Soil fertility constraints and limitations to fertilizer recommendations in

Soils of Cambodia are low in fertility and conventional rice cultivation destroys any structure that they have. Usage of inorganic fertilizers is low and farmers are encouraged to use animal manure. Much of the research conducted on crop responses to manure is based on trials where unrealistically high application rates have been used so the farmers are given false hopes as to what they might achieve through its use. Little response curve data exists on which to base fertilizer rate recommendations and general recommendations have been formulated for the different soil groups. An economic analysis comparing the general recommendation with site specific nutrient management (SSNM) recommendations has been made on the results of a published experiment and shown substantial increases in both profitability and benefit/cost ratio in using the SSNM recommendations on four soil types. Cambodian farmers, like many in the developing world, have to be careful with their limited cash resources in purchasing plant nutrients and more attention needs to be paid to producing profitable and reliable fertilizer and manure recommendations