Fire‐Free Fallow Management by Mechanized Chopping of Biomass for Sustainable Agriculture in Eastern Amazon: Effects on Soil Compactness, Porosity, and Water Retention and Availability

Abstract

AbstractMany Amazon soils are naturally fragile and develop under intense rainfall and high temperature climate. Soil structural quality is improvable through vegetation management systems providing abundant soil mulch and little soil disturbance. We tested the effect of the chopping‐and‐mulching systems of secondary forest‐vegetation on selected soil physical properties of a sandy Oxisol, located in the eastern Brazilian Amazon. The treatments consisted of two fallow forest‐vegetation, namely, chop‐and‐mulch of secondary vegetation with a dual vertical‐rotor chopper (VC) and with a horizontal‐rotor chopper (HC) and a control composed of standing secondary forest‐vegetation (SF). Six months after vegetation chopping, we evaluated soil bulk density (BD), degree‐of‐compactness (DC), pore‐size distribution and soil hydraulic properties. Compared with SF, the VC and HC systems did not affect soil BD in surface layer (0·00–0·05 m) but increased BD in subsurface layers. DC in surface layer are below the range of the optimum values for most crops (77%–88%), while for other layers DC was within this optimum range. High macroporosity and sandy granulometry were responsible for high drainable water from soil saturation until field capacity, down to 0·20 m depth in all systems. Pore‐size distribution was influenced by vegetation chopping with increase in smaller pores. These pores represent a small percentage of total porosity and contribute more to water retention and availability. Chopping by VC and HC mechanisms was effective in maintaining soil physical quality, characterized by lower soil bulk density, higher porosity and water retention, build up during growth of secondary vegetation in fallow period between cash crops. Copyright © 2015 John Wiley & Sons, Ltd.