The Mineralization And Kinetic Characteristics Of Organic Carbon In Yellow Soil Under Long-term Fertilization At Different Temperatures

It is of great significance for the management of soil organic carbon to study the characteristics of organic carbon mineralization,active components and extracellular enzyme activity in yellow soil under different fertilization,and to understand the rate and direction of soil organic carbon.After 80 days of constant temperature culture?10?,15?and 20?,hereinafter referred to as T10,T15,T20?and variable temperature?10?,20??,using outdoor sampling and indoor culture,using alkali absorption method,?TC?the characteristics of organic carbon mineralization in long-term fertilized yellow soil drylands in Guizhou and the temperature sensitivity of organic carbon mineralization at different temperatures.Fertilization including non-fertilization?CK?,single fertilizer?NPK?,single organic fertilizer?M?and organic inorganic combined application of?MNPK?.The results show that:?1?In the culture of 80 days,the mineralization rate and cumulative mineralization amount of soil organic carbon increased with the increase of temperature,and gradually showed a steady trend at the later stage.Long-term fertilization in yellow soil showed that T20>T15>T10,which indicated that higher temperature was beneficial to mineralization of soil organic carbon,and it was significantly higher than that of T10?p<0.05?.The temperature-varying TC?except for single application of organic fertilizer M?showed constant temperature T15>variable temperature TC,and the difference was significant?p<0.05?.The effect of increasing temperature on the mineralization rate of soil?MNPK?organic carbon was the greatest,and it was significantly higher than that of inorganic fertilizer?NPK?and?CK?without fertilization.?2?Q₁₀?Temperature sensitivity?ranges from 2.45 to 3.93.Among different fertilization treatments,there was significant difference between organic-inorganic combination application of?MNPK?and single fertilizer?NPK?,and no fertilization of?CK?,and there was significant difference between single application of organic fertilizer?M?and non-fertilization of?CK?.There was no difference between the other two treatments?p<0.05?.The organic-inorganic combination application of?MNPK?was 1.60,1.38 times as much as that of?CK?without applying chemical fertilizer?NPK?,alone,and 1.51 times as much as that of non-fertilizing?CK?by applying organic fertilizer?M?alone.It is indicated that the combination of organic and inorganic application?MNPK?The mineralization rate of soil was significantly higher than that of inorganic fertilizer and unfertilized soil.The mineralization rate of single organic fertilizer was significantly higher than that of unfertilized soil under the influence of temperature.?3?Under the condition of constant temperature,the change of active component was not obvious,and the dynamic change was disturbed by temperature.Under constant temperature condition,the change of active component was higher at the initial stage,increased and decreased at the middle stage,and finally tended to a mild decline.At different temperatures,ROC was significantly correlated with SOM,and T15,TC culture temperature were significantly and extremely significant correlation with cumulative mineralized amount of T15,TC culture temperature,respectively,and there was a significant correlation between T15,TC culture temperature and accumulative mineralized amount,and there was a significant correlation between T15,TC culture temperature and cumulative mineralized amount.It is indicated that ROC,as an active component which is easy to use by microorganisms,is closely related to the mineralization of organic carbon.?4?The relationship between the accumulation and mineralization of soil organic carbon and the culture time was fitted,and the k value was 0.005⁰.054 d^-1.It does not accelerate with the increase of temperature,and is not similar to C0 trend,which may be related to the substrate and parent material type that microorganisms can use in the process of soil carbon mineralization.?5?Soil extracellular enzymes generally showed a great downward trend after culture.There was a significant correlation between soil extracellular enzymes and soil physical and chemical properties,organic carbon mineralization index,and significant correlation between SOM,CBH and NAG,and between CBH and SOM at T10 and T15,respectively.There is a negative correlation between AP and total phosphorus and fast phosphorus,as well as a negative correlation between ROC and cumulative mineralization amount and mineralization index.The results indicated that soil extracellular enzymes could indicate the change characteristics of microbial activity before and after culture.In conclusion,the mineralization rate of soil organic carbon increases with the increase of temperature,and the mineralization ability of soil can be significantly improved by applying organic fertilizer.Under the condition of variable temperature,the characteristic law of change is not obvious,and the disturbance of temperature is greater.The changes of active components and extracellular enzymes were correlated with soil organic matter.