Effect of Organic Manure, tuber weight and ascorbic acid spraying on some tubers chemical components of potato ( Solanum tuberosum L.) grown in sandy soil

Field experiment was conducted in AL-Najaf Governorate during the season of 2011 in two cultivations (spring and autumn) .The aim was to study the effect of different conc. of organic manure, different weights of tuber seeds and Ascorbic acid spraying on tuber content of N, P, K, total soluble solid and ascorbic acid on potato plant (Solanum tuberosum L.) cv. Proventa.The experiment included 24 treatments, i.e. the interactions of four levels of organic manure (0, 75,100 and 125 kg/furrow), three tuber weights at cultivation (big, medium and small) and two concentrations of ascorbic acid (0 and 150 mg/l., sprays were done twice during the season with 15 days interval, that was done on 45 days from cultivations.Factorial conducted with Randomized Complete Block Design (R. C. B. D.) was used with three replications.Means were statistically compared according to Duncan s Multiple Range test at probability of 0.05.Results indicated that the use of different levels of organic manure had significant effect on most of chemical parameters N, P, K, total soluble solids and amount of vitamin C content in tubers. 125 kg/furrow gave the highest means for the measured parameters for both cultivations compared with control treatment which gave the least values for these parameters. On the other hand, tuber size treatment had a significant effect on the most of chemical parameters that surpassed plants produced from big size tuber compared to that plant produced from small and medium tubers.Ascorbic acid spraying had significant effects on most of chemical parameters compared with plants with out spraying of ascorbic acid. The interactions among the three factors were showed presence of significant effects on the most of chemical studied parameters for both seasons.