1988 Annual Report for LS88-011
Developing and Extending Minimum Input Strategies for Weed Control in Agronomic and Horticultural Crops
Summary
The coordinator of this project is Ford Baldwin, Arkansas Cooperative Extension Service. A grower advisory panel, consisting of one soybean/cotton and wheat grower and one soybean/vegetable grower have helped with planning, conducting and evaluating the project. This project is a major component of Baldwin's ongoing research program consisting of about 50 studies annually.
Findings of this project show that reduced herbicide programs are both possible and practical with no loss in weed control and crop yield in many locations and crops in Arkansas. Major findings have shown that herbicide inputs can be greatly reduced by substituting mechanical weed control, spraying herbicide in narrow bands, targeting herbicides to most susceptible weed species, and making very early applications.
Project Results
The data base for minimum herbicide rates continues to be expanded. The reduction in inputs has progressed from labeled broadcast rates to labeled band rates to reduced broadcast rates to reduced band rates. The progression from reduced broadcast
rates has been the primary objective of this LISA project.
For horticultural crops in 1991, we took the weed control methods that we had tested on a small plot basis in 1990 and applied them on a commercial scale. Our farmer-cooperator committed 10 acres which were planted cantaloupes. No herbicides were used for weed control on these 10 acres. Non-chemical weed control measures were: (1) seeding crimson clover the previous fall for weed suppression between the rows and (2) using 36 inch wide, brown, photodegradable plastic mulch for weed control in the rows. This commercial scale project was a failure in terms of crop production due to heavy weed pressure and the inability to keep the crop watered. In spite of the band of plastic in the row, morning glories and spurge grew from the row middles onto the mulch creating excessive competition. The crimson clover provided some weed suppression but it was not sufficient for the weed population present in this field. Reduced effectiveness of the cover crop in 1991 was due in part to reduced stand density compared to 1990. We suspect the reason for this was that the seed was incorporated in 1990 and left on top of the soil in 1991. Rodent damage to the drip irrigation lines was so great that it was impossible to keep them patched which resulted in drought stressed plants. We suspect that the heavy cover of weeds and cover crop in the row middles attracted the rodent population.
We located a small plot, replicated study in the corner of the commercial field to evaluate methods not studied in 1990. These included using heavy brown wrapping paper as mulch to overcome the disposal problem associated with plastic mulch, adding cereal rye to crimson clover to gain an allelopathic effect, no-till seeding directly into the cover crop using either mowing or herbicides to kill the cover crop and adding conventional black plastic and IRT (infra-red transmitting) green plastic to be compared with the photodegradable brown plastic.
The direct seeded no-till plots did very poorly from the beginning of the season. It may be that transplants would improve the potential for success in a no-till situation. The other treatments worked well in the beginning but ultimately failed for the same reasons as the commercial scale trial. The paper mulch was difficult to apply with the mechanical mulch layer due to its brittleness. Once in place, it did well early in the season until the problems mentioned above caused the plant to succumb to drought stress and weed competition. The cereal rye did not enhance weed control.
Lessons learned from this year's studies were obvious: (1) some sites may have weed populations that make the plastic mulch/cover crop combination unworkable as the sole means of weed control. In these situations, wider plastic mulch would be beneficial. (2) Heavy weed and cover crop populations may encourage the presence of rodents that damage drip irrigation lines. (3) No-till, direct seeding of cantaloupes into cover crops will not work under some conditions. (4) Cover crop seed should be drilled or otherwise incorporated into the soil to ensure a thick stand. (5) Paper mulch seems better suited to small operations where it can be laid by hand.
The program of spraying 6-inch bands on 30-inch rows effectively integrates cultivation with chemical methods. In this program, weeds are controlled by cultivation on 4/5 of the area and by a combination of chemicals and cultivation on 1/5 of the area. Beginning in 1991, studies were initiated to incorporate cover crops in both flat-planted and ridge tillage continued into the reduced input programs.
During the course of the LISA funding, one reduced herbicide rate for the use of Whip herbicide in rice and one for the use of Harmony Extra in wheat has been incorporated into the University of Arkansas Weed Control recommendations.
Research by Carol Becton, Dr. Oliver's graduate student, is currently being published in M.S. thesis. Her research confirms that the Soybean Weed Control computer program accurately predicts both weed losses and reduced rate herbicide recommendations. In addition, her contour graph work should allow us to further refine the program.
Approximately 75% of the research and demonstration work supported by this project has been conducted on-farm with the remainder conducted on University Experiment Stations.
No formal materials have been prepared. However, Missouri has added reduced rates to the state weed control recommendations using Arkansas' as the pattern. North Carolina has added reduced rates to their computer program. In addition, we continue to receive a lot of requests to speak on the program in other states and several states have expressed an interest in adding reduced input recommendations.
A survey of county extension agents is conducted annually. Below are the three year averages from that survey.
Postemergence Herbicides - 1,845 growers used reduced rates on 749,000 acres at a savings of $6.90/A or a total of $5.3 million annually.
Soil-applied Herbicides - 1,645 growers used reduced rates on 706,000 acres at a savings of $5.25/A or a total of $4.2 million annually.
Objectives
(1) Develop a data base for the minimum herbicide rates required to control broadleaf and grass weeds causing the major economic losses in the major agronomic and horticultural crops in the South.
(2) Integrate the minimum herbicide rates with non-chemical methods of weed control.
(3) Develop minimum input weed control programs for multispecies weed situations in the major crops using combinations from (1) and (2) above.
(4) Develop written information and computer programs to facilitate the minimum input weed control technology adoption.
(5) Conduct extensive on-farm test demonstrations to facilitate adoption.
(6) Develop research guidelines and in-service training package for use in the states desiring to implement similar programs.