DPRT)] and three sowing dates (SD) (June 10–15, June 25–30, and July 10–15) in drained paddy fields. Flowering phenology (R2) was accelerated by 5 days with each 15-day delay in SD. This resulted in a significant reduction in vegetative growth up to R2, with subsequent reductions in CGR and NAR through R2–R5 (beginning of grain filling). With a 30-day delay in SD, yield was significantly reduced by 27.0%. The better performance of RT over DPRT was demonstrated by greater yields (13.7%). In addition, yield was greatly varied with weather volatility among years, ranging from 123.8 to 552.0 g m−2. Weather volatility was the greatest contributor to yield variability (30.4%), followed by SD (17.0%) and TS (10.3%). Our results suggest that the yield might be mainly determined by how much growth has already been achieved before flowering and through R2–R5.

Sampling Optimization and Crop Interface Effects on Lygus lineolaris Populations in Southeastern USA Cotton.

Simple SummaryTarnished plant bugs (Hemiptera: Miridae) are an important agricultural pest in cotton across the United States. Tarnished plant bugs reduce cotton yields and lower lint and seed quality by feeding on reproductive structures. Effective management of this pest requires timely insecticidal control when populations reach established economic thresholds. Reliable determination of the economic threshold in cotton depends on effective scouting. To evaluate the efficacy of current tarnished plant bug scouting strategies, we surveyed 120 commercial cotton fields across the southeastern USA to quantify (1) variation in tarnished plant bug populations across the production region, (2) evaluate current sampling plans for economic threshold determinations, and (3) examine landscape-scale risk factors associated with tarnished plant bug infestations in cotton. We observed the greatest variability in tarnished plant bug density at the field scale followed by within-field variation, emphasizing the importance of scouting individual fields. Additionally, we determined the sampling size needed for accurate threshold estimates for sweep net (8 sample units of 100 sweeps/sample) and drop cloth sampling (23 sampling units of 1.5 row-m/sample). Furthermore, tarnished plant bugs densities were positively related to the proportion of agriculture and double-crop winter wheat and soybeans and negatively related to contiguous cotton.Tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), is an economically damaging pest in cotton production systems across the southern United States. We systematically scouted 120 commercial cotton fields across five southeastern states during susceptible growth stages in 2019 and 2020 to investigate sampling optimization and the effect of interface crop and landscape composition on L. lineolaris abundance. Variance component analysis determined field and within-field spatial scales, compared with agricultural district and state, accounted for more variation in L. lineolaris density using sweep net and drop cloth sampling. This result highlights the importance of field-level scouting efforts. Using within-field samples, a fixed-precision sampling plan determined 8 and 23 sampling units were needed to determine L. lineolaris population estimates with 0.25 precision for sweep net (100 sweeps per unit) and drop cloth (1.5 row-m per unit) sampling, respectively. A spatial Bayesian hierarchical model was developed to determine local landscape (<0.5 km from field edges) effects on L. lineolaris in cotton. The proportion of agricultural area and double-crop wheat and soybeans were positively associated with L. lineolaris density, and fields with more contiguous cotton areas negatively predicted L. lineolaris populations. These results will improve L. lineolaris monitoring programs and treatment management decisions in southeastern USA cotton.

Wheat Production Alters Soil Microbial Profiles and Enhances Beneficial Microbes in Double-Cropping Soybean

Plant-parasitic nematodes represent a substantial constraint on global food security by reducing the yield potential of all major crops. The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is widely distributed across important soybean production areas of the U.S., being the major soybean yield-limiting factor, especially in the Midwestern U.S. Double cropped (DC) soybean is commonly planted following winter wheat. We previously reported double-cropping soybean fields with reduced SCN counts compared to fallow at both R1 growth stage (beginning of flowering) (−31.8%) and after soybean harvest (−32.7%). To test if higher counts of beneficial and SCN antagonistic microorganisms could be correlated with the suppression of SCN in fields previously planted with wheat, three field locations with noted SCN suppression were selected for a metagenomics study. Ten subplots were selected (5 wheat and 5 fallow pre-soybean) from each location. A total of 90 soil samples were selected: 3 fields ×2 treatments × 3 timepoints × 5 replications. Three DNA markers targeted distinct microbial groups: bacteria (16S V4-V5), fungi (ITS2), and Fusarium (tef1). Amplicons were sequenced using an Illumina MiSeq platform (300 bp paired-end). Sequencing datasets were processed in R using the DADA2 pipeline. Fungal populations were affected by location in all sampling periods and differed significantly between DC and fallow plots at soybean planting and after harvest (P &amp;lt; 0.001). Several enriched fungal and bacterial taxa in wheat plots, including Mortierella, Exophiala, Conocybe, Rhizobacter spp., and others, were previously reported to parasitize SCN and other plant-parasitic nematodes, suggesting a potential role of beneficial microbes in suppression of SCN in soybean fields double-cropped with wheat.

Impacts of Row Spacing and Fungicide Timing on Foliar Disease, Greenstem, and Yield in Double-Cropped Soybeans Grown in the Chesapeake Bay Region of the United States

Double-cropped soybean crops are planted on approximately one-third of crop acres in the Chesapeake Bay region of the United States. Producers have asked whether foliar fungicides are required to optimize yields in this region. We assessed the impacts of foliar fungicide application timing and row spacing on foliar disease, greenstem, and yield from 11 site-years spanning 2017 to 2019. Foliar diseases only developed at rateable levels in one location. Fungicide application, regardless of timing, increased percent greenstem over nontreated controls. Fungicide application did not affect soybean yield. Yield was greater in 38.1-cm rows when compared with 19-cm rows. Our data do not support the use of foliar fungicides in double-cropped soybean production in this region.

Agro-Ecological Alternatives to Chemical Weed Control in Single and Double Cropped Soybean

Agro-Ecological Alternatives to Chemical Weed Control in Single and Double Cropped Soybean

Season-specific management strategies for rainfed soybean in the South American Pampas based on a seasonal precipitation forecast

CONTEXTGlobal climate change is resulting in more frequent and more damaging extreme events affecting the performance of production systems. It is imperative to develop good season-specific crop management recommendations to help farmers to improve their adaptive capacity to a changing climate one season at a time. OBJECTIVEWe aimed to evaluate the skill of the International Research Institute for Climate and Society (IRI) seasonal precipitation forecasts and the interaction between the forecasted seasonal precipitation scenarios and management practices for rainfed soybean cropping systems using a crop simulation model. METHODSWe used a crop simulation model (CROPGRO-Soybean) coupled with weather data to assess the potential use of the IRI seasonal precipitation forecasts as a tool to optimize season-specific management strategies for rainfed soybean in Uruguay. We used a total of 620–668 IRI seasonal precipitation forecasts released from 2003 to 2016 for each of the five weather stations located in the main soybean producing area. The analysis was performed for two soybean cropping systems (i.e., sown as a single crop or as double-cropped soybean), for which we considered combinations of sowing dates and maturity groups (11 sowing dates × 3 maturity groups combinations for each soybean cropping system). RESULTS AND CONCLUSIONSThe IRI seasonal precipitation forecasts were able to successfully forecast below-normal precipitation scenarios in 77% of the total predictions developed for this scenario considering all weather stations during the study period (2003–2016), while it was less accurate in forecasting above-normal precipitation scenarios (60% of success). We found that earlier sowing dates were a better strategy for years when an above-normal precipitation forecast was released for the December–January-February period (4.7 Mg ha−1 average seed yield). In contrast, delayed sowing dates were more appropriate for below-normal precipitation forecasts (3.7 Mg ha−1 average seed yield). Applying season-specific management practices farmers could potentially increase their soybean yields by up to 0.6 and 1.6 Mg ha−1, in years with below- or above-normal forecasted precipitations, respectively. The benefit of season-specific management will depend on the interaction among all management practices, the effective capacity of farmers to implement it, and the risk profile the farmer adopts and it is exposed to. SIGNIFICANCEHere we built a novel approach to assess the impact of considering seasonal precipitation forecasts for optimizing crop production. This assessment provided insights on how farmers can use seasonal precipitation forecasts to optimize rainfed soybean yield for a specific cropping season.

Impact of Wheat on Soybean Cyst Nematode Population Density in Double-Cropping Soybean Production.

Double-cropping is defined as producing more than one crop on the same parcel of land in a single growing season. It is reported to have many benefits when incorporated in cropping systems, including improving soil health. In some double-cropping systems, soybean is planted following winter wheat. The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is a major soybean pathogen, and several reports suggest suppressive effects of wheat on SCN populations. Field trials were conducted from 2017 to 2018 to investigate the effect of wheat on SCN populations in double-cropping soybean. Nine fields with three levels of initial SCN populations (low, moderate, and high) were selected in Illinois. Wheat was planted in strips alternating with strips-maintained weed-free and under fallow over winter and early spring. Soybean was planted in all strips after wheat harvest. SCN egg densities were acquired at four time points: wheat establishment, post-wheat/pre-soybean, mid-soybean (R1 growth stage or beginning of flowering), and post-soybean harvest. Wheat strips reduced SCN egg densities compared with fallow strips at the R1 stage (−31.8%) and after soybean harvest (−32.7%). Double-cropping soybean with wheat has the potential to suppress SCN field populations and is a system with the potential to provide additional farm income. This study is meant to be a first step toward a better understanding of the mechanisms that govern the suppression of SCN by wheat.

Seed yield, seed quality, profitability, and risk analysis among double crop soybean maturity groups and seeding rates

AbstractDouble crop soybean [Glycine max (L.) Merr.] production is common after soft red winter wheat (Triticum aestivum L.) harvest in the Upper Mid‐South and Ohio River Valley regions. However, optimal maturity group and seeding rate information is needed because most double crop soybean research is at least 45‐yr old. Relative maturity groups (rMG) 2.8, 3.5, 4.1, and 4.7, which ranged from a very short to an adapted long maturity group for the area, were evaluated at five seeding rates (123,600, 247,100, 370,700, 494,200, and 617,800 seeds ha−1) in a double crop soybean study at Princeton KY, from 2017 to 2019. The longest rMG (4.7) had the greatest seed yield and seeds m−2. However, rMG did not influence V2 and R8 plant population. The highest seeding rates of 494,200 and 617,800 seeds ha−1 had the greatest yield and seeds m−2 as well as the greatest V2 and R8 plant populations. Seeding rate did not affect protein or oil concentrations. Partial budget analysis determined that the combinations of rMG 4.1 at 494,200 seeds ha−1, rMG 4.7 at 494,200 seeds ha−1, and rMG 4.7 at 617,800 seeds ha−1 had similar economic net benefits as the University of Kentucky recommendation of rMG 4.7 at 370,000 seeds ha−1. However, the risk analysis predicted that rMG 4.7 at 494,200 seeds ha−1 would have the highest probability of a positive net return. These findings support the use of a longer rMG for the region as well as an increased seeding rate to maximize yield and economic net benefit.

Integrated Weed Management Systems to Control Common Ragweed (Ambrosia artemisiifolia L.) in Soybean

As resistance to herbicides limits growers' weed management options, integrated weed management (IWM) systems that combine non-chemical tactics with herbicides are becoming critical. A 2 year integrated weed management (IWM) study was conducted at three locations in VA, USA. The factorial study evaluated: (1) soybean planting date (early or late planted) (2) with or without winter cover (cereal rye/wheat or no cover), and (3) with or without harvest weed seed control (HWSC). Prior to soybean planting in the first year, winter cover resulted in a 22% reduction in common ragweed density compared to no cover. At soybean harvest in the first year, the lowest common ragweed densities were in the late planted plots following winter wheat, and common ragweed aboveground biomass was reduced by 46 and 22% at two locations in late planted compared to early planted soybean. To evaluate the impact of the first year's treatments and HWSC, full season soybeans were planted across the trial in the second year. Prior to soybean planting in the second year, late planting in the first year common ragweed density was reduced by 83% at one location, but significant reductions were not observed elsewhere. When comparing winter cover to no cover, common ragweed densities were reduced by 31 and 49% at two locations and densities were similar at the third location. Harvest weed seed control reduced common ragweed density by 43% at one location compared to the conventional harvest plots but no significant reductions were observed at the other locations or at other rating timings. However, there was a significant location by planting date by winter cover interaction and the overall lowest common ragweed densities (4.1 to 10.3 plants m−2) were in the late planted plots with winter cover. This research indicated that winter cover, late planting, and HWSC can reduce common ragweed populations with late planting being the most influential. Therefore, double-cropping soybean after wheat is likely the most viable means to better control common ragweed using IWM as it combines both winter cover and late planting date.

Cropping system-imposed yield gap: Proof of concept on soybean cropping systems in Uruguay

Favorable weather conditions prevailing on most South American Pampas allows to grow more than one crop per year. Indeed, increasing crop intensity per unit area has been highlighted as an opportunity to increase crop production in a high food demanding world scenario. Previous studies have analyzed cropping-system yield gap by aggregating crop yields either as total amount of grain or as unit of energy. However, few cropping-system yield gap analysis have made a distinction between single (i.e., soybean sown as a single crop per year) and double-cropped soybean (i.e., soybean sown immediately after harvest of a winter cereal crop), and none of them at a country level. This article focuses on the estimation of cropping system-imposed yield gap (CSIYg), which is defined as the difference of seed yield between single soybean and double-cropped soybean. The aims of the present study were: (i) to analyze yield potential (Yp), water-limited (Yw) and yield gap (Yg) spatial and interannual variability; (ii) to investigate the concept of CSIYg for soybean using cropping systems in Uruguay as a proof of concept; and (iii) to assess differences on yield variability between single and double-cropped soybean. Yp and Yw were estimated for single and double-cropped soybean in specific locations within the major soybean crop producing areas using CROPGROW model coupled with long-term good quality weather data, soil types and dominant management practices. Estimations were scaled up following the protocols of the Global Yield Gap Atlas project. We applied a boundary function analysis to assess the differences on Yw variability between single and double-cropped soybean. At country level Yp was estimated on 6.6 and 5.7 Mg ha−1 for single and double-cropped soybean, respectively. However, we found lower differences on Yw between single and double-cropped soybean (3.6 and 3.4 Mg ha−1, respectively). We estimated CSIYg due to combined effect of weather condition and water regime on 3.2 Mg ha−1. The CSIYg representing the combined effect of weather condition, water regime and management was estimated on 1.6 Mg ha−1. Double-cropped and single soybean showed the same Yw response to precipitations and a similar Yw variability (t-test P = 0.55). Our results highlight double-cropped soybean cropping systems as an alternative for increasing grain production in this main agricultural region of the world.

Nitrogen fertilization offsets the N2O mitigating effects of cover‐crops and double‐crop soybean in a wheat–sorghum system

AbstractCover crops (CCs) have been promoted as a key strategy to reduce nitrous oxide (N2O) emissions by scavenging excess mineral nitrogen (N) after cash crop harvest. Optimum N fertilizer application rates are also critical to minimize N2O emissions. Integrating these strategies requires research to understand how they interact to drive N2O emissions. The objective was to evaluate N2O emissions from winter wheat (Triticum aestivum L.) harvest through the subsequent fallow period and grain sorghum [Sorghum bicolor (L.) Moench] production phase of a long‐term, no‐till winter wheat–grain sorghum–soybean [Glycine max (L.) Merr] cropping system. Fallow management treatments included chemical fallow (CF), double‐crop soybean (DSB), and two CCs: sorghum‐sudangrass (Sorghum bicolor × sorghum bicolor var. sudanese) and daikon radish (Raphanus sativus L.). Nitrogen fertilizer rates (0, 90, and 180 kg ha−1) were applied within 1 wk after sorghum planting. Soil nitrate‐N was consistently greater in CF than in the other treatments during the fallow period. Although, on average, CCs and DSB decreased cumulative N2O emissions (cN2O) by 1.75‐fold, during the fallow period compared to CF, they significantly increased cN2O in the following sorghum crop. Emissions increased with greater applications of N regardless of how the fallow was managed, indicating that N fertilizer application in the following sorghum tended to offset any potential mitigating effects of CCs and DSB. These results highlight the importance of evaluating N2O emissions for the system (fallow + following cash crop) to account for potential tradeoffs that could offset cN2O mitigation when N fertilizer is applied.

Estimating the effect of winter cover crops on nitrogen leaching using cost-share enrollment data, satellite remote sensing, and Soil and Water Assessment Tool (SWAT) modeling

This study employed a novel combination of data (winter cover crop [WCC] cost-share enrollment records, satellite remote sensing of wintertime vegetation, and results of Soil and Water Assessment Tool [SWAT] water quality simulations) to estimate the environmental performance of WCC at the watershed scale, from 2008 through 2017, in the Tuckahoe Creek watershed, located within the Choptank River basin. The Choptank River is a tributary of the Chesapeake Bay, and, as a focus watershed for the USDA9s Conservation Effects Assessment Project, has been the subject of considerable study assessing linkages between land use and water quality. Farm enrollment data from the Maryland Agricultural Cost Share (MACS) program documented a large increase in the use of WCC within the Tuckahoe Creek watershed during the study period, rising from 27% of corn (<i>Zea mays</i> L.) fields and 9% of soybean (<i>Glycine max</i> L.) fields in 2008 to 89% of corn fields and 46% of soybean fields in 2016. Satellite remote sensing of wintertime ground cover detected increased wintertime vegetation following corn crops, in comparison to full season and double cropped soybean, consistent with patterns of cover crop implementation. Although interannual variation in climate strongly affected observed levels of vegetation, with warm winters resulting in increased vegetative cover, a 30-year analysis of wintertime greenness revealed significant increases in wintertime vegetation associated with increased adoption of WCC. The MACS WCC enrollment data were combined with output from the SWAT model, calibrated to streamflow and nutrient loading from the Upper Tuckahoe watershed, to estimate water quality impacts based on known distribution of cover crop species and planting dates (2008 to 2017). Results indicated a 25% overall 10-year reduction in nitrate (NO₃⁻) leaching from cropland attributable to cover crop adoption, rising to an estimated 38% load reduction in 2016 when 64% of fields were planted to cover crops. Results suggest that increased environmental benefits would be achieved by shifting agronomic methods away from late-planted wheat (<i>Triticum aestivum</i> L.), which comprised 34.7% of all WCC planted between 2008 and 2017.

Agronomic Management of Malting Barley and Research Needs to Meet Demand by the Craft Brew Industry

Core Ideas Agronomic management and environment affect malting barley yield and quality.Most agronomic guidelines are from the Northwest and Northern Rockies and Plains.Breweries in the Upper Midwest, Ohio Valley, and Northeast want local grain.Research on cropping sequence, seeding date and rate, and N management is needed. Malting barley (Hordeum vulgare L.) requires agronomic management that maximizes grain yield while meeting quality standards. The majority of published literature on agronomic management of malting barley is from the US Northwest and Northern Rockies and Plains where barley is traditionally grown. However, the majority of craft breweries are located in the Upper Midwest, Ohio Valley, and Northeast, creating a demand for locally sourced grain. The objectives of this review were to: (i) summarize the current body of knowledge regarding agronomic management of malting barley, and (ii) identify research needs in the Upper Midwest, Ohio Valley, and Northeast. Across all regions, planting date and N management were major factors influencing grain yield and quality. Timely planting of malting barley generally improved yield and quality. Barley yield tended to increase with N application rate while quality decreased due to increased protein concentration. Planting malting barley following corn (Zea mays L.) or small grains resulted in disease problems that could affect grain quality and yield. In the Upper Midwest, Ohio Valley, and Northeast regions, the prospect of double crop soybean [Glycine max (L.) Merr.] production after winter malting barley should be investigated, in addition to typical cropping sequences. Agronomic strategies to mitigate the negative effects of late‐planting situations are also needed as these regions often have delayed planting due to wet soil conditions. Furthermore, N fertilizer management is much different in humid regions compared with the Northwest and Northern Rockies and Plains, and warrants future research on developing in‐season N management strategies.

Herbicide Options for Control of Palmer Amaranth (Amaranthus palmeri) and Common Waterhemp (Amaranthus rudis) in Double-Crop Soybean

AbstractDouble-crop soybean after winter wheat is a component of many cropping systems across eastern and central Kansas. Until recently, control of Palmer amaranth and common waterhemp has been both easy and economical with the use of sequential applications of glyphosate in glyphosate-resistant soybean. Many populations of Palmer amaranth and common waterhemp have become resistant to glyphosate. During 2015 and 2016, a total of five field experiments were conducted near Manhattan, Hutchinson, and Ottawa, KS, to assess various non-glyphosate herbicide programs at three different application timings for the control of Palmer amaranth and waterhemp in double-crop soybean after winter wheat. Spring-POST treatments of pyroxasulfone (119 g ai ha–1) and pendimethalin (1065 g ai ha–1) were applied to winter wheat to evaluate residual control of Palmer amaranth and waterhemp. Less than 40% control of Palmer amaranth and waterhemp was observed in both treatments 2 wk after planting (WAP) double-crop soybean. Preharvest treatments of 2,4-D (561 g ae ha–1) and flumioxazin (107 g ai ha–1) were also applied to the winter wheat to assess control of emerged Palmer amaranth and waterhemp. 2,4-D resulted in highly variable Palmer amaranth and waterhemp control, whereas flumioxazin resulted in control similar to PRE treatments that contained paraquat (841 g ai ha–1) plus residual herbicide(s). Excellent control of both species was observed 2 WAP with a PRE paraquat application; however, reduced control of Palmer amaranth and waterhemp was noted 8 WAP due to subsequent emergence. Results indicate that Palmer amaranth and waterhemp control was 85% or greater 8 WAP for PRE treatments that included a combination of paraquat plus residual herbicide(s). PRE treatments that did not include both paraquat and residual herbicide(s) did not provide acceptable control.

Double-Crop Wheat and Soybean Yield Response to Poultry Litter Application

Poultry litter (PL) application and double cropping are management practices that could be used with conservation tillage to increase yields compared with conventional mono-cropping systems. The objective of this study was to evaluate winter wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] yield response to PL alone and combinations of PL and inorganic N versus inorganic N alone when applied to the winter wheat in a double-cropping system. The study was conducted from 2014 to 2016 at two locations on a Marvyn loamy sand and a Lucedale fine sandy loam. Experimental design at each location was a randomized complete block design. Fertility treatments for winter wheat included an unfertilized control (PL₀N₀), inorganic N fertilizer (120 lb acre–¹, PL₀N₁₂₀), PL at the rate of 40 lb N acre–¹ plus 80 lb acre–¹ inorganic N (PL₄₀N₈₀), PL at the rate of 80 lb N acre–¹ plus 40 lb acre–¹ inorganic N (PL₈₀N₄₀), and PL at the rate of 120 lb N acre–¹ (PL₁₂₀N₀). An unfertilized winter fallow treatment was also included to enable a comparison of yield between the mono- and double-cropped soybean. A combination of PL and inorganic N resulted in wheat yields comparable to those with inorganic N alone while PL alone yielded less. Double-cropping soybeans with winter wheat tended to improve soybean yield when compared with mono-cropped soybeans planted on the same date; however soybean yield was not consistently enhanced by the residual PL nutrients applied to wheat when compared with N fertilizer only treatment.

Management Strategies for Double-Crop Soybean Planted After Wheat

Management Strategies for Double-Crop Soybean Planted After Wheat

Biochar In Situ Decreased Bulk Density and Improved Soil-Water Relations and Indicators in Southeastern US Coastal Plain Ultisols

Biochar may improve soil physical properties for crop growth, but multiyear, multicrop field studies are lacking. To determine the effects of biochar on soil physical properties, we applied 0, 10, 20, 40, and 80 Mg ha biochar with/without NPK fertilizer to the surface 15 cm of 1 × 1 m plots in a single association of fine-loamy, siliceous, subactive, thermic Oxyaquic and Aquic Paleudults under a 2-year corn-winter wheat–double-crop soybean rotation. After 3 years, we sampled soil to 7.6 cm, measured bulk density and water retention, and then derived pore-size distribution and related physical and water retention model parameters. Fertilizer had little to no effect. Among the statistically significant results, biochar increased structural porosity (3- to 59-μm effective pore diameter [EPD]) but neither matrix- (0.2- to 3-μm EPD) nor macro (EPD >59 μm) porosity. Biochar ≥40 Mg ha decreased bulk density 16%; 80 Mg ha increased total porosity 14%. However, it also increased water content at −1,500 kPa 22.5%. Biochar ≥40 Mg ha increased the drained upper limit (DUL) by 15%; relative field capacity, 3%; and total and structural plant-available water (PAW: held between the DUL and −1,500 kPa), 7 and 18%, respectively. Increases were greatest at −10 kPa and least at −33 kPa. At −10 kPa, 80 Mg ha biochar increased total PAW 4.0-mm equivalent depth compared with 5.7 mm for structural PAW, approximately 0.5-day demand for actively growing corn. Modeled saturated water content increased with total porosity. Biochar improved plant-soil-water relations, but required high rates.