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Persistence of chlorsulfuron and other sulfonylurea herbicides, measured by sorghum injury, was determined on a Pullman clay loam (fine, mixed, thermic family of Torrertic Paleustolls) with soil pH varying from 6.5 to 8.1 in a 3-yr winter wheat-sorghum-fallow crop rotation. As pH increased from 6.5 to 8.0, chlorsulfuron persistence increased greatly. With soil pH of 6.5, chlorsulfuron at 34 g ai/ha used on growing wheat did not injure sorghum planted 16 months later. If pH was 7.5 or above, chlorsulfuron persisted and injured sorghum planted within 25 months after herbicide application. Persistence of sulfometuron and metsulfuron was about the same as chlorsulfuron, all of which persisted longer than metribuzin applied at normal use rates. Four annual applications of chlorsulfuron at 71 g/ha did not accumulate when soil pH was 6.5.

Four field experiments were conducted to measure the effects of sevenIpomoea hederacea(L.) Jacq. densities onGossypium hirsutumL. lint yield, stripper-harvest efficiency, and fiber properties. The seven densities were 0, 2, 4, 6, 8, 10, and 12 weeds 10 m−1of row. Data were used to develop prediction models to compare with those previously constructed that used fewer experiments and fewer weed densities in this range.Gossypium hirsutumlint yield in kilograms per hectare and as a percentage of the weed-free control best fit a linear regression model.Gossypium hirsutumlint yield reductions for each increase of one weed 10 m−1of row ranged from 30.7 to 36.2 kg ha−1at Chickasha and from 35.4 to 36.4 kg ha−1at Perkins. Lint yield reductions for each weed 10 m−1of row ranged from 3.8 to 6.9% at Chickasha and from 3.9 to 6.0% at Perkins. All plots could be mechanically stripper harvested, except for the 12-weed density at Chickasha in 1994 and the 10- and 12-weed densities at Perkins in 1996. Harvest efficiencies were not significantly different in any experiment. The only fiber properties to display significant differences were micronaire and strength at Chickasha in 1994. Prediction models calculated herein were highly similar to those previously constructed.

Field experiments were conducted in 1996 and 1997 to evaluate the effects of six johnsongrass densities on picker- vs. stripper-harvest efficiency, fiber properties, loan rate, and lint yield loss of cotton. The weed densities employed were 0 (the check), 3, 4, 5, 8, and 15 plants/15 m of row. With three or fewer weeds in 1996 and four or fewer in 1997, harvest efficiencies were 4.9 to 7.6% higher for stripper- than for picker-harvested cotton. At four and higher weed densities in 1996 and at five and higher in 1997, differences in harvest efficiency between the two machines were not significant. For each weed per 15 m of row, stripper-harvest efficiency in 1996 and 1997 was reduced 0.3 and 0.6%, respectively; picker-harvest efficiency was not affected by the johnsongrass densities included herein. Fiber fineness (i.e., micronaire) was significantly reduced at densities of 8 weeds/15 m of row in 1997 and at 15 weeds in both years. A questionable increase in staple length was detected at the 3-weed density in 1996. Reductions in fiber strength were noted in 1997 at densities of 3, 8, and 15 weeds/15 m of row. No influences on fiber length uniformity were shown. In 1996 the loan rate for picker-harvested lint was 570 points/kg higher than for stripper-harvested lint at 8 weeds/15 m of row. In 1997 it was 741, 801, 1,058, 1,225, 1,074, and 1,329 points/kg higher at weed densities of 0, 3, 4, 5, 8, and 15 plants/15 m of row, respectively. In 1997 picker-harvest loan rate was reduced 49 points/kg of lint, and stripper-harvest loan rate was reduced 85 points. Over both years, picker-harvest lint yield was reduced 32 to 43 kg/ha (3.9 to 5.5%) for each weed per 15 m of row, and stripper-harvest lint yield was reduced 29 to 43 kg/ha (3.5 to 5.2%).

The irrigation of pasture for the dairy industry accounts for a large proportion of Australia’s total irrigation water use, particularly in the Murray–Darling Basin. Most pasture is irrigated using the border-check method. The dairy industry is under increasing pressure to use water more efficiently in response to water market reforms and restrictions on future irrigation water availability, creating interest in the potential of alternative irrigation methods. A field experiment was conducted at Tatura, Victoria, Australia between July 2000 and July 2002 to quantify the differences in water use, perennial pasture production and pasture composition under border-check, surge, sprinkler and subsurface drip irrigation. The experiment aimed to assess each irrigation method as it would perform under farm best management practices. Measurements included applied water, tailwater runoff, soil water status, dry matter production and botanical composition. This experiment found that sprinkler and subsurface drip irrigation used on average 2 ML/ha.year (17–23%) less water than border-check irrigation while maintaining or increasing pasture production, consequently having a significantly higher water use efficiency. Surface runoff was significantly reduced under sprinkler and subsurface drip irrigation. Surge irrigation had no advantages over border-check. Although some differences in pasture composition were observed between irrigation treatments, the trends were inconsistent from one season to the next. The high water use by gravity fed irrigation methods is attributed to a combination of higher evaporation and groundwater accessions.