Effect of Roundup-Salt Mixtures on Weed Control and Soil Microbial Biomass Under Oil Palm

  • BN Nuertey
  • FM Tetteh
  • A Opoku
  • AP Afari
  • TEO Asamoah


Field experiments were conducted at Oil Palm Research Institute, Kusi from 2002 to 2004 to evaluate the effect of roundup – salt mixtures on the control of weeds and soil microbial biomass. The efficacy of roundup at 0.47 kg a.i./ha mixed with either 0.23 kg/ha of sodium chloride or 0.53 kg/ha of ammonium sulphate or 0.24 kg/ha of urea was compared with roundup at 1.44 kg a.i/ha and manual weeding. The treatments were arranged in randomized complete block design and replicated four times. The roundup and its salt mixtures effectively controlled weeds up to 3 months after treatment (MAT) in both 2002 and 2003 trials. In 2002, roundup with sodium chloride, roundup with ammonium sulphate and roundup with urea maintained a substantial weed control of 77%, 79% and 87% respectively at 3 MAT compared to the 80% and 41% weed control by roundup only and manually weeding. By 3 MAT in 2003, the % weed control for roundup with sodium chloride, roundup with ammonium sulphate, roundup with urea, roundup only and manual weeding were 63%, 60%, 63%, 65% and 43% respectively. These weed control measures were however ineffective in the 2004 trial. The addition of ammonium sulphate or urea to roundup increased soil microbial C accumulation significantly by 115% and 650% respectively while the application of roundup with sodium chloride, roundup only and manual weeding stimulated microbial C accumulation slightly by 57%, 33% and 30% respectively. Microbial P also increased by 267%, 137%, 81%, 75% and 45% following the application of roundup with urea, roundup with ammonium sulphate, roundup only, roundup with sodium chloride and manual weeding respectively. The use of roundup – salt mixtures reduced the annual cost of manual weeding per hectare by 76% (¢1,735,000) and annual cost of applying roundup at the labeled rate also by 47 % (¢480,000). The addition of salts to reduced rate of roundup is therefore a cost efficient strategy to control weeds in oil palm plantations.

Journal of the Ghana Science Association Vol. 9 (2) 2007: pp. 61-75

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