EFFECT OF IRRIGATION AND INCREASED POTASSIUM SUPPLY ON THE YIELD AND NUTRITIVE COMPOSITION OF CARROT

As yields are already at a quite high level in the European vegetable industry, nowadays the main emphasis is on the nutritive value of the vegetable products. Our objective was to investigate the effects of irrigation and increased potassium supply on the nutritive composition and yield of carrot. The experiment was conducted in 2010 in central Hungary on a sandy soil. Sprinkler irrigated stand and rainfed control, and potassium supply of 150 and 300 kg K₂O ha^-1 were compared. Dry matter, fructose, glucose, saccharose, six different carotenes, polyphenol and nitrate concentrations were measured as nutritive constituents. Because of the unusually high amount of precipitation just three irrigations were necessary to apply with a total amount of 69 mm during a rainless period in July. Irrigation has significantly increased the marketable carrot root yield (by 59%, 108 t ha^-1 opposed to 68 t ha^-1), due to higher average root weight (124 g opposed to 79 g). Contents of nutritive components were not negatively affected by the irrigation. Moreover, dry matter, α-carotene and nitrate contents were significantly better for the irrigated treatment. This result can be explained by the fact that during the last two months of the experiment the water supply was the same for every treatment through the natural precipitation, but in July at the beginning of photosynthate accumulation water supply was higher in the irrigated stand. The similar nutrient content and the higher root yield resulted in significantly higher nutrient yield in case of every investigated nutritive compound. Potassium supply of 300 kg K₂O ha^-1 did not improve the yield and the nutritive value compared to the 150 kg K₂O ha^-1 rate.