Two winter field experiments were carried out at the Agricultural Research Experiment Station, King Abdulaziz University, Hada-Alsham, Saudi Arabia, during the two years of 2007 and 2008, in order to assess the response of the two potato cultivars Diamont and Nicola to two rates of chicken manure (15 and 30 m3 ha.-1) as well as control treatment (without addition), three levels of mineral NPK fertilizer (200-100-100, 300-150-150 and 400-200-200 kg N-P2O5-K2O ha.-1) in addition to control (without application), and their combinations on vegetative growth, yield and its components, and chemical compositions characters of potato.
The obtained results indicated generally that the comparisons among the mean values of the studied vegetative growth, yield and chemical composition for each factor (main effects) appeared to be significant in most cases, during the two growing seasons. The results illustrated also that the cultivar Diamont gave the highest mean values of all studied characters, with few exceptions, in both seasons. An application of either organic manure at the rate of 15m3. ha.-1 or mineral NPK at the level of 300-150-150 kg.ha.-1 gave significantly the highest mean values of most studied vegetative growth, yield and its components and chemical compositions, during the two years.
The results concerning the first-order interaction indicated that the combination between cultivar Diamont and either of organic manure at the rate of 15m3 ha.-1 or mineral NPK fertilizer at the rate of 300-150-150 kg ha.-1, and the interaction effects between the treatment combination of organic manure and mineral NPK fertilizer at such rates, resulted in the highest significant mean values of the vegetative growth characters, most of the studied yield components and some of chemical compositions, in the two seasons.
The obtained results indicated also that the treatment combination of cultivar Diamont with organic manure at the rate of 15 m3 ha.-1 plus mineral NPK fertilizer at the level of 300-150-150 kg N-P2O5-K2O ha.-1, gave the best second-order interaction treatment for most studied vegetative growth, all potato yield and its component characters, and some of the chemical composition parameters, during the two growing seasons of the years 2007 and 2008.