Short-term buildup of carbon from a low-productivity pastureland to an agrisilviculture system in the Brazilian savannah

Abstract

Agrisilviculture systems that combine two or more species with agricultural practices may potentially increase soil organic matter (SOM) quality due to its diversified and large carbon (C) inputs. The implementation of integrated agricultural systems in Brazil has reached over 11 Mha of area and is a promising strategy to revert widespread land degradation and increase ecological intensification for cropping systems. This study aimed to evaluate the transition of a low-productivity pasture to an agrisilviculture system (corn + Gliricidia sepium + Panicum maximum cv. Massai) along a four-year field experiment under a clayey Oxisol on SOM fractions, C stocks and C management index (CMI). A native Cerrado vegetation was used as a reference. Soil samples were collected in four cropping seasons: T0 - under low-productivity pasture, T1, T2, T3 – 2nd, 3rd and 4th years after implementing the integrated production system, respectively. Both mineral associated and total soil organic C (TC) increased from T0 to T3. Accordingly, C from the particulate SOM increased by 476%, 305% and 368% at 0.00–0.10, 0.10–0.20 and 0.20–0.40 m layers, respectively, and was found to be the most sensitive indicator for changes in soil management systems. Surprisingly, inert C increased up to 0.20 m layer from T0 to all the other seasons and represented 21 to 42% of TC. C stocks at the 0.00–0.40 m layer increased from 52.6 Mg ha−1 at T0 to 66.5 Mg ha−1 at T3. The CMI significantly increased from T0 to T3 – reaching CMI of native vegetation (considered CMI = 100%). The no-till agrisilviculture system with the use of Panicum maximum cv. Massai and Gliricidia sepium managed to accomplish the goal of building up soil organic C and increasing SOM quality, thus showing its potential to be used as a sustainable agricultural practice in terms of soil quality improvement and short-term C sequestration.