No description available.

Research was conducted at Maricopa, AZ with EPTC (S-ethyl dipropyl carbamothioate) (1.0 lb/a) and butylate (S-ethyl bis (2-methylpropyl)carbamothioate) (2.0 and 3.0 lb/a) in 1986 and 1987 to measure the response of cotton to preplant application methods. Butylate and EPTC were applied as either a preplant incorporated or preharrow treatments. The greatest injury to cotton and poorest weed control resulted when butylate or EPTC were applied on flat ground and incorporated to a depth of 2 inches or 4 to 6 inches. Adequate weed control and minimal injury to cotton was observed when these two thiocarbamates were applied preharrow.

Research was conducted at Maricopa, AZ in 1986 and 1987 to measure cotton and weed control response to preplant applications of cyanazine (Bladex) and prometryn (Caparol). Cyanazine was applied in combination with pendimethalin and trifluralin as either preplant incorporated or preharrow treatments. Neither cyanazine or prometryn significantly reduced cotton stands or yields.

No description available.

No description available.

No description available.

Field experiments were conducted in 1992 and 1993 to determine the crop safety and efficacy of norflurazon applications for control of purple and yellow nutsedge in cotton. Norflurazon was applied preplant-incorporated (PPI) or in two applications, PPI and postemergence (POST) when cotton was 3 to 4" tall. As the PPI norflurazon application rate increased from 0.5 to 0.75, 1.0, and 1.25 lb a.i./A, early season nutsedge control increased from 29 to 49, 58, and 76% of control. Early season weed control declined after about 6 weeks. POST emergence applications of norflurazon prolonged the period of nutsedge control. Data collected 71 and 21 days after the PPI and POST applications, respectively, showed that the 0.5 +1.5, 0.75 +1.25, and 1.0+1.0 lb a.i./A (PPI +POST) treatments resulted in 85, 76, and 73% control of nutsedges. Nutsedge control declined throughout the season with the 0.5 +1.5, 0.75 +1.25, and 1.0+1.0 lb a. i./A split applications all resulting in about 27% control 3 months after the POST applications. PPI rates 1.5 to 2 times the labeled rate for a particular soil type caused cotton injury in several experiments in the 1993 cotton season although no injury was observed in the 1992 season.

Two dinitroaniline herbicides, Prowl and Treflan, were tested in field experiments with cotton to determine their differences, if any, in terms of weed control and crop injury potential. Plots treated with the lowest rate of Treflan (0.125 lb a.i./A at one location and 0.25 lb a.i./A at a second location) exhibited reduced weed control in comparison to the other herbicide treatments. Although root inhibition was slight, lateral root growth of cotton was inhibited more by the higher rates of Treflan (0.75 and 1.0 lb a.i./A) than by the higher rates of Prowl (1.0 and 1.25 lb a.i./A). However, differences in weed control and crop injury were not reflected in differences in cotton stand counts, height measurements and yield as there were no significant differences in these parameters between treatments.

The goal of our research is to determine the effects of yellow nutsedge competition on cotton and to examine how the competitive relationship between these two species is modulated by soil moisture. In support of this goal, a competition experiment with various nutsedge densities and three irrigation regimes was conducted at the University of Arizona, Maricopa Agricultural Center. The results of this study indicate that increasing nutsedge density caused a significant linear decrease in cotton seed yield in both 1993 (p=0.03) and 1994 (p=0.002). The cotton yield reductions caused by the highest nutsedge densities, 33 and 50 tubers /m of crop row in 1993 and 1994, respectively, were 13.5 and 15.5 percent, respectively. Stem biomass, an indicator of total above ground biomass, increased significantly with increasing soil moisture. There was also a trend of increasing seed cotton yield with increasing soil moisture with the wet treatment (i.e., irrigation at 35 percent soil moisture depletion) resulting in the highest biomass and yields. In 1994 this trend was significant (p=0.0001) but in 1993 it was not (p=0.098) probably because fewer replications were used in 1993. An important goal of this research was to determine if cotton, with its deeper tap root type of root architecture, is more competitive against yellow nutsedge, which has a fibrous root system, when irrigation is less frequent. However, analysis of variance showed that there was no significant interaction between soil moisture availability and seed cotton yield reductions caused by nutsedge competition in either 1993 (p=0.44) or 1994 (p=0.62).

This paper offers practical advice to growers interested in precision guidance technologies. Various types of guidance systems are described, along with their potential applications and benefits in a farming operation. Also discussed are some of the techniques which can be employed with precision guidance, including mechanical removal of weeds in the row, improved nutsedge control, and precision herbicide applications.