The Effect of Green Manures and Nitrogen Fertilizer on some Characteristics of Quantity and Quality of Potato

This study was conducted during 2009 and 2010 to investigate the effect of green manure and nitrogen fertilizers on the yield, dry matter, starch, protein and reducing sugars content in potato. A split plot experiment based on a randomized complete block design with 3 replications was carried out. Green manures were applied at 5 levels (barley, canola, clover, vetch and without green manure) as main plot and nitrogen fertilizer were applied at 4 levels (100, 75, 50 and 25% of recommended) as sub-plot. The results for both years were statistically analyzed separately and also combined. Dry matter, starch, protein, reducing sugars percent and also potato tuber yield were affected by green manures and nitrogen manure levels. Also the interaction of treatments was significant on the yield, protein and reducing sugar percentage of potato tubers. The vetch green manure and 75% of recommended nitrogen was the best green manure. This treatment significantly increased dry matter and starch percentage of potato tuber by 22.3 and 12 percent, respectively. Also, the vetch green manure and 100% of recommended nitrogen increased protein percentage of tuber significantly; and the interaction of green manures and nitrogen fertilizer on the reducing sugars percentage was within the permissible limit. In terms of tuber yield per area unit, the interaction of clover with 75% of recommended nitrogen was the best treatment and resulted in a 33% increase in tuber yield. In addition, it decreased the amount of nitrogen consumption by 25%.