What are the options for desiccating clover in a wet season?
The recent wet weather in Canterbury will be a factor when deciding how to proceed with clover desiccation, as crops that have been wet for extended periods will be more difficult to deal with. The preferred desiccant for many growers has traditionally been Reglone® (MOA group 22, active ingredient diquat). However, as Reglone® desiccates green tissue soon after contact, its effectiveness is limited when canopies are multi-layered and dense, thus reducing canopy penetration. Wet soil conditions prior to harvest lead to rapid growth, or the unrestricted production of new leaves, which makes desiccation with Reglone® alone difficult, or at least a multi-application process. The dense canopy that results from increased soil moisture shades flowerheads and increases canopy humidity, thus reducing drying and increasing the risk of seed sprouting.
With these issues in mind, FAR has been conducting trials to identify alternative pre-harvest pre-desiccation and desiccation strategies for white clover seed crops. Products such as Buster® (MOA group 10, active ingredient glufosinate), Granstar® (MOA group 2, active ingredient tribenuron-methyl) or Versatill® (MOA group 4, active ingredient clopyralid) give comparable seed yields to Reglone®, and are often more effective in wetter than average conditions. However, these products negatively affect post-harvest grazing, and may not be suitable when the crop is to be maintained into the following year. An organic product, GreenMan™ (MOA group 0, active ingredient fatty acids), provides effective desiccation and increased post-harvest regrowth, although it tends to be more expensive.