Effect of re-scheduling of initial and last irrigation on root growth, soil water extraction, yield and water use in cotton (Gossypium hirsutum)

A field investigation was undertaken during 2004-05 at Bathinda to quantify the effect of different timings of initial and last irrigation on root growth and its distribution in soil profile and subsequent effects on water extraction, yield and water use in cotton (Gossypium hirsutum L.). The initiation of irrigation at 28 days after sowing restricted root growth to surface layers which remained confined to 0-60 cm soil depth throughout the cropping season. On the other hand, higher root mass density and vertical distribution up to 180 cm was observed when the initial irrigation was applied at 42 days after sowing. Delayed first irrigation resulted in 28% increase in seed cotton yield and 16% in stick biomass. The improved yield was accompanied by 24% increase in number of bolls/plant and 8% increase in harvest index. The efficient water use in delayed first irrigation in terms of higher seed cotton yield resulted in an increase of 27% in water-expense efficiency. Application of first and last irrigation at optimum time (after 42 and 170 days after sowing) resulted in an increase of 35% in seed cotton yield and 33% in water-expense efficiency without involving any additional cost.