IN SITU CONSERVATION OF RUNOFF , SOIL AND NUTRIENTS

Abstract

THIS STUDY WAS CONDUCTED IN A FIELD HAVING 0.75% SLOPE AND CLAYEY SOILS ( 45% CLAY) IN THE SOUTH- EASTERN PART OF RAJASTHAN, INDIA. THE CLIMATE OF THIS TRACT IS SEMI- ARID TROPICAL, RECEIVING 798 MM ANNUAL AVERAGE RAINFALL. ABOUT 10-12% OF THE TOTAL ANNUAL RAINFALL ARE USUALLY LOST AS RUNOFF. ZINGG TYPE CONSERVATION BENCH TERRACES WERE TESTED IN THE YEARS 1977-78 AND 1978-79 TO CONSERVE RUNOFF , SOIL AND NUTRIENTS IN SITU ND TO UTILIZE RUNOFF FOR RAISING CROPS HAVING HIGHER WATER REQUIREMENTS. YIELD OF PADDY WAS SIGNIFICANTLY IMPROVED BY THE HARVESTED WATER. UNDER RAINFED CONDITIONS OF THE TRACT, IT WAS POSSIBLE TO OBTAIN 9q /ha YIELD OF UPLAND PADDY. THE RATIOS DID NOT DIFFER SIGNIFICANTLY IN THE YEAR 1977-78 BUT IN 1978-79 , THE 8:1 AND 12:1 RATIOS PRODUCED SIGNIFICANTLY HIGHER GRAIN YIELD THAN THE 4:1 RATIO AND CONTROL. THE RESULTS INDICATED THAT THE LOWER 10M OF 50M SLOPE LENGTH CAN BE CONVERTED TO CONSERVATION TYPE TERRACES FOR TRAPPING RUNOFF, SOIL AND NUTRIENTS. THE AMOUNT OF RUNOFF CONSERVED ON THESE CONSERVATION BENCH TERRACES RANGED FROM 86MM IN 1977 -78 TO 199MM IN 1978-79. THE SYSTEM ALSO CONSERVED 2-3 TONNES SOIL, 3-6 KG NITROGEN, 10-12 KG POTASSIUM AND ABOUT 1 KG PHOSPHOROUS HA/ANNUM SITU, WHICH COULD HAVE BEEN LOST IN THE RUNOFF WATER.