Effect of defoliation on yield and yield components of chickpea (Cicer arietinum L.) under different amount of nitrogen fertilizer and irrigation regimes

IntroductionChickpea (Cicer arietinum L.), an annual with indeterminate growth habit, is one of the most important food legumes. Loss of foliage due to leaf diseases or environmental hazards are prevalent for many crops. Such loss of foliage affects the yield and also the carbohydrate and protein status of leaves and seeds. The source-sink relationship change during growth stages. Few factors including nitrogen fertilizer and water influence this relationship. This experiment was conducted in order to study the effects of nitrogen fertilizer, supplementary irrigation and defoliation on yield and yield components of chickpea.
Materials & MethodsThe experiment was conducted as split-split plot based on randomized complete block design with three replications in research farm of Faculty of Agriculture, Ferdowsi University of Mashhad, Iran in 2012. Main plot was nitrogen fertilizer including 30, 75 and 150 kg N/ha and sub-plot was irrigation regimes including full irrigation, supplemental irrigation at flowering and supplemental irrigation at flowering and seed filling stages. Defoliation including 0, 25%, 50%, 75% and 100% was considered as sub-sub plot. Leaf and stem dry weight, seed yield, biological yield, pod number per plant, grain number per plant, 100 grain weight and harvest index were all recorded.
Results & DiscussionThe results indicated that all traits excluding harvest index were higher in 150 kg N.ha-1 treatment compared to other levels of nitrogen. Nitrogen rate of 150 kg.ha-1 produced the highest grain yield (135.7 g.m-2). The highest harvest index (40.7%) was obtained at 30 kg.ha-1 N treatment. Full irrigation and supplemental irrigation at flowering and poding stages with average grain yield of 146 g.m-2 were higher than supplemental irrigation at flowering (83 g.m-2). Supplemental irrigation at flowering and poding stages showed the highest harvest index (41.2 %). The highest biological yield was obtained from 150 kg N.ha-1 (413 g.m-2) and full irrigation (415 g.m-2). Nitrogen rate 75 kg.ha-1 at 0% defoliation (control), resulted in the highest seed yield (177 g.m-2). The lowest seed yield (58 g.m-2) was obtained from 75 kg.ha-1 nitrogen treatment and complete defoliation. By increasing of N fertilizer application, the negative effects of defoliation in some traits such as pod number and seed and leaf weight decreased. In 30 and 75 kg.ha-1 nitrogen treatment, 100% defoliation decreased pod number to 50%, but this was 20% in 150 kg.ha-1 nitrogen treatment. Full irrigation with 0% defoliation produced the highest (196 g.m-2) and supplemental irrigation at flowering stage with complete defoliation the lowest (56 g.m-2) grain yield. Defoliation decreased the most of mentioned traits significantly. Complete defoliation decreased grain and biological yield to 46% and 56%, respectively compared to the control. The lowest harvest index (29%) was obtained in complete defoliation. All of traits including pod number, seed number, harvest index and biological yield had positive and significant correlation with seed yield. Biological yield (83%) had highest correlation with yield.
ConclusionGenerally, defoliation decreased grain yield. However, application of nitrogen fertilizer at low levels could decrease the negative effects of defoliation. High N application improved the ability of plant to compensate the leaves that removed grain yield in treatments of full irrigation and supplementary irrigation at flowering and depoding stages was equivalent, therefore under water deficit condition, supplementary irrigation at flowering and podding stages recommend.