Temporal Variations of Runoff and Sediment Generation during the Growing Season in Rain-Fed Lentil: A Case Study in Tikmehdash Region of Eastern Azerbaijan

The contribution of crop cover to reducing runoff and erosion depends on the type, height, density and stage of plant growth. The literature review indicates that because of the different life forms, the effect of plants on the reduction of runoff and erosion are different at different growth stages [13]. However, no comprehensive studies have been conducted in Iran in this field. Therefore, the aim of this study was to investigate the changes of runoff and sediment production during the growing season and in different densities of lentil dry farming in the soil conservation research station of Tikmeh in eastern Azerbaijan.
This study was carried out in nine experimental plots (4.8 × 40 m2 in size), with three treatments including three levels of sowing densities (30, 35 and 40 kg of seed per hectare) of Kimiya cultivar of lentil (Culinaris L.), in three blocks. For this reason, in spring, plots were plowed and sowed on 8 April 2013. The amount of runoff in each plot during the growing season after each rainfall was measured through volumetric method and the amount of sediment in the runoff was determined. Moreover, some agronomical characteristics of lentil such as the canopy cover and plant height were measured. The results were analyzed as split-plot design in time by MSTATC and SPSS softwares.
In this study, only in three growth stages, rainfall resulted in runoff and sediment. The first stage of sampling in this research was consistent with the stage of the plant establishment; the second stage was in accordance with plant growth; and the third stage of sampling was consistent with the plant ripening. Results showed that the amount of runoff decreased from the first event to the last one. In other word, after the lentil germination, its efficiency in soil conservation dramatically increased, so that the amount of runoff at the stage of plant growth and ripening stage respectively was 44.71% and 54.31%, and the amount of sediment was 67.10% and 75.20% less than the plant establishment. During the growing season, through increasing the density of lentil dry cultivation from 30 to 40 kg of seed per hectare, the amount of sediments declined significantly. The total amount of sediment resulting from a density of 30 kg seed per hectare was almost two times more than the density treatment of 40 kg of seed per hectare.
The results showed that, over the time, the difference between the treatments in the weeds increased, so that, at the stage of the plant establishment, although there was no significant difference between the treatments, the treatment of 30 kg per hectare had the highest percentage of weed density at ripening stage.
CONCLUSIONS AND SUGGESTIONS: Reducing the runoff and sediment at the end of the growing season can occur due to the reduction in the amount and intensity of rainfall in the above three events, and also due to the increased canopy density of the lentils during the growing season. In addition, results showed that during the growing season, the lentil role in reducing soil loss was more effective than the runoff.
Since in the dry farming of lentil in the study area, crop density of 40 kg per hectare resulted in a minimum amount of runoff and sediment compared to the other treatments; therefore, the sowing rate of 40 kg per hectare is recommended to the farmers of this region.