Flooding is a major problem that reduces soybean [Glycine max (L.) Merr.] growth and grain yield in many areas of the USA and the world. Our objective was to identify the plant and soil characteristics associated with different flooding durations in six fields in central Ohio. The soybean plants were at the V2 and V3 stages when rainfall‐induced flooding occurred. The outer perimeters of the flooded areas were mapped, using GPS (global positioning system) technology, several times during the flooding event to delineate the change of the flooded area over time. Two 9‐m wide transects across the flooded area within each field were divided into plots of 9 m by 9 m according to flooding duration: no flooding, 1 to 3 d, 4 to 6 d, and 6 to 8 d. Soil and plant nutrient levels, grain yield data and grain protein and oil content were determined for each plot. The soil cation‐exchange capacity (CEC), pH, P, Ca, Mn, and Zn concentrations had significant positive correlation with flooding duration. There was a significant negative correlation of flooding duration with the population, height, number of pods, and yield of soybean. There was no significant correlation of flooding duration with seed weight, oil, or protein content of the seeds. Leaf tissue Ca, Mg, B, Fe, Cu, and Al concentrations had a significant positive correlation with flooding duration, whereas leaf tissue N concentration had a significant negative correlation with flooding duration.

Determinate semidwarf cultivar of soybean [Glycine max (L.) Merr.] were developed to overcome the lodging barrier to high yield, but little work has been reported on their response to production systems or environments. The objective of this study was to determine the effect of planting date, row spacing, seeding rate, and their interactions on determinate vs. indeterminate cultivars. The cultivars ‘Sprite’ (determinate semidwarf) and ‘Williams’ (indeterminate) were compared at two Ohio locations over a 3‐yr period. Planting dates were 1 May, 20 May, and 10 June, and row spacings were 7, 10, 14, and 20 in. Seeding rates of 150 000 and 200 000 seeds/acre for Williams, and 150 000, 200 000, 250 000, and 300 000 seeds/acre for Sprite were used. Delayed planting reduced yield significantly. The response to increasing row spacing was a small decrease in yield for both cultivars, which was moderated by both planting date and seeding rate. The yield of Sprite—but not Williams—increased as seeding rate was increased, regardless of planting date or row spacing. Mean yield decreased 30% from the first to third date of planting, while row spacing and seeding rate effects were in the range of 5 and 6%, respectively. While Williams did not respond to seeding rate, there was a planting date × seeding rate interaction. Sprite responded to seeding rate, but there was no planting date × seeding rate interaction; however, there was a three way interaction (environment × seeding rate × planting date).

The effects of leaf age and light acclimation on apparent photosynthesis (AP) rates of single attached leaves of highly productive, field‐grown, ‘Wayne’ soybeans (Glycine max L. Merr.) were determined. AP measurements were made on leaves at nodes along the main stem of plants 5 cm apart in 76‐cm rows (normal canopy plants) and on leaves at different nodes of widely spaced (76 cm ✕ 76 cm) plants without branches. The response to light in the range of 2,000 to 15,000 ft‐c of fully expanded leaves of the two types of plants was also measured.The AP rates of upper and lower leaves of the normal canopy plants averaged 33 and 20 mg CO2/dm2/hour, respectively. AP rates of upper and lower leaves of spaced plants were equal and averaged 50 mg CO2/dm2/hour. Leaves from the upper part of normal, field‐grown canopy plants became light saturated at 10,000 ft‐c but the leaves of spaced plants were not light saturated at 15,000 ft‐c.

Winter-hardy small grains produce abundant forage in the spring, but have low forage yield in autumn in the U.S. Midwest. Our objective was to evaluate the effectiveness of mixing annual forages with winter-hardy small grains to improve forage supplies in late autumn without compromising yield the following spring. Field studies were established in mid-September 2001 and 2002 at two locations in Ohio to compare autumn and spring forage yield and nutritive value of the winter-hardy species (WHS) rye (Secale cereale L.), winter wheat (Triticum aestivum L.), and winter triticale (Triticum 3 Secale) seeded alone and in binary mixtures with the winter-sensitive species (WSS) oat (Avena sativa L.), spring triticale (Triticum 3 Secale), annual ryegrass (Lolium multiflorum L.), and rape (Brassica napus L.). The WHS 1 WSS mixtures had greater forage yield in autumn than the corresponding WHS monocultures in 29 of 44 comparisons. Oat and spring triticale mixtures with WHS usually had the greatest autumn yield, greater than the yield of corresponding WHS monocultures in 91% of all comparisons. Forage yield of mixtures was usually similar to that of WHS monocultures in the spring. Forage nutritive value was high for all treatments. Oat, spring triticale, and rape were productive species to include with WHS for optimizing autumn and spring forage yield, but oat and rape had low seed cost ha 21 , and thus were the most economical options.

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