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Wheat (Triticum aestivumL.) is frequently grown in rotation with summer annual crops. These crops are usually grown in widely spaced rows that can easily adapt to controlled‐traffic management, but high soil strengths prevent crop establishment into controlled‐traffic lanes, eliminating one or more rows of wheat. Wheat can compensate (within limits) for lost cropping area, but the effect of no‐tillage culture with controlled traffic is not known. We conducted this study to compare two tillage systems, conventional and no‐tillage with controlled traffic, on grain yield and yield components of wheat. It was conducted over a 3‐year period on an Austin silty clay (fine‐silty, carbonatic, thermic Entic Haplustolls). The no‐tillage treatment confined all wheel‐induced compaction to controlled traffic zones at 2‐m intervals. Crop residues were destroyed completely by repeated tillage and wheel traffic occurred randomly under the conventional tillage treatment. Hard red winter wheat (cv. Sturdy) was grown in rotation with row crops that were subjected to the same tillage and wheel traffic practices. Rows were spaced 20 cm apart in each tillage system, but two rows were deleted in the traffic zones of the no‐tillage treatment, resulting in 20% less cropped area. Plants on rows adjacent to the controlled‐traffic zones compensated for the absence of wheat within the traffic zones during years of adequate precipitation (1981 and 1983) by producing more tillers and grain than plants in rows within the no‐tillage treatment and those grown under conventional tillage. Drought in 1982 significantly lowered tillering and grain yields under no‐tillage. The study established that wheat can be grown using no‐tillage with controlled traffic. Wheat should be grown with no‐tillage controlled‐traffic technology where drought is minimized or as a component of a total management system where yield increases from alternative crops and/or lower production costs are primary issues.

Conservation tillage systems, such as no‐tillage, have shown tremendous potential for controlling erosion, yet results in crop growth and yield have varied with location, environment, and soil type. The objectives of this study were to evaluate the effects of no‐tillage (NT) and conventional tillage (CT) on growth and development of grain sorghum (Sorghum bicolorL. Moench) grown on a heavy clay soil in a humid, subtropical climate. The study was conducted over a 2‐year period on an Austin silty clay (fine‐silty, carbonatic, thermic Entic Haplustolls) with grain sorghum grown in rotation with winter wheat (Triticum aestivumL.). Grain sorghum yields did not differ significantly between NT and CT. Soil water contents were not significantly different between the tillage treatments, but there were consistent trends toward more soil water under NT throughout sorghum development each year. The tillage treatments did not have a major effect on soil temperature. Reductions in the leaf area index at panicle initiation noted under the NT treatment, however, were not reflected in differences in grain yield. Therefore, no‐tillage may become an attractive management alternative for areas with similar soil and climatic conditions.

Dark respiration is a key physiological process of plant growth and maintenance, but information is limited regarding its genetic variability in grain sorghum. The objectives of this study were i) to determine the range of variability for genetically diverse grain sorghum [Sorghum bicolor(L.) moench] lines and hybrids over a range of temperatures, and ii) to characterize the relationship between dark respiration of a plant during vegetative development and a panicle during grain filling. Dark respiration rates of shoots were determined under controlled conditions at temperatures ranging from 13 to 40°C. At 23°C, the mean rate of dark respiration was 27 μmol CO2kg−1s−1with a range of 32 μmol CO2kg−1s−1. Plant growth at near optimum temperatures (30/25°C; day/night) was correlated with dark respiration rates (measured at 29°C) when the rates were expressed on a per shoot basis, but not when expressed on a dry weight basis. Genotypes differed in their sensitivity to temperature. for the genotypes studied, the linear regression coefficients of dark respiration on temperature ranged from 1.1 to 2.5 μmol CO2kg−1s−1°C−1over the 13 to 40°C range. Within the limits of this experiment, there appears to be sufficient variability to select high and low respiring grain sorghum genotypes and to distinguish those which possess high or low sensitivity to temperature. Panicle dark respiration rates were 50% lower than those of the vegetative portion of the plant. Both panicle and vegetative shoot dark respiration responded in a linear manner to temperature from 13 to 40°C. The panicle dark respiration increased at a rate of 0.75 μmol CO2kg−1s−1°C−1compared with 1.5 for the vegetative shoot indicating that panicle dark respiration was less sensitive to temperature than was shoot dark respiration. This may be related to the linear nature of dry matter accumulation in grain sorghum panicles grown under divergent temperature environments.