Evaluation of different pre-and post-emergence herbicides on forage yield, quality and disease reaction of multi-cut forage sorghum (Sorghum bicolor)

A field experiment was carried out during the rainy (kharif) seasons of 2013 and 2014 at Ludhiana, Punjab, to study the efficacy of different weed-management techniques on weed dynamics, fodder yield, quality and disease reaction in multi cut sorghum [Sorghum bicolour (L.) Moench]. The sorghum crop was infested with grassy, broadleaf weeds and sedges, which reduced 28.1 and 32.7% of green-fodder and dry-fodder yields respectively. Handweeding (at 20 and 30 days after sowing) and application of atrazine @ 0.375 kg a.i./ha + pendimethalin @ 0.750 kg a.i./ha as pre-emergence spray significantly reduced total weed population and dry weight of weeds in comparison to the other weed-control treatments. These treatments showed higher weed-control efficiency (WCE) than that of the other weed-control treatments. Application of propaquizalofop as post-emergence spray was also effective in reducing weed population and dry matter but had phytotoxic effect on the crop and recorded significantly lower fodder yield. Hand-weeding resulted in significantly higher green-and dry-fodder yield of sorghum over all the treatments, but was statistically at par with the applicatio of atrazine @ 0.375 kg a.i./ha + pendimethalin @0.750 kg a.i./ha as pre-emergence spray. These 2 treatments enhanced the green-fodder yield by 39.0 and 36.7% and dry-fodder yield by 48.5 and 45.1% respectively, over weedy check. Hand-weeding and application of atrazine + pendimethalin (0.375 + 0.750 kg a.i./ha) resulted in 58.7 and 53.9% more crude protein yield than weedy check respectively. The maximum net returns ( 37, 790/ha and 36, 320) and benefit: cost ratio (1.46 and 1.28) were realized with atrazine @ 0.375 kg a.i./ha + pendimethalin @ 0.750 kg a.i./ha (PE) and hand-weeding at 20 and 30 days after sowing respectively. The leaf-spot disease was the minimum (8.54%) in hand weeded plots and plots sprayed with atrazine @ 0.375 kg a.i./ha + pendimethalin @ 0.750 kg a.i./ha as pre-emergence spray showed moderate leaf spot severity of 15.7% as the weed population was less in these plots.