Effect of crop density and sowing date on the growth indices and weed control of chickpea (Cicer arietinum L.)

One of the important requirements in agronomic planning is to determine the best and most suitable sowing date in order to achieve high quality and desirable quality of yield. Therefore, this experiment was conducted in order to determine the most suitable planting date and plant density in terms of weed control in dryland chickpea in Koohdasht, Lorestan, Iran.

The experiment was conducted as split plot in randomized complete block design with four replications with three planting dates (20 January, 8 February and 28 February) as main plot and four densities (16, 32, 48 and 64 plant m-2) as sub plot in 2016-2017 in the climate conditions of Kohdasht. Sampling from chickpea and weeds was done four weeks after planting until the end of the growing season with a time interval of 7-10 days. In order to describe the changes in total dry matter (wmax) and leaf area index (LAI) against time after planting (t), the truncated expolinear and beta model was used, respectively.

The results showed that the dry matter changes and leaf area index during the growing season are consistent with the truncated expolinear and Beta models. So that the parameter wmax at the first, second and third sowing dates at 16-64 plants m-2 in weed free conditions, ranged from 154.90-371.70, 119.60-310.80 and 60.87-187.90 g Dry matter m-2 and in weed infested condition ranged from 98.69-266.60, 56.78-186.90 and 35.53-114.00 g dry matter m-2. Regarding the lmax parameter, at the first, second and third sowing dates at 16-64 plants m-2 in weed free conditions, ranged from 0.49-9.32, 0.46-7.97, 0.39-4.50 g and in infested conditions 0.39-6.25, 0.69-5.18 and 0.21-2.79 g was estimated. Weed dry weight increased in weed infected plots over time. So that weeds dry weight on 28 February were more than other sowing dates. Also, the highest percentage of yield loss occurred in the second planting date at a density of 16 plants per square meter. In general, the first sowing date with density of 48 plants m -2 with a yield of 1703.327 kg ha-1 of chickpea was the best treatment compared to the same sowing density at the second sowing date (1534.7 kg ha-1) and the third sowing date (470.55 kg ha-1).

In the present study, the maximum dry matter and the leaf area index of chickpea plants were decreased in weed infested conditions compared to weed free conditions in all three sowing dates. So that the reduced values in the less sowing densities were more than the higher sowing densities. In the other words, by increasing the planting density in the presence of weeds, the farmer will be able to avoid a significant reduction in the yield loss due to competition with weeds. By comparing the sowing dates of chickpea in terms of maximum dry matter, leaf area index and yield loss percentage of chickpea plants, it can be stated that the conditions for chickpea growth and development in the first sowing date were better than the other sowing date.