Sodininkystė ir daržininkystė - Sodininkystės ir daržininkystės institutas

yield, quality, nutrient balance, energy efficiency and profitability. Very early potatocrop was cultivated on the well-tamed soils rich with phosphorus and average rich withpotassium. Crop yield was higher in the plots where the complex fertilizers containingN, P, K and microelements were applied before planting, and lower in the plots fertilizedwith simple fertilizers containing either nitrogen or phosphorus, or potassium.Depending on the fertilization, the yield of tubers was decreasing in the following order:1) high rate of complex fertilizer Cropcare 10-10-20 N 120P 120K 240applied before planting,side-dressing with ammonium nitrate N 30rate during the growing period; 2) moderaterate of complex fertilizer Cropcare 10-10-20 N 90P 90K 120applied before planting; 3)simple fertilizers ammonium nitrate, simple super phosphate and potassium sulphateapplied before planting, the rate depended on the results of agrochemical testing of thesoil and it was N 113P 27K 117on the average.Spray-dressing (two times during the growing season) of potato crop with 0.2%solution of complex fertilizer Ferticare 14-11-25 containing nitrogen, phosphorus,potassium and microelements increased the tuber yield only once in three years, andthe increase was 4% only.All the fertilizers decreased the starch content in tubers and increased the totalamount of sugars and nitrates. The largest amounts of sugars and nitrates were found inthe variant with the highest nitrogen fertilization rate. The tubers of the crop fertilizedwith the simple fertilizers and additionally spray-dressed during the growing seasoncontained more of sugars and less solids.It is difficult to select the complex fertilizer best covering potato crop needs for thenitrogen, phosphorus and potassium. In this experiment the amount of nitrogen andpotassium supplied by the complex fertilizers matched the amount taken by the plants,but the overdose of phosphorus was 50-75 kg ha -1 . The potato crop fertilized with thesimple fertilizers at rates based on the results of agrochemical testing of soil receivedthe amounts of nitrogen and phosphorus almost adequate to the need, but the crop wasmissing even 60 kg ha -1 of potassium. This is a clear message that the potassium rates forthe very early potato crop should be revised.One third of the total energy used for production of potatoes was taken by thesimple fertilizers, and the high rate of the complex fertilizer has taken even a half of it.The best energy efficiency rate in the experiment was in the variant where the simplefertilizers were applied.In spite of the fact that the fertilization with the high rate of complex fertilizerincluding the side-dressing with the ammonium nitrate was 2.9 times more expensivethan the fertilization with the simple fertilizers, the gross profit was bigger when thevery early potato crop was fertilized with the high rate of complex fertilizers. It was 16%higher than in the variant fertilized with the moderate rate of complex fertilizer and35% higher than in the variant fertilized with the simple fertilizers.Key words: potato, complex fertilizers, simple fertilizers, leaf-feed fertilizers,quality of potato tubers.227