2.2 Experimental design
The long-term experiment was set up in 2003 using a randomized complete
block design with three replicates. Each plot size was 5 m × 5 m, the
crop was continuous spring maize and there was a fallow period from
November to March.
Three N fertilizer rates were applied under two tillage treatments in
this study and the two tillage practices were CT (conventional tillage
with maize stalk removed after harvesting, plowed twice to about 25 cm
depth using moldboard plow after harvesting and before seeding, and
fertilized before plow in April) and NT (no-tillage with the maize stalk
mulched after harvesting, then seeded with a no-till planter and
N fertilizer were applied in small holes between two maize in each row
in April). The three N fertilizer
rates were N1 (105 kg N ha-1), N2 (180 kg N
ha-1), and N3 (210 kg N ha-1) using
urea. The row and plant spacings were 60 and 30 cm, respectively.