Object of investigation – Svetus river basin. The purpose of reasearch – 1) to estimame the nurture of phytomass qantity in Svetus river basin, 2) to estimame formerly and newly formed plant community‘s botanic composition, it‘s change in diferent year seasons, and source of chage, 3) to estimame eatability do dominating grass, 4) to provide thr utilization of phytomass. The reasearch was carry out during the period 2003 – 2004. The method of reasearch – the phytomass was estimated by dry digging 50x50x20 monolith. The distance between two monolith –about 100 m., and it is about 30m from river centre. 24 monolith was digged every year (48 at all), which underground part of phytomass was taken from roots. The roots was washed, all plant parts was dryed and waighed (the weatherdry biomass was estimated). Over the period 2003-2004 the biggest amount of phytomass was in natural plant community (haying and grazing) – about 1503,5g/m2 (dry). In newly formed plant community, during 2 year period, the phytomass quantity was twice less than in formerly formed meadow plant community. The growing grass eatability in reasearched plant community was 6 points. The area of Svetus river basin – 36 ha. According two years informatikon, the increase of phytomass sutable for cattles was 118,98 t. The most sutable for second breedng.