A meta-analysis on biochar's effects on soil water properties - New insights and future research challenges

Abstract

Biochar can significantly alter water relations in soil and therefore, can play an important part in increasing theresilience of agricultural systems to drought conditions. To enable matching of biochar to soil constraints and ap-plication needs, a thorough understanding of the impact of biochar properties on relevant soil parameters is nec-essary. This meta-analysis of the available literature for thefirst time quantitatively assess the effect of not justbiochar application,but different biochar properties on the fullsets of key soilhydraulic parameters, i.e., the avail-able water content (AWC), saturated hydraulic conductivity (Ksat),field capacity (FC), permanent wilting point(PWP) and total porosity (TP). The review shows that biochar increased soil water retention and decreasedKsatin sandy soils and increased Ksatand hence decreased runoff in clayey soils. On average, regardless of soiltype, biochar application increased AWC (28.5%), FC (20.4%), PWP (16.7%) and TP (9.1%), while it reduced Ksat(38.7%) and BD (0.8%). Biochar was most effective in improving soil water properties in coarse-textured soilswith application rates between 30 and 70 t/ha. The key factors influencing biochar performance were particlesize, specific surface area and porosity indicating that both soil-biochar inter-particle and biochar intra-particlepores are important factors. To achieve optimum water relations in sandy soils (N60% sand andb20% clay), bio-char with a small particle size (b2mm)andhighspecific surface area and porosity should be applied. In clayeysoil (N50% clay),b30 t/ha of a high surface area biochar is ideal. Show more