JWSS - Journal of Water and Soil Science

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  Effect of change from the conventional (flooding) to subsurface irrigation system was studied on mature pistachio trees (Cultivar Ohadi) in Kerman pistachio research station for four years. This experiment was carried out in a randomized complete block design including 7 treatments and 3 replications. The experiment also used two irrigation intervals (7&14 days) and three water rates according to pan coefficient (20%, 40%& 60% evaporation from surface of class A pan) for subsurface irrigation system with 6 treatments the conventional (flooding) irrigation system was tested as control. The pipes of subsurface irrigation system were installed at 90cm distance from trees trunk at each side of trees, and 50cm from soil surface. Mean of pressure and discharge in the pipes was 0.8 to 1 atmosphere and 5.4 Lh^-1m^-1, respectively. Different factors of quantity and quality pistachio yield, current vegetative growth, water use efficiency and soil electrical conductivity were measured. The results showed that change of conventional (flooding) to subsurface irrigation system is possible and the best treatment can have water rate of 7174 m³ha^-1y^-1 with 14 days irrigation interval. In comparison with other treatments, this treatment has better quantity and quality pistachio yield. Water use efficiency (WUE) of this treatment was 164g dry yield per cubic meter. Nevertheless, application of water rate of 4783 m³ha^-1y^-1 can result in the deficiency of irrigation water. At this water rate, WUE was 177g dry yield per cubic meter. However, it was found that the application of lower water rate (<4783 m³ha^-1y^-1) produced severe effects on the treated pistachio trees, e.g. decreasing the growth rate, yield and increasing the early splitting in pistachio fruits. Finally, it is concluded that 14-day interval irrigation is the preferred treatment for pistachio trees. Also, soil salinity showed considerable change in subsurface irrigation treatments after irrigation system was changed, especially in the first year.

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This study was conducted to determine the effect of 3 extractants on K release from biotite, phlogopite and muscovite. The minerals were grouped to <60 and 60-100 µm size classes. Particles CEC were saturated with calcium. Sequential extraction up to 30 times was carried out using 0.01M HCl, 1M NH4OAc and 0.05M BaCl2 solutions and cumulative concentration of K was calculated for each extractant. There was a difference among the 3 extractants in cumulative K release values from the three minerals. The highest values of cumulative K release were obtained by 0.01M HCl and 1M NH4OAc for less than 60 and 60-100 µm particle sizes, respectively. The amount of K release from muscovite was even higher when 1M NH4OAc and 0.05M BaCl2 solutions were used as extractants. This might indicate that muscovite cannot be considered as an ineffective source of available K in soils. Furthermore, particle size had a great impact on nonexchangeable K release from micaceous minerals. Coarser particles released higher quantity of K as compared to that of finer particles. Therefore, particle size distribution of different micaceous minerals in soils may be a factor that causes a difference in the amount of K release from soils.