Reuse of drainage water for rice and wheat growth during reclamation of saline-sodic soils in Pakistan under the national drainage program (NDP)

Pakistan is facing scarcity of canal water for irrigated agriculture on 16 mha land. This problem is caused, among others, by the loss of surface storage capacity and by the current prolonged dry spell lasting over the several past years. Siltation of Mangla, Tarbela and Chashma Dams have caused a loss of . 5 km3 which is 25 % of the design capacity. Since this problem is increasing, there may be a gradual decrease of food production for a population of 140 million, which is expected to have doubled by 2025. Water shortage is the most serious for the provinces of Punjab and Sindh, where ground water is of hazardous quality and about 75 % of pumped ground water is not safe for irrigation without amendments. In this scenario, it appears wise and timely to study the prospects of growing food grains during reclamation of salt-affected soils using ground water to save good quality canal water for irrigating good soils. Under arid and semi-arid conditions of Pakistan with scarce and irregular rainfall, limited leaching of salts promotes soil salination followed by sodication, induced by irrigation with ground water of high EC, SAR and RSC without amendments or other agronomic management practices. In this way, 6 mha of soils have become salt-affected, of which 60 % are saline-sodic and needs a source of calcium for amelioration. For initial reclamation of salt-affected soils, low quality irrigation waters are generally useful and some times even better than canal water, due to favorable effects of electrolytes on infiltration rate and hydraulic conductivity. For a variety of reasons, farmers are not properly applying the technologies for reclamation and management of saline-sodic soils. To improve this situation on sustainable basis, Univ. Agri., Faisalabad has launched a three-year research study on reclamation of saline-sodic soils by reusing drainage water, in which farmers are participating. The experiments were started in June 2001 in the Fourth Drainage Project Area located in the Central Punjab and are funded by the National Drainage Programme. The reclamation technologies include split application of gypsum @ soil or water GR alone and in combination with FYM or green manure, and on-farm wheat seed priming. This paper will present preliminary results and recommendations pertaining to economical as well as sustainable reuse of drainage water on saline-sodic soils, farmers' constraints and limitations for adapting the required technologies in this regard on the basis of the on-going experiments.