Cover crops (CC) in vineyards and olive groves provide an alternative to conventional tillage (CT) for land management. Runoff, sediment and nutrient loss from six sites in France, Spain and Portugal were compared over 3–4 yr. In general, runoff loss was not significantly reduced by the CC alternatives: average annual runoff coefficients ranged from 4.9 to 22.8% in CT compared with 1.9–25% in the CC alternatives. However, at two sites, reductions in average annual runoff coefficients were greater for CC: 17.2 and 10.4% in CT, 6.1 and 1.9% in CC. Nutrient loss in runoff followed a similar pattern to runoff, as did pesticide loss on the one site; reductions occurred when runoff losses were significantly reduced by CC. The lack of differences at the other sites is thought to be due to a combination of soil conditions at the surface (compaction and capping) and sub‐surface (low‐permeability horizons close to the surface). In contrast, CC always resulted in reductions in soil erosion loss, plus similar reductions in nutrients and organic matter (OM) associated with sediment. Soil erosion loss ranged from 1.4 to 90 t/ha/yr in CT compared with 0.04–42.7 t/ha/yr in CC. Overall, reductions in runoff and associated nutrient and pesticide loss from vineyards and olives occurred with the introduction of CCs only when soil permeability was sufficiently high to reduce runoff. In contrast, reduction in soil erosion and associated nutrients and OM occurred even when the amount of runoff was not reduced. In the most extreme encountered situations (highly erodible soils in vulnerable landscape positions and subject to highly erosive rainfall), additional conservation measures are needed to prevent unsustainable soil loss.

In traditional simulated herbicide drift research, dose response is evaluated using a constant carrier volume. The influence of carrier volume was evaluated in field experiments with drift rates representing 12.5 and 6.3% of the use rates of 1,120 g ai/ha glyphosate (140 and 70 g/ha, respectively) and 420 g ai/ha glufosinate (53 and 26 g/ha, respectively). Corn and soybean were exposed to herbicide rates applied in constant carrier volume of 234 L/ha and in proportional carrier volumes of 30 L/ha for the 12.5% rate and 15 L/ha for the 6.3% rate. Averaged across herbicides, corn height reduction 14 d after treatment (DAT) was greater for the 12.5% rate when applied in proportional 30 L/ha carrier volume (45%) compared with constant 234 L/ha carrier volume (28%). The 6.3% rate reduced corn height 38% when applied in proportional 15 L/ha carrier volume but not when applied in 234 L/ha carrier volume. When carrier volume was changed from constant to proportional, corn injury 14 DAT increased from 33 to 51% for the 12.5% rate and 18 to 38% for the 6.3% rate. Compared with constant spray volume, corn yield reduction was 1.5 times greater for the 12.5% rate but 4 times greater for the 6.3% rate when spray volume was varied proportionally to the herbicide rates. Differential response due to carrier volume was not observed when herbicides were applied to soybean. Soybean was injured more by glyphosate than by glufosinate, but recovery was rapid and yield was not negatively affected. Results suggest that drift research using constant spray volume may underestimate the yield reduction expected for sensitive crops exposed to glyphosate or glufosinate.

The influence of carrier volume was evaluated in field experiments for glyphosate applied to wheat at rates representing 12.5 and 6.3% of the usage rate of 1,120 g ai/ha (140 and 70 g/ha, respectively). Wheat at first node and at heading was exposed to glyphosate applied in a constant carrier volume of 234 L/ha, where herbicide concentration declined with reduction in dosage, and in proportional carrier volumes of 30 L/ha for the 12.5% rate and 15 L/ha for the 6.3% rate, where herbicide concentration remained constant. At 28 d after treatment, glyphosate applied at first node in proportional carrier volume (an average for 30 and 15 L/ha adjusted proportionally to glyphosate rate) reduced wheat height 42% compared with 15% when glyphosate was applied in 234 L/ha. Height reduction was no more than 15% when glyphosate was applied at heading in 234 L/ha or in the proportional carrier volumes and at first node in 234 L/ha. Wheat yield was reduced 42% when glyphosate at 140 g/ha was applied in 234 L/ha but was reduced 54% for the same rate applied in proportional carrier volume. For 70 g/ha glyphosate, wheat yield was reduced 11% when applied in 234 L/ha, but was reduced 42% when the same rate was applied in proportional carrier volume. Wheat yield reduction was equivalent when glyphosate was applied in 234 L/ha at first node and at heading (29 and 24%, respectively), but yield reductions of 60% for first node application and 36% for heading application were observed when glyphosate was applied in a proportional carrier volume. When averaged across carrier volumes and glyphosate rates, the greater yield loss from application at first node was attributed to decreased number of spikelets per spike and seed weight per spike.

Field studies were conducted to evaluate red morningglory control with 2,4-D alone and in combination with dicamba, along with other postemergence herbicides applied both over the top and as directed treatments. For red morningglory 30 and 60 cm in height, complete control 14 or 21 d after treatment (DAT) was obtained during 2 yr with 2,4-D at 0.53 kg ai/ha, 2,4-D at 0.4 kg/ ha or more plus dicamba, atrazine at 2.23 kg ai/ha, flumioxazin at 0.10 kg ai/ha, and sulfentrazone at 0.35 kg ai/ha. When red morningglory were 1.8 m, weed control with most herbicides was less consistent than when applied to smaller plants. Red morningglory (1.8 m) was controlled 100% 28 DAT the first year with 2,4-D at 1.06 kg/ha and 78% the second year. In the first year, the 2,4-D plus dicamba prepackaged mixture at 0.8 + 0.28 kg ai/ha or 2,4-D plus the 2,4-D/dicamba prepackaged mixture (0.53 + 0.2/0.07, 0.53 + 0.4/0.14, or 0.79 + 0.1/0.04 kg/ha) provided control equal to that by 2,4-D alone at 1.06 kg/ha. In the second year, when herbicides were applied 3 wk earlier than the previous year and when weed growth was more vigorous, the 2,4-D plus the 2,4-D/dicamba prepackaged mixture at 0.79 + 0.1/0.04 kg/ha provided control equal to that by 2,4-D alone at 1.06 kg/ha but was the only 2,4-D plus dicamba treatment to control red morningglory equal to that by 2,4-D at 1.59 kg/ha (87%). Directed applications to the lower 45 cm of 1.8-m red morningglory plants with atrazine at 4.47 kg/ha and sulfentrazone at 0.35 kg/ha controlled weeds at least 96% 28 DAT in 2001, but control was 23 and 30 percentage points less, respectively, the second year.

Research was conducted in 1997 and 1998 to evaluate narrow row spacing and glufosinate in glufosinate-resistant corn. Glufosinate-resistant corn was planted in 51- and 102-cm row spacings at the same plant populations. Herbicide treatments included glufosinate alone and in different herbicide combinations. Atrazine plus glufosinate enhanced Palmer amaranth control compared to glufosinate alone. Control of johnsongrass, ivyleaf morningglory, entireleaf morningglory, Texas panicum, smellmellon, browntop panicum, and toothed spurge with glufosinate was greater than 82%. Common sunflower control with glufosinate was greater than 95%. Atrazine followed by glufosinate applications provided at least 94% control of all species and was the most consistent herbicide system used. Row spacing had little effect on weed control. Crop injury to glufosinate-resistant corn was minimal with glufosinate and atrazine plus glufosinate combinations.