Nguyễn Thanh Lâm, Trần Đức Viên
Từ khoá: động thái, dinh dưỡng, đất, nương rẫy, bỏ hoá
Nutrient dynamics in composite swiddening farming with shortened fallow
Study was in Tat hamlet, Hoa Binh province. 4 field, representing the individual years of cropping and 3 fields representing the 1st, the 3rd and the 5th years of bush-tall grass fallow were selected for field measurements. Soil samples were taken from all the fields at the beginning and at the ed of cropping year and were analyzed for N, P, K and organic carbon. Results: a sharp decline of total organic carbon during the 1st two years of upland rice cropping, then a stabilizing trend in the subsequent 2 years of cassava cropping. Total P had similar trend as total C, but extractable P as well as total mineral N and K declined throughout the cropping period. During fallow period, a continuous building up of C and N to a comparable level at the beginning of the cropping year but a decline of both total P and K. Results: a decline in soil fertility during cropping period and partial restoration of soil fertility during the fallow period. However, 5 years of bush-tall grass fallow was not sufficient to restore the original level of soil fertility.