Foliar feeding to increase yield value and quality in strawberry ( Fragaria ananassa) under meteorological stresses

In formation of fruit quality, an application of bio-stimulants that can protect plants against external unfavorable factors and regulate specifically the plant growth, development and metabolism, is prospective, enabling full realization of the varietal potency. In this paper, the data are summarized on studying influence of meteorological conditions of the growing season and the growing factors on the yield and quality of strawberries grown in the southern Russia in 2006-2010. There are reported the results of using GUMI 20K fertilizer and growth regulators Mival-Agro, Stimolante 66f, Alga mix B Mg at the phases of stem extension, early flowering and ripening of berries to control yield formation and chemical composition of strawberries under extreme weather conditions. Due to application of tested preparations, in the varieties Cleary, Arosa, Marmolada the weight of a berry was by 0.7-2.2 g higher as compared to the control. That improves trade quality and ultimately has a positive effect on productivity. Joint use of growth regulators Mival-Agro and fertilizer GUMI 20K improves the quality according to the content of dry matter and sugars (by 7-10 %), organic acids (by 10-15 %), vitamin C (by 9-14 %), and P-active substances (by 3-12 %). It was found out that the use of growth regulators Stimolante 66f and Alga mix B Mg on the Marmolada plants contribute to increased resistance to late spring frosts occurred in 2009. The number of flowers exceeded the control by 9.1 %, and the number of berries was higher by 18.5 % with an average weight of a berry increased by 1.7 g. The berries also accumulated more soluble dry matters (9.0 %) and sugars (6.8 %), their acid content increased (1.0 %), but the synthesis of vitamin C and P-active substances slowed. A response of varieties to the treatments differed. In Arosa variety the similar treatments resulted in decrease of sugar content and acidity, but the concentration of biologically active substances increased as compared to the control. Thus, the application of fertilizers together with growth stimulants can reduce the impact of stresses, improving productivity, fruit quality and content of biologically active substances in strawberries.