Abstract
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 need to be paid to producing profitable and reliable fertilizer and manure recommendations.
Highlights
Cambodia covers a wide range of climate/ soil/vegetation regimes and considerable attention has been given to rice breeding, soil classification and land class assessment[1,2].The cultivated rice areas in Cambodia increased from 1.44 M ha in 1980 to 2.8 M ha in 20103 which included about 88% of rainfed lowland areas, and the average grain yield increased from 1.19 to 3.00 t/ha over the same period (Fig 1)
A considerable amount of soil analysis data has been entered into a CARDI database which currently holds over 3000 individual data items. An analysis of this database confirms the contention that most of Cambodian agriculture is practiced on soils with low chemical fertility (Tables 2, 3 and 4)
Research by CIAP and CARDI has shown that the growth and yield of rice in rainfed lowland soils in most areas of Cambodia is restricted by inadequate supplies of N, P and K . 16,12,17 Despite the recommendations made based on this research many farmers have insufficient money to buy fertiliser or think that the coming season will be an average one and that the recommended fertiliser application rate is too high
Summary
Cambodia covers a wide range of climate/ soil/vegetation regimes and considerable attention has been given to rice breeding, soil classification and land class assessment[1,2].The cultivated rice areas in Cambodia increased from 1.44 M ha in 1980 to 2.8 M ha in 20103 which included about 88% of rainfed lowland areas, and the average grain yield increased from 1.19 to 3.00 t/ha over the same period (Fig 1). Research by CIAP and CARDI has shown that the growth and yield of rice in rainfed lowland soils in most areas of Cambodia is restricted by inadequate supplies of N, P and K . This large body of research results has been blended with experience to establish a general set of fertiliser recommendations for the individual soil groups.
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