Halosulfuron (Sandea) soil dissipation as affected by soil pH and carryover potentail to autumn crops

Summary

Halosulfuron (Sandea herbicide) is commonly used in transplanted cucurbit crops to control purple and yellow nutsedges. Crucifers of cabbage and turnip greens are often planted in the autumn following cucurbit crop harvest. Understanding halosulfuron soil dissipation under variable soil pH conditions and how it is applied may impact how it is utilized.

Situation

In 2006 Georgia grown cantaloupe and watermelon were produced on over 5000 and 30,000 acres, respectively. Both crops have similar cultural practices and systems of weed control. The majority (67%) of the plantings are hybrid transplants on low density polyethylene mulch (LDPE) covered seedbeds. Farm gate values of cantaloupe and watermelon production in Georgia were estimated at $21 and $55 million, respectively, that year. Cantaloupe and watermelon are transplanted in March on conventionally tilled, elevated seedbeds. This production system tends to have multiple crops grown in quick succession using the same LDPE. Halosulfuron is registered to control perennial nutsedges and broadleaf weeds in transplanted cantaloupe and watermelon, making it an alternative to methyl bromide fumigation. Halosulfuron dissipation increases with increasing temperature and lower soil pH, and with variable soil moisture content. Injury from halosulfuron carryover to rotational crops has occurred as a result of its variable soil behavior. Crucifer crops are commonly grown in autumn in Georgia, with 2006 plantings of cabbage and turnip estimated at 10,000 and 19, 500 acres, respectively. Most often, cabbage are transplanted and turnip green direct-seeded. Halosulfuron registration has planting restrictions for crucifers ranging from 15 to 18 months after application. Growers are interested in cropping systems of cruciferous crops planted in direct rotation with cucurbit crops. Therefore, field trials were initiated to determine the relationships among soil pH, method of halosulfuron application, and rate on the carryover from use on cantaloupe to future plantings of transplanted cabbage and direct-seeded turnip green.

Response

The objective of this project was to determine halosulfuron carryover from cantaloupe on variable pH soils, then using cruciferous crops as bioassays.

Impact

Research indicated that direct-seeded turnip green exhibited some stunting to residual halosulfuron, but stunting was transient, with no yield reduction. Transplanted cabbage was not affected by previous applications of halosulfuron. These results indicate that six months after halosulfuron application in cantaloupe, registered rates of halosulfuron did affect future plantings of direct-seeded turnip green and transplanted cabbage due to dissipation. However, excessive halosulfuron rates increase chance for carryover, without regard to soil pH or application method. Therefore, the halosulfuron label registration must be followed in order to prevent potential crop failure.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2009
• Geographic Scope: Multi-State/Regional
• County: Tift
• Program Areas:
  • Agriculture & Natural Resources