Long‐Term Biochar‐Based Amendments Enhance Soil Aggregation and Litter Decomposition in Low‐Input Cropping Systems

Although the addition of biochar has been shown to improve soil quality, previous studies have applied biochar at a far higher rate than is realistic for many resource‐poor farmers in the tropics. Thus, in order to be able to draw general conclusions, long‐term experiments are required that mimic low‐input cropping systems. This study aimed to determine the effect of continuous application of biochar‐based soil amendments in a low‐input cropping system on selected soil quality attributes, such as soil aggregation, labile carbon fractions, and litter decomposition rate. Different biochar‐based soil amendments, namely (i) lignocellulosic biochar, (ii) bone char, and (iii) a biochar and compost mixture, were applied continuously for 9 years at a rate of 4 t ha −1 y −1 . The effect of the biochar‐based soil amendments was then compared with the mineral fertilizer treatment and the control (i.e., without chemical fertilizers and organic amendments). Compared with the control, the biochar‐based soil amendments increased the mean weight diameter of soil aggregates (MWD) by 40%–70%, permanganate oxidized carbon (POXC) content by 45%–98%, particulate organic matter (POMC) content by 200%–300%, and microbial biomass carbon (MBC) content by 80%–180%. Similarly, the biochar‐based soil amendments increased MWD, POXC, POMC, and MBC contents compared with the mineral fertilizer treatment ( p < 0.001). This study demonstrates the benefits of applying biochar‐based soil amendments for a long period, despite their low application rate. Such long‐term experiments are crucial for sustainable environmental management because biochar remains in soils for centuries.