ABSTRACT Temperature and moisture are widely recognised controls of soil microbial activity, yet the role of soil development in shaping microbial processes remains underexplored. Here, we used a factorial field design across two sites of differing elevation on the Banks Peninsula in Aotearoa New Zealand to disentangle the relative influences of site/environment versus parent material on soil microbial functioning. At each site, we selected soils derived from contrasting parent materials (basalt and loess) and measured a suite of soil physicochemical properties including elemental concentrations, pH and electrical conductivity, soil exchange complexes and C and N pools. We also measured soil biological properties including microbial biomass C and N, activities of eight extracellular enzymes, and the temperature response of microbial respiration. Both site and parent material strongly influenced physicochemical properties, creating distinct edaphic environments influencing microbial function. Microbial biomass and enzyme activities varied with site, parent material and season, reflecting interacting controls of nutrient availability, moisture and temperature. Extracellular enzyme activities were associated with indicators of soil chemistry and nutrient supply, particularly exchangeable Mg, acid‐oxalate‐extractable Fe, electrical conductivity and exchangeable Al, highlighting the importance of mineralogical and geochemical context in regulating microbial metabolism, rather than commonly assumed drivers such as pH, organic carbon or microbial biomass. In contrast, the temperature optimum of microbial respiration did not differ with soil chemistry, only with site, while the temperature inflexion point remained invariant, suggesting some aspects of microbial activity remain more constrained than others. Overall, our results demonstrate that soil microbial functioning emerges from interactions of multiple factors rather than any single driver; parent material indirectly regulates microbial processes through its influence on soil chemistry and mineralogy, while elevation, as a proxy for climate and/or management differences, modifies these effects. These findings underscore the need to integrate soil physicochemical properties, microbial physiology and environmental context to improve predictions of soil C cycling.
ABSTRACT Soil maps are consulted as descriptions of a current state, used to assess what can be done today in a given area. The metadata through which these maps are published contain dates, and users have no obvious reason to question them. This article presents a documentary audit of publicly available soil mapping in two Italian regions, examining what the published products disclose rather than what the respective agencies know. Of the dates reported in the metadata, none describes the period during which the field surveys were conducted; the only date in the corpus that does so appears in a narrative report hosted on a server that is no longer responding. Of the 22 information fields documented in the semi‐detailed layer of one region, none contains a directly measured soil property: each substantive field corresponds to a classification or interpretation whose input data are not included in the distributed artifact. In the 15 documented circumstances in which use could have been restricted, none associates a soil attribute with an expiration date, validity period, or obligation to verify its currency; the cautionary language used by these products is cartographic in nature. This pattern follows from the format rather than from the sample: republication of derived data can make a product appear more recent without renewing the observations on which it is based. Consequently, exposure to risk increases with the amount of derivative processing an agency performs and is greatest for the layers into which the most work has been invested. The resource date dates the resource, but the resource is not the observations. The metadata framework can convey temporal provenance through lineage information, but it does not require observation or source dates to be made systematically available in a structured, user‐accessible form; a comparative check finds the same pattern in two German national records. This study identifies where temporal provenance can already be recorded within the existing standard, sets out a minimal profile of the dates an agency should expose, and argues that source and observation dates be routinely made visible to users; the audit protocol can be applied to any agency's products.
Biochar is a promising soil management strategy to reduce reactive nitrogen (Nr) losses from agricultural soils, and replacing mineral fertilizers with organic amendments (OAs) can improve soil health and enhance nutrient recycling. We conducted a three-year field experiment with maize (Zea mays) in Lower Austria to compare organic waste compost and digestates with mineral nitrogen-phosphorus-potassium (NPK) fertilization (175 kg N ha-1, 39 kg P ha-1, 187 kg K ha-1) and to evaluate the effects of biochar application on nitrous oxide (N2O), ammonia (NH3) emissions, and crop yield. Compost and digestates were applied at higher total N rates (350 kg N ha-1). Biochar (approximately 7.5 t ha-1) was applied in combination with NPK or compost at the same fertilizer application rates as the respective non-biochar treatments to assess its potential to mitigate gaseous Nr losses. Treatment effects on soil properties and microbial functional gene abundances were also evaluated. Overall, compost reduced cumulative N2O and NH3 emissions by 66% and 68%, respectively, whereas digestate increased emissions by 21% (N2O) and 32% (NH3) compared to NPK. Biochar-amended soils mitigated N2O emissions by 48% under NPK and 39% under compost. Moreover, NH3 volatilization was reduced by 51% for NPK and 26% for compost when biochar was added. In reference to yield, digestates successfully substituted NPK, whereas compost did not provide equivalent short-term nutrient supply due to limited N-mineralization rates. Soil organic carbon and total nitrogen (TN) increased under OAs, indicating long-term fertility benefits. Reduced N2O emissions under biochar amendment could be linked to a lower denitrification potential in these treatments, while the availability of nitrate ( NO3-$$ {\mathrm{NO}}_3<^>{-} $$ ) and ammonium ( NH4+$$ {\mathrm{NH}}_4<^>{+} $$ ) was not affected by biochar amendment, as confirmed by analysis of abundance of N cycling genes and soil extractions. Our research demonstrates that both OAs and biochar can serve as climate-smart agriculture tools by improving soil fertility and supporting C sequestration while reducing direct N2O and NH3 emissions. However, effective fertilization management is necessary to maintain high yields, requiring integrated nutrient management strategies that strategically combine OAs with mineral N fertilization.
ABSTRACT Moisture is the most significant limiting factor for the field application of soil spectroscopy. Understanding this impact on spectra qualitatively and quantitatively will help identify ways to eliminate it, enabling cost‐effective use of the technology for field‐level applications. Considering this, two objectives were identified and tested: (1) to evaluate how the moisture systematically impacts visible/near‐infrared (VisNIR) and mid‐infrared (MIR) spectra at different moisture levels, (2) to compare three different calibration transfer techniques to enable the transferring of field level scans to airdry condition. Spectra were collected by three spectrometers in the VisNIR and MIR regions. From a total of 473 soil samples, 272 samples were used to develop dry ground models with partial least square regression to predict different soil properties. The remaining 201 samples were rewetted to nine different moisture levels. One hundred samples were used for calibration transfer and the rest as the test set. The results showed that MIR spectra were significantly affected by moisture. Spiking with extra weights outperformed other techniques and the improvements were consistent across different moisture levels. With spiking, Calcium showed the highest improvement with an increase of R 2 from 0.05 to > 0.84 and the ratio of performance to interquartile range from 0.14 to > 1.60. The study showed that the optimum number of samples for the calibration transfer depends on several factors including spectrometer, moisture correction method and the moisture content of the testing set. The study concluded that spiking can be considered a reliable and robust approach for moisture correction in in situ soil spectroscopy.
