Phosphate fertilizer and weed control effects on growth and yield of field pea on Nitisols of central highlands of Ethiopia

Soil acidity and the associated low phosphorus availability and poor crop management practices are among the major factors constraining field pea productivity in the highlands of Ethiopia. The effect of phosphate fertilizer and weed control on yield and yield components of field pea ( Pisum sativum L.) were studied on acidic Nitisols of farmers’ fields of Welmera Woreda, West Shoa. Factorial combinations of four levels of phosphate fertilizer (0, 10, 20 and 30 kg P ha -1 ) as triple super-phosphate (TSP) and two levels of weeding (w 0 = no weeding and w 1 = hand weeding once) were laid out in randomized complete block design with three replications. Results indicated that a highly significant positive response of plant height, number of pods per plant, total biomass and grain yields of field pea were noted to phosphate fertilizer and weeding treatments. Application of phosphate fertilizer at the rates of 10, 20 and 30 kg P ha -1 increased mean grain yields of field pea by 36, 67 and 57%, respectively compared to the control. Weeding once by hand increased mean grain yield of field pea by 15% compared to the unweeded check. The interaction between applied phosphate fertilizer and weed control (P×W) significantly affected field pea grain yield and total biomass. Grain yield was very significantly and positively correlated with plant height, number of pods per plant and total biomass (r = 0.59 ** , 0.68 *** and 0.94 *** , respectively). The results of economic analysis indicated that the treatment with application of 20 kg P ha -1 and weeding once during the 4 th week after sowing by hand was identified to be the best option with a marginal rate of return of 277%, well above the minimum acceptable rate of return of 100%, which is economically the most feasible alternative.