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Boreal lands have long been considered unsuitable for agriculture. Climate change projections support a shift towards increased agricultural production in boreal ecosystems via land use conversion. Depending on the conversion protocol, the new plough layer may variably reflect the properties of different soil depths. This study assessed how adding mineral or organic fertilizer sources to distinct soil layers within ploughing depth (0–15 cm [topsoil] or 15–30 cm [subsoil]) affects nutrient uptake and crop productivity. Locally relevant organic waste fertilizers (dairy manure [DMN], recirculating aquaculture system supernatant [SUP] and slurry [RAS]), were compared against mineral fertilizer. Tall fescue was used to verify agronomic responses. Starting available nutrient concentrations were balanced as necessary with mineral N and P fertilizers. Except for NH4‐nitrogen, both soils were of apparent similar fertility (total C < 1%); unfertilized, neither could support significant plant growth. Subsoil‐based growth was fast but limited in time reflecting immediately available nutrients. Topsoil led to delayed, extended growth. This might be due to dichotomous priming effects: during the duration of the experiment up to 36% of subsoil carbon was lost, while the topsoil gained up to 49% carbon, most apparent for DMN. While RAS led to the greatest N and P acquisition efficiencies for topsoil, it had no such effect for subsoil, suggesting distinct fixation and mineralization processes. Dissimilar C cycling and nutrient acquisition for the two soil depths indicates that site‐specific considerations that include soil health parameters with commonly tested available nutrients are needed where podzols are farmed after land‐use conversion. [ABSTRACT FROM AUTHOR]

Under climate change and local and global food security pressures conversion to agricultural lands on Podzols developed under boreal forests is accelerating across the global north. After conversion Podzols, acid and sandy, are infertile requiring significant management to allow economic production. Biochar, while less useful on fertile soils, may accelerate fertility gains on such marginal lands; it is already considered or land-applied by local farmers, under minimal guidance. A multi-year experiment assessed the utility of single or split application of biochar (BC), and of BC doses, for beet yields and nutrient uptake on newly converted Podzols. Time and rate-dependent progression of yields, macro- and micro-nutrients uptake, all parameters identified of interest by northern farmers, were evaluated. Kiln-derived hardwood biochar was added at 0, 10, 20, 40 or 80 Mg BC-C ha−1 (BC 0 to 80) either as single or as double application. Beet yields and elemental compositions were assessed over 4 years after biochar application. Work was done on a private farm in Labrador, Canada, under a scenario relevant to the boreal north. BC 0 could not sustain significant crop growth, suggesting that post-conversion mineralization of residual soil organic matter cannot support plant growth. In the first one to three years after application of biochar yields increased above the control, but statistically independent of application rates. A statistically significant positive biochar-rate to yield dependency was verifiable only in year 4. Nevertheless, biochar's positive effect on yields declined with time after application: e.g., BC 10 matched BC 0 yields in year 4. For the first three years, root nitrogen (N) concentrations were inversely correlated to yields and plant N% declined with biochar rate. In year 4 plant N% was directly correlated to plant biomass. In general, partitioning of nutrients between beet leaves and roots was not discernibly affected by the rate of biochar; an exception was boron whose preferential accumulation in leaves was directly related to the rate of biochar, indicating a role for the biochar for its mobilization. Biochar had an immediate positive effect on the beet yields and affected plant stoichiometry. Initially this was independent of the biochar rate. Biochar's utility declined with time at a rate inversely related to its application rate. Biochar is a recommendable fertility management tool for infertile, newly converted boreal Podzols; rates in the range of 10 Mg BC-C ha-1 may be repeated annually or every few years as practically feasible. Long term utilization requires further monitoring of micronutrients availability and uptake to inform any necessary management adjustments. Fertilizer management must consider the time since biochar's addition to soil. • Unmanaged Podzols on freshly converted boreal forest are infertile. • Biochar addition increases beet yield and yield quality, initially rate-independent. • A rate-dependent impact of biochar on yields and yield quality was noted in year 4. • Biochar's benefit fades over time at a rate inverse to its application rate. • Repeated, small biochar doses are recommendable over large single applications. [ABSTRACT FROM AUTHOR]

The spatial variability in soil physical and hydraulic properties for a managed podzol was assessed using soil apparent electrical conductivity (ECa). Two EMI sensors, the multi-coil (MC) and multi-frequency (MF), were adopted for measurement of ECa on a silage- corn experimental plot in western Newfoundland, Canada. Results demonstrated a significant relationship between the ECa mean relative differences (MRD) and the soil moisture content MRD (R2 = 0.33 to 0.70) for both MC and MF sensors. The difference in depth sensitivity between MC and MF sensors accounted for the variation (0.015 to 0.09) in ECa standard deviation of the relative differences. A significant linear relationship was found between the ECa MRD and sand (R2 = 0.35 and 0.53) or silt (R2 = 0.43), but not with clay (R2 = 0.06 and 0.16). The spatial variability of the ECa-based predictions (CV = 3.26 to 27.61) of soil properties was lower than the measured values (CV = 5.56 to 41.77). These results inferred that the temporal stability of ECa might be a suitable proxy to understand the spatial variability of soil physical and hydraulic properties in agricultural podzols. [ABSTRACT FROM AUTHOR]

Electromagnetic induction (EMI) technique is an established method to measure the apparent electrical conductivity (ECa) of soil as a proxy for its physicochemical properties. Multi-frequency (MF) and multi-coil (MC) are the two types of commercially available EMI sensors. Although the working principles are similar, their theoretical and effective depth of investigation and their resolution capacity can vary. Given the recent emphasis on non-invasive mapping of soil properties, the selection of the most appropriate instrument is critical to support robust relationships between ECa and the targeted properties. In this study, we compared the performance of MC and MF sensors by their ability to define relationships between ECa (i.e., MF–ECa and MC–ECa) and shallow soil properties. Field experiments were conducted under wet and dry conditions on a silage-corn field in western Newfoundland, Canada. Relationships between temporally stable properties, such as texture and bulk density, and temporally variable properties, such as soil water content (SWC), cation exchange capacity (CEC) and pore water electrical conductivity (ECw) were investigated. Results revealed significant (p < 0.05) positive correlations of ECa to silt content, SWC and CEC for both sensors under dry conditions, higher correlated for MC–ECa. Under wet conditions, correlation of MF–ECa to temporally variable properties decreased, particularly to SWC, while the correlations to sand and silt increased. We concluded that the MF sensor is more sensitive to changes in SWC which influenced its ability to map temporally variable properties. The performance of the MC sensor was less affected by variable weather conditions, providing overall stronger correlations to both, temporally stable or variable soil properties for the tested Podzol and hence the more suitable sensor toward various precision agricultural practices. [ABSTRACT FROM AUTHOR]