Eight-year impacts of conservation agriculture on soil quality, carbon storage, and carbon emission footprint

Abstract

The conventional method of intensive tillage alters the soil environment, destroys soil aggregates, depletes soil organic carbon (SOC), emits more carbon, requires higher energy, alters microbial activities and ultimately degrades the soil health. These ill-effects of conventional tillage can be severe in rainfed soils with poor workability such as Vertisols of Central India. To minimize these negative effects of conventional tillage (CT), conservation agricultural (CA) practices such as reduced tillage (RT) and no-till (NT) with crop residue retentions are advocated as sustainable practices that can improve the soil health. Four cropping systems [soybean+pigeonpea (CS1); soybean–wheat (CS2); maize–chickpea (CS3); maize+pigeonpea (CS4)] were established as sub-plots under CT, RT and NT management. Soil samples were collected at 0–10 cm, 10–20 cm and 20–30 cm depths. The effects of 8 years of continuous use of CA were evaluated on soil physical, chemical and biological properties in Vertisol of Central India. After that, 20 key soil properties were subjected to calculating soil quality indices (SQI) in each tillage systems. Results indicated that mean weight diameter (MWD) and water-stable aggregates (WSA) were significantly higher (P < 0.05) in NT (1.57 mm and 79.4%) and RT (1.05 mm and 76.2%) than CT (0.71 mm and 63.8%) at 0–10 cm depth, respectively. The soil under NT had the highest SOC concentration (1.12%) followed by that under RT (1.02%), and the least was found in CT (0.91%) at 0–10 cm depth. The proportion of large macro-aggregates (LM) was the highest under NT than CT (P < 0.05) whereas that of micro-aggregates was highest under CT. The aggregate associated organic C (AOC) tended to decrease with the decrease of aggregate size. Soil dehydrogenase activity, fluorescein diacetate hydrolysis activity, β-glucosidase activity and easily extractable glomalin content were significantly higher under NT than CT (P < 0.05). The soil quality index was significantly highest in NT, followed by RT and CT at all soil depths. CA based practices favoured carbon storage, lowered carbon emission, foot print and soil quality compared to conventional farming. Therefore, under Vertisols, 8 years of CA practices likely to improve several soil quality indicators, allowing a positive trend for soil preservation.