Nitrate Accumulation and Oxalate Formation in Spinach Plants (Spinacia oleracea, L.) as Affected by Nitrogen Fertilization levels and Iron Foliar Application.

Abstract

Two field experiments were organized at the Tag Elez Station Experimental Farm; Governorate of Dakahlya, during the two successive winter seasons of 2014-2015 and 2015-2016 using spinach plant (Spinacia oleracea, L. cv. Balady). Spinach seeds were sown on 2nd and 6th of December, seasons 2014 and 2015, respectively. Ten treatments were arranged in split plot design with 3 replicates to evaluate the combination effect of five levels of N-fertilizer {50, 75, 100, 125 and 150 %} from the recommended dose (RD) by the Ministry of Agric. and Soil Recl. (MASR) in the form of NH4 NO3 (33.5% N) as soil application in the presence and absence of Fe as foliar way FeSo4 (20%Fe) was used as a source of Fe at the rate of 300 ppm Fe. The obtained results indicated that: * A nitrogen fertilizer application at the rates of this survey significantly increased the average values of dry weigh, chlorophyll contents, N, P, K, Fe and VC in the leaves of spinach plant tell the rate of 100% RD. increasing the rate of N-fertilizer from 100% to 150% RD significantly decreased the mean values of all the aforementioned traits during both seasons of the experimentation. At any level of N-fertilization; foliar applied of Fe has been recorded a pronounced high effects on the average values of all parameters under the current study. * Increasing the rate of N-fertilization from 50 to 150%RD sharply and significantly increased the average value of nitrate and nitrite accumulation in spinach leaves, while such effect significantly decreased the activity of nitrate reductase enzyme in spinach plant. Moreover, foliar application of Fe in combination with any rate of N-fertilizer has been corrected this trend. * A favorable effect on oxalate formation in spinach leaves due to an addition of iron in foliar way combined with any level of N-fertilization as compared to the plants treated with the same levels of nitrogen in single form.