Effect of Different Irrigation Periods and Methods on the Growth, Biomass, Nutrient Uptake and Physiological Traits of Leucaena Leucocephala (Lam.) De Wit Saplings Planted in the Bardarash District, Kurdistan Region, Iraq

Background:Irrigation management is one of the most crucial silvicultural practices in enhancing the growth and establishment of tree plantations in arid and semi-arid regions. Therefore, the present study evaluated the effects of different irrigation periods, methods and their interactions on the growth, biomass allocation, nutrient uptake, and physiological traits of Leucaena leucocephala saplings in Bardarash District, Kurdistan Region, Iraq. Methods:A factorial randomized complete block design (RCBD) with two factors was conducted. The first factor was three irrigation periods (every 3, 6, and 9 days) and the second factor was three irrigation methods (surface irrigation, deep irrigation without wicks, and deep irrigation with wicks).Results:Results displayed that growth and biomass traits were significantly influenced by irrigation periods. Saplings watered every three and six days revealed greater growth, biomass, and relative water content compared to those watered every nine days, which showed growth reduction due to drought. Irrigation methods showed that stem growth and root biomass were improved under surface irrigation, whereas leaf mass ratio enhanced under deep irrigation with wicks. Different nutrient uptake patterns were observed among treatments. The highest nitrogen content was under less frequent (9 day) deep irrigation without wicks, the best phosphorus content was under moderate (6 day) surface irrigation, and potassium under more frequent (3 days) wick irrigation. Physiological traits revealed that protein content, chlorophyll content, and water-use efficiency improved under moderate and less irrigation frequency (6–9 days), while relative water content enhanced under more frequent irrigation (3 days). Irrigation techniques revealed that protein content and relative water content declined under subsurface irrigation with wicks. Conclusion:The results showed that using surface or deep non-wick irrigation every six days maximizes water savings without compromising sapling development and nutrient efficiency. The findings enhanced knowledge about irrigation management for afforestation and reforestation programs in semi-arid regions.