EFFECT OF RICE STRAW APPLICATION ON CH4 EMISSION FROM PADDY FIELDS .3. EFFECT OF INCORPORATION SITE OF RICE STRAW ON CH4 EMISSION RATES AND THEIR VARIATION AMONG SHOOTS OF A RICE PLANT

The effect of the incorporation site of rice straw (RS) on CH4 emission rates from flooded soils planted with rice was studied in pot experiments. The incorporation of RS into the lower layers of soil increased the CH4 emission rates during the early period of rice growth compared with the incorporation into the upper layers or the uniform incorporation into the whole soil. Methane emission rates from a rice plant were also markedly different between tillers whose associated roots grew close to RS and those away from it. Methane emission rates from a rice plant varied among shoots. Methane emission rates through the older shoots were larger than those through the younger ones at the tillering and milky stages, although the difference was not significant at the harvesting stage. Methane emission rates fluctuated 3-5 times among shoots of a rice plant throughout the growth stages.