The Effect of Surface and Subsurface Irrigation with Saline Water and Mulch on Corn Yield, Water Productivity and Solute Distribution in the Soil

With due attention to the limitation of water resources in Iran and specific geographical conditions of the country, using modern methods of irrigation with low water usage is inevitable. By applying
suitable management in water system, soil and plant, while increasing product, we can establish a sustainable agriculture. Today, subsurface irrigation systems are used in various methods around the world, especially in the countries encountering water shortage. One of the newest methods is applying sponge plastic pipes such as tuporex which is installed in the area of plant root. Then, water with the pressure of 0/6-2 atmosphere flows inside it and by exuding, it dampens the area. For this purpose, in this study number of 12 concrete lysimeters with the dimension of 2×2×1/25 m was used to investigate the effect of vegetation (mulch) on the efficiency of water consumption
and product function for corn, salt accumulation as well as the amount of nitrate wash on soil profile under two permeable subsurface irrigation and surface irrigation. For irrigation, a body of water with salinity of 4 ds/m was used. The plan includes two main treatments (permeable subsurface and surface irrigation) and two subtreatments (mulch and without mulch) withfactorial experiment in a randomized complete block design with three replications at the College of Agriculture Research Campus, Tehran Universityof technology Located in Karaj, Iran in 2010. Surface irrigation was performed based on the moisturein the soil and permeable subsurface irrigation was performed per dayas much water as was consumed.. Lysimeters soil is prepared from farm soil and through examination, its appearance special weight was registered to be 1.4 gr per cm3 equals to 1400 kg per m3. The amount of nitrogen fertilizer (Urea) was applied on the lysimeters according to the region convention,
was 300 kg per hectare (120 gram per each lysimeter). A half of this amount was used at the time of cultivation and another half was used for the plant 60 days after cultivation; because the amount of water given in this type
of system is higher.On the other hand due to the lack of vegetation, the significant amount of evaporated water and water productivity have decreased. Results disclosed that the subsurface irrigation system has important effect in decreasing consumed water (58% with mulch and 40% without mulch) and increasing crop yield (46% in seed
corn yield, 50% in forge yield and 12% in weight of one thousands seed corn) in comparison with the surface irrigation system. As well as the subsurface irrigation has prevented lower soil layer from contamination and being salty by decrease salt and nitrate leaching. Besidespresence of mulch in lysimeterhas shown important role in decreasing water consumption and seed corn yield. The important thing is that the highest yield in two type of performance, was recorded in subsurface irrigation treatment with mulch (TM) and this subject is so important when we remind that (TM) treatment had the least amount of water uses. Itmeans that with the least amount of water consumed the highest amount of product was obtained among the treatments.On the other hand, surface and non-mulching (SO) irrigation is expected to have the lowest yield per unit water consumption. Also in both subsurface irrigation with preamble tube and surface irrigation system, existence of mulch caused to decrease salt concentration to 40% and 30% in soil surface respectively which makes it
suitable for the areas facing water shortage. It can be concluded that, existence of mulches in the both subsurface  irrigation with permeable tube and surface irrigation system causing water saving 13 and 23 percent, respectively and the rate of saving water in surface irrigation system with presence of mulch has also increased. Thus, it is recommended that some of the plant residuals, like mulch remain on the ground after harvest. The subsurface irrigation with permeable tube system has been prevented from washing nitrate to the depths of the soil. As a result, the environmental pollution caused by nitrate losses in this system is minimal and this system saves fertilizer. Also the concentration of salt solution in the soil profile in subsurface irrigation system was significantly lower than the salt concentration in surface irrigation. As a result in areas that use the saline water for irrigation, the subsurface irrigation with preamble tube confirm better function than surface irrigation system
and use mulch can increase yield and reduce leaching.