مدلسازی عملکرد سویا تحت برهمکنش دزهای علفکش ایمازاتاپیر و تراکم علف هرز گاوپنبه

A field experiment was laid out in a factorial design based on randomized complete block design (RCBD)
with three replicates in research field of Sari Agriculture Science and Natural Resources University in
2013. Considered factors included 4 levels of weed densities (0, 5, 10, and 15 velvetleaf m-2) and 5
levels of Imazethapyr doses (0, 0.25, 0.5, 0.75, and 1 lit ha-1). A combined model was developed by
incorporating the standard dose-response curve into the rectangular hyperbola competition model to
describe the effects of weed density and herbicide dose on soybean yield and yield loss. Based on
prediction of combined model, when no herbicide was applied, soybean yield was decreased by 29, 45,
and 55% at densities of 5, 10, and 15 plant m-2, respectively. Applying herbicide at half of the
recommended dose at low density of velvetleaf was (5 plant m-2), the yield decreased 6%. However with
increasing weed densities to 10 and 15 plant m-2, 11 and 16% yield loss was caused in soybean yield,
respectively. Combined model predicted parameters consist of soybean yield at weed free treatment,
weed competitivity at no-herbicide treatment, dose required to reduce weed competitivity by 50%, and
steepness of the dose-response curve, respectively 2361 kg ha-1, 0.08, 0.34 lit ha-1, and 4.7.