The effects of biochar addition on phosphorus transfer and water utilization efficiency in a vegetable field in Northeast China

The excessive application of fertilizer has become a serious problem for vegetable farming in China and aggravates agricultural non-point pollution. As a soil amendment, biochar has obtained worldwide attention. Irrigation and fertilization management also play an important role in controlling agricultural non-point pollution. To investigate the effects of biochar addition, irrigation and fertilization management on phosphorus (P) leaching as well as water utilization efficiency (WUE) in vegetable fields in northeast China, a field experiment with three treatments, i.e., regular fertilization and irrigation (CK), regular fertilization and irrigation with biochar addition (100WF+B) and 20% reduction of chemical fertilizers and irrigation compared to 100WF+B (80WF+B), was conducted. The P leaching amounts in 100WF+B and 80WF+B were only 15.91% and 11.36%, respectively, of that in CK. The P uptake amounts in the three treatments in descending order were 100WF+B, 80WF+B, and CK. The WUE in 100WF+B and 80WF+B were 15.3 and 25.2 kg/(ha mm) higher, respectively, than that in CK. There were no significant differences between the yield of CK and 80WF+B. The yield of 100WF+B was 3.4 t/ha higher than the yield of CK. Biochar significantly increased WUE, yield, TP (total phosphorus) and AP (available phosphorus) contents in the surface layer as well as P uptake and decreased P leaching when comparing 100WF+B to CK. Fertilization and irrigation reduction decreased P leaching and significantly increased WUE, but the yield was affected when comparing 80WF+B to 100WF+B. Biochar combined with fertilization and irrigation reduction significantly increased WUE and decreased P leaching without affecting yield when comparing 80WF+B to CK.