Response of Yield and Yield Components of Field Pea to Tillage Frequency, Phosphorus Fertilization and Weed Control on Nitisols of Central Ethiopian Highlands

Abstract: The effects of tillage frequency, phosphorus fertilizer and weed control on yield and yield components of field pea ( Pisum sativum L.) were studied in the 2003 and 2004 main cropping seasons on farmers’ fields in the Chelia and Welmera Districts of west Shewa, Ethiopia. Four levels of tillage frequency (T4 = April, May, early June and at planting; T3 = May, early June and at planting; T2 = May and at planting and T1= at planting) as main plots and factorial combinations of four levels of phosphorus fertilizer (0, 10, 20 and 30 kg P ha-1) and two levels of weeding (W1 = no weeding and W2 = hand weeding once) were arranged as sub-plots in split-plot design with three replications. The results indicated a highly significant positive response of mean field pea seed yield, total biomass and number of pods per plant to tillage frequency, phosphorus fertilizer and weeding treatments. Plowing twice, three and four times including the last pass for seed covering resulted in mean seed yield advantages of 38, 55 and 43%, respectively, compared to the control. Application of phosphorus fertilizer at the rates of 10, 20 and 30 kg P ha-1 increased mean seed yields by 30, 53 and 50%, respectively, compared to the control. Weeding once by hand increased mean seed yield by 16% compared to the unweeded check. Tillage frequency by P fertilizer and weed control interaction significantly affected seed yield. The highest mean seed yield of two years for the tillage, P fertilizer and weed control interaction was obtained from three plowings, 20 kg P ha-1 and weeding once by hand. The yield increment was higher by 232% compared to the control, namely planting with the first pass of ox-drawn implement, with no P application and unweeded condition. Seed yield was highly significantly and positively correlated with total biomass (r = 0.93**), pods per plant (r = 0.54**), plant height (r = 0.54**), seeds per pod (r = 0.41**) and thousand seeds weight (r = 0.37**). The results of economic analysis indicated that the treatment with three times tillage, application of 20 kg P ha-1 and weeding once by hand is the best option with a marginal rate of return of 423%, which is economically the most feasible alternative. Keywords: Field Pea; Nitisols; Phosphorus; Tillage Frequency; Weed Control