A piece of paddy field (Fig. 2) belonging to a local farmer was
selected for observation. It is surrounded by large paddy fields cultivated
by other local farmers. The paddy field was treated with
urea at rates of 300 kg N ha−1 for rice season and 200 kg N ha−1 for
wheat season. For N application, 30% was basally applied, 40% was
top-dressed at the tillering stage, and the remaining 30% was topdressed
at the ear differentiation stage for each crop. Phosphate
and potassium fertilizers were applied basally in the form of superphosphate
at a rate of 60 kg P2O5 ha−1 and in the form of potassium
chloride at a rate of 45 kg K2O ha−1.