长期施肥措施下土壤有机碳矿化特征研究

研究长期不同施肥措施下旱作农田土壤有机碳的矿化特征及其温度敏感性可为加深理解土壤碳循环过程提供理论依据。本文以半干旱黄土区粮-豆轮作体系为研究对象,通过两种不同温度(15℃和25℃)的室内培养试验,分析了长期不同施肥措施下土壤有机碳矿化的动力学特征及其温度敏感性。研究结果表明,土壤有机碳矿化速率在培养初期较高,之后缓慢下降。施肥措施和培养温度对土壤有机碳矿化均具有显著影响。与不施肥对照(CK)相比,在15℃培养条件下,长期单施磷肥(P)、氮磷配施(NP)和氮磷有机肥配施(NPM)处理的土壤有机碳累积矿化量(C_(min))分别增加41%、85%和89%,在25℃培养条件下,分别增加7%、46%和77%。另外,与CK处理相比,P、NP和NPM处理土壤有机碳矿化的温度敏感性(Q_(10))分别降低25%、21%和6%。施肥改变了土壤有机碳矿化的动力学参数,其改变程度与施肥种类和培养温度有关。与CK处理相比,在15℃培养条件下,P、NP和NPM处理的土壤潜在矿化有机碳量(C_p)分别增加29%、65%和48%;在25℃培养条件下,NP和NPM处理的C_p分别增加2%和21%,而P处理则减少36%。不同施肥处理土壤有机碳矿化速率常数(k)在15℃培养条件下变化较小,在25℃培养条件下则有较大幅度的增加。在25℃培养条件下,C_(min)和Cp随土壤有机碳和全氮含量的增加而显著增加。可见,长期施肥显著促进了半干旱黄土区粮-豆轮作体系土壤有机碳的矿化,减弱了土壤有机碳矿化的温度敏感性。

Mineralization characteristics of soil organic carbon under long-term fertilization management

Mineralization of soil organic carbon (SOC) is a vital link in carbon cycle in terrestrial ecosystems and has a significant effect on soil productivity and CO2 exchange in the soil-atmosphere system. Studies on the response of SOC mineralization and its temperature sensitivity to long-term fertilization could provide essential information for the understanding of SOC dynamics in semiarid agro-ecosystems. In this paper, we analyzed the characteristics of SOC mineralization for soils collected from legume-grain rotation systems with 27 years of application history of different fertilizers in the semiarid Loess Plateau of China. We also analyzed SOC mineralization sensitivity to temperature and its response to different fertilizations. The objective of the study was to build a deeper insight into how SOC mineralization responds to long-term fertilization in semiarid agro-ecosystems. The results showed that SOC mineralization rates were high at the initial stage and then slowly decreased at different temperature (15℃and 25℃) and fertilization treatments. Fertilization and cultivation temperature significantly influenced SOC mineralization. Compared with the no fertilization treatment (control), long-term application of phosphorus (P), combined nitrogen and phosphorus (NP), and combined nitrogen, phosphorus manure (NPM) increased cumulative mineralized SOC (Cmin) by 41%, 85%and 89%, respectively, at 15℃, and by 7%, 46%and 77%, respectively, and 25 ℃. Also compared with control, P, NP and NPM application conditions decreased SOC mineralization sensitivity to temperature by 25%, 21% and 6%, respectively. Long-term fertilization changed the parameters of SOC mineralization, which varied with fertilizer type and cultivation temperature. SOC mineralization potential (Cp) of P, NP and NPM treatments increased by 29%, 65%and 48%, respectively, compared with that of control at 15 ℃. However, at 25 ℃, Cp increased by 2% under NP condition, increased by 21% under NPM condition, and decreased by 36% under P treatment compared with that under control. SOC mineralization constant (k) varied slightly at 15 ℃, but greatly increased due to fertilization at 25 ℃. Additionally at 25 ℃, cumulative Cmin and Cp were enhanced positively with increasing of both SOC and soil total nitrogen content. But at 15 ℃, Cmin and Cp were barely positively correlated with SOC and soil nitrogen. In conclusion, long-term fertilization increased SOC mineralization in legume-grain rotation systems in semiarid Loess Plateau, and decreased SOC mineralization sensitivity to temperature.