红壤旱地玉米开花期土壤酶活性对长期施肥的响应

【目的】长期施肥条件下，土壤酶活性与土壤养分周转和作物生长密切相关，因此，研究驱动土壤速效氮磷钾养分和作物养分吸收的关键土壤酶活性因子十分重要。【方法】基于始于1986年的红壤旱地长期施肥定位试验，于试验进行31年时的早玉米开花期 (2017年6月18日) 采集不施肥 (CK)、氮磷钾化肥 (NPK)、两倍氮磷钾化肥 (2NPK)、氮磷钾化肥配施有机肥 (NPKM)、单施有机肥 (OM) 5个处理的土壤样品，分析土壤蔗糖转化酶 (INV)、脱氢酶 (DEH)、纤维素酶 (CEL)、脲酶 (UR)、多酚氧化物酶 (PHOX)、酸性磷酸酶 (ACP) 和β-葡萄糖苷酶 (BG) 的变化规律，并利用冗余分析 (RDA) 探讨了驱动红壤旱地速效养分和玉米氮磷钾含量的关键土壤酶活性因子。【结果】与CK处理相比，施肥可以显著增加红壤旱地的土壤酶活性，且以NPKM处理的土壤酶活性最高。NPKM处理下INV、DEH、UR、PHOX、ACP和BG活性分别比OM处理增加了13.7%、13.5%、10.6%、10.5%、5.6%和13.4%，比2NPK处理增加了32.4%、112.2%、22.8%、33.3%、27.6%和50.4%。但是，在氮磷钾化肥用量之间，呈现出2NPK处理的CEL和UR活性显著高于NPK处理 (增幅为26.0%和50.6%)，而INV、DEH、PHOX、ACP和BG均无显著差异。土壤pH、有机碳、速效氮磷钾和植株氮磷钾含量也呈现出NPKM处理显著高于其他处理的规律。RDA结果表明，INV、CEL和UR是影响土壤速效氮磷钾和植株养分含量的关键酶活性因子 (R2 > 0.90， P < 0.001)。【结论】在红壤旱地上，玉米开花期土壤酶活性对不同施肥处理的响应规律不同，其中有机无机肥配施更有利于提高土壤酶活性，且纤维素酶和脲酶活性对氮磷钾化肥用量改变的响应比较敏感。土壤蔗糖转化酶、纤维素酶和脲酶可以作为关键酶活性因子表征玉米开花期红壤旱地的养分周转和迁移。

Response of soil enzyme activity in flowering stages of maize to long-term fertilization in red soil

【Objectives】Soil enzyme activity is closely related to soil nutrient turnover and crop growth, especially in long-term fertilization. It is important to study key soil enzyme activities which drive soil available nutrients and crop uptake.【Methods】Based on a long-term fertilization experiment in a red soil since 1986, which included treatments of CK (no fertilization), NPK (NPK fertilizers), 2NPK (double rates of NPK fertilizers), NPKM (NPK fertilizers and manure), OM (manure). After 31 years of fertilization treatments, soil samples were collected at the flowering stage of maize (18th, June, 2017), and soil sucrose invertase (INV), dehydrogenase (DEH), cellulase (CEL), urease (UR), polyphenol oxide (PHOX), acid phosphatase (ACP) and β-glucosidase (BG) were analyzed. Key soil enzyme activity indices were explored by redundancy analysis (RDA).【Results】The application of fertilizer improved soil enzyme activities. Compared to CK treatment, NPKM treatment was more beneficial to increase soil enzyme activity than OM, NPK and 2NPK treatments. Compared with OM, the activities of INV, DEH, UR, PHOX, ACP and BG of NPKM treatment were increased by 13.7%, 13.5%, 10.6%, 10.5%, 5.6% and 13.4%, respectively; they were all improved than 2NPK treatment by 32.4%, 112.2%, 22.8%, 33.3%, 27.6% and 50.4%, respectively. However, there was no significant difference between NPK and 2NPK, excepted for CEL and UR. Soil pH, organic carbon, available nutrient contents and plant nutrient uptake in NPKM treatment were significantly higher than those in other treatments. The result of RDA indicated that INV, CEL and UR were the key enzymatic indices affecting soil and plant nutrient contents (R2 > 0.90, P < 0.001).【Conclusions】In the red soil, soil enzyme activities in response to different fertilization treatments were different at the flowering stage of maize. Compared with the application of chemical fertilizers, or manure alone, combination of organic and inorganic fertilizers could increase soil enzyme activities. The response of CEL and UR were sensitive to rates of nitrogen, phosphorus and potassium fertilizers. Furthermore, INV, CEL and UR were key indices to indicate soil nutrient turnover and movement in red soil.