Effects of soil water matric potential (SWMP) on growth, yield and quality of two potato cultivars

Two field experiments were carried out during the summer seasons of 2003 and 2004. the objective of this study was to investigate the effects of soil water matric potential (swmp) treatments (-35, -45, -55, -65 and -75 jkg^-1) on vegetative growth, yield and quality of the two potato cultivars diamont and draga. the obtained results of the two seasons showed that irrigation at - 55 j.kg^-1 was superior and significantly increased plant height, leaf area, foliage fresh and dry weights, average tuber weight and tuber yield compared with the other four swmp treatments. results also showed that the lowest swmp (-75 jkg^-1) decreased the previously mentioned parameters more than the highest one (-35 jkg^-1). dry matter, starch and specific gravity of tubers increased significantly,as the swmp treatments decreased, while total sugars decreased by increasing swmp. there were some insignificant differences in nitrogen, phosphorus and potassium contents due to swmp treatments. the cultivar diamont showed higher weight and total tuber yield compared with draga cultivar. tubers’ quality;in terms of dry matter, starch, total sugars and nitrogen contents appeared significantly better for diamont than draga. the greatest response in terms of vegetative growth, yield and quality of potato were obtained when diamont cultivar was irrigated at -55 j.kg^-1 swmp.