Impact of supplemental poultry manure application on potato yield and soil properties on a loam soil in north-western New Brunswick

The effect of timing of supplementary poultry manure applications on potato (Solanum tuberosum L.) yield and quality and soil properties of degraded soils in the New Brunswick potato belt were assessed. Four treatments on an 11% slope consisted of a control (11% - Ctrl) and applications of 4 Mg ha-1 of fresh broiler poultry manure applied either in late fall (11% - F), pre-planting (11% - PP) or pre-hilling (11% - PH). Similar treatments were set out on an 8% slope with exception of the pre-planting treatment. Manure applications enhanced potato plant N status as measured by petiole NO-3 concentration. Over the 3-yr experiment, poultry-manured treatments averaged 13 to 17% more annual total tuber yield and 19 to 34% more annual marketable tuber yield than the unmanured control. Poultry-manured treatments had fewer tubers in the small category and increased the proportion of tubers in the No. 1 and 10 oz. categories. Tuber yields were similar with fall-applied manure and with manure applied at pre-hilling. Manure did not induce either scab or hollow heart. Manure reduced tuber specific gravity. After three annual applications of poultry manure, soil P, K, B, Cu, Na, S and Zn increased significantly. Soil organic carbon did not change significantly after three annual poultry manure applications, but there was an increase in soil CO2 concentrations, earthworm populations and infiltration. Repeated manuring did not improve saturated hydraulic conductivity, matrix bulk density, field capacity, available-water-holding capacity or wet aggregate stability, and no consistent response in soil temperature or soil water content occurred. We conclude that low, repeated applications of poultry manure would benefit tuber yield and soil biological properties, but soil physical properties would be slower to change.