Simultaneous water, salinity and nitrogen stresses on tomato (Solanum lycopersicum) root water uptake using mathematical models

Salinity and nutrient deficiency, especially nitrogen, are two important factors that reduce the crop yield in arid and semi-arid regions. Water absorption by root is an important factor in the distribution of soil-water and solute transport. In order to investigate of water uptake by the plant roots under simultaneous water, salinity, and nitrogen stresses by mathematical models, four levels of soil water content (50, 75, 100, and 120 percent of water requirement), six levels of salinity (1, 2, 4, 6, 8, and 10dS/m) and three levels of nitrogen (zero, 50, and 100 percent of the fertilizer demands) was applied on tomato plant with three repetitions. The experiments were carried out in a factorial randomized complete block design. Mathematical models of the root water uptake under simultaneous salinity and nitrogen stresses showed modified Mitscherlich-Baule (MB) model fitted better while under simultaneous water and nitrogen stresses, Mitscherlich-Baule and Feddes (MB-F) has best fitted regarding measured data. The results showed that derived models of Mitscherlich-Baule and Homaee (MB-H), Mitscherlich-Baule and Feddes (MB-F), Mitscherlich-Baule and Dirksen (MB-D), Mitscherlich-Baule and van Genuchten (MB-VG) have more accuracy under simultaneous water and nitrogen stresses and MB-F model has the best fit for measurement of data in comparison with other models. Under simultaneous water, salinity, and nitrogen stresses, multiplicative MB-MB-F model best fitted in comparison with other proposed models. Moreover, the research results showed that in severe salinity, increasing the amount of fertilizer doesn't increase crop yield while increasing the amount of irrigation water increases yield.