Simulation of soil moisture distribution under drip irrigation pulsed and continuous in dimensional analysis method.

Background and Objectives: In recent decades, drip irrigation to reduce applied water, increasing yield and better distribution of fertilizer have been considered.in drip irrigation the soil around root zone of plants is moisten instead of whole soil surface which resulted in Reducing applied water. Pulse irrigation is a series of cycles, each cycle of an irrigation phase and a resting phase is formed (12). Water Alternating used in drip irrigation due to completed the wetting front with less water than a continuous stream. Pulse drip irrigation with good management, have great potential to improve the uniformity distribution of water in the soil and association with rise uptake by plant roots.
Materials and methods: In this study, using a physical model to simulate the condition of drip irrigation was used on the farm. Three soil textures including heavy, medium and light, and two discharge of dripper 2.4 and 8 liter per hour (respectively Q1 and Q2) and two pulse and continuous drip irrigation method was used. In addition, by using one of the proposed method of simulation water movement in soil, means dimensional analyses and by using Buckingham π theorem to obtain Dimensionless numbers with communication between them due to get some equation which allow to estimate moisture distribution, progressive front pattern and manner of distribution in wet soil. Finally, in order to compare simulated and measured values of statistical indicators maximum error (ME) and root mean square error (RMSE) was used.
Results: The results showed that the horizontal component of moisture respectively in clay, loam and sand soils are 33, 30 and 20.5 is more than in pulse method (respectively are 28, 26 and 18.6). Vertical component of moisture in discharge of dripper 2.4 L/h in pulse method (respectively for clay, loam and sand are 21.2, 27 and 50) was more than the continuous method (respectively are 19, 22 and 43) for all soils. By comparing the distribution of moisture in the horizontal direction indicates the horizontal component of moist soil for both pulsed and continuous in 8 L/h is more than 2.4 L/h. Increase moisture in the vertical and horizontal components can be argued that the use of intermittent irrigation water in drip irrigation makes up the wetting front with less water than continuous stream was completed. As well as by use of dimensional analysis for simulation water distribution around emitters for both pulse and continuous irrigation, equations was obtained.
Conclusion: Assessment by statistical indices show that the proposed equations were desirable and their results are of considerable reputation.