EFFECT OF ROCK PHOSPHATE AND SUPERPHOSPHATE APPLICATION WITH ORGANIC MANURES ON GROWTH, YIELD AND QUALITY OF POTATO (Solanum tuberosum L.)

Abstract

Two field experiments were carried out at El-Zahraa, Belqas, Dakahlia Governorate, Egypt, during the two summer seasons of 1997 and 1998 on potato cv. Diamant to evaluate the effect of rock phosphate application as a natural source of P in comparison with single super-phosphate (75 kg P2O5 for both sources) and four sources of fertilizers, i.e. farmyard manure, livestock manure, poultry manure and mineral fertilization in addition to their interactions on vegetative growth, tubers quality, total tuber yield and the concentrations of N, P and K (%) in both foliage and tubers.Results indicated that application with rock phosphate increased significantly both fresh and dry weight of foliage plant in the first season and average of tuber weight in both seasons. On the other hand, plant height, number of main stems / plant, total tuber yield ton/fed., tuber dry matter, starch content in tuber, content of N, P and K in foliage and tuber in both seasons were not affected by phosphorus sources (rock or super-phosphate).Mineral fertilization increased significantly plant height, tuber dry matter, content, N and K content in foliage in both seasons, while application of farmyard manure increased average of tuber weight in both seasons. Results also indicated that applying either farmyard manure or mineral fertilization increased significantly the total tuber yield in both seasons. The interaction between rock phosphate and farmyard manure increased total tuber yield and average tuber weight in both seasons.Generally, using rock phosphate, or super phosphate together with farmyard manure at the rate of 15 ton/fed. in addition to 180 Kg N + 96 kg P2O5/fed. increased total yield of tubers / fed., but economically application of rock phosphate would save a considerable amount of phosphate fertilizers and consequently would decrease the total costs/fed. as compared with super-phosphate fertilizer. In the meantime, the price of one ton of rock phosphate powder (Abo-Tartour rook 26-28.5% P2O5) evaluate between 90-110 L.E., whereas the price of one ton of super-phosphate is about 300 L.E. Moreover, application of rock phosphate together with organic manure may help in decreasing the pollution of environment.