Soil microbial community structure and enzymatic activity responses to nitrogen management and landscape positions in switchgrass (Panicum virgatum L.)

Abstract

Switchgrass (Panicum virgatum L.) is usually grown on marginal land for biofuel system, in which nitrogen (N) is an essential management practice, and landscape position is a key topographical factor in impacting the production. However, limited information is available regarding how the N application and landscape positions affect soil microbial communities and enzyme activities under switchgrass. Thus, the specific objective of this study was to evaluate the responses of N rate (high, 112 kg N/ha; medium, 56 kg N/ha; and low, 0 kg N/ha) and landscape positions (shoulder and footslope) on soil biological health under switchgrass field. Data showed that N addition significantly influenced carbon and N fractions. The hot water‐soluble organic carbon (HWC) and nitrogen (HWN) fractions were significantly higher at footslope position than the shoulder position. The amount of total phospholipid fatty acid (PLFA), total bacterial, actinomycetes, gram‐negative and gram‐positive bacteria, total fungi, arbuscular mycorrhizal (AM) fungi, and saprophytes PLFAs were highest with medium and high N rates and footslope position. The N addition increased total PLFAs in N fertilizer treatments, viz. medium (5,946 ng PLFA‐C/g soil) and high N rates (5,871 ng PLFA‐C/g soil). Microbial biomass carbon and nitrogen and enzyme activities (urease, β‐glucosidase, acid phosphatase and arylsulfatase) were significantly enhanced by N fertilization (medium and high N rates) compared to control (low N rates) under footslope position. The urease activity under medium (36.3 µmol N‐NH4+ g−1 soil hr−1) and high N rates (31.4 µmol N‐NH4+ g−1 soil hr−1) was 42.9% and 23.6% higher than low N rates, respectively. This study suggests that the application of medium N rate in footslope position to switchgrass can enhance the soil biological properties and hence can protect the environment from the excessive use of N fertilizer.

Long‐term nitrogen loading alleviates phosphorus limitation in terrestrial ecosystems

“…For example, arbuscular mycorrhizal fungi symbionts enhanced soil available P content, stimulated plant P absorption, and decreased the plant N:P ratio with N loading, which could help alleviate N‐induced P limitation over time (Mei, Yang, Zhang, Zhang, & Guo, 2019; Wang et al., 2018). However, it should be noted that responses of arbuscular mycorrhizae are ecosystem specific (Cusack et al., 2016; Sekaran, McCoy, Kumar, & Subramanian, 2019; Treseder, 2008; Wang et al., 2018), and that N loading typically decreases the abundance of arbuscular mycorrhizae (Treseder, 2004). As such, the potential of mycorrhizae to alleviate P limitation with N loading is still unclear.…”

Soil hydrological properties as influenced by long‐term nitrogen application and landscape positions under switchgrass seeded to a marginal cropland

“…Pearson's correlation coefficients between the soil physical, hydrological, and biological properties were determined using correlation (CORR) procedure in sas 9.4. Microbial biomass carbon and soil organic carbon values used for correlation were extracted from previous published studies (Sekaran, Mccoy, Kumar, & Subramanian, ) and (Lai et al, ), respectively, from the same experiment. Furthermore, principal component analysis (PCA) was employed to define the most significant and important soil properties influenced by varying N rates and landscape positions.…”

Evaluation of Organic Substrates and Microorganisms as Bio-Fertilisation Tool in Container Crop Production

“…The yield increase in DHA and β-GLU is largely due to the increased amount of nutrients in mineral forms derived from biological processes of fixation, solubilisation and mineralisation of the organic forms present in the substrates, coinciding with [3], who mentioned that substrates with higher vermicompost ratios contain more anions and cations forms compared than coconut fibre as substrate. On the other hand, [8] mentioned that the higher enzymatic activity could be explained in terms of a larger microbial population, which in addition to fixing atmospheric N and mineralisation and solubilisation of essential nutrients, metabolises amino acids, sugars, acids phytohormones and other compounds from the roots of plants and soil OM.…”

“…Enzymatic activity is also considered indicative of changes in soil quality that occur as a result of management practices and the biotic and abiotic factors to which it is subjected and is used to monitor microbial activity [7]. Enzymes are also indispensable in soil function because they play a vital role in organic matter decomposition and nutrient cycle transformation [8,9].…”