The effect of green manures and nitrogen fertilizer on some morphological characteristics and tuber yield of potato

In a two years research, during 2009 and 2010, the effect of green manures and nitrogen fertilizer on the number of stems and stolens, plant height and tuber yield of potato have been examined in the research field of Ehyayi. In this experiment, green manures were applied at 5 levels (barley, canola, clover, vetch and without green manure) as main factors and nitrogen fertilizer were applied at 4 levels (100, 75, 50 and 25% of recommended) as sub-factors in 3 replications in the form of randomized complete block design and as split plots; and the results for each year were statistically analyzed separately and also combined. According to the results of the combined analysis of all traits measured in the terms of the separate effects of green manures and nitrogen were highly significant. Interaction of factors tested in the first three traits at 1% and in the terms of potato tuber yield at 5% level were significance. Comparison of the interaction of green manure and nitrogen showed that the interaction of clover green manure with 100% of recommended nitrogen had the most effect on the number of stems per plant in comparison with control and it increased stem number per plant by 21.8%. In the terms of height per potato plant, the interaction of clover and vetch green manures with 100% of recommended nitrogen had the most effect on plant height and increased plant height mean by 17.6 and 17.4%, respectively; in comparison with the control. In the terms of the interaction of experimental factors on stolen number, clover green manure with 100% of recommended nitrogen was the best treatment and increased number of stolen per potato plant by 38% in comparison with the control and finally in the terms of tuber yield per unit area, the interaction of clover green manure with 75% of recommended nitrogen was the best treatment and it had significant difference at 1% with the control and it increased tuber yield by 33%. In addition, it decreased the amount of nitrogen consumption by 25%.