IN-SITU RAINWATER MANAGEMENT FOR IMPROVING SOILPRODUCTIVITY IN A MICRO-WATERSHED IN RAINFED NORTH -WESTERN SUBMONTANEOUS TRACT OF INDIA

摘要

The rainwater is the sole natural resource with deep to very deep underground water tablein the North-Western tract of India which receives about 4.2 x 105 ha-m of rainwater in a year. Someobservations at 3-4 sites in the tract show that runoff varies from 35 to 45 per cent of rainfall and soil lossvaries from 25-225 t/ha/yr on a small to large watersheds in the tract mostly in the summer monsoonmonths. It impairs the productivity of land which is not only physically based but more complex in nature.In order to improve the productivity of the land in the area, large scale development works are beingproposed for water harvesting and erosion control. It was observed that a minimum rainfall depth of 10mm is sufficient to cause runoff and overland flow in the area. These runoff producing rainstorms occur in15-20 number and their duration varied from 1 to 16 hours. Their maximum fifteen minutes intensity andrainfall erosion index ranges from 4.25 to 240 mm h-1 and 203.6 to 1523.5 m tons/ha cm/h, respectively.The mean rainfall aggressiveness for ten years (1990- 2000) at Ballowal saunkhri, District Nawashaharwas 224.8 thereby yielding an annual soil loss of 112.8 t/ha/yr. This placed it into a category that suffersfrom high erosion risk. The soils of the area are medium to coarse in texture with low to medium moistureretention capacity. Keeping these points in view, some of the proposed management options of rainwaterat on-site and off-site are based in reducing the erosivity of rainfall by manipulating the soil surface, premonsoonploughing, haloding, use of crop residues @ 6-8 t/ha through vertical mulching (bandplacement), timely and deep tillage operations and adoption of land modifying measures and provision ofstructures and vegetative barriers for safe disposal of excess runoff water at a non-erosive velocity. Alsocollecting harvested runoff water in suitable inverted, truncated and pyramid type of tanks or smalltributaries in the vicinity of cultivated area. In a recently developed micro watershed, on–farm experimentswith participatory approach showed an increase in yield of maize with sowing of maize in raised beds (15-20 cms) which was comparable with the application of 50 % NPK+ 150 % FYM. This suggests that sowingof maize in raised beds could be practiced to economize on the use of chemical fertilizers and manures inthe area. Also raised beds conserved more in-situ rainwater over the other practices. Application of Farmyard manure also helped in conserving in-situ soil moisture and improved the crop yields in the area. Awater harvesting tank of capacity 0.8 ha-m was excavated in Kokowal-Majari-Jhunewal micro-watershedof 17 ha catchment in Hoshiarpur district of Punjab. The excess rainwater is collected in it and utilized forsupplemental irrigation in rabi crops. This method of rainwater collection had proved to be effective inimproving productivity of rabi crops mainly wheat thus improving the socio-economic status of the farmersin the region.