[Effects of biochar application on the vertical transport of NO(3-)-N in the red soil and its simulation].

Soil column experiments in laboratory were conducted to determine the effect of biochar application on the vertical transport of NO(3-)-N in red soil. Biochar was mixed thoroughly with soil at rates of 0, 5, 10, 20, 30 and 40 t · hm(-2), i. e., biochar/soil ratios of 0, 2.22%, 4.459%, 8.95%, 13.37% and 17.80%. The CXTFIT 2.0 model was used to simulate the breakthrough curve of NO(3-)-N. The results were as follows: the breakthrough curve of NO(3-)-N varied remarkably with the increase of biochar application rate under saturated condition. The peak values of relative concentration (C/Co) , leaching rate and cumulative loss of NO(3-)-N all significantly decreased with the increasing biochar application rate. There existed a certain prolongation of the breakthrough curves among all treatments. The more the biochar was applied, the more obviously the break-through curve was prolonged. According to the correlation analysis between the NO(3-)-N break-through curves and soil properties, biochar affected the bulk density, organic carbon, total porosity, CEC of red soil, which would exert an effect on the breakthrough curves. The simulation value and the actual obtained value of the breakthrough curves were positively correlated with the correlation coefficients being over 0. 850 in all breakthrough curves, which indicated the CXTFIT 2.0 model could best fit the prediction of nitrate-N transport and relative infiltration. These results could provide a scientific basis for predicting the effect of biochar on nitrate-N in underground water after biochar incorporation into field.

[Effects of combined application of biochar and inorganic fertilizers on the available phosphorus content of upland red soil].

Aiming at the low content of available phosphorus in upland red soil of Southern China, this paper studied the effects of combined application of biochar and inorganic fertilizers on the available phosphorus and organic carbon contents and the pH of this soil. With the combined application of biochar and inorganic fertilizers, the soil physical and chemical properties improved to different degrees. As compared with the control, the soil pH and the soil organic carbon and available phosphorus contents at different growth stages of oil rape after the combined application of biochar and inorganic fertilizers all had an improvement, with the increments at bolting stage, flowering stage, and ripening stage being 16%, 24% and 26%, 23%, 34% and 38%, and 100%, 191% and 317% , respectively. The soil pH and the soil organic carbon and available phosphorus contents were increased with the increasing amount of applied biochar. Under-the application of biochar, the soil available phosphorus had a significant correlation with the soil pH and soil organic carbon content. This study could provide scientific basis to improve the phosphorus deficiency and the physical and chemical properties of upland red soil.