Phosphorus is absorbed in the two forms of monovalent (H2PO4-) and bivalent (HPO42-) phosphate ion. \u00b7 The availability of phosphate ions is influenced by the pH of the , soil, resulting in the availability of monovalent phosphate ions at pH values of less than 7 and the availability of divalent phosphate ions at pH values of more than 7. The monovalent form is that which is mainly absorbed by plants (Salisbury and Ross, 1992).<\/p>\n\n\n\n
As in the case of nitrogen, understanding how plants ingest phosphorus is a determining factor in determining the nutrient needs of the plant.<\/strong><\/p>\n\n\n\n vine plants begin to actively ingest phosphorus 22 days after the , buds have grown, with the root stocks supplying much of the required phosphorus from the newly growing shoots.<\/p>\n\n\n\n The intake of phosphorus increases rapidly during the period of decline with a small amount coming from the reserves of the roots. In the 35 days before the overcrowding some quantities begin to move towards the roots in order to form the new stock of the plant. The content of phosphorus in the plant from percussion to harvest remains relatively stable.<\/p>\n\n\n\n After harvesting and for about 33 days the uptake of phosphorus continues with its storage levels at the roots rising. * In the 44 days preceding normal defoliation, phosphorus uptake increases , by increasing its levels in , leaves at , roots in the vine and trunk.<\/p>\n\n\n\n \u00b7 Two distinct periods of phosphorus absorption were found during the vegetative period, with the first extending from bud bud development to overcrowding and the second from harvesting to normal , defoliation with maximum absorption in the 44 days prior to defoliation (Conradie 1981). <\/p>\n\n\n\n Conradie (1981) examined the seasonal intake of potassium. He found that the potassium content of the vine plant did not change significantly during the first 22 days of bud growth.<\/p>\n\n\n\n * After this , period potassium intake increased until the end of the period of rapid growth of shoots (74 days).<\/p>\n\n\n\n In the period from the end of flowering to the percussion the plant recruited 49% the annual potassium requirements.<\/p>\n\n\n\n Between passing and harvesting the intake of potassium decreased and at the same time its distribution in the plant is as follows: the grapes (66.1%) , the torso (4.7%) , the roots (6.9%) , the clarinets (11.7%) and leaves (10.7%).<\/p>\n\n\n\n \u00b7 A second peak of potassium intake occurred in the 33 days following the , harvest but did not extend beyond this point.<\/p>\n\n\n\n Source<\/em><\/strong> :Cooperative Research Center for Viticulture 2006. <\/em><\/strong>Grapevine Nutrition Literature Review.<\/em><\/p>\n