Climate Smart Agriculture practices improve soil organic carbon pools, biological properties and crop productivity in cereal-based systems of North-West India

Intensive tillage coupled with crop residue burning in rice-wheat (RW) system is a serious issue that causes soil degradation and environmental pollution. Soil organic carbon (SOC) is one of the main indicators of soil health and system's sustainability. Zero-tillage has been widely recommended as an alternative for improving carbon sequestration in soil under different ecologies. But the SOC sequestration is very inconsistent and varied as it depends on the crop management practices. This study was performed in the western Indo-Gangetic plains (IGP) of India where RW system contributes 40% to the total country's food grain basket; however there exists issue of its sustainability because of declining SOC coupled with open field crop residue burning. Therefore, we evaluated the effects of different management scenarios (Sc) namely Sc1 (conventional till rice-wheat cropping system; business as usual), Sc2 (partial climate smart agriculture (CSA)-based rice-wheat-mungbean system), Sc3 (CSA-based rice-wheat-mungbean system), and Sc4 (CSA-based maize-wheat-mungbean system) on SOC pools and biological properties after 4 crop cycles (year 2009-2013). Soil samples were collected from surface and sub surface layers (0-15 and 15-30 cm soil depth) after rice harvesting in 2013. Results showed that the SOC stock at surface layer was higher by 70% with Sc4 than Sc1 (16.2 Mg C ha(-1)) (P < 0.05). All the forms of carbon in different pools were higher (P < 0.05) with Sc4 and Sc2 over Scl at 0-15 and 15-30 can soil depths, respectively. At surface soil SOC pools were found in order of Sc4 > Sc3 > Sc2 > Sc1 (P < 0.05). Higher lability index (LI) (2.1) and stratification ratio (SR) (2.5) of organic carbon were observed in CSA-based systems (Sc2 and Sc4). At surface layer (0-15 cm) the CSA- based scenarios (mean of Sc2, Sc3 and Sc4) showed higher (P < 0.05) enzyme activities viz. dehydrogenase (641 mu gTPF g(-1) 24 h (-1)) and alkaline phosphatase (158 mu g pnitrophenol g(-1)), and microbial biomass carbon (MBC) (787 mu g g(-1)) and microbial biomass nitrogen (MBN) (98 mu g g(-1)) compared with Sc1. Higher value of the basal soil respiration (34%) was also observed with CSA-based scenarios (Sc2, Sc3, Sc4). Surface soil layer showed maximum counts of fungi, bacteria and actinomycetes in Sc4. MBC, fungal population and SOC were the most sensitive biological soil parameters identified through principal component analysis (PCA) which can be used for soil quality assessment. Therefore, medium term adoption of climate smart agricultural practices involving zero-tillage, crop establishment, residue management and crop diversification in rice-wheat system can significantly improve the systems productivity by improving SOC and soil biological quality.