1991 Annual Report for LS91-038
Developing and Extending Minimum Input Strategies for Weed Control in Agronomic and Horticultural Crops
Summary
Objectives
1.) Reduce soybean herbicide inputs to less than $10/A by spraying reduced rates on very narrow bands.
2.) Integrate new cultivation technology, especially the Buffalo Ridge till cultivator and Bezzirides in-the-row cultivator, with 1 above.
3.) Integrate ridge-till and crimson clover and rye cover crops, with 1 and 2 above.
4.) Determine which of the cover crops commonly used in this region are most effective for weed suppression; evaluate herbicides commonly used for cover crop destruction before planting; and compare yield obtained by no-till planting of southern peas in these cover crops versus conventional seedbed preparation and management practices.
Approach
Herbicide rates as low as one-fourth those recommended by the manufacturer were equally as effective as labeled rates on weed species, including cocklebur, annual morningglories, pigweeds, annual grasses, and hemp seshania in soybeans. Rates equivalent to one-half the labeled rate provided equal control of johnsongrass.
Herbicide inputs were even further reduced by taking the one-fourth to one-half labeled rates and reducing them two to three more times and applying them on a band. A Buffalo cultivator and precision guidance system was used to accomplish this. Soybean yields were statistically equivalent in treatments with herbicide costs under $7/A compared to the $27/A standard program.
Reduced rate herbicide programs were integrated with allelopathic cover crops, narrow rows and ridge tillage in five experiments in 1993.
Results: Objectives 1 and 2
To demonstrate progress in Objectives 1 and 2, results from one study are submitted. The data are presented in Appendix 1 in the complete text on file in the SARE/ACE office. In this experiment, reduced rate programs were compared with either labeled rate programs (Trt. 9) or grower standards that included reduced rates (Trt. 4). In addition, broadcast treatments of reduced rates were compared to those using similar treatments, but with rates further reduced and applied on a band. Cultivation was with a Buffalo cultivator using a precision guidance system. Even under extreme weed pressure, treatment 8 for example, with $6.52 in herbicide inputs, provided weed control and crop yields equivalent to or better than the standard treatments.
Results: Objectives 2 and 3
To demonstrate progress in Objectives 2 and 3, data from two soybean studies are presented in Appendix 2 and 3 in the complete text on file at the SARE/ACE office. The first study presented (Appendix 2) represents the third year of a cover crop, row spacing, herbicide input study. Rye was used as the cover crop and soybeans were planted in either 30" rows or 7.5" drills. Reduced rate and labeled rate herbicide programs were used in each. While rye has shown excellent allelopathic activity on certain weed species and excellent soybean yields have been produced, the presence of the cover crop has allowed for very little reduction in post-plant herbicide usage and has resulted in increased expenses due to the cost of establishment and the herbicide required to kill it.
This work has been expanded, through the SARE program, to ridge tillage as a means to grow the cover crop at a reduced expense. In two studies, flat planting with and without cover crops (F NOC Contill and F COV NOTILL) were compared to bed or ridge culture with and without cover crops. In the flat, cover, no-till plots, the soybeans were seeded directly into the standing rye with a drill. All others were planted in 30" rows.
The first year was primarily a learning year with the new equipment. Soybean yields were equivalent in the flat planted no-till, rye cover plots (Trts. 5 & 6) compared to conventional treatments (2 and 3). However, the herbicide costs were essentially double in the rye plots. In treatment 8 where the cover crop on the bed was removed with tillage and herbicides were banded, herbicide costs were similar to those in treatments 2 and 3, but the yields were down. It is felt this can be corrected and provides very promising future direction. Practices that are ready to go to the grower will be much slower to develop in the cover crop tillage system studies then in the conventional herbicide studies. However, excellent long-term results are anticipated.
Results: Objective 4
To demonstrate progress in Objective 4, we evaluated perennial ryegrass, annual ryegrass, grain rye, wheat, oats, crimson clover, red clover and hairy vetch for weed suppression potential and ranked them as follows, red clover > ryegrass > oats > wheat > grain rye > hairy vetch > crimson clover, from most to least effective.
The ranking of the nonselective, burndown herbicide treatments from most to least effective, with rates given in lb ai/a, was: glufosinate 0.75 > paraquat 0.56 > glyphosate 0.75 > glyphosate 1.5. Tank mixing photosynthetic inhibitor herbicides such as atrazine, cyanazine, metribuzin and fluometuron with paraquat did not significantly improve cover crop suppression.
None of the selective grass herbicides (fluazifop-P, sethoxydim, clethodim) evaluated provided acceptable suppression of the grass cover crops.
Southern peas did not emerge aggressively after no-till planting resulting in a poor stand in all treatments. This, combined with an exceptionally hot, dry growing season in 1993, eliminated the possibility of collecting any meaningful yield data. On the other hand it suggests that southern peas are probably not a likely candidate for no-till establishment in cover crops.
December 1994.