The influence of spacing and phosphorus fertilization on growth, fruiting and nutrient accumulation in sweet peppers (Capsicum annuum L.)

Abstract

The effects of six spacings (90 by 90, 90 by 60, 90 by 30, 60 by 60, 60 by 30 and 30 by 30 cm) and four levels of phosphorus (0, 44, 88 and 132 kg P/ha) on growth, fruiting and nutrient accumulation in sweet peppers were investigated on field plots at National Horticultural Research Station, Thika during the Short and Long Rains seasons of 1980 and 1981, respectively. Dry matter accrimulation and number of fruits per plant increased significantly with increasing spacing between and within the rows, while the total· fruit yield per hectare decreased. During the Short Rains the total fruit yield/ha increased from 11.17 to 35.22 "tons/ha when spacing was decreased from 90 by 90 to 30 by 30 cm in plants fertilized with 44 kg P/ha. Application of 44 kg P/ha significantly (xviii) increased dry matter production in plants harvested 8 and 12 weeks after transplanting in all spacings. There was no effect of P fertilizer on shoot dry weight in plants harvested during the 4th week after transplanting. Application of 88 and 132 kg Plha promoted less dry matter accumulation in shoots and fruits than 44 kg P/ha. Phosphorus fertilizer application also promoted earlier fruiting. Dry matter accumulation in shoots and fruits increased continuously throughout the growth of the plants and the optimum was attained 12 weeks after transplanting. However, during the Short Rains maximum dry matter was attained 16 weeks after transplanting In plants grown at the spacings of 90 by 60, 60 by 60 and 60 by 30 cm at all P levels. Plants at a spacing of 90 by 90, 90 by 30 and 30 by 30 cm attained maximum dry matter accumulation 12 weeks after transplanting when supplied with 44, 88 and 132 kg Plha, thereafter followed by a decrease or stabilizationof dry matter dependingon snacing. During the Long Rains all the plants supplied with 44, 88 and 132 kg Plha attained maximum (xix) dry matter production 12 weeks after transplanting. Thereafter, dry matter decreased. Spacing and P fertilization did not influence Vitamin C content in fresh fruits. There were no consistent significant effects of spacing on the concentration of N, P, K, Ca and Mg in shoot and fruit tissues. Application of 44 kg P/ha promoted an increase in N concentration in shoots during the 4th week after transplanting, but the concentration decreased during the 8th and 16th weeks and remained constant during the 12th week after transplanting, during the Short Rains. During the Long Rains application of kg P/ha promoted an increase in N concentration in shoots during the 4th and 12th week and a decrease during the 8th and 16th week. Phosphorus levels above 44 kg P/ha had a very slight effect on N concentration in shoots. There was no effect of P fertilization on N concentration in fruits. Phosphorus Qoncentration in shoots increased with application of 44 kg P/ha, while (xx) higher levels of P did not affect the P concentrations- Phosphorus fertilization had no effect on P accumulation in fruits although fruits picked 8 weeks after transplanting had higher P concentration levels than those picked 12 and 16 weeks after transplanting. Phosphorus fertilization had no effect on K concentration in shoots and fruits. Calcium and Mg concentration in shoots were highest with the P fertilization level of 44 kg/ha during the 4th, 8th and 12th weeks after transplanting, and decreased with application of higher P levels. Phosphorus fertilization levels did not affect the Ca and Mg concentrations in fruits.