Leachate Composition of Temperate Agricultural Soils in Response to Biochar Application

Buecker, J.; Kloss, Stefanie; Wimmer, B.; Rempt, F.; Zehetner, F.; Soja, G.

Leachate Composition of Temperate Agricultural Soils in Response to Biochar Application

2016

Biochar (BC) as a soil amendment has found considerable interest in global agriculture and food production. However, BC application to agricultural soils requires knowledge about side-effects on leachate composition potentially affecting deeper soil layers and groundwater. We investigated the effects of BC application on leachate water characteristics in a greenhouse pot experiment with two crops cultivated in series, mustard (Sinapis alba L., cv. Serval) and barley (Hordeum vulgare L., cv. Xanadu). The experiment was set up with three agricultural soils (Planosol, Cambisol, Chernozem), four different BC types, derived from three different feedstocks (wheat straw, woodchips, and vineyard pruning), added at two application rates of 1 % (w/w) and 3 % (w/w). Leachate sampling was performed five times from November 2010 to May 2011 by excess watering. The leachates were analyzed for their pH, electrical conductivity (EC), as well as their nitrate (NO₃ ⁻), dissolved phosphorus (PDISS), potassium (K⁺), and dissolved organic carbon (DOC) concentrations. The application of all BCs caused a significant pH increase in the leachates; EC increased most noticeably in the straw biochar treatment. All BC types significantly decreased leachate NO₃ ⁻ loads (by up to 80 % for woodchip-derived BC) compared to the control, while PDᵢₛₛ and K⁺ loads most significantly increased in the straw-derived BC treatment. The results show that BC may be suitable as soil amendment in soils prone to NO₃ ⁻ leaching; moreover, whereas straw-derived BC in particular may support soil nutrient status by introducing P and K.

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