Effect of wood ash and phosphorus fertilizer on the growth and yield of beans on poor soils in Uganda

Abstract

Soil fertility reduction on smallholder farms is a major problem in Uganda. The soils have been over cultivated in order to meet the ever-increasing food demand. This has led to soil exhaustion, coupled with acidification and consequently low yields for staple crops such as beans that are a source of proteins and income for the poor. The cost of replenishing the lost nutrients from the soil using inorganic fertilizers is high and many farmers cannot afford. Wood ash is generated in many rural households in Uganda and can serve as a source of nutrients and also help reduce acidity. This study was carried out to assess the effects of wood ash and phosphorous fertilizer on the growth of beans on poor soils that have low available phosphorus concentration in Uganda. The experiment was conducted at Makerere University, Department of Environmental Management backyard. Wood ash was obtained from the kitchens of Mary Stuart Hall, Makerere University. Soil was obtained from a farm in Semuto, Luweero District. The treatments were; T1-Control(just soil),T2-6.67g ash (5 tons/ha), T3-6.67 ash(5 tons/ha)+0.133g DAP (20kg P/ha), T4-6.67g ash(5tons/ha) +0.266g DAP(40kg P/ha), T5-6.67g ash(5tons/ha)+0.399g DAP(60kgP/ha), T6-6.67g ash (5 tons/ha) + 0.532g DAP(80kg P/ha) and T7-0.532g DAP (80kg P/ha). The ash and fertilizer were thoroughly mixed with 5 kg of soil then put in a bucket. The experiment was laid out in a completely randomized block design (CRBD) with 3 replicates and was conducted for 2½ months. Weeding was done by hand pulling and water was applied when necessary. Data were collected on plant height, number of green leaves shortly before flowering. Root nodules were counted after flowering and eventual number of seeds per pod counted at maturity. Results showed that all the parameters measured recorded highest results in Treatment 4 with an exception of root nodules and number of pods which recorded the highest result in Treatment 5 and 4 respectively. It is therefore recommended that wood ash be adopted by rural farmers to increase yield of beans in rural Uganda. This is because the ash can be gotten with a lot of ease given the fact that most rural households use wood as a source of fuel for cooking. Furthermore, the same study should be investigated in different localities with different soil types for optimum level of wood ash to produce beans.