Information is needed to characterize soybean [Glycine max (L.) Merr.] plant responses where cultural practices and environmental conditions are maintained at a level conducive to high yield. Field studies were conducted in 1985 and 1986 to determine the effect of row spacing and plant population on seed yield and yield components of soybean. Two determinate Maturity Group V cultivars, Essex and Deltapine 105, were grown at three row spacings of 25, 51, and 76 cm and three plant populations of 260 200, 390 400, and 520 400 plants ha−1. Seed yield was significantly higher in narrow rows (25 and 51 cm) than in the wide rows (76 cm) with the 25‐cm row spacing averaging 10% higher than the 76‐cm row spacing (3740 vs. 3361 kg ha−1). There was a row spacing × cultivar interaction due mainly to a greater reduction in seed yield of Essex than Deltapine 105 as row width increased. Weight of aerial plant parts during the mid seed‐fill growth period (R5) increased with decreasing row spacings. Plant number in plots with 76‐cm row spacing decreased approximately 23% between planting and harvest whereas, the plant number in 51‐ and 25‐cm row spacings decreased only 7 and 3% respectively during the growing season. Seed yield per plant was most uniform at the 25‐cm row spacing and became more variable as row width increased
Peanut (Arachis hypogaeaL. ‘Tifspan’ or ‘Florunner’) yields were not reduced when the crop was maintained free of Florida beggarweed [Desmodium tortuosum(Sw.) DC.] or sicklepod (Cassia obtusifoliaL.) for 4 weeks after crop emergence and when vigorous crop growth was maintained for the remainder of the season. Sometimes weed-free maintenance for only 2 weeks resulted in near-normal yields, which indicated that the canopy of peanut leaves effectively suppressed the weeds. Conversely, these weeds had to compete with peanuts for more than 10 weeks before crop yield was reduced. Weeds that overtopped the peanuts at harvest emerged during the first 6 weeks after planting.
Two varieties of corn (Zea mays L.) were evaluated for grain yield at row widths of 51 and 102 cm and within‐row spacings of 15, 23, 31, 38, and 46 cm. Both varieties, ‘Pioneer 309B’ (P‐309B) and ‘DeKalb XL 65’ (D‐XL 65), were grown with and without irrigation at Plains, Ga., in 1967 and 1968. Pioneer 309B was grown under irrigation at Calhoun, Ga., during the same years. Yields of irrigated corn were higher in 51‐cm than in 102‐cm rows. Without irrigation, P‐309B yielded more grain in 51‐cm than 102‐cm rows, but yields of D‐XL 65 were similar for both row spacings. Increasing populations in the 51‐cm rows from about 50,000 to 100,000 plants/ha did not increase yields except in irrigated D‐XL 65. Yield decreased with increased population in the above range for nonirrigated P‐309B. Increased populations within 102 cm rows increased yields except for P‐309B at Calhoun and unirrigated P‐309B at Plains. Optimum populations were estimated from relationships between log grain yield per plant and population. Estimated optimum populations were higher for 51‐cm than for 102‐cm rows, for irrigated than for nonirrigated corn, and for D‐XL 65 than for the P‐309B variety. Estimated optimum population appeared to be related to plant size with smaller plants requiring a higher population for maximum grain yield. Leaf area per plant for D‐XL 65 was only 0.7 of that for P‐309B. This difference in leaf area was also probably related to estimates of optimum population.
Succinic acid 2,2-dimethylhydrazide (SADH) was applied at 0.95 kg/ha 60 days after planting to seven peanut (Arachis hypogaea L.) cultivars in 1970 and eight cultivars in 1971 and 1972. Pod yield of all cultivars were increased by SADH in 1970 by an average of 20%. Yields of Spanish type cultivars were increased in 1971 but not in 1972, while yields of runner and Virginia cultivars were not affected in 1971 nor 1972. There was a trend for increases in the number of pods per plant in Spanish cultivars in all three years and in runner and Virginia types in 1970. Weight per 100 pods was reduced in the Spanish cultivars only in 1972. Main stem lengths were reduced by SADH treatment by an average of 32% in 1970 and 27% in 1971.
Succinic acid 2,2‐dimethylhydrazide (SADH) was applied to “Starr” peanuts (Arachis hypogaea L.) at the rate of 1.43 kg/ha in 1968, 1969, and 1970. Data were obtained on pod yield; stem length; peg and pod lengths; pod, stem and leaf weights; and leaflet area. The most consistent effect of SADH was a reduction of plant height. Stem lengths were reduced 30 to 40% by SADH application. Pod length was reduced by 6 to 10% in 1969 and 4% in 1970 when plants were treated with SADH. Peg length in 1970 was 2.7 cm on SADH‐treated plants compared to 3.4 cm for controls.Pod yields were increased in 1968, but not in 1969 or 1970. The increase in yield in 1968 was similar for irrigated and nonirrigated peanuts. Stem weight per plant was decreased by SADH in 1970 but not in 1969, and the pod‐vegetative ratio was increased in 1969 and 1970. Specific leaf area and area of leaflets were reduced in some cases by SADH applications. Dry weight per leaflet was not affected. Reduction of top growth may be beneficial because ground machinery can be used later than usual in the season to apply insecticides and fungicides without damage to the peanut plants.
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