圆叶决明添加量对红壤可溶性氮及酶活性的影响

为了探明圆叶决明(Chamaecrista rotundifolia)降解后红壤可溶性氮及氮水解酶活性的变化规律，本研究采用室内好气恒湿培养法，研究占红壤质量0.5%(T1)，1%(T2)和2%(T3)的圆叶决明添加至红壤中，培养7~88d内红壤硝态氮(NO^-₃-N)、铵态氮(NH⁺₄-N)和可溶性有机氮(Soluble organic nitrogen，SON)及脲酶、蛋白酶和天冬酰胺酶的变化。结果表明：添加圆叶决明后，红壤NO^-₃-N和NH⁺₄-N含量在培养前期降低，培养中期增加；而整个培养期SON含量及脲酶、蛋白酶和天冬酰胺酶活性均增加，且圆叶决明添加量越大，效果越显著。NO^-₃-N和SON含量及脲酶、蛋白酶和天冬酰胺酶活性可用2次或3次函数方程拟合；而NH⁺₄-N含量可用线性函数拟合。氮水解酶与NO^-₃-N负相关，与NH⁺₄-N和SON正相关，且相关性从大到小的顺序为蛋白酶>天冬酰胺酶>脲酶。综上，添加圆叶决明提高了红壤供氮水平和红壤氮转化能力。

Effects of Additions of Chamaecrista rotundifolia on the Soluble Nitrogen and Enzyme Activity of red soil

To evaluate the changes of soluble nitrogen and nitrogen hydrolase activities during the decomposition of Chamaecrista rotundifolia in orchard Red soil,4 different rates (T0-T3) of C. rotundifolia dried biomass were added to orchard Red soil and left to decompose for 7-88 days，the concentrations of NO^-₃-N,NH⁺₄-N,soluble organic nitrogen (SON) and urease,protease and asparaginase activities in soils were determined along this incubation experiment. The results showed that,the addition of dried biomass decreased NO^-₃-N and NH⁺₄-N concentrations in early stage,and increased in middle stage. The decomposition of C. rotundifolia dried biomass increased SON concentrations and urease,protease and asparaginase activities,and the greater amount of C. rotundifolia added,the more significant the effect on soluble nitrogen and nitrogen hydrolase activities. The NO^-₃-N and SON concentrations and urease,protease and asparaginase activities can be fitted by quadratic or cubic function equation,and NH⁺₄-N concentrations can be fitted by linear function equation. Nitrogen hydrolase was negatively correlated with NO^-₃-N,and positively correlated with NH⁺₄-N and SON;and the order of correlation was protease>asparaginase>urease. In conclusion,the addition of C. rotundifolia can improve the nitrogen supply and nitrogen transformation capacity of Red soil.