Adjuvants were evaluated to determine the effect on increasing spray droplet size and reducing the amount of spray dispensed in small driftable size particles when applying water and paraffinic oil at ultralow volume. Spray solutions were applied with an air-assist system at liquid flow rates of 28 and 56 ml/min and atomized with 14, 28, 42, 56, and 84 kPa of air pressure. Water and paraffinic oil were applied alone and with two drift retardant adjuvants mixed individually in each. The two water soluble adjuvants were mixed at concentrations of 0.25, 0.50, 0.75, 1.0, and 2.0%; oil soluble adjuvants were applied at 0.125, 0.25, and 0.50%. Adjuvants used in water and oil were effective at increasing droplet size and reducing the amount of liquid dispensed in small driftable size particles. Effectiveness of the adjuvants decreased as air pressures increased, with water soluble adjuvants being more susceptible to air pressure. Volume median diameters > 200 μm with water could be achieved without adjuvants; whereas with oil, an adjuvant was required.

There is limited information on the effects of within‐field variability in soil nutrient concentrations on seed composition in soybean [Glycine max (L) Merr.]. A study was conducted on a 18.8‐ha grower field in Stoneville MS in 2005 and 2006 to evaluate the effects of soil nutrient variability across field on seed composition constituents (protein, oil, fatty acids, and minerals). Soil and seed samples were collected from low yield (L), medium yield (M), and high yield (H) areas (plot) across the field. Results showed that seed collected from L areas had lower protein and oleic fatty acid percentages than those of M or H. Soil samples from L had lower organic matter and lower concentrations of N, C, K, B, and Zn in soil compared with those of either M or H. The results indicate that maintaining adequate nutrients in soil may result in higher seed protein and oleic acid, but lower seed oil and linolenic acid.

Methods were developed and evaluated that utilize state of the art weed-sensing technology in row-crop production systems. Spectral differences in green living plants and bare soil allowed ‘real-time’ weed detection, with intermittent spraying of herbicide only where weeds were present. Sensor units were mounted in 0.7-m-wide hooded sprayers providing sensors with an unobstructed view of the area between soybean rows. Single hood and commercial-size eight-row systems were evaluated, and savings in glyphosate spray solution applied using sensors ranged from 63 to 85%, compared to conventional hooded spray systems with continuous application. Weed control by the sensor-controlled spray system was equal to the conventional system. This technology can significantly reduce herbicide usage and decrease production cost without reducing weed control.

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Fenoxaprop, fluazifop/fluazifop-P, haloxyfop, and quizalofop at 0.14 kg ai ha−1and sethoxydim at 0.28 kg ai ha−1were applied broadcast over-the-top in spray volumes of 94 and 374 L ha−1, each at 138 and 345 kPa, to control johnsongrass in soybeans over a 5-yr period. The two spray volumes provided equal control, but control was better when treatments were applied at 345 kPa than at 138 kPa. There were no significant interactions among herbicides, spray volumes, or spray pressures. Most of the spray was deposited on the upper surface of the plant canopy. Less than 10% of the herbicide spray applied penetrated into the canopy onto water-sensitive spray cards located 10, 20, 30, or 40 cm above the ground.