Contribution of on-farm and industrial composts to soil pH and enrichment in available nutrients and metals

Soil composition following addition of on-farm manure composts should be investigated for better utilization of these products in the field. An experiment was conducted to evaluate the contribution of several on-farm and industrial composts to soil pH and its enrichment in available major nutrients and metals (Cu, Zn, Fe, Mn). Materials were mixed at a rate of 200 mg N kg-1 with an Arago sandy loam (Humo-Ferric Podzol), and incubated in glass jars at 35°C for 13 wk. Composts from poultry litter (PL), vegetable residue (VR), wood shavings and dairy manure were among those that provided the highest levels of available N and P at the end of incubation. The vegetable residue compost also substantially increased the levels of Mehlich-3 Ca and Mg, but it was a poor source of K. Most dairy manure composts (DM) contributed to increase the soil exchangeable K. The industrial yard trimming compost (YT) largely increased soil pH and available N and Ca, but it was a very poor source of P and K. The spent mushroom compost (MU) also increased soil pH and Mehlich-3 Ca. In contrast to the major nutrients, on-farm composts had a limited impact on soil pH and on the available metal contents. This study indicates that the enrichment in major nutrients and metals of this acidic sandy loam and the relative contribution of the studied elements were mainly related to composted material sources and their degree of decomposition. Key words: Composting, farm manure, soil composition