Investigating the effect of slope, furrow length and discharge on the use efficiency and water storage efficiency in sugarcane fields
Controlling the amount of water consumed during the sugarcane growth and providing the necessary solutions in water management by increasing the uniformity of water distribution and the efficiency of water consumption and storage in the soil are essential. In this research, by creating different slopes, discharges and lengths of furrows in sugarcane fields, the hydraulic conditions of the flow were practically managed and regulated in order to have a better application efficiency and uniformity of water distribution along the furrow. The purpose of this research was to determine the optimal slope, discharge and length of the furrow, in order to increase the water application and storage efficiencies in the furrow irrigation of sugarcane lands of Mirzakochek Khan Company.
This study was conducted from August 2018 to September 2019 in one of the farms of Mirzakochek Khan company in Khuzestan province of Iran. The experiment was done as split split plots in the form of a randomized complete block design with three replications. The treatments were included furrow slope as the main factor at three levels (0.02, 0.04 and 0.06%), flow rate as the subfactor at three levels ( 2, 2.5 and 3 lit/sec) and length of furrow as sub-sub factor at three levels (150, 200 and 250 meters). Soil moisture data before and after irrigation, underground water level, advancing and retreating speed, meteorological information and other information related to the quantitative and qualitative characteristics of sugarcane plants in each treatment were collected at two stations at the beginning and middle of furrow. Each plot included three furrows, and sampling was done from the middle furrow.
Regarding the index of water advance time, the mutual effect of the slope of the furrow, the discharge and the length of the furrow were significant. By increasing slope and discharge, the velocity of the flow increased and the time of water advance in the furrow decreased and caused more uniformity of water distribution. Regarding the application efficiency, the 2 lit/sec treatment was the first with 70.0 %, and the 2.5 and 3 lit/sec treatments were 68.8 and 66.3 %, respectively. By decreasing discharge, the amount of water volume decreased and the application efficiency increased. By increasing furrow length, the application efficiency also increased. Regarding the efficiency of water storage in the soil, the 2 lit/sec treatment was the first order by 89.2% and the 2.5 and 3 lit/sec treatments were the next orders, 80.8 and 77.8%, respectively. The maximum efficiency of water storage in the soil (100%) was achieved at the furrow with 250-meter in length and 2-lit/sec in flow rate. By increasing the slope, the water storage efficiency in the soil increased. Also, by increasing the length of furrow, the water storage efficiency in the soil increased. The efficiency of water storage in the soil increased by decreasing discharge.
The results of this study showed that the lowest advancing time (169 minutes) was belonged to the furrow with slope of 0.04%, flow rate of 3 lit/sec and length of 150 meters. The furrows with the slope levels of 0.02% and 0.06%, flow level of 2.5 lit/sec and the length of 150-meter were ranked the second and third in terms of advancing time with 174 and 179 minutes, respectively. By decreasing the length of the furrow and increasing the flow rate, the advance time decreased which caused the uniform distribution of water along the length of the furrow. Regarding application efficiency index, the flow rate of 2 lit/sec had the highest application efficiency of 97.7%, and in the treatments of 2.5 and 3 lit/sec, application efficiency was 68.81 and 66.3%, respectively. The maximum efficiency of water storage in the soil (100%) was obtained in the furrows with 250-meters in length and 2-lit/sec in flow rate. The best conditions for furrow irrigation in the company's fields were obtained with a slope of 0.04%, a flow rate of 2 lit/sec, and a length of 250 meters.