Phosphorus Fractions in Maize (Zea mays L.) Plants As Affected By Phosphorus and Zinc Sulfate Application.

Long-term phosphorus application on carbonate chernozem soil in legumes-winter wheat-maize-sunflower cropping system induced zinc deficiency in maize (Zea mays L.). Plants exhibited chlorosis, stunted growth due to shortening of stem internodes and decreased in leaf area. A field experiment with zinc sulfate supplements was conducted to study phosphorus fractions in maize plants during years 13 through 15 of systematic application of mineral fertilizers (No fertilizer control, P60, N60K60, N60P60K60, N90P60K60 and N60P90K60) to carbonate chernozem soil. Zinc treatments for three years were P60Zn10, N60P60K60Zn5, N90P60K60Zn5 and N60P90K60Zn10 on half of each long term treatment. The soil at the experiment site was a chernozem, containing: humus 4.3%, total nitrogen 0.29%, CaCO3 1.7%, plant available phosphorus and potassium averaging 0.88 and 34.5 mg/100 g respectively, extractable cations Ca2+ and Mg2+ 31 and 2.9 meq/100g respectively, with pHH2O value of 7.9 at the 0-20 cm soil depth. The results revealed that the zinc deficiency plants led to higher concentration of inorganic phosphorus in leaves and stems of maize, whereas concentration of sugar phosphorus + phytin, nucleoproteins, and phosphatides phosphorus were not largely changed at the 8-10 leaves stage. However, zinc treatment increased accumulation of inorganic phosphorus averaging from 36.2 to 60.6, as well as sugar phosphates + phytin from 11.8 to 40.4, nucleoproteins from 8.2 to 28.6 and phosphatides phosphorus from 4.9 to 15.3 mg plant-1 in leaves and inorganic phosphorus from 24.2 to 50.6, sugar phosphates + phytin from 7.6 to 37, nucleoproteins from 6.6 to 30.5 and phosphatides phosphorus from 3.1 to 13.1 mg plant-1 dry weight in stems at the 8-10 leaves stage compared to no zinc application (P60, P60Zn10). The observed accumulation of phosphorus fractions in leaves and stems related to the higher zinc accumulation in maize leaves. High positive linear correlations were observed between total zinc content in leaves and accumulation of organic form of phosphorus fractions in leaves of maize. Hence, maize grown on carbonate chernozem under long term phosphorus application increased the demand for zinc fertilization. Therefore, combined application of macro- and microelements to carbonate chernozem is important to improve maize phosphorus metabolism. *The results were obtained in Moldavian Scientific-Research Institute of Soil Science and Agricultural Chemistry, Chisinau, Moldova.