Effects of Agronomic Practices on Soil Co2 Emission in Upland Rice Production

Abstract

To explore effective ways to decrease soil CO2 emission and increase soil carbon storage and grain yield, field experiments were conducted on two upland rice soils (Lixisol and Gleyic Luvisol) in northern Benin. The treatments comprised two tillage systems (no-tillage, and manual tillage), two rice straw managements (no rice straw, and rice straw mulch at 3 Mg ha'1) and three nitrogen fertilizer levels (no nitrogen, 60 kg ha"1, and 120 kg ha-1). Soil CO2 emissions were higher in tilled treatments than in no-tilled treatments, and higher in fertilized treatments compared with non-fertilized treatments. Under the current management practices (manual tillage, with no residue and no nitrogen fertilization) in upland rice fields in northern Benin, the carbon added as aboveground and root biomass was not enough to compensate for the loss of carbon from organic matter decomposition, rendering the upland rice fields as net sources of atmospheric CO2. With no-tillage, 3 Mg ha’1 of rice straw mulch and 60 kg N ha’1, the soil carbon budget was zero on the Lixisol and 0.6 Mg C ha’1 on the Gleyic Luvisol. The highest response of rice yield to nitrogen fertilizer addition was obtained for 60 kg N ha’1 with 3 Mg ha’1 of rice straw mulch for the two tillage systems. Soil CO2 emission per unit grain yield was lower under no-tillage, rice straw mulch and nitrogen fertilizer treatments. No-tillage combined with application of 3 Mg ha’1 of rice straw mulch and 60 kg N ha’1 reduced soil CO2 emission, increased soil carbon budget and upland rice yield in northern Benin.