The effect of nutritional management on phenological stages, radiation use efficiency and seed yield of chickpea (Cicer arietinum L.) under influence of planting date

Chickpea (Cicer arietinum L.), is a cool season seed legume, serves as an important cheap source of protein and energy in developing countries. Plant phenology is an important aspect of plant adaptation to environmental conditions in order to match maximum the cropping cycle with the seasonal weather pattern (Vadez et al., 2013). Except of drought stress, other environmental factors such as temperature, photoperiod and nutrient deficiencies will affect the plant development stages (Soltani, 2009). The radiation use efficiency (RUE) indicates the amount of dry matter produced gram per unit of absorbed light (MJ) (John et al., 2005). Studies have shown that the supply of nitrogen and the change in planting date will affect on the time of entry into phonological stages and RUE and ultimately seed yield. Regarding the importance of chickpeas as supplier of protein for human and as fixation of nitrogen for plant, this experiment was conducted with the aim of evaluating the contribution of planting date, nitrogen and nitrogen fixation on phonological stages, RUE and seed yield in the climatic conditions of Gonbad Kavous.

The field experiment was conducted as factorial layout based on a randomized complete block design with three replications at the experimental farm of Gonbad Kavous University during the growing season of 2015-2016 and 2016-2017. Nitrogen (none consumption, consumption of 20, 40 and 60 Kg nitrogen ha-1), planting dates (early January and early February) and inoculation with Mesorhizobium (inoculation with Mesorhizobium and non inoculation) were considered as treatments. Half of nitrogen was used in planting time and the other half was used during seed filling stage due to the decrease of the symbiotic relationship between bacteria and chickpea. Seeds in inoculation treatments were inoculated with Mesorhizobium, strain SWRI14, which were obtained from the Soil and Fertilizer Research Institute, Tehran. The optical density (OD’s) were adjusted so that the cell concentration was 109 CFU ml-1. Plots (1.5 m×6 m) were designed with 5 rows per plot. Between blocks, 1.5 m alley was kept. Seeds were sown on 5 January and 2 February 2016 and 5 January and 4 February 2017. In order to obtain the desired density (33 plants/m2), two seeds were sown per hill and hand thinning (one plant hill–1) was performed when seedlings reached 4-6 leaf-stage. Phenological stages (including planting to emergence, planting to flowering and planting to physiological maturity), radiation use efficiency (RUE) and seed yield were studied. Comparison of means was performed by LSD test for 5% probability level by using of SAS statistical software version 9.1.3.

The results showed that planting date was the main cause of change of phenological stages of the plant in two years. Probably due to the presence of native rhizobium in the soil, nitrogen fertilizer and Mesorhizobium could not play the significant role in phenological stages and temperature and moisture had the main role in entering to the phenological stages. Generally with delay in planting time, the growth period of the plant decreased in both years. The seed yield of planting date in early-February compared to early-January in first and second year was decreased by 17.84% and 23.65%, respectively. This could be due to the short growing period of this planting date. The highest amount of this trait was obtained from 60 Kg N ha-1 in both years but there were no significant differences between 20, 40 and 60 Kg N ha-1 in both years. Seed inoculation with Mesorhizobium in the first and second year increased the seed yield by 242 and 170 Kg compared to non-inoculation, respectively. This is justifiable regarding to the role of nitrogen in improving plant growth, yield components and finally increasing of seed yield. The radiation use efficiency was fairly stable and was not affected by factors in both years. It seems that radiation use efficiency is relatively stable in similar environmental conditions. However, some environmental conditions such as drought stress have significant effects on leaf photosynthesis and thus the radiation use efficiency, so that drought stress reduced this efficiency in the second year compared to the first year.

The two years results showed that among factors, the role of planting date in chickpea was more than nutrient (nitrogen) and living factors (Mesorhizobium). Different climatic conditions between two years and between planting dates have significant role in the beginning and duration of phonological stages and seed yield. Therefore, considering the climate change and rainfall fluctuations in order to maximize the use of resources and achieving to high yield, it is necessary to select the planting date that provides the appropriate conditions for the plant in each region. Also the application of supplementation of adequate nitrogen for crops can increase seed yield.