Nutrient and water use by Bt. cotton (Gossypium hirsutum) under drip fertigation

Field experiment was conducted for three years from 20082010 on medium clay soil at Rahuri to find out the effect of drip fertigation on growth, yield, water use and nutrient dynamics for Bt Cotton {Gossypium hirsutum (L.)}. The experiment was laid out in a randomized block design with eight treatments replicated three times. Pooled data of three years indicated that drip resulted into 21.5 to 23% increase in yield with 53.7% water saving, whereas drip with fertigation resulted into 43 to 66% increase in seed cotton yield with equal amount of water sav- ing as compared to conventional method. The maximum seed cotton yield (4.53 t/ha) was recorded when 125% fertigation was given. However, it was on par with 100% and 75% fertigation treatments. The seed cotton yield (3.91 t/ha) obtained under 75% fertigation was on par with 100% conventional fertilizer applied through soil (3.46 t/ ha) indicated 25% fertilizer saving under fertigation. The mobility of nutrients was observed more in drip fertigation than conventional method. N and K moved upto 30 cm, while P moved 15 cm laterally and vertically. The uptake of nutrients was also relatively more in fertigation treatments than rest of the other treatments. Maximum water use efficiency (1.42 t/hacm) was obtained in treatment, where 125% water soluble fertilizers were applied through drip. The 75% drip fertigation as per schedule B was found best practice to obtain better yield and improve nutri- ent and water use of Bt. cotton.