Efficacy of Clomazone and Its Combinations with Lactofen against Weeds in Soybean and Their Carry-over Effect in Wheat

In a field experiment, pre-plant incorporation (PPI) or (PE) application of clomazone (0.5, 0.75 and 1.0 kg ha⁻¹), pre-emergence application of pendimethalin 0.75 kg ha⁻¹ PE, metolachlor 0.75 kg ha⁻¹ PE and pendimethalin 0.75 kg ha⁻¹ PE followed by (fb) post-emergence (POE) application of lactofen 0.09 kg ha⁻¹ controlled grass weeds, viz, Acrachne racemosa and Digitaria sanguinalis population more effectively than others. Clomazone (0.5, 0.75 and 1.0 kg ha⁻¹ as PPI or PE) also proved superior to pendimethalin, metolachlor and metribuzin in controlling Trianthema portulacastrum and its PPI was more effective than PE. It was even effective against Cyperus at 1.0 kg ha⁻¹ PE. Every herbicide treatment reduced composite weed population at 30 days after sowing (DAS) and dry weight at 30 and 60 DAS significantly, but clomazone, pendimethalin, metolachlor and metribuzin each combined with lactofen proved superior. All herbicide treatments resulted in significantly higher grain yield of soybean although clomazone 1.0 kg ha⁻¹ PE or PPI, clomazone 0.75 kg ha⁻¹ PE, clomazone 0.5 kg ha⁻¹ PE fb lactofen 0.09 kg ha⁻¹ POE, pendimethalln 0.75 kg ha⁻¹ PE fb lactofen 0.09 kg ha⁻¹ POE and metribuzin 0.05 kg ha⁻¹ PE fb lactofen 0.09 kg ha⁻¹ POE were superior to others on soybean dry weight and pod numbers per plantt Unweeded control as usual registered maximum reductton (52.3%) in soybean grain yield and pendimethalin 0.75 kg ha⁻¹ PE fb lactofen 0.09 kg ha⁻¹ POE the lowest (1.3%). Wheat did not receive phytotoxicity from the herbicides applied in soybean, which suggested that clomazone might safely be used in soybean-wheat sequence.