Within the territory of Latvia, grass biomass currently is considered to be one of the alternative sources for pellet production in the Baltic region and Northern Europe. The examined energy crops are characteristic with the persistence to the local climatic conditions and high biomass yield from 1 ha. The field trial was carried out during 2011-2013 in the research and study farm "Pēterlauki" (56º53'N, 23º71'E) of the Latvia University of Agriculture, in sod calcareous soils pH KCl 6.7,

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... ing available for plants P -52 mg·kg -1 , K -128 mg·kg -1 , organic matter content 21 to 25 g·kg -1 in the soil. The field test fertiliser norms applied were the following (kg ha -1 ): N 0 P 0 K 0 (control), P 2 O 5 -80, K 2 0 -120 (F -background), F + N 30 , F + N 60 , F+N 90 . Research objects: reed canary grass (Phalaris arundinacea L.), festulolium (× Festulolium Asch. & Graebn.), tall fescue (Festuca arundinacea Schreb.) and timothy (Phleum pratense L.) are perennials yielding for 8 -10 years, plant length up to 1.5 m. The sulphur content in the energy crops was 0.10 ± 0.01 %. The sulphur content in reed canary grass, festulolium, tall fescue and timothy was dependent (p < 0.005) on the growing year and the nitrogen fertilizer rate, and on the interaction between the growing year and nitrogen additional fertiliser contribution amount. That means that the air temperature and the amount of precipitation during the plant growth period are of great importance.