Department of Agricultural and Environmental Sciences, Tennessee State University, Nashville, TN, 37209, USA.
Sichuan Provincial Academy of Natural Resource Sciences, Chengdu, 610015, Sichuan, China.
Sci Rep. 2020 Nov 12;10(1):19681. doi: 10.1038/s41598-020-76837-1.
Extracellular glycosidases in soil, produced by microorganisms, act as major agents for decomposing labile soil organic carbon (e.g., cellulose). Soil extracellular glycosidases are significantly affected by nitrogen (N) fertilization but fertilization effects on spatial distributions of soil glycosidases have not been well addressed. Whether the effects of N fertilization vary with bioenergy crop species also remains unclear. Based on a 3-year fertilization experiment in Middle Tennessee, USA, a total of 288 soil samples in topsoil (0-15 cm) were collected from two 15 m plots under three fertilization treatments in switchgrass (SG: Panicum virgatum L.) and gamagrass (GG: Tripsacum dactyloides L.) using a spatially explicit design. Four glycosidases, α-glucosidase (AG), β-glucosidase (BG), β-xylosidase (BX), cellobiohydrolase (CBH), and their sum associated with C acquisition (C) were quantified. The three fertilization treatments were no N input (NN), low N input (LN: 84 kg N ha year in urea) and high N input (HN: 168 kg N ha year in urea). The descriptive and geostatistical approaches were used to evaluate their central tendency and spatial heterogeneity. Results showed significant interactive effects of N fertilization and crop type on BX such that LN and HN significantly enhanced BX by 14% and 44% in SG, respectively. The significant effect of crop type was identified and glycosidase activities were 15-39% higher in GG than those in SG except AG. Within-plot variances of glycosidases appeared higher in SG than GG but little differed with N fertilization due to large plot-plot variation. Spatial patterns were generally more evident in LN or HN plots than NN plots for BG in SG and CBH in GG. This study suggested that N fertilization elevated central tendency and spatial heterogeneity of glycosidase activities in surficial soil horizons and these effects however varied with crop and enzyme types. Future studies need to focus on specific enzyme in certain bioenergy cropland soil when N fertilization effect is evaluated.
土壤中的细胞外糖苷酶由微生物产生，是分解易分解土壤有机碳（例如纤维素）的主要因素。土壤细胞外糖苷酶受氮（N）施肥的显著影响，但施肥对土壤糖苷酶空间分布的影响尚未得到很好的解决。N 施肥的影响是否因生物能源作物种类而异也不清楚。基于美国田纳西州中部的一项为期 3 年的施肥实验，从柳枝稷（SG：Panicum virgatum L.）和大刍草（GG：Tripsacum dactyloides L.）下的三个施肥处理的两个 15 m 小区中，总共采集了 288 个表层土壤（0-15 cm）土壤样本，使用空间显式设计。量化了四种糖苷酶，α-葡萄糖苷酶（AG）、β-葡萄糖苷酶（BG）、β-木糖苷酶（BX）、纤维二糖水解酶（CBH）及其与 C 获得相关的总和（C）。三种施肥处理分别为不施氮（NN）、低氮输入（LN：尿素中 84 kg N ha 年）和高氮输入（HN：尿素中 168 kg N ha 年）。使用描述性和地统计学方法来评估它们的集中趋势和空间异质性。结果表明，N 施肥和作物类型对 BX 有显著的交互作用，使得 LN 和 HN 分别使 SG 中的 BX 提高了 14%和 44%。确定了作物类型的显著影响，除了 AG 外，GG 中的糖苷酶活性比 SG 中的活性高 15-39%。SG 中，酶内变异高于 GG，但由于小区间差异较大，与 N 施肥差异不大。与 NN 小区相比，SG 中的 BG 和 GG 中的 CBH 在 LN 或 HN 小区中，空间模式通常更为明显。本研究表明，N 施肥提高了表层土壤中糖苷酶活性的集中趋势和空间异质性，但其影响因作物和酶类型而异。在评估 N 施肥的影响时，未来的研究需要关注特定生物能源农田土壤中的特定酶。
