| Humic acid(HA)is an important agricultural means of agor-production.HA has many functions because it contains various functional groups such as carboxyl groups,phenolic hydroxyl groups,and guanidino groups.HA plays an important role in agroproduction,such as improving soil fertility,stimulating plant growth,enhancing crop resistance to stresses and increasing fertilizer efficiency.Its function and application in agriculture has been received extensive attention for many years in both China and the whole world.In the implementation of the “Zero-Growth Action Plan for Chemical Fertilizer Use”,the combined application of humic acid and fertilizer has important implications for promoting plant growth and nitrogen extraction,promoting phosphorus,stabilizing potassium,and reducing fertilizer use.However,the types of humic acid fertilizers are still mainly combined with conventional acidic fertilizers and humic acid,and the application of acid fertilizers on acidic soils is bound to produce acid superimposed hazards.However,there have been no reports of humic acid and alkaline fertilizers so far.Little is known about the effects of humic acid and alkaline fertilizers on tropical and subtropical(acidic soil)bananas.In this paper,the humic acid alkaline liquid fertilizer was used as the test fertilizer,and the humic acid-type conventional liquid fertilizer was used as the control to study the application effect and mechanism of alkaline humic acid fertilizer and humic acid concentration on the banana in a typical acidic region.It provides a theoretical basis for the application of humic acid alkaline fertilizers in the banana industry.The mian research results were as following.1)In the soil culture experiment,both the conventional and alkaline fertilizers,humic acid liquid compound fertilizer can significantly increase the plant height and leaf area of banana and promote its growth,in which the growth promoting effect of alkaline HALcomd is more obvious than that of conventional HALcomd.The plant height and leaf area of conventional HALcomd treatment increased by 8%~13% and 15%~16%,respectively,compared with the control.The height and leaf area of the banana treated with alkaline HALcomd increased by 12% compared with the control.19% and 16% to 19%.In the hydroponic banana test,it was found that when the humic acid concentration of the alkaline humic fertilizer was 5%,the growth of the banana was inhibited.2)The conventional HALcomd and the alkaline HALcomd can significantly increase the fresh weight of the ground and underground parts of bananas in the soil culture test.The fresh weight of the above ground and underground parts of the conventional HALcomd increased by 13%~19% and 29%~36%;the alkaline HALcomd treatment increased by 10%~21% and 6%~11%,respectively.In the hydroponics experiment,the above-ground fresh weight of 1% and 3% humic acid increased by 34% and 29%,respectively,compared with the control,while the above-ground fresh weight decreased by 37% and the humic acid concentration when the humic acid concentration was 5%.For the 1% and 3% treatments,the underground biomass increased by 54% and 63%,respectively,compared with the control,while it decreased by 30% when the humic acid concentration was 5%.3)When the conventional HALcomd and its humic acid content ranged from 1% to 5%,the total root length,total root surface area,and total volume of each treatment increased by 30% to 52% and 28% to 49%,respectively,compared to the control.26%~47%;the alkaline HALcomd with humic acid concentration of 1% and 3% increased total root length,total root surface area,total volume control by 24%~42%,45%~46%,54 %~83%,but the total root length,total root surface,and total volume of humic acid treated with 5% humic acid decreased by 38%,28%,and 30% compared to the control.It can be seen that when the humic acid content of conventional HALcomd increases from 1% to 5%,it can promote the growth of the root system,but the alkaline HALcomd increases the humic acid content from 1% to 3%.Can promote root growth and development,but inhibit root growth when the concentration is greater than 5%.4)Soil urease activity decreased with the increase of humic acid concentration in the humic acid-based conventional liquid fertilizer,and the urease activity in soil treated with humic acid decreased by 12% to 41%;however,the acid phosphatase activity in the humic acid-treated soil increased compared with the control 87~103%.The urease activity of soil treated with alkaline HALcomd was increased by 38%-64% compared with the control,and the activity of acid phosphatase was increased by 144%-163% compared with the control.The content of ammonium nitrogen in soil treated with conventional HALcomd increased by 40%~70% compared with the control,and the content of nitrate nitrogen increased by 30%~84%.The content of ammonium nitrogen in soil treated with conventional HALcomd was higher than that of conventional compound fertilizer.172%,the nitrate nitrogen content increased by 59%.The content of ammonium nitrogen in soil treated with alkaline HALcomd was increased by 105%~154% compared with the control,and the content of nitrate nitrogen was increased by 12%~23%.The content of available phosphorus in soil treated with conventional HALcomd was increased by 30%~77% compared with the control,while that of conventional liquid fertilizer treatment was increased by 46.38% compared with conventional compound fertilizer;the soil available for treatment with alkaline HALcomd The content increased by 38%~46% compared with the control,and the alkaline liquid fertilizer treatment was 1.42 times that of the conventional compound fertilizer.With the increase of humic acid concentration,the number of soil bacteria showed an increasing trend.The number of bacteria in soil treated with conventional HALcomd increased by 42% ~ 136% compared with the control,the number of fungi increased by 3% ~ 12%,and the number of actinomycetes increased.28% ~ 120%.The amount of soil bacteria treated with alkaline HALcomd increased by 16% ~ 960% compared with the control,the number of fungi increased by 293% ~ 5898%,actinomycetes increased by 21% ~ 100%.Application of humic acid can significantly increase soil fertility,improve soil microbial community,and provide a good environment for plant root growth. |
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