The Effect of Sub-irrigation on Rice Yield with Refined Municipal Wastewater

Due to limited water resources in the country, the use of new methods of irrigation with low water consumption seems necessary. Subsurface irrigation is one of the few methods to increase crop water productivity. Also, in order to cope with the water crisis, unconventional water can be used, in other words, poor water quality is being applied. There are several methods for improving the quality of water in the agriculture section, one of which is the use of magnetic fields. The purpose of this study was to investigate the effect of groundwater table management on reducing water consumption and to investigate the possibility of sub-irrigation (drainage controlled) with magnetized wastewater of Gorgan urban refinery on rice yield.

This study was conducted from May to September of 2018 in Gorgan Agricultural and Natural Resources University. The experiments were carried out in a lysimeter with a diameter of 30cm and a height of 50cm. The experiment was conducted as a factorial based on randomized complete block design with three replications. Treatments included water type factor (ordinary water (C) and sewage (W)) and water correction factor (magnetic (M) and non-magnetic (O)). To control the water level, two water tanks were used, one as a stabilizer water table and another to measure the amount of water used. Part of the ordinary water and wastewater was magnetized using a DC magnetic field generator with magnetic one tesla field intensity. Underground irrigation was then carried out on the soil columns in which the rice plant was cultivated so that the water table depth was fixed at 5 cm from the soil surface. The lysimeters were irrigated with ordinary water for one week, in the second week of treatments were applied. At the end of the growing season, traits such as rice husk yield, biological yield, harvest index, water use efficiency, physical water productivity and economic water productivity were determined. The measured data were analyzed using SPSS. Also, comparisons of means were performed by using the t-test and Duncan tests at 5% level of probability.

The results of the comparison mean water type factor showed that there was no significant difference between the wastewater and the normal water in the parameters of the measurements. Correction Water showed that non-magnetic water was significant in rough rice yield, water use efficiency, water physical productivity, and water economic efficiency compared to magnetite, but on biological yield and harvest index had not a meaningful effect. Also, the comparison of the mean of water type and correction water method on all measured parameters indicated that the nonmagnetic wastewater was superior to the rest of the treatments at the 5% level.

This study was conducted to investigate and further study two methods of controlled drainage management and underground irrigation for rice cultivation with the Gorgan municipal wastewater treatment plant. Based on the results of the comparison of mean interaction effects of treatment compounds, non-magnetic effluent was identified as the best treatment composition in this experiment. According to the results of this research, we can say:  Rice cultivation in terms of irrigation does not require the formation of a standing water layer on the surface of the soil. Also, by using wastewater of Gorgan urban refinery for irrigation water, in addition to reducing the harvesting of high-quality water resources, the cost of fertilizer use (chemical and organic) in the production of crops can be reduced. Overall, the results of this study showed that the magnetic factor had no effect on the improvement of rough rice yield, water use efficiency, physical productivity water and economic efficiency of water under underground irrigation conditions. However, it should be noted that the results of this research are only It is obtained by a magnetic device model. Therefore, it is possible that the use of different models of magnetic devices results in different results. It is also probable that the passage of irrigation water with different compositions (percentage of cations and various anions) from the magnetometer can lead to different results on other crops or cultivars of a crop.