Biochar application to temperate soils: effects on nutrient uptake and crop yield under field conditions

The benefits of biochar (BC) application to fertile, non-acidic soils in temperate climate regions might not always be as evident as for highly weathered tropical soils. The aim of our study was to investigate the effects of BC on soil characteristics, nutrient uptake and crop yield in field experiments on two temperate soils (Cambisol and Chernozem) in Austria. Maize and wheat (Cambisol), and barley and sunflower (Chernozem) were grown in successive vegetation periods following different BC application rates (0, 24 and 72 t ha(-1) at the start of the experiment), supplemented with identical mineral N supply in 33 m(2) plots. BC treatments showed varying impacts on nutrient uptake of the investigated crops. The first growing season in the Chernozem region was affected by a prolonged drought period, which resulted in positive effects of BC on soil water-holding capacity (WHC) and barley crop yield (+ 10%) for the 72 t ha(-1) BC + N treatment compared to a control with identical nutrient supply but without BC. However, maize and wheat grain yield decreased by 46 and 70%, respectively, after the highest BC application rate (72 t ha(-1)) in an additional treatment without supplementary N-fertilisation. Still, even with high BC application rates we did not observe any adverse effects on crop yield and nutrient uptake, as long as the soil was supplied with sufficient N according to local agricultural practice.