Effect of variable rates of gypsum application on wheat yield under rice-wheat system

A field experiment was initiated during 2005-2006 to study the effect of gypsum application on rice and subsequent wheat crop. The direct, residual and cumulative effects of gypsum were also noticed under rice-wheat system. The gypsum was applied as 0, 1 and 2 t ha(-1) with the basal dose of N, P2O5, K2O as 120, 90 and 60 kg ha(-1) to both crops. Rice variety IRRI6 and wheat variety Naseer 2000 were planted in Randomized Complete Block Design with three replications in a permanent layout. The soil samples were collected from both crops before earing to study P and K concentrations. The rice yield was significantly affected by gypsum application that ranged from 4807-5472 kg ha(-1). The highest rice yield was recorded by the application of 2.0 t gypsum ha(-1) with an increase of 13.8% over control. Similarly all the yield components like number of panicles m(-2), panicle length, plant height and 1000 grain weight were also significantly affected by gypsum application. The wheat grain yield ranged from 2598 to 4304 kg ha(-1). The cumulative application of 1 and 2 t gypsum ha(-1) increased the wheat yield by 25.25 and 65.66% over check, respectively. The direct and residual application of 2 t gypsum ha(-1) gave an increase of 46.80 and 15.05% over the check, respectively. The application of gypsum significantly affected the P and K that ranged from 4.50-7.50 and 4.70-9.32 mg kg(-1) P while 70-110 and 78-112 mg kg(-1) K in rice and wheat, respectively.