Ten % of greenhouse gas is methane (CH4) produced from the paddy field on the earth, s surface. The Global Warming Potential (GWP) of CH4 is about 25 times than that of CO2 (IPCC, 2007). CH4 emission from paddy soil will changed by the fertilizer we used. A pot experiment was conducted to evaluate the effects of application of slag fertilizer (Material M) and biochar on methane emission, soil chemical property (pH) and rice growth, yields.
The pot experiment was conducted from May 13 to September 21, 2018. Three kg sandy soil was placed into plastic pot (3L), five treatments were set up as allows: (1) NPK (39kg/10a); (2) NPK＋slag fertilizer (200kg/10a); (3) NPK＋biochar (1%); (4) NPK＋slag fertilizer (200kg/10a)＋biochar (1%); (5) soil only, all with 3 replications and three rice seedlings. All with top dressing twice with urea (0.125g) at Day 41-51 with mid-drainage. CH4 flux was measured by closed chamber method and gas chromatograph, soil pH was measured with pH meter.
Soil pH after harvesting was increased by slag fertilizer and biochar, because slag fertilizer and biochar contains alkaline. Soil Total C increased by biochar, which is considered to contribute to carbon sequestration. Total N was not significantly different in each treatment. There was also a tendency that the soil solution pH increased in slag fertilizer and biochar treatments, but there was not much difference. Total CH4 emission during crop season from slag fertilizer treatment decreased about 28% compared with NPK treatment, biochar treatment decreased about 35% compared with NPK treatment, slag fertilizer＋biochar treatment decreased about 47% compared with NPK treatment. Panicle number and tiller number increased compared with chemical fertilizer treatment. Combined application of slag fertilizer and biochar also increased the field grain. Interaction to trace elements is discussed.