Soil water balance and wettability methods in soil treated with biochar and/or compost

Abstract

AbstractThe impacts of biochar application in combination with compost on soil hydrological conditions such as infiltration, water-storage capacity, and methods of soil wettability, are not well understood. The aim of this study was to fill this knowledge gap and propose the best composition proportion of compost and/or biochar to improve sand soil water balance. For this purpose, we examined three different mixtures of sand and compost and six different mixtures of sand, compost, and biochar with respect to their wettability and water infiltration using tree methods, (I) Water Droplet Penetration Time Test (WDPT test), (II) Wilhelmy Plate Method (WPM) and (III) Capillary Rise Method (CRM) applied at different soil water potential (pF) levels. The different mixtures were characterized by texture, bulk density, field capacity, and soil water holding capacity through measurement of the water content of soil columns. Increasing biochar plus compost or compost alone had contributed to increasing the soil water holding capacity and water available content. The best composition with the highest water storage capacity, plant-available water, and wettability was: 0.6% of biochar, 5.4% soil organic matter (SOM), and 93.99% of sand. According to the WDPT test, the increased content of biochar contributed to improving the soil wettability, this test was preferred since 1) WDPT appeared to allow the best estimates of wetting behavior of the different mixtures, 2) the column samples were the least disturbed, and 3) the test was particularly feasible at different water content levels. However, WDPT was strongly dependent on the conductor of the experiment and the accurate measurement of short infiltration times (0s - 2s) proved challenging. The WDPT results indicate that biochar might enhance the infiltration capacity under natural conditions and the combined results indicate that biochar-compost-applications are not expected to cause ecologically critical hydrophobicity or a critical lowering of the sandy soil infiltration capacity. Graphical abstract