Field crop productivity in relation to soil properties in basaltic soils of eastern Cambodia

The basaltic landscapes of eastern Cambodia offer opportunities for increased production of non-rice crops but there is limited experimental data on the performance of these crops in relation to sowing sea son and soil types. The objective of the present study was to determine the emergence, growth and yield of maize. mungbean, peanut, sesame and soybean in farmers’ fields in relation to time of sowing (early wet season, EWS or main wet season, MWS), soil types and soil properties in the basaltic landscapes of eastern Cambodia. Experiments were conducted in Ou Reang 0v district during two years with contrasting rainfall. Peanut was the most reliable crop with successful establishment in both EWS and MWS, and harvestable yield at 80% of sites. Consistently high peanut yields were obtained on Koinpong Siem soils (2.1-3.4 t/ha), but MWS yields were depressed on average by 0.5 t/ha, possibly due to greater waterlogging. On Ou Reang 0v and Labansiek soils, peanut yields varied with site and season, but were generally higher in 2005 than 2004, again possibly due to lower waterlogging prevalence. By contrast, soybean failed on all occasions in the EWS either due to lack of crop establishment or yields that were too low to justify growing this crop. In the MWS, soybean yields of up to 3.3 t/ha were attained on Kompong Siem soils. Like peanut, soybean yields in the MWS were inconsistent on the Ou Reang 0v and Labansiek soils. Mungbean failed to produce harvestable yield on 63% of EWS sites, but on Kompong Sieni and Ou Reang 0v soil, if establishment was successful, mungbean produced grain yield of 0.9-1.3 t/ha. On the same soils in the MWS, mungbean yields were 0.2-1.5 t/ha. Mungbean failure on Labansick soils, in both EWS and MWS in 2004 and 2005 was attributed to soil acidity. Maize was inconsistent in its performance. Over 50% of sowings in 2005 failed due to drought which caused poor crop emergence and establishment. Yields up to 4.5 t/ha were obtained on Labansiek soils in 2004, but no yield was obtained in the same soil type in 2005. Drought, soil acidity and inadequate N fertilizer are suggested to be the main factors accounting for the unreliable performance of maize. High yields of all crops except sesame were achievable but actual yields were variable among soils, sites and season. Overcoming the unreliable performance of crops is the key to decreasing the risk associated with non-rice crop production on the basaltic soils