Influence of herbicides in wheat grown on normal and saline soils.
In a field trial conducted in Haryana the effects were evaluated of post-em. 2,4-D at 1.5 kg/ha, isoproturon at 1.0 kg, metoxuron at 1.4 kg and methabenzthiazuron at 1.6 kg, each applied alone or in combination with hand weeding once, for weed control in wheat growing on non-saline (normal) or saline soil (the latter achieved by irrigating the previous season with saline water). The most problematic weeds were Phalaris minor, Chenopodium album, Melilotus indica, Lathyrus aphaca and Vicia sativa. C. album was the most common weed under saline soil conditions, and P. minor was the most common under normal soil conditions. Weed DW 85 d after sowing was significantly greater under normal soil conditions. Isoproturon, metoxuron and methabenzthiazuron controlled weeds significantly under both conditions, but 2,4-D performed well in saline conditions only. Wheat grain yields were greater under normal soil conditions compared with saline conditions. Under normal conditions, isoproturon and methabenzthiazuron, both alone or with hand weeding, resulted in the greatest crop yields, close to those achieved in the weed-free control. However, under saline conditions, 2,4-D + hand weeding was the most effective treatment. The effects of the weed control treatments on yield attributes were recorded and it was noted that metoxuron was phytotoxic. In a pot experiment it was found that there was a positive interaction between increasing soil salinity and the concn of metoxuron (0.5-2.0 kg) which caused damage to wheat; at low salinity, only the greatest herbicide concn affected the crop, but at high salinities (4.0 and 6.0 dS/m), metoxuron at 0.5 kg significantly reduced DM accumulation.