Depletion of Organic Carbon, Phosphorus, and Potassium Stock Under a Pearl Millet Based Cropping System in the Arid Region of India

Abstract

Carbon, phosphorus and potassium stock for a meter soil profile were determined in 2002 for a 22860 km2 area under pearl millet (pm) -pearl millet (pm) (pennisetum americanum Linn.) cropping system and the results were compared with the database of 1975. The influence of alternate land use systems on organic carbon, phosphorus and potassium density under the similar set of conditions was also evaluated. Soil organic cabon (SOC), phosphorus, and potassium stocks were depleted by 9.7, 17.1, and 9.0% from 1975 to 2002. Typic Torripsamment (19.7%) and Lithic Torriorthents (17.7%) suffered from the highest SOC loss, while coarse loamy, Typic Haplocambids registered the lowest (0.9%) SOC depletion. Equivalent CO2 emission was 11.5 Tg, while 0.37 Tg CO2 was sequestered as inorganic carbon. Trends of phosphorus and potassium depletion was similar to that of SOC. Silvipasture, Silviculture, agroforestry and pearl millet-legume sequence on Typic Torripsamments from last thirty years at CAZRI Research Farm contained 185,141,121, and 50% higher SOC and could sequester 9.6, 7.4, 6.3 and 2.6 kg=m2 higher CO2, respectively than the similar soils used for pm-pm sequence. Potassium depletion and phosphorus accumulations were significantly higher in pm-legume than other land use systems. Cropping intensity, fertilizer application, soil texture, initial organic carbon, organic residue recycled and period of canopy cover alone or in combination explained the extent of variation. The study reveals that silvipasture and silviculture are the better option for increasing SOC sequestration. Agroforestry and pearl millet-legume sequence may be grown for arresting SOC and nutrient depletion.