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.
