Recent years have been marked with a more common use of mineral fertilizers comprising marine algal extracts in horticultural production. Seaweed extracts are reported to possess, among others, biostimmulatory potential that improves yield growth and its quality as well as promotes plant resistance to adverse environmental agents. The marine alga processing technologies facilitate the extraction of active substances valuable for plant crops as stimulants for a number of plant physiological processes. The substances can be incorporated into both, soil or foliar applied fertilizers. The present research objective was to assess the influence of N Pro technology and Seactiv complex based on marine algal extracts on apple tree ‘Szampion’ growth, yield quantity and quality. The experimental material comprised ‘Szampion’ apple trees grafted on M.26 stock, the trees were aged 10 years at the experiment onset. The study aimed at evaluation of growth, yield quantity and quality of ‘Szampion’ apple trees fertilized according to two following programs. The measurements performed showed that introduction of the fertilization programs based on marine algal extracts had significant effect on total yield, one fruit weight, firmness and sugar extract content in apple tree ‘Szampion’ fruits. It was found that the N Pro technology and Seactiv complex had significantly beneficial influence on the percentage of big fruits, i.e. above 7.5 cm diameter and marketable yield in each experimental year. Cropping efficiency coefficient (CEC) of ‘Szampion’ apple trees fertilized according to N Pro technology and Seactiv base was significantly higher compared to control solely in 2008, in the other research years the differences were insignificant. The fertilization program based on marine algal extracts had positive influence on the ‘Szampion’ apple tree`s annual increments and each year the trees under N Pro and Seactive complex fertilization technology produced higher increments as against control; the differences in the last research year were significant. The N Pro technology and Seactiv base had positive impact on ‘Szampion’ apple tree leaf surface area, significant influence was observed in the second and third research year.

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