Mulching has become increasingly common during recent decades not only in commercial horticulture. Mulching is especially important in organic farming. Crops are influenced by many factors when mulches are used. The field experiment was carried out in Aleksandras Stulginskis University (54º53'N, 23º50'E) in 2007–2009. The soil type – Calc(ar)i – Endohypogleyic Luvisol. Factor A – mulching: 1) without mulch; 2) straw; 3) peat; 4) sawdust; 5) grass. Factor B – thickness of mulch layer: 1) 5 cm; 2) 10 cm. The aim of this investigation was to evaluate the influence of organic mulches and different thickness of mulch layer on agrocenosis. The effect of grass mulch on vegetable agrocenosis was stronger compared with straw, peat and sawdust mulches. Mulching with 10 cm thickness of grass mulch layer had stronger effect compared with 5 cm thickness of grass mulch layer only at the 2^nd and 3^rd year of mulching. The condition of agrocenosis in plots without mulch declined and in plots mulched with 10 cm thickness of mulch layer improved.

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