517 Effect of Planting Density and Plastic Soil Mulch on Strawberry Plant Development, Yield and Fruit Quality V. Laugale and L. Lepse Pūre Horticultural Research Centre Pūre, Tukuma nov. Latvia S. Strautina, I. Krasnova and D. Seglina Latvia State Institute of Fruit-Growing Dobele Latvia Keywords: Fragaria × ananassa Duch., cold stored plants, growth, productivity, chemical composition Abstract The present work was carried out in the Pūre Horticultural Research Centre, Latvia during 2008-2009. Cold stored strawberry plants of cultivars ‘Polka’, ‘Elsanta’ and ‘Honeoye’ were planted on two row beds with planting densities 3.3 and 6.6 plant m -2 . Beds were mulched by white plastic with black lower side (white on black) or unmulched. Split-split block design with four replicates was used for the experi- ment. Plants were evaluated for two growing seasons. The following features were evaluated: plant development, yield, fruit quality, biochemical composition and radical scavenging activity (ARA), susceptibility to gray mold (Botrytis cinerea Pers.). There was no difference in the plant development between two tested planting densities in the first growing year, but in the second growing year plants were weaker developed in the denser planting than in the sparser planting. In the first production year the marketable yield was for 127% higher in two times denser planting (6.6 plant m -2 ) than for planting density 3.3 plant m -2 . In the second growing year the obtained yield from double density planting was only for 32% higher than in sparser planting. Using of white plastic with black lower side mulch increased the yield and fruit size in both planting densities and reduced Botrytis incidence compared with the unmulched variant. Significant differences of fruit chemical content between straw- berry cultivars, planting densities and mulching were stated. Biochemical content and ARA were mostly influenced by genotype, and in less importance by cultural methods. INTRODUCTION Programmed “out-of-season” production of strawberries has become more important in several European countries (Lieten, 2002). Using of cold stored plants is the most important part in this production system. The interest on use of cold stored plants in strawberry production is increasing also in Latvia. Previous studies show that cold stored plants can be successfully used for obtaining of late yield on open fields (Laugale, 1998; Laugale and Bite, 2002). The higher planting density is preferable for obtaining higher yield in the planting year from smaller size cold stored plants. Usually farmers in Latvia are keeping strawberry fields for berry production for more than one year, even 3 or more years. The influence of denser planting on the productivity, fruit quality and spreading of gray mold in planting and further growing year were studied in this experiment. Mulching plays an essential role in soil moisture conservation, weed control, regulation of soil hydrothermal regime, besides keeping the delicate fruit neat and clean (Singh et al., 2009). According to Lieten (2002) black polyethylene mulch is preferred for the early plantings, from early April to late May, but white polyethylene is preferred for the plantings in June. There is a lack of investigations about using of different colors plastic mulch on strawberry in Latvia. White plastic with black lower side soil mulch was tested in our trial. MATERIALS AND METHODS Investigations were carried out at the Pūre Horticultural Research Centre (Pūre HRC) during 2008-2009. Cold stored A grade (average crown diameter 10.4 mm) Proc. XXVIII th IHC – International Berry Symposium Eds.: B. Mezzetti and P. Brás de Oliveira Acta Hort. 926, ISHS 2012