Abstract:

Three biochar treatments of 0 kg/m², 3 kg/m² and 5 kg/m² were set as C₀, C₃ and C₅ under a drip irrigation with salinized water (5.1 g/L) to determine their effects on the particle composition of soil aggregates and on the extent of soil saline-alkality in comparison with a treatment of fresh water and no biochar as the control (D₀). With a continuous irrigation at the location for three years, the accumulation of mechanical soil aggregates with different sizes in the 20 cm deep soil, soil electrical conductivity (EC) and pH were investigated. The results showed that: (1) compared with fresh water, salty one tended to reduce the size of large aggregates, indicating the ratio of particle/size at 5-10, 3-5 and 2-3 mm in the C₀ treatment reduced by 10.12%, 19.06% and 5.78%, respectively, while that at 1-2, 0.5-1 and < 0.5 mm in the same treatment increased by 4.1%, 43.77% and 75.68%, respectively, in comparison with all those measurements in the D₀ treatment; (2) application of biochar promoted the formation of large aggregates at the ratio of particle/size over 0.5 mm, and more large soil aggregates accumulated in the deep soil with more biochar added; (3) the different ratio of particle/sizes of soil aggregates was negatively correlated with the soil EC; (4) biochar application was beneficial to reduce the soil EC in the 0-20 cm deep soil, and the soil EC value of each treatment showed C₀ > C₅ > C₃. In conclusion, the application of 3-5 kg/m² biochar under the salted water irrigation could promote the formation of large soil aggregates >0.5 mm and reduce the soil salinity in the 0-20 cm soil layer.

Key words: biochar, saline water, drip irrigation, soil aggregate, particle size composition, soil salinity