Improvement of soil properties and fruit yield of native lowbush blueberry by papermill sludge addition

Abstract

Combined primary and secondary papermill sludge (PS) is a good potential source of C and other nutrients to restore low organic matter sandy soils supporting native lowbush blueberry (Vaccinium angustifolium Ait.). A 3-yr field study was conducted to compare the effect of PS with mineral fertilizers (MF) on the blueberry yield and soil chemical properties and enzyme activities of a l'Afrique sand (Humo-Ferric Podzol) in the Saguenay-Lac Saint-Jean area (Quebec, Canada). The PS was applied in the spring of the sprout year at 0, 8.5, 17 and 34 Mg ha-1 and MF was applied at 0, 13, 26 and 52 kg N ha-1. The highest fresh fruit yields were obtained at 8.5 and 17 Mg PS ha-1. The 34 Mg PS ha-1 treatment produced berry yield comparable to the control. This PS rate reduced pH, but increased inorganic N, Mehlich-3 extractable P and Mn in the 0- to 15-cm soil layer. The NO3--N content of the 15- to 30-cm and 30- to 60-cm soil layers was also increased by PS, suggesting leaching. The MF significantly affected soil inorganic N content only at 3 wk after its application in the first year. The PS rate linearly increased the soil acid phosphatase activity in the first year. The arylsulfatase activity was also higher in PS than in MF treatment, but was severely depressed by 34 Mg PS ha-1 in the last 2 yr. This study indicated that PS, when used at low rates, improves lowbush blueberry yield and the soil enzyme activity on this low fertility sand.