| High input and low use efficiency of fertilizers is a common phenomenon during the cultivation process of sugarcane in southern China.Excessive application of chemical fertilizers,especially nitrogen fertilizers,often causes accelerated soil acidification in continuous cropping fields,constant decline in soil fertility and quality,as well as imbalances of soil microbial community structure and function.Moreover,a large amount of fertilizer nitrogen loss may cause anthropogenic emissions of greenhouse gases such as nitrous oxide and agricultural non-point source pollution.A large number of studies have shown that biochar is a soil amendment with broad application prospects.Biochar can be granulated with fertilizer at a certain ratio to produce biochar-based fertilizers,which combine with both advantages of biochar and fertilizer,potentially to be used for improving acidified soil,crop growth and yields.Therefore,the present study on improvement of the acidified soil from sugarcane field and growth regulation of the typical variety ROC22 in the sugarcane cultivating area was performed through the pot and field experiments.Aiming to evaluate the regulation effects of biochar and biochar-based fertilizer,the response characteristics of sugarcane seedlings growth physiology,carbon and nitrogen nutritions in root soil and soil enzyme activities were investigated under simulated reduction of nitrogen fertilization combined with biochar and biochar-based fertilizer treatment.The influences of chemical fertilizer application partially replaced with biochar-based fertilizer on sugarcane yield property,its root soil nutrient and soil microbial community composition were further investigated under the field farming condition.The results of this study showed as follows:1)The biochar and biochar-based fertilizer treatments resulted in a significant increase in plant height,biomass,chlorophyll and nitrogen balance index of sugarcane seedlings under simulated reduction of nitrogen fertilization.Compared with conventional application of nitrogen NT,the chlorophyll index in biochar treatments(NC1 and NC2)was increased by 16.92%and 12.10%,respectively(P<0.05,P>0.05),while the nitrogen balance index was accordingly increased by 11.50%and 11.23%(P>0.05,P>0.05).The biochar-based fertilizer treatments(NF1 and NF2)increased the chlorophyll index by 31.54%and 29.40%(P<0.05,P<0.05),and the nitrogen balance index by 49.82%and 41.76%(P<0.05,P<0.05),respectively.The biomass of sugarcane seedlings in treatments(NF1,NC1 and NC2)was increased by 11.87%,9.67%and26.90%(P>0.05),respectively.The combined application of biochar and biochar-based fertilizer treatments had a significant effect on regulating the root shoot ratio,root biomass and root surface area of sugarcane seedlings under the simulated condition of nitrogen fertilizer reduction.The analysis results of root soil of sugarcane seedlings showed that compared to conventional nitrogen application,the simulated nitrogen fertilizer reduction combined with biochar treatments increased soil p H by 0.42-0.68 and decreased the exchangeable aluminum content by30.29%-42.97%,while the content of soluble calcium and magnesium was significantly increased.Compared with the NT control,the content of TC and TN in the root soil was increased significantly by55.95%-114.77%and 4.84%-12.90%under the application of biochar treatment,respectively.While the content of soluble organic carbon and total nitrogen in the combined application of biochar and biochar-based fertilizer treatments was increased by 2.95%-25.35%and 4.91%-202.02%.Under the simulated experiment conditions of the present study,the reduction of nitrogen fertilization combined with a suitable amount of biochar and biochar-based fertilizer could improve the supply of carbon and nitrogen in the root soil of sugarcane seedlings,and suggested a certain effect on soil enzyme activities.2)The investigation result of sugarcane yield character in field showed that the partially replaced treatment of chemical fertilizer with biochar-based fertilizer increased sugarcane plant height,stem diameter,stem biomass and yield by 9.26%-14.82%,10.24%-11.49%,18.24%-24.71%,31.10%-31.80%,respectively,when compared with conventional fertilization.The result suggested that the appropriate amount of biochar-based fertilizer to partially replace chemical fertilizer may have the potential application for reducing fertilization and increasing yield during the first-year cultivation of sugarcane.The analysis result of sugarcane root layer soil showed that the TC and TN content in the biochar-based fertilizer treatments(NBF1 and NBF2)did not change significantly compared with the control,but the content of AN and AP was increased significantly by 2.27%-19.23%and24.31%-40.02%,respectively.Compared with the control,the NBF1treatment increased the content of NH4~+-N in root soil by 25.23%(P<0.05),and NBF2 increased the NO3~--N content significantly by191.60%(P<0.05).The result of high-throughput sequencing analysis of soil microbes showed that there was a significant difference in the diversity and community structure of soil bacteria and fungi in the field sugarcane root layer when treated by partially replacing chemical fertilizer with biochar-based fertilizer.The main environmental factors affecting soil microbial diversity and community structure may be due to p H,AN content and C/N ratio of the root layer soil from sugarcane field. |
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