Direct use of phosphate rock to improve crop production in Indonesia

In Indonesia most of the areas left for producing crops have soils such as Ultisols and Oxisols that are highly weathered, acid and of low fertility. One of the main constraints is their low available P to support food crop production. P inputs such as inorganic fertilizers, organic matter, and phosphate rock (PR) must be applied. Phosphate rock is one of the options for farmers to use as a P-source for food crops. In the frame of the coordinated research program three pot and five field experiments were conducted to determine the agronomic effectiveness of PR for food crops using 32P isotopic techniques. Crops used in the pot experiments were lowland rice, soybean, and mungbean. One of the pot experiments was a crop rotation simulation where upland rice, soybean, and mungbean were grown in sequence. Two of the field experiments were a crop rotation of upland rice, soybean, and mungbean. In the field experiments, 32P was used to determine the agronomic effectiveness, whenever possible. In general, the direct application of PR was able to increase plant growth in the pot experiments and crop production in the field experiments. Use of 32P was a good tool to determine the agronomic effectiveness of PR in the pot and field experiments. (author)