RECLAMATION OF SODIC SOILS BY DIFFERENT DOSES OF GYPSUM TO ENHANCE GRAIN YIELD AND QUALITY OF RICE (ORYZA SATIVA L.) IN SULTANPUR DISTRICT, U.P.

Abstract

Salinity is a global problem reducing plant growth and productivity worldwide, and affects about 7% of the world’s total land area (Flower et al. 1997). In the world about 1200 million hectare (Mha) of land is affected with salinity and, therefore, poses a challenging task of taking up agriculture and enhancing productivity in these areas (Poonamperuma 1984; Tanji 1990). Some of the most severe problem in soil salinity are reported in arid and semiarid regions of the world (Pesarrakli 1999), where limited rainfall, high evapo-transpiration and high temperature play an important role in increasing the salt concentration in the root zone. There could be two possible ways to overcome salt stress (i) either improve the soil environment for the normal plant growth through leaching of salts from the profile through chemical amendment like gypsum (CaSO4.2H2O) (Meri 1984; Al-Nabulsi 2001) or (ii) improve the plant itself which can be grown in that environment (Jardat et al. 2004; El-Hendawy et al. 2005). The first approach is resource costly and the second is based on the development of salt 
tolerant varieties. There could be a third approach, i.e. hybrid approach, based on exploitation of synergies between gypsum and salt tolerant varieties (Singh et al. 2009). Although million of hectares of salt-affected soils are potentially suitable for crop production with appropriate improvement measures, they are left uncultivated or are grown with crops with very low yields because of salinity problem. 
Rice (Oryza sativa L.) is one of the most important cereal crops grown in wide range of climatic zones to nourish the mankind. Rice varieties suited to normal conditions may rarely or mostly not adapt under salt stress conditions. Few screening studies have been reported based on stability of rice genotypes across sodicity stress and non-stress environments (Zapata et al. 1991; Shylaraj et al. 1994) while no such study has been reported for sodicity stress. Sodicity being a specific agroedaphic environment spread over about 3.8 Mha area of the country (NRSA and Associates 1996) for which gypsum (CaSO4.2H2O) is generally recommended for the reclamation. Cultivation of rice is generally recommended as first crop after application of gypsum because continuous submergence improves soil properties. Gypsum application markedly decreased the soil pH, exchangeable sodium percentage (ESP) and significantly increased the yield and nutrient uptake by rice (Singh et al. 2008).

More than 70% farmers in the region of sodic soils belong to small and marginal categories and the initial cost of reclamation is beyond the reach of this category of farmers because of heavy investment on account of gypsum (Dutta et al. 1996). Earlier studies revealed that judicious and proper use of gypsum can markedly increase the yield and nutrient uptake of rice. However, little information is available on the combined effect of gypsum and varieties on soil amelioration, grain yield and quality of rice. Therefore, given the importance of gypsum on sodic soil amelioration and grain yield of rice, it is necessary to know the extent of benefit a rice variety, which can confer to increase yield and associated components. Therefore, a three years study was undertaken to have a detailed account of the response of rice varieties and soil reclamation to gypsum.