Identification of research needs for quantification of nutrient dynamics in integrated crop/livestock systems in East Asia and Latin America with a focus on conservation and sustainability issues

Between 1979/81 and 1999 livestock numbers increased throughout S.E. Asia and Tropical America despite the increasing human population density in these regions Indonesia, Myanmar and Thailand dominate the large ruminant population in S.E. Asia. . The large ruminant population in these countries is dwarfed by that in China. In tropical America Brazil, Colombia and Venezuela have the largest large ruminant populations . In S.E. Asia, between 1979/81 and 1999, cattle numbers increased by 91% but buffalo numbers decreased by 3%. The cattle population in Tropical America has increased by 19%. The largest small ruminant population in S. E. Asia occurs in Indonesia and, in Tropical America, in Brazil and Mexico. There has been a very significant (90%) increase in small ruminants in S.E. Asia. The major needs of the largely cut and carry systems used in much of S E Asia and Africa is to provide a year-round supply of high quality forages to supplement low quality crop residues and forages cut from roadsides and wastelands. Because of the reluctance of farmers to fertilise forages in these systems it is an imperative that the flow of nutrients from the soil to the plant and then to the animal be as efficient as possible. In the past legumes, particularly tree and shrub legumes, have been the preferred supplementary forage supply but as systems become more intensive increased attention needs to be paid to N fertilised grasses and direct supplementation of animals with N, P, and other nutrients. The research to be undertaken needs to trace the flow and balance of nutrients (particularly N,P,K,S,Zn and C) through the plant production cycle, particularly the recycling of nutrients when associated with carbon in crop residues and specialist supplementary fodder crops. Studies are also needed on the efficiency of animal feeding and nutrient utilisation, especially in the re- utilisation of manure, urine and bedding material in subsequent crop production. Additional research is required at providing minimal nutrients to specialist forage crops and to directly supplementing animals to enhance their performance and to provide manure and urine of better quality for application to following food crops. In systems where biogas is generated studies are needed on the losses and transformations of nutrients that take place in the biogas generator and the fate of nutrients when the various liquid and solid residues from the generator are re-used in agriculture. In order to study the primary and interaction effects of nutrients in the plant/animal/soil system, it will be necessary to produce multi-labelled plant material. Because of the widespread occurrence of P deficiency it is recommended that labelled legume forages be produced with a range of P application rates (from farmer practice to high rates). Plant production data should be collected to assess the direct benefits of P fertilisation on biomass production and quality. The forage should be fed to penned sheep or goats (or other appropriate livestock) at a range of supplementary levels to assess animal production gains. Partitioning of 15N and 34S in the animals can be estimated. Manure, urine, and bedding samples need to be analysed to determine inorganic and organic nutrient concentrations. These .waste. products need to be managed using both local farmer practice and best practice prior to their application to the food crop. These materials should then be applied to soil and the contribution of N, S, and C to crop production and soil organic matter and fertility determined It is recognised that the research outlined above is complex and expensive but I feel that continuing research on single nutrients, and studying only part of the system will add little to our understanding of the nutrient cycles in plant/animal/soil systems. (author)