Amongst the agrochemicals, fertilizers have been the most frequently applied through microirrigation systems (fertigation). Although the method has been developed to a high technical level, there is yet a lack of information concerning the optimum timing and the doses under multiple fertilizer applications. The subject of the present article is the fertilizers' fate in the root zone and the raspberry plants' nutritional status between the fertigation events, under three levels of drip water supply-100%, 75%, and 50% of the estimated crop evapotranspiration. The study was based on laboratory analyses of soil, soil solution and plant samples. It was found that fertigation maintained constant and sufficient concentrations of N, P, and K in the soil providing optimum mineral nutrition for the raspberry plants. Proper irrigation and fertigation management could successfully retain the fertilizers in the root zone, thus preventing losses and eventual pollution of soil and groundwater.

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Raspberry descends to plains occupying more and more territory. There, however, plants have to cope with unfavorable climatic conditions. This necessitates technological improvements and additional investments, e.g. for irrigation. The aim of this publication is to evaluate the economic efficiency of the technology for raspberry production in lowland conditions. The study was carried out in the course of eleven years with the 'Lyulin' primocane-fruiting cultivar and spanned the whole life of the plantation. During the main phenological phases-intensive growth, blossom, and fruiting-water was applied in amounts equaling to 100%, 75% and 50% of crop evapotranspiration, respectively. Fertilizers were applied through the irrigation system, the fertilization rate being equal for all treatments. A costs and returns balance was applied for establishing the economic efficiency of the studied variants at exchange rates: 1.95583 BGN for 1.00 EURO and 1.47 BGN for 1.00 USD. The raspberry fruit production is not profitable with a price of 1.50 BGN per kilo. Prices of 2.00 BGN kg-1 and higher provide very good profitability. With a price of 2.00 BGN kg-1 , the costs are paid back during the fourth vegetation, and with prices of 2.50 BGN kg-1 and 3.00 BGN kg-1 during the third vegetation. When growing the 'Lyulin' primocane-fruiting cultivar in lowland conditions the irrigation rates may be decreased by 25% in a particular phenophase without a negative effect on the yield and the economic effectiveness. During the intensive growth phase the reduction may be even by 50%. Under the conditions of a severe water shortage, irrigation may be realized with half of the recommended application rates, on behalf of a quite acceptable decrease in the economical results. When the daily yield drops below 50 kg ha-1 , the profit decreases to values that stultify further harvestings.

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