Top removal effect on yield, yield components and the dry matter production of faba bean (Vicia faba L.)

Faba bean with scientific name Vicia faba L one of the very old legume crops, is widely planted in temperate regions and high altitude tropical regions. Faba bean used in the human diet and also dry beans, green pods and dry straw used as livestock feed. One way to increase the yield in crop plants unlimited growth such as faba bean is top removal or cut off part of the plant after flowering. So in this regard the effect of top removal and variety on yield and yield components, grain filling rate, grain filling period and chlorophyll of Faba bean were studied. A factorial experiment was carried out based on randomized complete block design with three replications at farm research of Gonbad University in crop year 2014-2015. The first factor was included faba bean varieties (Zohreh, Shami, Sheshband, Saraziri and Barekat) and the second factors include top removal and non-top removal. In the experiments, seeds of different cultivars of faba bean were planted by hand in ten rows with four meter long and spacing of 12.5-cm between rows. Phenological stages, including the number of days from planting to poding (R5) and the number of days from planting to physiological maturity (R7) were recorded. Phenological stages on 10 plants were determined based on methods Fehr & Cavieness (1977). Top removal treatment was in stage poding. At harvest, after all plants reached physiological maturity, three m2 of each experimental plot was harvested to determine the yield components, number of pods per m2 and number of grains per pod. In addition, weight of pods, vegetative tissue weight, and seperated leaves from stems with petioles, were measured. Grain yield and weight of thousand grains as dry weight in three m2 of each experimental unit were evaluated. Harvest index was obtained by dividing grain dry weight on the total dry weight at the time of physiological maturity. Grain filling period was calculated from the difference between the number of days from planting to start filling pods and number of days from planting to maturity, respectively. Average of grain filling rate was calculated by dividing the grain yield on the grain filling period (gr/m2/day). Total chlorophyll was measured by using chlorophyll meter device (SPAD) DELTA-T model Results showed that pod length, 100-seed weight and plant height were affected by top removal. While on other traits there was no significant effect. The effect of variety on biomass, chlorophyll, the number of days from planting to filling and the number of days from planting to maturity was not significant but on the other components of the yield (number of branches per plant, number of pods per plant, number of seeds per pod, pod length, 100- seed weight, grain yield and harvest index), rate and grain filling period was significant. While the interaction of top removal and variety was significant on plant height. Top removal reduced the length of the pod and 100-seed weight. The highest 100-seed weight and grain yield for Saraziri variety was 83.23 gr/m2 and 77.65 gr/m2 respectively. While the lowest of 100-seed weight and grain yield belonged to Shami variety with 63.74 gram and 180 gr/m2, respectively. The lowest harvest index with 32.32% and the highest of harvest index with 24.54% were observed in Saraziri and Shami varieties, respectively. The results correlation analysis indicated that positive correlation between seed weight with grain yield (r = 0.64) and the harvest index (r = 0.59) were significant, which shows that these two have an important role on seed weight. Strong positive correlation was observed between grain yield with biological yield and harvest index. Top removal did not have a great impact on study traits because of dry conditions of the farming location. Low rainfall in the time of poding and high temperature during growth season, especially in after poding stage decreased the growth length of Faba bean. Overall, results of this study revealed that according to the condition of Gonbad-Kavoos, Sarazeri, Zohreh and Barekat varieties were more favorable than other varieties.