Study of different levels of nitrogen in decreasing boron toxicity on citrus seedlings in Haji-Abad.

Hormozgan province with 14.4 percentage of citrus cultivated is the fourth in Iran. Looking out attentive to cultivated area and suitable climate of the region, prosper that province citrus production from a particular position in country but unfortunately citrus production in Hormozgan because of some problems to respose in lower position (production average is 15 ton in hectare). One of this difficulties is boron high concentration in soil and water, therefore attentive to citrus sensitiveness to boron toxicity it is necessary to be accomplished essential actions. Application of nitrogen fertilizers is one of confrontation remedies with this problem. Researches have indicated consumption nitrogen decrease boron concentration in different plants. Therefore present research design arranged in a factorial manner in a randomized complete blocks design with six nitrogen levels ( 0. 50, 100, 150, 200 and 250 kg nitrogen in hectare) as ammonium solphate and four boron levels (0, 30, 60 and 90 kg boron in hectare) as boric acid with plantation two root stocks Bacraei and Suor orange (C. Aurantium) as source plants. This experiment was done in three replicates (two trees in each replication) in Haji-Abad agricultural research station. Measured plant responses sach as nitrogen and boron concentration in leaf after the end of the experiment. The results obtained in the study indicated that application of B in soil increased boron concentration in leaves of Bacraei and Suor orange. Furthermore, consumption of N decreased B concentration in plant such that application 100 and 150 kg nitrogen in hectare decreased significantly amount of B in Bacraei and Suor orange, respectively. In the same boron levels, B concentration in Suor orange root stocks were lower then leaves of Bacraei. Therefore Suor orange resistance to B high concentration in soil and water is higher then Bacraei because the lower amount of B absorbed in toxicity conditions. So the better making use of Suor orange as root stock when B amount was high in soil and water and as far as possible not used of Bacraei because it,s sensitivity to boron toxicity.