Assessment of agricultural land use and management practices on carbon sequestration in soils of arid and semi-arid regions of North-Western India
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Date
2019-05
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CCSHAU, Hisar
Abstract
Improving soil organic carbon (SOC) stocks is of a vital important for enhancing soil productivity of different land use systems, particularly, in arid and semi-arid regions of the country. The study was carried out to evaluate the SOC fractions and their relationships with soil properties as influenced by different cropping systems and management practices. Thirteen sites under different land use systems were selected for soil sampling from the States of Rajasthan and Haryana. Soil samples were analysed for various soil properties and SOC fractions, and their relationships were established. The soils at different sampling sites were alkaline in reaction and non-saline. Higher bulk density was observed in coarse textured fallow soils and in soils under rice-wheat system. Significantly lower bulk density observed under plantation forest and agro forestry than field crops was attributed to greater inputs of plant biomass and/or application of manures and fertilizers. Among different cropping systems, sugarcane and rice-wheat systems found to have higher SOC content due to their potential for higher biomass production. At all sited, the SOC content found to be decreased with depth due to reduced amount of organic matter. Aggregation, CEC and nutrients status of soils were higher under agro-forestry, sugarcane, horticulture and cotton-wheat than other systems due to higher SOC status and clay contents. Similarly, the oxidizable fractions of carbon (very labile, labile, less labile and non-labile) were also significantly higher under plantation forest, sugarcane, agro-forestry and rice-wheat land use systems because of higher biomass input. Upon differentiating the SOC into active (AC) and passive carbon (PC), the AC was found variable under different cropping systems, and significantly higher under plantation forest, sugarcane and agro-forestry land use systems. Therefore, the AC and their proportion to total SOC could be use as sensitive indicator of soil health. As per physical classification of SOC, coarse particulate organic carbon (POC) was significantly higher under plantation forest, horticulture, agro-forestry and mung bean-mustard land use systems due to heavier texture of soil and/or introduction of legume in crop rotation. For the surface layers, the largest differences in POC content were observed for the aggregate associated POC, which was apparent in soils with more effective native vegetation. Significantly higher microbial biomass carbon (MBC)content under plantation forest, horticulture and agro-forestry land use systems was attributed to the production of high quantity of litter fall (substrate) for microbial decomposition every year. Among the different cropping systems, sugarcane and rice-wheat systems had significantly higher MBC content probably due to higher accumulation of SOC and relatively higher inputs of manures and fertilizers included in management practices. Significantly higher SOC stock under plantation forest and agro-forestry systems obtained were attributed to relatively more litter biomass production, stubble and rhizo deposits and slower decomposition of soil organic matter in the undisturbed soil. Variation in texture of soils and management practices in different land use systems were found responsible for organic carbon storage in soils. Use of poor quality irrigation water in sugarcane, rice-wheat and guar-wheat cropping systems adversely affected the SOC pools and soil properties. The Carbon Management Index found effective in assessing C sequestration potential of soils under different cropping systems. Very labile carbon was significantly correlated with SOC (r = 0.98), CEC (r = 0.82), aggregation (r = 0.63) available N (r = 0.94), available P (r = 0.81), available K (r = 0.64).The higher value of correlation coefficient between labile carbon pools with total SOC indicated that these pools were most affected by changes in land use and management practices. The MBC was correlated with total SOC (r = 0.85), coarse (r = 0.85) and fine (r = 0.91) POC, AC (r = 0.85) and PC (r = 0.85). There was a dynamic relationship between different pools of SOC and their relative proportion was greatly influenced by land use systems. It was concluded that the changes in labile fraction of SOC may be considered as a sensitive indicator for assessing the quality of SOC being added in soils under different land use systems in arid and semi-arid regions of North-Western India.