Preliminary results of studies on the effects of organic fertilization and mulching on the growth of one-year old European larch (Larix decidua Mill.) seedlings and occurrence of soil mites under micro-sprinkler irrigation in two sylvan-natural regions of Poland

The aim of the study was to determine the influence of organic fertilization and mulching on the seedling vigour of European larch (Larix decidua Mill.) and occurrence of soil mites (Acari) in forest- and post-arable soils. Two different nursery experiments were carried out in the vegetation period of the year 2005 on light soils at two sylvan-natural regions of Poland. The first trial was conducted at Białe Błota near Bydgoszcz – on a brown podzolic soil. The second experiment – at Lipnik near Stargard Szczeciński – on an acid brown soil. The higher was the rainfall amount during the vegetation period, the lower was the seasonal irrigation rate supplied to European larch seedlings. Because of this the seasonal irrigation water rate applied at Białe Błota was higher than that at Lipnik. European larch seedlings grown on the forest soil were characterized by the increased height and the fresh mass than those cultivated on the post-arable ground. Seedlings grown in the forest soil on treatments mulched with litter were characterized by the increased height and the fresh mass of above-ground parts as compared to those cultivated on control plots (without mulching). Mulching with litter increased the number of mites, especially oribatid mites, as well as their species diversity. It can be recognized as the result of the positive influence of the mulching on the biological properties of the studied soils.