Terminal evaluation of agronomic - economic research on tropical soils

Final evaluation, prepared by an outside team, covers the period 1972-81 and is based on document review, site visits, and interviews with project staff and concerned officials. The project has produced a number of outstanding results. Continuous annual cropping has been demonstrated to be feasible on infertile acid soils (Ultisols) in the humid tropics, with adequate lime and fertilizer inputs and climatically adapted crop varieties. Soil chemical and some soil physical properties have been monitored for 9 years to determine the effects of land clearing and cropping systems, providing baseline information of value throughout the humid tropics. Subsoil acidity and low fertility have been ameliorated by downward movement of calcium and magnesium under continuous high input cropping systems, permitting deeper rooting of crops. Kudzu as a managed fallow has been found effective in recycling nutrients and increasing nitrogen fertility for subsequent crops. Small farm extrapolation and validation trials are helping develop a methodology potentially important to the whole Peruvian Selva. Besides the above areas (especially continuous cropping), the proposed Collaborative Research Support Program (CRSP) should place high priority on minimum or zero tillage cropping systems, chemical weed control, and legume-based pastures. Areas better left to other institutions are multiple cropping, nitrogen in multiple cropping, magnesium/potassium ratios, lime placement studies, and composting. The Amazon Agricultural Research Network (REDINAA) should be used to extend project results within the Amazon Basin and to develop the project"s soil management research activities in the CRSP. Care should be taken not to overload the CRSP with complementary research requirements, e.g., the need for work in pest and disease control. The effort to develop economically effective soil-crop management systems employed a sound methodology, but was hampered by a severe lack of data; a strong effort should be made to develop data sets of reliable quality. National and international priorities for future economic research are provided.