EFFECTS OF DIFFERENT RATES OF N FERTILIZER ON PHYSIOLOGICAL INDICES OF GROWTH AND YIELD COMPONENTS OF CUMIN

Abstract

Cumin (Cuminum cyminum L.) is one of the most important medicinal plants and is one of the non-oil items for export. It has devoted about 40000 ha of Khorasan lands for its cultivation. Despite of its extensive cultivation, unfortunately, few researches have been conducted on its fertilizers, and on its other agronomic aspects. So, effect of different rates of N fertilizer (50, 100, 150, and 200 Kg N/ha) was investigated on Cumin growth indices, yield and yield components in the statistical method of R.C.B.D with four replications. Characters measured were: Total of dry weight (TDW), leaf area index (LAI), leaf dry weight (LW), Crop growth rate (CGR), net assimilation rate (NAR), leaf area ratio (LAR), leaf weight rate (LWR), specific leaf area (SLA), relative growth rate (RGR). Growth parameters were calculated during six growth stages by harvesting samples from leaf area and dry weight and determination of regression coefficients. On the basis of obtained results, in the early stages of growth, due to low use of N by plant, nitrogen has less effect on growth indices and by advancing in time, and development of growth stages, rate of N use increases in plant and LAI, CGR, LWR, and LAR, and SLA have increased and among rates of N, difference was observed. NAR of photosynthetate and RGR during Cumin growth showed a decreasing trend, as well. With respect to obtained results, 100 kg N/ha, had lowest effect on number of umbel, biomass, 1000 seed weight, and yield and 150 kg/ha N had highest effect on 1000 seed weight and yield. Highest biomass and number of umbel was obtained in 200 kg N/ha.