Improved N management and balanced fertilization are key components
of the site-specific nutrient management (SSNM) approach developed
by the International Rice Research Institute (IRRI) in partnership
with the National Agricultural Research and Extension Systems in
Asia. Field studies in major irrigated rice areas have shown significant
yield and profit increases with SSNM over typical farmer fertilizer practice
(Dobermann et al., 2004). These studies revealed that sub-optimal N
management by farmers is a key constraint to increasing yield (Figure
1). Improved N management caused greater yield responses to fertilizer 1
N application compared to farmer practice, and yield responses to fertilizer
phosphorus (P) and potassium (K) application often only occurred
after yields increased through improved N management with SSNM. Leaf
color charts are an effective, low-cost tool that can assist farmers in improving
their N management, and efforts are underway
to promote the technology at wider scale
among Asian rice farmers.