Effects of nitrogen fertilizer and plant population on growth, yield and harvest index (HI) of chickpea (Cicer arietinum L.) under dryland conditions in Kenya

Abstract

Objective: To evaluate the dry matter, grain yield and harvest index of chickpea under four different levels of nitrogen fertilizer and plant population density of chickpea within the dryland areas of Kenya. Methodology and results: Field experiments were conducted at the National Animal Husbandry Research Center (NAHRC), Naivasha, Kenya, during the long (season 1) and short (season 2) rains of the year 2005. Four different nitrogen fertilizer levels (0, 20, 40 & 60 Kg N/ha) and four plant population densities (PPD) (74,074; 88, 889; 111, 111 and 148,148 plants/ha) of chickpea were evaluated. The experiment was laid out as a factorial design. Laid out in a Randomized Complete Block Design (RCBD) and replicated three times. It had 16 treatment combinations. At final harvest (120 Days After Sowing -DAS), there were significant effects of nitrogen fertilizer application (P<0.05) on dry matter throughout the growth stages. The dry matter production varied with plant population density ranging from 3,429 to 4,689kg DM/ha in season I and 2,955 to 3,854 kg DM /ha in season II. The highest grain yield was 2,574.4 and 2,353.7kg grain/ha under 20 and 40kgN/ha, respectively in seasons I. Grain yields as influenced by planting population densities ranged from 1,273.8 to 3,271.2 kg/ha in season I and 1,027.4 to 1,994.2 kg/ha in season II. Nitrogen fertilizer application at 0, 20, 40 and 60kgN/ha produced an average of 1,099.6; 1,570.5; 1,658.7 and 1,675.8 kg/ha of grain, respectively. Plots without nitrogen fertilizer (0 kg N/ha) had significantly (p<0.05) lower yield while the other treatments showed no difference in terms of grain yield. An interaction of nitrogen fertilizer rates and plant population density caused a significant (P<0.05) increase in both dry matter and grain yield. Increasing nitrogen application rates from 0 to 20, 40 and 60kgN/ha caused a decline in harvest index from 0.689, 0.657, 0.577 to 0.428, respectively, during the long rain season. During the short rain season, 40kg N/ha treatment had the highest harvest index followed by 20kg/ha, 0kgN/ha and 60kgN/ha (0.494, 0.489; 0.424 and 0.384), respectively. The harvest index only increased with an increase in plant population during the second season. Increasing plant population density from 74,074(P1) to 89,889(P2) to 111,111 (P3) and 148,148 (P4) per hectare resulted in significant (P<0.05) increases of harvest indices from 0.372, to 0.544, 0.633 and 0.698, respectively, during the long rains and from 0.348 to 0.408, 0.476 to 0.517 respectively, in the short rains season. Conclusion and application of findings: Increasing fertilizer rates and plant population increased dry matter at all stages and also the grain yield. However, increasing nitrogen doses lowered the harvest index (HI), whereas an increase in plant population density increased the harvest index (HI). These findings should be considered when determining the optimal conditions to maximize chickpea yields in dryland areas.