In order to examine the effect of irrigation on wheat yield with a high specific surface area in a soil comprising illite clay that causes reduced usability of potassium for wheat and loss in potassium absorption and yield, three dry- farming treatments (which includes transparent, black mulches and non- plastic mulch) and irrigated treatments (consist of saturated flooding and unsaturated rain and drop irrigations) were compared in a completely randomized block design within three repeated processes, after applying basal fertilizer from potassium and nitrogen composition in all treatments. Intensity rates of flooding, rain- water and dropping types of irrigation were 240, 144 and 60 mm/h, respectively and every plot was irrigated with 140 mm of water during an interval of 6 months each time. Potassium absorption and a number of clusters were increased with three irrigated treatments than dry-farming treatments in biological yield and per unit of area. It is likely that moisture may improve potassium diffusion intensity toward roots and increase its usability. Increasing humidity by soil reduced mechanical resistance may also result in improvement of roots’ development, potassium absorption and number of clusters and yield at the unit area. Among irrigated treatments, the maximum density of soil nitrate, nitrogen absorption and biological yields resulted from flooding treatment. Probably, by flooding method (with maximum intensity of irrigation), water depth penetration might be lower than that in two other techniques (unsaturated irrigation methods) and this caused lesser washing nitrate and further improved its yield. It is probable that yield of irrigation treatments is a function of usability of soil nitrogen.
Key words: Wheat, soil with high specific surface area, illite clay, intensity of irrigation, nutrients.
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