Effects of tillage (T), i.e., rotary tilling to 25 cm depth, reduced tillag
e (RT), rotary tilling to 5-6 cm depth and application of farmyard manure (
M), chemical fertilizer (F), and mixed application of manure-chemical ferti
lizer (MF) on crop yield and some soil characteristics were investigated du
ring two years of upland cropping (with a rotation of oat - soybean and whe
at - field corn) in an Andosol field.
Regardless of the tillage method applied, MF resulted in higher yields of o
at, wheat and field corn than M or F. Soybean yield was not influenced sign
ificantly by either treatments, although the highest yield occurred in the
RTM plot. The tillage treatment did not significantly affect soil pH, total
nitrogen and microbial biomass nitrogen, but the application of farmyard m
anure increased these parameters in the soil surface layer (0-20 cm). Amoun
ts of soil organic matter changed in accordance with the amount of crop res
idues reincorporated, especially in the surface layer.
During wheat and field corn cropping, RTM plots resulted in larger amounts
of leached nitrate than the other plots. This was caused by continuous mine
ralization of organic nitrogen from the manure and increased water permeabi
lity of soil in these plots.