Full-season Soybean Research Articles

Double-Crop Soybean Leaf Area and Yield Responses to Mid-Atlantic Soils and Cropping Systems

Double-crop soybean (Glycine max L.) often yields less than full-season soybean, due in part to decreased leaf area development. Information is lacking on the effect of cropping system and plant-available water holding capacity (PAWHC) as affected by soil type on LAI in field-scale environments. The objectives of this research were to (i) determine the effect of three cropping systems and three soil types that vary in PAWHC on double-crop soybean leaf area and yield; and (ii) validate the LAI–yield relationship in a field-scale experiment. Soybean LAI and yield were measured at random geographically located positions during the 1999 to 2001 cropping seasons. During years of early season or little drought stress, LAI and yield were 1.1 to 1.2 units and 480 to 558 kg ha−1 less on the lowest PAWHC soil compared with the soil with the highest PAWHC. Soybean LAI and yield were reduced 0.4 units and 301 kg ha−1 when soybean experience early season drought stress and was not rotated. Under conditions of late-season drought stress, LAI and yield of rotated soybean were 1.6 units and 1350 kg ha−1 less on the lowest PAWHC soil. When soybean was not rotated and under conditions of late-season drought stress, LAI and yield were reduced by 2.9 units and 1770 kg ha−1 for the soil with the lowest PAWHC, and 1.6 units and 760 kg ha−1 for the soil with intermediate PAWHC. Soybean LAI was linearly related to yield only on the lowest PAWHC soil where LAI was low.

Relationship between leaf area index and yield in double-crop and full-season soybean systems.

Previous research indicates a correlation between leaf area index (LAI) and yield of full-season soybean [Glycine max (L.) Merrill], which is a single crop planted early in the season. Leaf area index values of at least 3.5-4.0 in the reproductive stages are required for maximum potential yield. It is unknown how yields of double-crop soybean, which is planted late into harvested small grain fields, respond to changes in leaf area index. We hypothesized that double-crop soybean would be more sensitive to defoliation than full-season soybean. This study used linear and linear plateau models to describe the yield response of full-season and double-crop soybean to reductions in leaf area index through manual defoliation, and evaluated the yield response of double-crop soybean to reductions in leaf area index through natural insect defoliation. From 15 manual defoliation experiments over 3 yr, significant linear decreases in yield occurred in both full-season and double-crop soybean when leaf area index values were below 3.5-4.0 by developmental stages R4 to R5, whereas yields usually reached a plateau at higher leaf area index levels. Average yield loss was 769 +/- 319 kg ha(-1) for each unit decrease in leaf area index below the plateau; average maximum yield was 3,484 +/- 735 kg ha(-1). From eight field experiments over 2 yr, insect defoliators had no effect on double-crop soybean yield; leaf area index levels were above 4.0 by the developmental stage when leaf area index estimates were taken (R3 to R6). Therefore, double-crop soybean that maintains leaf area index values above the 3.5-4.0 critical level by mid-reproductive developmental stages can tolerate defoliating pests.

Relationship Between Leaf Area Index and Yield in Double-Crop and Full-Season Soybean Systems

Relationship Between Leaf Area Index and Yield in Double-Crop and Full-Season Soybean Systems

Herbicide Effects on Visible Injury, Leaf Area, and Yield of Glyphosate-Resistant Soybean (Glycine max)1

The failure of glyphosate to control all weeds throughout the entire growing season has sometimes prompted growers to use herbicides other than glyphosate on glyphosate-resistant soybean. Field studies were conducted in 1999 and 2000 to investigate potential crop injury by several herbicides in glyphosate-resistant soybean and to determine the relationships between soybean maturity group, planting date, and herbicide treatment on soybean injury, leaf area index (LAI), and yield. Glyphosate-resistant soybean generally recovered from early-season herbicide injury and LAI reductions; however, some treatments reduced yield. Yield reductions were more common in double-crop soybean than in full-season soybean. In full-season soybean, most yield reductions occurred in the early-maturing ‘RT-386’ cultivar. These yield reductions may be attributed to reduced developmental periods associated with early-maturing cultivars and double-crop soybean that often lead to reduced vegetative growth and limited LAI. Reductions in LAI by some herbicide treatments were not necessarily indicative of yield loss. Further yield reductions associated with herbicide applications occurred, although soybean sometimes produced leaf area exceeding the critical LAI level of 3.5 to 4.0, which is the minimum LAI needed for soybean to achieve maximum yield. Therefore, LAI response to herbicide treatments does not always accurately indicate the response of glyphosate-resistant soybean yield to herbicides.Nomenclature: Glyphosate; soybean, Glycine max (L.) Merr.Additional index words: Double-crop soybean, full-season soybean, soybean maturity group.Abbreviations: EPSPS, 5-enolpyruvylshikimate-3-phosphate synthase (EC 2.5.1.19); fb, followed by; LAI, leaf area index; PRE, preemergence; POST, postemergence; WAP, weeks after planting.

Evaluation of row-spacing, seedbed preparation, and weed control options for dryland soybean

Production systems for dryland full season soybean consist of seedbed preparation, planting operations, weed control activities and harvesting operations. Often production system choices are interdependent across seedbed preparation, planting equipment and weed control options. For example, the selection of one system option such as no-till seedbed preparation restricts planting equipment choices. Evaluating production systems requires that a holistic approach be employed to account not only for agronomic factors but economic ones as well. Experiments were conducted in 1992, 1993, and 1994 at Keiser, AR and in 1992 and 1993 at Marianna, AR on clayey and silt loam soils, respectively. Treatments consisted of various combinations of preplant tillage (yes or no), row-spacing (narrow or wide), and post-plant cultivation (yes or no) for weed control. Grain yield data was collected and analyzed using SAS. In addition, economic analysis consisted of generating crop production budgets that were used to estimate returns to land, labor and management as well as to conduct breakeven and sensitivity analysis. A no-till system lead to higher grain yield and net returns on clayey soils at Keiser, AR, while the tilled system lead to more stable returns on silt loam soils at Marianna, AR. Results showed that narrow row spacing was superior regardless of soil type and location. Finally, post-plant cultivation was of little consequence given the above recommendations.

Preplant and post-plant tillage for full-season soybean on clayey and silt loam soils

Definitive responses to pre- and post-plant tillage are hard to locate in the literature. These tillage responses are usually confounded with other factors. A 2×2 factorial treatment design for pre- and post-plant tillage was implemented in a modified split plot experimental design. Main plots were preplant tillage and sub-plots were post-plant tillage. The experiment was conducted from 1992 through 1994 on a clayey soil at Keiser, AR; 1992 through 1993 on a silt loam at Marianna, AR; and in 1994 on a silt loam at Pine Tree, AR. Grain yield was determined. Soil samples were taken for soil moisture determinations at depths of 0–5 cm, 5–15 cm, 15–30 cm, and 30–45 cm. Crop budgets were generated using production practices and equipment commensurate with commercial farming operations in the area. Results showed that preplant tillage and no-till resulted in equivalent grain yields on clay soil. However, net returns on no-till were equal to or superior to preplant tillage on clay soils across all years. On silt loam soils, both preplant and post-plant tillage main effects were significant for both yield and net returns. Results varied with year on both clayey and silt loam soils. Breakeven analysis indicated that breakeven yield differences were relatively minor across tillage systems. Further, breakeven prices on the clayey soils were generally lower than on the silt loam soils reflecting changes in relative profitability across soil type. Soil water measurements clearly demonstrated the soil's function of water storage for ultimate release to the plant during droughty periods. This function was not affected by tillage system in this study.

Effects of Wheat-Residue Management on Double-Cropped Soybean and Subsequent Crops

Management of wheat (Triticum aestivum L.) residue is an important consideration in production of double-cropped soybean [Glycine max (L.) Merr.]; however, little information is available concerning long-term effects of wheat-residue management on subsequent crop yield and soil quality. A 12-yr study was conducted in southeastern Kansas to evaluate the agronomic effects of three wheat-residue management practices (moldboard plow, burn then disk, and disk only) on: (i) grain yield, seed weight, and leaf nutrient concentrations (N,P,K) of double-cropped and full-season soybean and winter wheat in a 2-yr cropping rotation; (ii) soil moisture and bulk density at the R5 soybean growth stage; and (iii) changes in soil fertility properties (pH, organic matter [OM], P, and K). Double-cropped soybean yield varied with wheat-residue management and available soil moisture, but no residue practice was superior in all years. Seed weight and leaf K concentration of double-cropped soybean were highest with plowing, whereas disking resulted in greater soil bulk density, regardless of year. Grain yield, seed weight, and leaf N, P, and K concentrations of subsequent full-season soybean and winter wheat were not affected significantly by previous wheat residue management. After six 2-yr cropping cycles, soil pH, OM, available P, and exchangeable K had changed very little from initial values. In rotations where double-cropping occurs only once every 2 or 3 yr, wheat-residue management may not have significant long-term effects on subsequent crop yield or soil quality.

Soybean Mosaic Virus Resistance Improves Productivity of Double‐Cropped Soybean

Double‐cropped soybean [Glycine max (L.) Merr.], an important production system in the upper south and southeastern USA, has lower productivity than full season soybean. Soybean mosaic virus (SMV) appears to be prevalent in soybean in the upper south of the USA. Yield losses due to SMV infection are greater the earlier infection occurs in relation to soybean developmental stages. Soybean may be infected by SMV at earlier developmental stages when planted late than when planted early, thus double‐cropped soybeans may be more susceptible to yield reduction caused by SMV infection. The objectives of this study were to determine whether SMV resistance provided an average yield benefit in late planting and whether the expression of this benefit was dependent on background genotypes. In 18 resistant/susceptible genotype pairs the resistant genotypes, overall, provided 283 kg ha−1 (12%) resistance benefit for yield over susceptible genotypes in late plantings. This benefit was independent of background genotype and significantly correlated with the difference between early plantings and late plantings in the incidence of SMV infection at growth stage R1 (r = 0.72, P < 0.01). In late planting environments resistance also provided benefits for seed quality traits, i.e., no seed transmission of SMV and low seed coat mottling. We recommend that resistance to SMV should be incorporated into soybean cultivars which will be used in the double‐cropping production system.

A conservation tillage research update from the Coastal plain soil and water conservation research center of South Carolina: A review of previous research

In the U.S. Southeastern Coastal Plains conservation tillage (CT) became useful as a management system with the development of in-row subsoiling systems capable of planting into heavy residues. Research priorities associated with the development of CT included: reducing cover crop water loss, improving stand establishment, assessing nutrient and water management requirements, determining optimal subsoiling strategies, understanding long-term conservation tillage effects on soil properties, evaluating the interaction of crop residue removal with tillage systems, and documenting tillage impact on pests and beneficial organisms. Since the late 1970s the Coastal Plains Soil and Water Conservation Research Center in Florence, SC has made a concerted effort to study these interactions and alleviate them as obstructions to the use of CT management. These studies showed that for Coastal Plain soils such as Norfolk sandy loam (fine-loamy, siliceous thermic, Typic Paleudults) winter cover crops such as rye ( Secale cereale L.) desiccated the soil profile by evapotranspiration in the spring. This delayed emergence and early season growth of corn ( Zea mays L.) but not full-season soybean ( Glycine max (L.) Merr.). Conservation tillage helped manage soil strength by gradually increasing soil organic matter content, restricting traffic patterns and maintaining higher soil water contents. Laboratory studies demonstrated a negative correlation ( R 2=0.85) between proctor soil strength and organic matter content. Conservation tillage affected nematode, Bradyrhizobium japonicum and Heliothis species populations. Alternate cropping systems using rapeseed ( Brassica napus L.) as a winter crop or sunflower ( Helianthus annuus L.) either before soybean or after corn provided crop cover against potential soil loss from late autumn through early spring, when bare soil is exposed to intense rainfall. Water quality questions associated with CT have been raised but remain unanswered. Although CT can reduce runoff and erosion, the crop residues can support higher insect populations and pathogen inoculum levels, and thus prompt greater pesticide use. Quantifying relationships between soil strength, macropore formation and persistence, and water infiltration with surface and subsurface water quality is the focus of new long-term evaluations. The findings of these studies, published to date, are summarized in this paper.

Effect of Risk Preferences on Incorporation of Double-Crop Soybeans into Traditional Rotations

Six enterprise combinations, four including a double-crop sequence of wheat followed immediately after harvest by soybeans, were evaluated for southeastern Kansas given the requirements for participation in the government commodity program. Stochastic dominance analysis was used to select the preferred combination under six different classes of risk preferences. A two-year sequence of wheat double-cropped with soybeans followed by full-season soybeans was the preferred combination for all classes of risk preferences analyzed. Sensitivity analysis indicated that if labor, machinery, or field time constraints limit the number of acres of double-cropped soybeans and/or if farm yields are sufficiently less than those included in the data set, results would either favor rotations that do not double-crop or those that double-crop less than the maximum number of acres each year.

Potassium Utilization by No‐till Full‐Season and Double‐Crop Soybean

AbstractAlthough K accumulation by soybean [Glycine max (L.) Merr.] has been studied extensively, data on differential K utilization by full‐season and double‐crop soybean are not available. Potassium utilization by no‐till soybean grown at two levels of soil K fertiliiy and two row widths was evaluated under full‐season and double‐crop planting dates. Plant component dry weight and K concentration were determined at growth stages R1, R5, and R7. For both planting dates, high soil K fertility resulted in elevated tissue K concentration and K accumulation in all plant parts at all three growth stages. At R1, double‐crop soybean tissue K concentrations were greater than that of full‐season soybean. At R7, double‐crop soybean leaf and abscised tissue K concentrations were lower than those of full‐season soybean, suggesting a disproportionately greater translocation of K out of the double‐crop soybean leaf during seed‐fill. At R7, seed K accounted for 64 and 38% of total plant K for low and high K fertilily regimes, respectively. seed IC at R7 was a constant proportion of total K accumulated for both full‐season and double‐crop planting dates. Row spacing did not alter shoot K concentration or accumulation for either planting date. Potassium accumulation rate was greatest between R1 and R5, was increased by high K fertility conditions, and was not different between full‐season and double‐crop planting dates except during the seed‐filling period when the fullseason soybean K uptake rate was greater. Full‐season soybean maintained a greater soil K uptake rate during seed‐fill while double‐crop soybean seed K supply was apparently more dependent on redistribution of K from other plant tissues.

Horseweed (Conyza canadensis) Control in Full-Season No-Till Soybeans (Glycine max)

Cyanazine and 2,4-D were the most effective herbicides for horseweed control before establishing full-season no-till soybeans. Paraquat plus 2,4-D was less effective than 2,4-D alone but superior to paraquat alone. Chlorimuron plus metribuzin or chlorimuron plus linuron was less effective than cyanazine but controlled horseweed better than metribuzin, linuron, or imazaquin. Herbicides were generally more effective when applied early. These studies indicate paraquat was antagonistic to 2,4-D for horseweed control when these herbicides were combined.

Reducing Herbicide Inputs When Establishing No-till Soybeans (Glycine max)

In full-season soybean experiments, adding glyphosate, paraquat, or HOE-0661 to chlorimuron, chlorimuron plus linuron, chlorimuron plus metribuzin, or imazaquin was required for effective weed control, especially eastern black nightshade. In double-crop soybean experiments, chlorimuron plus linuron provided similar weed control and yields with or without either glyphosate, paraquat, or HOE-0661. In both full-season and double-crop soybeans, metolachlor combined with chlorimuron mixtures did not enhance weed control or increase yield. These studies indicate a potential for reducing the use of nonselective herbicides or metolachlor when chlorimuron or imazaquin are components of tank mixes, particularly in double-crop no-till soybeans.

Giant Foxtail (Setaria faberi) Control in Full-Season No-Till Soybeans (Glycine max)

Alachlor plus linuron tank mixed with paraquat and applied preemergence (PRE) did not control giant foxtail all season in full-season no-till soybeans. Alachlor applied early preplant (EPP) plus PRE was necessary to control (>70%) giant foxtail acceptably all season. Metolachlor applied PRE or EPP plus PRE were equally effective in controlling giant foxtail (71 to 74%). Oryzalin at 1.7 or 2.2 kg ai/ha applied fall or spring EPP controlled giant foxtail better than 70% through July. Oryzalin applied PRE did not control giant foxtail acceptably.

Green Cloverworm and Green Stink Bug Control in Full Season Soybeans, 1986

Abstract Larvin 3.2F and Pounce 3.2EC were evaluated for efficacy in controlling green stink bugs and green cloverworms in soybeans. Effects on the arthropod predators (spiders, nabids, and big-eyed bugs) also were examined in the conventionally planted soybeans being grown on the Z. L. Newsome Farm in Richmond County, VA. Soybeans were planted on a 36-inch row spacing on 26 May. Insecticides were foliar-applied on 22 Aug with a CO2-powered compressed air sprayer at 30 psi that delivered 28.7 gal of finished formulation per acre. Individual plots were 4 rows by 75 ft with 4 replications. Individual treatments were evaluated 1-, 3-, 7-, 14-, and 21-days after application by comparing the number of pests and predators per 25 sweeps (using a 15-inch diameter net) in the treated plots to those in the untreated checks. Yield estimates were obtained by harvesting 25 feet of row from the center rows in all plots.

Analysis of producing vegetable oil as an alternate fuel

Small-scale, on-farm oil production and extraction were evaluated for four oilseed crops produced in full-season or double cropping systems. Economic feasibility was determined by calculating the per-liter cost of vegetable oil based on total costs of production and processing as well as credits for feeding values of the oilseed residues. Per-liter costs ranged from a high of $1.76 for soybean oil (no-till, full-season soybeans) to a low of $0.97 for the conventionally tilled winter rape/soybeans cropping system (processing labor not included) for a 25% vegetable oil/diesel fuel mix for a typical 240-ha farm. When processing labor changes were included, all per-liter costs were increased accordingly. Total energy and fuel energy inputs and outputs were analyzed for winter rape, soybean, sunflower, and peanut oils. All four oilseeds yielded a positive energy balance (output greater than input). The total energy output-to-input ration range from 2.62 for conventional tillage sunflowers to 7.47 for no-till soybeans. The fuel energy output-to-input ratio ranged from 1.43 for conventionally tilled full-season soybeans to 13.52 for the no-till winter rape/sunflower cropping system.

Conservation tillage for soybean in the U.S. Southeastern Coastal Plain

Double cropping of soybean has progressed less rapidly in the U.S. Southeastern Coastal Plains than expected by the ample rainfall and long frost-free season. Post-emergence herbicides, the management of plant residues to reduce water use by cover crops, and a no-till planter with a combination subsoiler are the innovations that have facilitated this new production. Full-season soybean ( Glycine max L.) was planted following a grazed cover crop of winter rye ( Secale cereale L.) or late-season soybean was planted following winter wheat harvest. In both cases, a special planter was used with an integral subsoil shank ahead of the opener. Full-season soybean under conservation tillage produced yields equal to or better than yields in conventional clean tillage. In a dry summer, soybean yields under conservation tillage exceeded conventional tillage because of suppressed early biomass production which conserved stored soil water and favored growth during the reproduction phase of the crop-cycle. Late-season soybean yields behind wheat favored the conservation tillage practice of in-row subsoil-planting into stubble. However, planting in burned-off wheat stubble produced the highest yields in this study. In a dry spring, the cover crop accelerated soil water use which resulted in lower soybean yields under conservation tillage. Comparisons of 76 vs. 97 cm row spacing were inconclusive, but the trend suggests that wider rows conserve water under periods of drought and that the narrower-row configuration favors adequate water regimes.

Ground- and Foliage-Dwelling Spiders in Four Soybean Cropping Systems

Five dominant spider families were found on Virginia soybeans, two on the ground (Lycosidae and Linyphiidae) and three on the foliage (Oxyopidae, Thomisidae, and Salticidae). Total foliage-dwelling spiders peaked in early August and again in early September 1981, and in early to mid-August in 1982. Ground spiders peaked in June with the greatest abundance of Lycosidae. While higher spider populations were collected from foliage in soybeans double-cropped after barley harvest and in full-season soybeans that were drill-planted, the ground spiders were more numerous in both barley- and wheatsoybean double-cropped systems. Over 25,000 spider specimens from 17 different families were observed in soybean ecosystems during this 2-year study.

Influence of subsoil amelioration with lime, phosphorus and potassium on the yield of soybeans and barley

Abstract The effects of mixing lime and large quantities of phosphorus and potassium fertilizers with the subsoil were studied on 16 Maryland subsoils. These subsoils were covered with 10. cm of a fertile surface soil so the subsoils’ effect would be the major variable. Soybeans were grown on these soils in the greenhouse. These subsoils received 65.2 and 83.0 ug/g of phosphorus and potassium respectively. Two treated subsoils were also studied in the field. Simulated subsoiling in the field was accomplished by digging to a depth of 50.8 cm. Lime, 148 or 440 Kg P/ha, and 186 or 558 Kg K/ha were mixed with each 15 cm depth of subsoil. Soybeans and/or barley were planted on the field plots. In general, the subsoils studied in the greenhouse indicated that the combined amendments of lime, phosphorus and potassium to the subsoils increased root production in the subsoil, nitrogen content in the soybean shoots, and yield. First year field results on the Othello (Typic Ochraquult) soil indicated that soybean yields on treated subsoil plots were not significantly different from soil receiving the same surface applications of fertilizer. However the second year after treatment, the yields of double cropped soybeans and barley were increased by 706 Kg/ha (10.5 bu/acre) and 710 Kg/ha (14.4 bu/acre) respectively when compared to similar quantities of phosphorus and potassium applied to the surface soil of nonsubsoiled plots. On the Monaouth (Typic Hapludult) soil, the first year yields of subsoil plots treated with lime, phosphorus, and potassium also failed to improve yields compared to surface application of the fertilizer. Lime, 440 Kg P/ha, and 558 Kg K/ha applied to the subsoil did significantly improve yields of full season soybeans over the untreated soil by 720 Kg/ha (10.7 bu/acre).