METHAM IN COTTON
Mar 10, 2017

Agronomy & physiology WCRC Agro-Physio-north-america WCRC1
Abstract                                                                         Back to Table of contents

Metham is a soil fumigant which is used to kill germinating weed seeds and organisms in the  soil such as nematodes and fungi.  In cotton, nightshade and nutsedge are among the most difficult weeds to control.  Several trials were conducted in the southern San Joaquin Valley in 1991 through 1993 to evaluate different rates and methods of metham application to Acala cotton.  Metham treatments demonstrated good to excellent control of black nightshade and gave good suppression of purple nutsedge.  Good control of black or hairy nightshade was obtained with a single 20 cm-wide blade injecting metham into preirrigated beds at rates of 19 to 77 liters per treated hectare.  Nutsedge control was erratic.  The best nutsedge suppression was obtained by injecting metham with a 3-tiered fertilizer knife at rates between 138 and 184 liters per treated hectare.  This treatment held for 30 to 40 days after the application of metham; thereafter, nutsedge emerged through the treated band.

Conclusion

Metham test results have been variable.  Failures most often occur because incorrect application methods or the lack of sufficient soil moisture allow metham to volatilize and escape too fast.  Also some planting procedures and cultural practices move treated soil which diminishes the efficacy of metham treatments.  Applied and managed correctly, metham minimizes weed competition and prevents potential yield reduction.

Best results have been obtained when:

  1.  Metham is applied with a single spray blade for annuals and double spray blades or fertilizer knives for perennials.

  2. Rates of 38 to 77 liters per treated hectare are used for nightshade and > 115 liters for nutsedge.

  3. A firm, trash and clod free seedbed is prepared.

  4. The soil is preirrigated previous to application to insure that weed seeds have imbibed water.

  5. No tillage is performed between metham application and planting.

  6. Cotton is planted as soon as the required 14-21 day waiting period is met.

  7. Treated soil is not contaminated with untreated soil during planting.

  8. Soil Temperature is greater than 10 ˚C.


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