| Aiming at the problems of soil environmental quality deterioration caused by unscientific management measures in current agricultural production,this paper investigated the effects of continuous application of humic acid(HA),nitrogen(N)regulator,i.e.dicyandiamide(DCD),and its combination(AD)on soil chemical and biological properties,yield and nutrients use efficiency of wheat and maize.The objective was to provide theoretical basis and technical support for the green and high-efficient development of modern agriculture.The main research results were summarized as follows:(1)The application of N,phosphorus(P)and potassium(K)fertilizers significantly affected the soil fertility and its contribution on crop yield.Maize yield in the fifth season was decreased by 31.98%,27.18% and 25.71% in the treatment without N,P and K fertilization,respectively,compared with the first season.Besides,the contribution rate of soil N,P and K on maize yield was decreased by 3.24%,10.44% and 5.33%,respectively,and the soil nutrient supply rate was decreased by 24.59%,19.19% and 35.34%,respectively,compared with the first season as well.Moreover,wheat yield in the fourth season was decreased by 10.97%,11.84% and 9.69% in the treatment without N,P and K fertilization,respectively,the nutrient contribution rate was decreased by 8.02%,8.91%and 6.70%,respectively,and the soil nutrient supply rate was decreased by 14.03%,22.41% and 15.96%,respectively,compared with wheat in the second season.Therefore,it is important to enhance soil fertility by reasonable fertilization to obtain the high and stable yield.(2)The application of HA for 3 consecutive seasons had no obvious effect on the content of soil organic matter(SOM)in 0-20 cm soil layer.However,the content of SOM was significantly increased by 11.32%-13.05% after application of HA for 5 consecutive seasons.Furthermore,the enhancing effect of SOM was higher in the treatment with HA and DCD application in 0-40 cm soil layer,being 9.22%-28.49% higher compared with control treatment.Compared with the control,continuous application of HA and DCD for5 seasons could decrease soil nitrate-N content by 31.02%-38.17%,while increase the contents of available P and K by 22.35%-37.16% and 8.31%-22.82%,respectively.However,the effect on soil available K was not obvious when DCD was applied alone without combination with HA.(3)After continuous application of HA or DCD for 5 seasons,soil urease activity in the 0-40 cm soil layer was significantly reduced,and AD had the best effect by decreasing soil urease activity by 24.79%-69.80% compared with CK.The effects of combined application of HA and DCD were more obvious than those of single application of HA or DCD,i.e.the activities of sucrase,dehydrogenase,catalase and alkaline phosphatase in0-40 cm soil layer were increased by 46.88%-75.48%,52.57%-98.99%,12.39%-81.76%and 23.67%-33.05% compared with CK,respectively.(4)The application of HA had little effect on crop yield in the first season,while the effect of continuous application on increasing yield was obvious in the following seasons.Compared with control,the wheat yield in the fourth season was increased by 15.31%,and the maize yield in the fifth season was increased by 24.60%.The effect of DCD and its combination with HA on crop yield were both significant,and the combined application was better than the single application.The wheat yield in the fourth season and the maize yield in the fifth season were increased by 22.90% and 35.54%,respectively,compared with the control treatment.(5)The accumulative nutrients utilization rate,agronomic effect and partial productivity of N,P and K were also significantly increased by HA application,and the nutrient utilization rate of N,P and K after rotation for five seasons was increased by41.63%,58.04% and 48.82%,respectively.The agronomic efficiency of N,P and K as well as the partial productivity of fertilizer were all significantly increased after DCD application,but the effect on accumulative potassium utilization rate was not obvious.The synergistic effects of the combination of HA and DCD were also found.In conclusion,the application of HA or DCD significantly improved soil fertility,increased crop yield and nutrient utilization efficiency,especially when HA and DCD were applied together. |
PDF Full Text Request