D. E. Longer

Residue Management Practice Effects on Soil Surface Properties in a Young Wheat-Soybean Double-Crop System

ABSTRACT Approximately 25% of the soybean [Glycine max (L.) Merr.] grown in the mid-South is produced in a wheat (Triticum aestivum L.)-soybean double-crop system. Pre-soybean field preparations often consist of removing wheat residue by burning followed by conventional tillage (CT). However, crop residue burning has serious negative environmental consequences and will likely be outlawed in the future. Therefore, the objective of this study was to evaluate the short-term effects of alternative wheat-residue management practices, tillage [no-tillage (NT) and CT], burning (burn and no burn), and wheat-residue level (low and high), on soil surface properties after two full cropping cycles in a wheat-soybean double-crop production system on two silt-loam Alfisols in east-central Arkansas. Soil bulk density increased over time, but the increase was unaffected by imposed treatments. Changes in soil pH and electrical conductivity (EC) were generally unaffected by tillage or burning, whereas soil EC increased by 7% under the high and decreased by 8% under the low wheat-residue level treatment at one location, but not the other. Mehlich-3-extractable Mg and Zn increased more and Na decreased less under NT than CT at one location or the other. Soil organic matter and total N and C also increased more under NT than CT at one location, but not the other. The results of this study indicate that, in a wheat-soybean double-crop production system in a relatively warm and wet environment, numerous soil properties can be improved more under NT than CT and more when crop residues are left unburned than when they are removed by burning. Extended use of alternative wheat-residue management practices that improve soil tilth will result in more sustainable agriculture and likely increase production.

Residue Management Practice Effects on Soybean Establishment and Growth in a Young Wheat-Soybean Double-Cropping System

ABSTRACT Double-cropping wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] is popular throughout the mid-southern United States. To ensure an adequate stand, it is imperative that soybean be planted as soon as possible after wheat harvest due to an already shortened growing season following wheat. Typically, wheat residue is burned, and then conventional tillage (CT) is used to prepare a seedbed for soybean planting. However, residue burning has serious negative environmental consequences. The objective of this study was to examine effects of tillage [CT and no-tillage (NT)], residue burning (burn and no burn), and wheat-residue level (high and low) on soybean stand establishment, growth, and production over three cropping cycles at two locations on silt-loam Alfisols in eastern Arkansas. Soybean plant populations between 10 and 30 days after planting were higher (p < 0.02) under NT than CT in most year-location combinations, while most without wheat residue burning were equivalent to those with burning. Soybean plant populations were unaffected by N rate/wheat-residue level in most year-location combinations. Mid-season soybean leaf area index was higher (p < 0.03) under NT than CT for two of four year-location combinations. Soybean yields under NT were equivalent to yields under CT in all year-location combinations. Results indicate that the alternative pre-plant field preparation combination of no residue burning followed by NT can perform as well as the more traditional combination of burning followed by CT in the wheat-soybean double-crop system in the mid-southern United States.

Irrigation and Planting Date Effects on Seed Yield and Agronomic Traits of Early-Maturing Soybean

ABSTRACT Soybean [Glycine max (L.) Merr.] growers in the mid-south United States have increasingly practiced early planting and double-cropping systems. Information on crop management is desired by soybean growers to improve production and profitability. Effects of irrigation and planting date on seed yield and other agronomic traits were investigated in soybean cultivars from eight maturity groups (MG) in 2002 and 2003 at two locations in Arkansas. The planting date (April, May, and June) and irrigation treatments significantly affected seed yield, plant height, and maturity. Significant effects were also observed for number of nodes, number of pods, and number of seeds per plant, whereas number of branches per plant was not affected by planting date and irrigation treatments. Irrigation improved seed yield by an average of 83% (986 kg/ha) in all experiments conducted across two years. Highest seed yield was achieved when soybeans were planted in May, followed by April and then by June planting. The MG V and VI cultivars, conventionally grown in Arkansas, produced higher seed yields than other maturity groups and were the most suitable cultivar selections when considering seed yield alone. Significant interactions were observed among planting date, irrigation, and maturity groups/genotypes. The MG IV was a better candidate for the double-cropping system (June-planting) because of its earlier maturity and high seed yield. For the early soybean production system (April-planting), MG I and II cultivars were potentially good selections because of their short growing periods and acceptable seed yields. The various planting dates and irrigation systems combined with proper cultivar selections provide soybean producers with more options for using the land and water efficiently.

Planting Date and Irrigation Effects on Seed Quality of Early-Maturing Soybean in the Mid-South USA

ABSTRACT Information is lacking in soybean [Glycine max (L) Merr.] on whether or not variety selection and management practices can improve seed quality in early production systems. Effects of planting date, irrigation, genotype and maturity on seed quality traits in soybean were investigated in Arkansas for two years. Irrigation (I), planting dates (PD), and maturity groups/genotypes (MG/G) significantly affected seed quality traits. The MG/G, followed by I and PD treatments, made the largest contribution to variations in seed quality traits. Irrigation and late planting significantly improved seed standard and cold germination for most maturity groups. Irrigation also tended to increase seed protein content, whereas planting dates had no impact on seed protein and oil content. Both irrigation and planting dates had little or no effect on visual seed quality and seed pathogen infection. Maturity group and genotype significantly affected all seed quality traits. Late-maturing genotypes exhibited significantly higher standard and cold germination rate, fewer pathogen-infected seed, and better visual seed quality than early-maturing genotypes. Wide-row spacing improved seed germination. Seed germination and vigor of early-maturing genotypes decreased, whereas those of late-maturity genotypes improved when planting was delayed from April to June. Early-maturing genotypes were more responsive to irrigation when planted late. Significant correlation was found between cold and standard germination with other seed quality traits, including visual seed quality rating, disease-free seeds, and Phomopsis-infected seeds. We demonstrated that variety selection and irrigation were important in achieving high seed quality of early-maturing soybeans.

Wheat Response to Nitrogen under Low Phosphorus and Potassium Fertility in a Wheat–Soybean Production System

Abstract Producers control crop fertilization practices. If the amount of grain yield per unit of aboveground biomass produced can be optimized with proper fertilization, nongrain aboveground biomass will be minimized. Achieving this goal would be especially beneficial in a wheat (Triticum aestivum L.) and soybean (Glycine max L.) double‐crop production system where proper fertilization could promote a residue‐management shift from burning and conventional tillage to a conservation or no‐tillage system. The objectives of this study were to i) determine the effect of nitrogen (N) rate on wheat yield, aboveground biomass, and partial harvest index (PHI), and ii) identify an appropriate predictive response model for wheat yield and PHI as a function of total N applied under low phosphorus (P) and potassium (K) fertility. This study was conducted over two cropping seasons at two locations on similar silt‐loam Fragiudalfs in eastern Arkansas where wheat was fertilized at 10 N rates ranging from 0 to 101 kg N ha−1 applied once at the early‐jointing stage and from 151 to 269 kg N ha−1 applied in a split application at the early‐jointing stage and at the late‐jointing stage as depicted in the Feekes staging method. The effects of N fertilization on wheat growth and production varied somewhat between locations and from one year to the next. However, the current N recommendation for wheat in Arkansas (i.e., a single application of 101 kg N ha−1) appears to be too low to produce maximum yields under low P and K fertility. Differing yield responses between locations were likely due to the combination of inherent P and K fertility differences and carryover N from the previous crop during the first year of the study. Capitalizing on the relationship among N rate, grain yield, and PHI will allow wheat producers to minimize N applications and production of excessive aboveground biomass, while still being able to produce an economically viable yield.