Integrating New Cultivation Technology and Photocontrol of Weeds to Reduce Herbicide Use in Vegetables
Cultivation can replace herbicides in short-season vegetable crops such as transplanted broccoli and snap beans, and can supplement banded herbicides in sweet corn and potatoes. However, environmental conditions, particularly precipitation, can have a severe negative impact on the timeliness and eventual success of cultivation, and can significantly increase a grower’s economic risks.
Growers who intend to rely on cultivation for the majority of their weed control, must cultivate the first time before the weeds even appear (preemergence cultivation).
With longer season crops, growers must be prepared to use strategies other than or in addition to cultivation if yield reductions are to be avoided. Hand weeding may be cost-effective in fresh market vegetable production; it is cost-prohibitive in processing vegetable production.
Timeliness is of the essence, whether with the first cultivation event or a later one. If cultivation is missed at the appropriate time, yield reductions are almost guaranteed.
Growers are best served if they have the potential to be flexible, having different types of cultivation tools for different stages of crop growth and herbicides for use on an as-needed basis.
* To determine the feasibility of use and limitations of different types of cultivation implements in snap beans, transplanted broccoli, potatoes, beets, and sweet corn.
* To determine the effect of weed growth stage on selectivity to flex-time implements.
* To investigate the potential for the photocontrol of weeds common to northeastern agricultural fields.
Methods and Findings
After three years of cultivation trials in transplanted broccoli, snap beans, sweet corn, and potatoes research for this project has been completed. The flex-tine cultivators, used once and followed by an inter-row cultivation, were able to replace herbicides. While two cultivations could also provide adequate weed control in a mid-season crop such as snap beans, untimely precipitation can cause cultivation failure resulting in reduced yields.
In a long-season crop like potatoes, cultivation alone can also result in yields equal to those with the use of broadcast herbicides, though weed control is less effective. Greater weed populations may reduce potato yields in years of low precipitation or produce large amounts of weed seeds that cause severe weed infestations in subsequent crops. For these reasons, the use of banded herbicides and inter-row cultivation in snap beans and potatoes provides the least risk and greatest economic returns to growers.
Sweet corn, a long-season crop, cannot compete effectively with weeds early in the growing season; therefore, cultivation must be supplemented with banded herbicides. Expected herbicide reductions with banded applications would be 1.25, 6.25, 1.67, and 2.5 lb ai/A for broccoli, snap beans, potatoes, and sweet corn, respectively.
Initial analysis of cost of production data from sweet corn and snap bean grower surveys indicate that cultivation combined with banded herbicides could reduce weed control costs at least $15/A and $6/A in snap beans and sweet corn, respectively, without a reduction in yield.
Research trials and experimentation by growers indicate that, to be effective, the flex-tine harrows must be used when weeds are at the two-leaf stage or smaller. The currently available cultivator models are also limited in that they are not appropriate in size for all crop row spacings and/or cannot be easily adjusted, particularly in wet soils. Overall, it is expected that for long-term economic viability, growers will face less risk if they are flexible and are equipped to use both cultivation and herbicides on an as-needed basis. Attempts to employ cultivation in the dark or with shielded implements (photocontrol) have met with variable success. Though in some instances weed emergence can be reduced by as much as 50%, the practical significance of photocontrol has yet to be determined.
A fact sheet for distribution to extension agents and growers was published and more detailed research results will be available shortly in the annual publication, “Cornell Vegetable Weed Science Research Results.”
Farmer Feedback on Cultivators
In 1997, four growers had an opportunity to use the brush hoe and the flex-tine harrows in a variety of vegetable crops and strawberries. The growers found the flex-tine harrows to be effective in a number of crops, including potatoes, carrots, snap beans, sweet corn, and strawberries. These tools did cause significant crop injury and stand reduction, however, depending upon the crop (even crop variety) and stage of crop development.
Additional limitations mentioned by all growers were the size and lack of adjustment of the implements. The width of the cultivators works well with the 30-inch row spacing used at the research farm, but many growers use other spacings and/or a variety of row arrangements. With some row spacings, growers found it necessary to overlap passes with the cultivator to achieve adequate weed control, thereby increasing the time required and the cost of cultivation. In some situations, the cultivators could not be used without damaging one or several crop rows.
The current design of these implements makes it difficult if not impossible to adjust to all row arrangements. Simply increasing the width of the implements could overcome some of these difficulties, while other problems would require redesigning certain features of the tools. Nevertheless, grower experience suggests that the currently available cultivators can provide satisfactory weed control after determining where their use is most appropriate. Equipment dealers have realized that there is a new market for cultivation tools and have taken steps to bring in some of the types being sold in Europe.
Reported December 1997. 1999 Northeast Region SARE/ACE Report.