Effect of various levels of gypsum application on the reclamation of salt affected soil grown under rice followed by wheat crop

Pot experiment was conducted to evaluate the effect of various doses of gypsum on the yield of crops and properties of salt affected soils at Agricultural Research Institute (A.R.I.) Tarnab, Peshawar during 2000-2001. Sodic soil in bulk was collected from Nowshera area and homogenized after grinding. Earthen pots eighteen (18) in number were filled with this soil. There were six treatments comprising of gypsum @ 0, 25, 50, 75, 100 and 200 % of the gypsum requirement (G.R.). Each treatment was replicated three times. Rice seedlings were transplanted in the pots having been added the required amount of gypsum. pH, electrical conductivity (EC, and sodium adsorption ratio (SAR) were monitored in the first 9 leachates, received after irrigation. After the harvest of rice, every pot soil was analyzed for pH, EC and G.R. Then every pot soil was remixed and wheat was grown in it at field capacity with out further addition of gypsum. Initial 5 leachates of drained water of all the pots were collected after respective irrigation and checked for the same characteristics, which were done during rice crop. The results showed that pH, EC, and SAR of the leachates samples were decreased with increasing level of gypsum and with the number of leachates. EC and SAR decreased considerably relative to pH. Gypsum application in different doses increased yield of rice by 9.8 to 25.3% and that of wheat crop by 10-80% over control treatment. Maximum increase occurred with the application rate of 200% of G.R. in both the cases. The data further indicated that soils were also improved with gypsum application especially with respect to pH and SAR. It was found that pH of soils was decreased considerably with increasing level of gypsum. G.R. of the gypsum treated pots after rice crop decreased by 40-89%, while after wheat crop they showed nil requirement of gypsum.