The study assessed the effect of composted municipal sewage sludge on the wood yield of an experimental willow short rotation coppice (SRC) during the second harvest cycle. The mean values of BOD7, total N and total P met the legislative limits set to prevent groundwater pollution at the soil depth of 40 cm. We demonstrated that more productive plants of the first harvest cycle could lose that trait during the next. The second harvest cycle was more productive in terms of wood yield than the first for plants of both treatments. Sludge treated willows had significantly higher wood yield.
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We define a general framework of partition games for formulating two-player pebble games over finite structures. The framework we introduce includes as special cases the pebble games for finite-variable logics with and without counting. It also includes a matrix-equivalence game, introduced here, which characterises equivalence in the finite-variable fragments of the matrix-rank logic of [Dawar et al. 2009]. We show that one particular such game in our framework, which we call the invertible-map game, yields a family of polynomial-time approximations of graph isomorphism that is strictly stronger than the well-known Weisfeiler-Leman method. We show that the equivalence defined by this game is a refinement of the equivalence defined by each of the games for finite-variable logics.