BIOCHAR AS SOIL CONDITIONER IN THE SUCCESSION OF UPLAND RICE AND COWPEA FERTILIZED WITH NITROGEN

Neyton De Oliveira Miranda,Alexandre Santos Pimenta,Ermelinda Maria Mota Oliveira,Gualter Guenther Costa Da Silva,Mary Anne Barbosa De Carvalho

doi:10.1590/1983-21252017v30n206rc

Abstract

ABSTRACT The effects of biochar and nitrogen application on yields of upland rice and cowpea and on soil fertility were determined in a greenhouse in Macaíba, RN, Brazil. The trial consisted of the succession of two crops in a completely randomized design and a factorial scheme, with four replicates. Initially, four doses of biochar and four doses of nitrogen were tested for cultivation of rice. Subsequently, four doses of biochar and two doses of nitrogen were tested in half of the pots maintained for planting cowpea. Soil was sampled after rice harvest for half of the pots and at end of the trial for the remaining pots. We evaluated the following parameters: mass of hundred grains of rice, dry shoot mass, panicle number, number of filled spikelets and of empty spikelets, and grain production. Determinations for cowpea were: pod number per pot, grain number per pod, and grain production per pot. Measured soil parameters were: pH, contents of organic carbon, P, K, Ca, Mg, Na, cation exchange capacity, and exchangeable sodium percentage. Biochar addition did not influence yield components of upland rice and cowpea, but resulted in increased soil N retention, which influenced rice dry shoot mass, spikelets sterility, panicle number, and grain mass. Biochar also promoted increased soil pH, potassium content, and exchangeable sodium percentage and decreased calcium and magnesium concentrations.

Highlights

According to the FAO (2011), the degradation of natural resources due to population pressure, climate change, and competition for land and water has social and cultural implications and affects biomass production, carbon accumulation, soil quality, water availability, biodiversity, and greenhouse gas emissions
Dryland farming systems in semi-arid regions lead to water scarcity, salinization, pollution and sediment deposition in water reservoirs, degradation of the soil structure, reduction of soil fertility and carbon content, and nutrient depletion
Population growth is accompanied by increased agricultural production, which should be accomplished in a sustainable way, using already existing crop areas and employing practices of soil and water conservation to increase carbon stocks via organic matter, thereby increasing water and nutrient retention erosion control and reducing greenhouse gas emissions

Summary

Introduction

According to the FAO (2011), the degradation of natural resources due to population pressure, climate change, and competition for land and water has social and cultural implications and affects biomass production, carbon accumulation, soil quality, water availability, biodiversity, and greenhouse gas emissions. In this context, dryland farming systems in semi-arid regions lead to water scarcity, salinization, pollution and sediment deposition in water reservoirs, degradation of the soil structure, reduction of soil fertility and carbon content, and nutrient depletion. Another approach is to use coal rich in pyrogenic carbon as agricultural soil conditioner (CARVALHO et al, 2013), because it resists decomposition and can remain in the soil for centuries (SOMBROEK et al, 2003)

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