Effects of Irrigation Water Salinity and Macronutrients on Soil Chemical Properties and Yield of Wheat

In order to investigate the effects of irrigation water salinity and nitrogen، phosphorus، and potassium fertilizers on wheat yield، three separate experiments were conducted in Ismael Abad Agricultural Research Station، in Qazvin، using randomized complete block design. Salinity treatments included three irrigation water salinities with EC values of <2، 6-8، and 10-12dSm-1 (W1، W2، and W3، respectively). Fertilizer treatments included four nitrogen levels (60% and 30% less and 30% more than the recommended fertilizer rate based on soil test)، phosphorus had 3 levels (30% less than the recommended fertilizer rate، recommended rate، and 30 % more)، Potassium had 3 levels (30% less than fertilizer recommended rate، recommended rate، and 30% more) and were studied in three separate experiments. The results showed that increase in irrigation water EC increased soil salinity and reduced yield significantly. Phosphorus application up to the recommended rate increased grain yield significantly (P<5%) and decreased effects of salinity of water on straw yield up to W2=6-8 dS. m-1، i. e. difference between the effects of EC <2 and EC=6-8 dSm-1 on straw yield was not significant. Application levels of nitrogen fertilizer up to 30% more than the recommended rate slightly decreased irrigation water salinity effects، but the decrease was slight and insignificant. As to the effects of potassium، soil pH decreased from 8. 2 to 7. 6 after the harvest and potassium fertilizer increased wheat grain yield up to W2 salinity level. This means that under saline conditions great care must be taken in the application of chemical fertilizers