Forage Crop Productivity and Nutrient Use Efficiency on Newly Converted Boreal Podzolic Soils in Central Labrador

Abstract

Climate change is driving agricultural expansion into Canada’s boreal north, however, the sandy acidic, and nutrient poor Podzolic soils resulting from forest-to-farmland conversion remain severely under studied for their capacity to support crop production. This study evaluated the effects of soil fertility enhancing treatments, including nutrient sources; inorganic mineral fertilizer, organic marine waste (e.g., shrimp compost, shrimp waste, and fish meal), forage biomass incorporation, and liming agents/organic matter inputs; limestone, peat moss, their combination, and biochar, on forage crops (e.g., oat, pea, and oat-pea intercrop). Yields, nutrient uptake, and nutrient use efficiency for N, P and K were evaluated across three boreal farmlands near Happy Valley-Goose Bay, Labrador, Canada. The three farmlands, Birch Lane (BL), Taiga Valley (TV), and Natures Best (NB), differed in conversion history, baseline soil fertility, and management, spanning a gradient from infertile, recently bulldozed mineral soil at TV to a moderately rehabilitated pasture under long‑term agricultural management at BL. Field experiments were conducted over two growing seasons (2023 and 2024) using randomized complete blocks with factorial design (factor 1: nutrient source, factor 2: liming agents/organic matter inputs). Results showed that forage crop yields and nutrient uptake for N, P, and K were influenced by both nutrient sources and liming agents/organic matter inputs applied (p<0.05), with the largest effects seen in the least fertile soils. While treatments were distinct but comparable across the three farms, forage responses were site specific, reflecting the overriding role of inherent soil fertility. In the longer-term managed BL field, inorganic and organic nutrient sources as well as application of limestone with peat, influenced yields, nutrient uptakes and nutrient use efficiencies (p<0.05). At BL, when shrimp compost was applied at similar N rates to the inorganic mineral fertilizer, shrimp compost produced higher yields. At the very recently converted TV, meaningful yields (above 1 t/ha) required the combined application of strong nutrient inputs with organic matter and acidity improving amendments (p<0.05). The application of hardwood biochar at TV, produced the highest yields and nutrient uptakes on the farm when paired with fish meal in the first year. At the intermediate fertility site NB, organic fertilizers, including shrimp compost and shrimp waste, performed similarly to inorganic mineral fertilizer, showing promise as locally useful organic marine waste by-products. Biomass incorporation contributed negligible available nutrients within a single season and did not improve yields above control. Nutrient use efficiency metrics revealed that high efficiencies were not solely a product of experimental soil inputs, but were likely influenced by inherent soil conditions, underscoring the importance of conversion history and cumulative land management on nutrient cycling in boreal agricultural soils. These findings provide evidence that northern boreal farms, such as those in Happy Valley-Goose Bay, can have agronomically meaningful forage crop production (5-7 t/ha) if soil fertility management is matched to site-specific constraints. The conversion history of these lands determines how intensive agricultural management must be to achieve crop productivity. As boreal agricultural development continues to expand in Newfoundland and Labrador and across northern Canada, this study highlights the importance of soil fertility management strategies that consider the interacting roles of nutrient supply, soil acidity, and organic matter status.