Modeling Palouse hills to quantify moisture redistribution from the selective non-uniform application of biochar

Abstract. The Palouse is a highly fertile agriculture region in the Northwest United States. This region commonly deals with significant erosion due to a hilly topography causing low soil depth, low organic matter, and poor water retention in top 1/3 of the hills. These issues culminate in the Palouse region having a high degree of variability in crop yields throughout the region. Seeking a cost-effective solution to these problems, we examined the moisture redistribution by selectively applying biochar to only top 5% of the hillslopes. Change in hydraulic properties of Palouse Silt Loam soil from 5 ton/acre application of biochar (4% biochar by mass) was measured in our laboratory. The collected data was used into a mathematical model which simulated the moisture redistribution of a typical Palouse hill over 60 days from the end of rainy season. The model showed three primary effects of biochar application on the hillslope. First, biochar held more moisture closer to the surface than 100% soil especially drier part of the season. Second, biochar application only on hilltop showed an increase in moisture content over a wider width of the hillslope. Third, the application of biochar held less moisture in the center portion of the hillslope, hinting at moisture being pulled away from the hillslope center.