Managing straw residue in wheat (Triticum aestivum L.)‐soybean [Glycine max (L.) Merr.] double‐cropping systems can be a problem, and many management systems are currently being used. Type of tillage used is, to some extent, determined by the straw management practice. In this study, five tillage‐straw management practices were studied on Brooksville silty clay (fine, montmorillonitic, thermic Aquic Chromudert) for 4 years. Only 3 years' data are reported, however, since all treatments failed 1 year because of extreme drought. Objectives were to determine effects of tillage‐straw management practices on (a) stand establishment, growth and yield of double‐cropped soybeans, (b) surface soil organic matter content, and to (c) compare costs and net returns of the wheat‐soybean systems and the monoculture soybeans. In 1 of 3 years when rain did not soon follow planting, preparing the soil by disking, whether the straw was burned or not, resulted in reduced germination and growth. During 1 year, germination was adversely affected when the straw was shredded and left on the soil surface. Yields were highest and most consistent when soybeans were no‐till seeded into the burned stubble, but these yields did not differ from systems where straw was burned followed by conventional tillage or where straw was shredded followed by no‐till planting. The average soybean yield was 29% less for the best double‐crop practice than for monoculture soybeans (1,370 kg/ha vs. 1,927 kg/ha). Wheat yields averaged 3,384 kg/ha and were not affected by the tillage‐straw management practices. Excluding a year in which all double‐crop systems failed, all double‐crop systems except where the wheat straw was incorporated in land preparation gave greater economic returns than monocrop soybeans. The double‐crop system in which straw was burned followed by no‐till seeding and cultivation, gave the greatest average net return.

This study was prompted by the huge feed grain deficits which increase annually in the Southeast. The need exists to find ways of increasing grain production efficiently. Cropping‐tillage systems designed to accomplish this were studied. Soybeans [Glycine max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench.] were double cropped following wheat (Triticum aestivum L.) on a Blackbelt soil. No‐tillage and conventional tillage methods were compared for soybeans and grain sorghum; Conventional tillage was used for wheat. The 2‐year average yield of soybeans was 1,708 kg/ha (25.4 bu/acre) for no‐tillage and 2,250 kg/ha (33.4 acre) for conventional tillage. This difference was significant (P = .05) and was due mainly to lack of nutsedge (Cyperus sp.) control by herbicide alone in no‐tillage plots. In the third year when the crop was hand‐hoed, no yield differences occurred due to tillage methods. The 2‐year average yield of grain sorghum was 3,249 kg/ha (48.3 bu/acre) for no‐tillage and 3,868 kg/ha (57.5 bu/acre) for conventional tillage. When the crop was handhoed yield of grain sorghum was significantly higher for no‐tillage (5,072 vs 4.335 kg/ha). Wheat grown after soybeans yielded significantly (P = .05) more than wheat grown after grain sorghum. This difference was attributed primarily to the bneficial effect of residual N from the previous crop of soybeans. Based on current costs and prices, the soybean‐wheat double cropping system produced significantly higher net returns over specified production costs than the wheat. grain sorghum system.

The grain yield and several yield components of a cytoplasmic, male‐sterile, single cross, corn hybrid and its fertile counterpart were measured in relation to imposed soil water tension regimes and applied nitrogen levels. The male‐sterile strain consistently yielded more grain than its fertile counterpart, primarily because of the greater number of second ears produced. A maximum soil water tension of nearly 6 bars, imposed during the fruiting period, significantly accentuated the observed difference in ear production. At the 6‐bar maximum soil water tension imposed during fruiting, the ear length and diameter of male‐sterile corn were significantly greater than those of the male‐fertile; however, at the 0.3 bar maximum soil water tension imposed during fruiting, ear dimensions of the two strains were similar. Although the sterile strain consistently produced a greater number of ears under all conditions of these experiments, reduced levels of nitrogen and soil water more seriously affected ear diameter and length of the fertile strain.

Synopsis Considerably more N accumulated in fertile tassels than in sterile tassels. Subsequent to the shedding of pollen, there was no difference in the N content of fertile and sterile tassels. Sterile plants accumulated more N in ears and husks than did fertile plants due to the greater yield and number of ears produced by sterile plants. There were only slight differences between fertile and sterile plants in N content of leaves and stalks. The data suggest that the comparatively fewer ears per plant produced by the fertile versions were due to competition for N between the ear primordia and the pollen.

Doublecropped soybean (Glycine max (L.) Merr.) following winter wheat (Triticum aestivum L.) is usually planted past the optimum date for monocropped beans. To make good yield, early growth of doublecropped soybean is very important. The purpose of this experiment was to determine wheat straw leachate, wheat straw management, and supplemental N effects on soybean germination, growth, and yield. Leachate concentrations of 0, 20, and 100 g L -1 (straw to deionized water) were used for germination and radicle growth studies. Leachate concentrations of 0, 2, and 20 g L -1 were used in sand culture and the Ap horizon of Okolona silty clay (fine, montorillonitic, thermic Typic Chromudert) to study germination and early growth of soybean. A 3-yr experiment on Okolona silty clay, consisting of six management practices and two N levels (0 and 28 kg ha-1 ), was used to study soybean growth and yield in the field. Management practices consisted of monocropped soybean planted near the optimum date and at the doublecropped date and doublecropped soybean planted where wheat straw was either burned, physically removed, soil-incorporated, or left standing. Germination was not significantly affected by leachate but was reduced by late planting in the field. The 100 g L -1 leachate inhibited radicle growth, while 20 g initially inhibited but then stimulated radicle growth. The 20 g L -1 leachate inhibited early growth in the laboratory but only in the silty clay, while the 2 g L -1 leachate stimulated growth, especially in the sand. Wheat straw inhibited growth and yield in the field. Supplemental N was most effective in overcoming depressed growth and yield where straw was left on the soil surface. Early monocropped soybean produced the largest average yield, but doublecropped soybean where straw was burned produced the greatest economic returns.