The Effects of some Inorganic-, Synthetic- and Organic-Fertilizers on the Vegetative Growth and Iron Content in Pistachio cv. Ghazvini under Alkaline Conditions

In the current research, the effects of some organic fertilizers as fulvic and humic acids on the vegetative growth of pistachio seedlings in a semi-hydroponic culture containing Fe-EDDHA (as a synthetic fertilizer) and FeSO4 (as an inorganic fertilizer) were investigated. The alkalinity is recognized as a main problem in pistachio orchards, therefore the pH of nutrient solution was adjusted to 7.5 and 8.5 (as two alkaline pHs) versus 6.5 (as the optimum pH of hydroponics) in this study. Plants were treated for 9 months under greenhouse conditions. The results demonstrated that the organic fertilizers (especially humic acid) reduced plant growth in acidic condition (pH 6.5). It can be related to precipitation of humic acid under acidity and thereby removing some essential elements for instance Fe form plant growth medium. In contrast, humic substances increased plant growth up to 2.3 times under alkalinity. The analysis indicated that these organic-stimulants can improve plant growth under alkaline conditions by increasing Fe content to about 2 times in pistachio seedlings, especially in shoots. It was noted that this result was somewhat similar in plants grown in media containing Fe-EDDHA and FeSO4. In addition, environmental and economic importance of the application of humic and fulvic acids makes them proper candidates to substitute synthetic fertilizers for agricultural improvement under alkalinity.