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Using chemical seed dormancy breakers with herbicides for weed management in soyabean and wheat

Das, T K, Das, D K
Weed research 2018 v.58 no.3 pp. 188-199
Cyperus rotundus, annual weeds, cost effectiveness, costs and returns, germination, gibberellic acid, herbicide mixtures, imazethapyr, isoproturon, metsulfuron, pendimethalin, perennial weeds, periodicity, potassium nitrate, seed dormancy, soybeans, tubers, weed control, wheat
Variable dormancies result in periodicity in the germination of weeds and make weed control a repetitive practice. Under some conditions, repeated applications of selective herbicides can lead to the dominance of perennial weeds like Cyperus rotundus. Our hypothesis was that applying a chemical dormancy breaker (DB) plus herbicide mixture would better control a mixture of weed species. Three experiments were designed to develop a cost‐effective DB treatment and to evaluate its dose with herbicides tank‐mixtures for effective weed management. KNO₃ and gibberellic acid GA₃ as dormancy breakers offered comparable effects, but KNO₃ was more economical than GA₃. KNO₃ at a 6% concentration was more effective in promoting weed germination than a 3% concentration in soyabean. A combination of KNO₃ (6%) and pre‐emergence pendimethalin 0.75 kg a.i. ha⁻¹ + imazethapyr 0.10 kg a.i. ha⁻¹ controlled annual weeds by 99% and reduced C. rotundus growth by 83%. This treatment gave significantly higher soyabean yield and net returns. Similarly, a tank‐mixture comprising of clodinafop 0.06 kg a.i. ha⁻¹ + metsulfuron 0.006 kga.i. ha⁻¹ was more effective against weeds than pre‐emergence tank‐mix application of pendimethalin 0.75 kg a.i. ha⁻¹ + carfentrazone‐ethyl 0.02 kg a.i. ha⁻¹ and isoproturon 0.75 kg a.i. ha⁻¹. The use of pre‐emergence tank‐mixture of pendimethalin 0.75 kg a.i. ha⁻¹ + imazethapyr 0.10 kg a.i. ha⁻¹ should exhaust seed/tuber bank if repeated and reduce the application cost of herbicides by 50% and the dose, residue and cost of pendimethalin by 25%.