Synergistic effect of biochar and livestock manure on soil hydro-physical properties under field conditions in Rwanda

Biochar (B) in combination with organic manure could improve the biochar efficacity in improving soil functions related to hydrophysical properties. Short-term field experiments were conducted with three levels of B and livestock manure (LM) (0, 1, and 3 tons/hectare (t/ha)) to assess its effect on physical properties of soils such as bulk density (BD), soil porosity (SP) and aggregate stability (AS), along with soil hydro properties, including field capacity, permanent wilting point (PWP), Plant available water (PAW), and hydraulic conductivity (Ksat). Each treatment was replicated four times in a factorial randomised block design (RBD) using French beans as a test crop in sandy soils and sandy clay loam-textured soils in Rwanda. The data were analysed using analysis of variance (ANOVA) together with the Duncan test at P < 0.05 using R Studio. The findings demonstrated that the co-application of B and LM at varying application rates significantly (P < 0.05) reduced soil bulk density (BD), with the lowest BD observed at the highest application rate (3t/ha). Additionally, the results indicated that the combined application of B and LM at lower rates significantly affected soil water retention characteristics, including permanent wilting point (PWP), field capacity (FC), and saturated hydraulic conductivity (Ksat). The improvements in these properties became more pronounced with increasing B rates when mixed with LM. These results contribute to a better understanding of soil water dynamics following B and LM applications and suggest a promising approach to mitigating water loss, especially in sandy soils.