Amendment-driven changes in nutrient availability and forage uptake in a recently converted boreal soil

Climate change and concerns over regional food security and sovereignty are accelerating the expansion of land-based agriculture into northern boreal regions. This requires tailored solutions to overcome the severe fertility constraints of recently converted Podzolic soils. Organic matter additions and liming agents have been proposed as rapid-solution soil amendments due to their capacity to reduce soil acidity, mediate nutrient availability and uptake, and improve crop nutrient use efficiencies. A randomized complete block design field trial was established in Central Labrador, Canada, from May to September 2023, the first-year post-conversion from forest to agriculture. Treatments included: mineral fertilizer (300 kg/ha 20:10:5 N:P:K + 176 kg/ha potash) or fish meal (1,075 kg/ha), as nutrient sources; biochar (20.8 Mg C/ha), peat (25.1 Mg C/ha), or peat with limestone (25.1 Mg C/ha peat + 5,400 kg/ha limestone), as organic matter inputs / liming agents; and monocrop oat, pea, and oat-pea intercrop, as cropping systems. All 36 treatment combinations were replicated across three blocks. Biochar-amended and peat with limestone-amended plots produced the highest forage crop aboveground biomass, nutrient (N, P, K) uptakes, and use efficiencies ( p < 0.05). Treatments that increased soil pH and nutrient supply had immediate positive effects on soil fertility parameters in this sandy acidic Podzolic soil. Biochar, as well as peat with limestone, provided immediate alleviation of Podzolic fertility constraints (low pH, low CEC, poor organic matter functionality) in the first-year post-conversion, enabling oat and pea crop production before long-term soil organic matter accumulation can develop.