Effects of Biochar on Paddy Soil Fertility Under Different Water Management Modes

In order to ascertain the effects of biochar on paddy soil fertility under different water management modes, two types of biochar as rice straw biochar (RSC) and rice husk biochar (RHC) were applied into two types of paddy soils, sandy loam (soil I) and silty loam (soil II). Five biochar application rates as 0 (CK), 5 (C1), 10 (C2), 20 (C3), and 50 (C4) g kg−1 were used under three water management modes, i.e., flooded irrigation (FI), intermittent irrigation (II), and wet irrigation (WI); all treatments are incubated for 60 days. The biochar application increased soil water holding capacity (WHC) (0.88–47.93%), pH (− 0.03–1.61 units), cation exchange capacity (CEC) (0.1–3.4 cmol kg−1), soil organic matter (SOM) (2.35–229.31%), total nitrogen (TN) (4.88–86.84%), available phosphorus (P) (0–171.74%), and potassium (K) (0.25–14.47 times). The increased nutrient content of soil I was higher than that of soil II, and the increase by RSC was significantly greater than that by RHC. In addition, the II mode or WI mode was more beneficial to increase soil pH, available P, and CEC. The water management modes, biochar types, and its dosage, as well as soil type and their interaction, had remarkable effects on soil improvement of paddy soil fertility. The study showed that biochar applied under intermittent and wet irrigation modes offers a good potential for the improvement of paddy soil fertility than flooding irrigation mode.