ARS | Publication request: Economics of supplemental weed control applications on spring-transplanted onions

Submitted to: National Allium Research Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 5, 2013
Publication Date: N/A

Technical Abstract: Field research conducted to determine the relative benefits among alternative herbicides for weed control in onions (Allium cepa L.) measured weed control efficacy, impact of herbicides on crop injury, and the resulting weed competition on crop yields and marketable bulb size. Weed competition produced disproportionate reductions in total onion yields and size of marketable bulbs. There were 21 treatments [12 synthetic herbicide treatments, 5 corn gluten meal (CGM) applications, a full-season weed-free (hand-weeded) treatment, a full-season weedy-check, a partial-season weed-free (weed-free for the first half of the growing season by hand weeding, then the weeds were allowed to grow), and a weedy-check without onions]. The synthetic herbicides and CGM provided crop safety, and to some extent early weed control. However, reductions in crop yields and marketable bulb sizes as a result of weed competition demonstrated the need to include supplemental weed control with post-emergence herbicides or other weed control methods. Within all 21 treatments, 10 treatments provided a positive net return. Of this group, only one of the weed-free treatments did not demonstrate a positive net return, although all treatments had considerable hand-weeding expenditures. This highlights the economic importance of weed pressures on onion yields, sizes and profitability. Eleven of the treatments had a negative net return. All of the CGM treatments had negative net returns due to the excessive cost of the CGM. Assuming that an acceptable return on the investment costs and risk factors of production is at the 15% level, data developed indicated that a complete or at least high level of weed control is justified for the farmer to have a high yielding harvest with large bulb sizes. The budget indicated that weed control expenditures which included both chemical control and hand weeding only comprised five percent of the total cost of production. If a field is expected to produce a high-yielding crop and the farmer observes an increase in weed pressure at an early stage of production, then the farmer should feel confident that the return on the expenditure for complete weed control above the planned expenditure can be justified with up to $3,898 increased cost per hectare.