Optimal fertilizer management for cassava yield and economic return

Sustainable cassava production is gaining a lot of attention, which aims to reduce production costs and increase the income of cassava farmers. This study examined the optimization of soil fertilizer management at two research locations in Northeastern Thailand, which are primarily cassava-growing regions. The experiment was conducted as a randomized complete block design (RCBD) with five replications. The eight differences of fertilizer management were con-ducted in two study sites (Nampong and Seungsang), consisting of (1) no fertilizer application (control), (2) recommended dosages of chemical fertilizer (RDCF), (3) 500 kg/rai of chicken manure (CM), (4) 150 L/rai of swine manure extract (SME), (5) CM + SME, (6) ½ RDCF + ½ CM, (7) ½ RDCF + ½ SME, and (8) CM + PGPR (stake soaking with plant growth-promoting rhizobacteria solution). At Nampong site, the application of CM+PGPR has the mostpotential for increasing cassava yield in terms of fresh tuber yield than no fertilizer andRDCF applications. For Seungsang site, the application of CM gave the high fresh tuberyield, without significant difference with RDCF applications. Furthermore, as comparedto the RDCF treatment, both soil fertilizer managements produced positive marginal rate of return values, which may recognize the contributions of numerous smallholder farmers to sustainable cassava production.