Papermill biosolid and hog manure compost affect short-term biological activity and crop yield of a sandy soil

Soils used for intensive vegetable production often become depleted in their organic matter content, and consequently low in their microbial activity. Papermill sludge compost may be an efficient way to improve the biological activity of these soils. An experiment was initiated to determine the effects of a co-composted papermill sludge and hog manure (PHC), applied alone or in combination with mineral fertilizers (MF), on several biochemical properties and crop yield of a Bevin loamy sand (Orthic Humo-Ferric Podzol) located at Saint-Ubalde, province of Quebec, Canada. The PHC was applied in the spring of 1997 at rates of 0, 11.5,23 and 34.5 Mg dry weight ha-1 with and without MF equivalent to 150 N-200 P2O2-200 K2O kg ha-1 Potatoes (Solanum tuberosum L.) were planted the first year and the residual effect of PHC was evaluated on a spring wheat (Triticum aestivum L.) crop in 1998. Enzymatic activity of (beta)-glucosidase, (beta)-galactosidase, acid phosphatase, urease and fluorescein diacetate hydrolysis, microbial biomass C (MBC) and CO2-C release in incubation were measured throughout both growing seasons. Application of 11.5 Mg ha-1 of PHC resulted in the highest enzymatic activities and MBC, representing a mean increase of respectively 30 and 55% over the control. Addition of MF to PHC resulted in a greater increase in enzyme activities (12-18%) than PHC alone but had little effect on MBC. Generally, enzyme activities and MBC decreased in the second season. The carbon mineralization potential was low, indicating that the composted material was relatively stable. The addition of 11.5 Mg PHC ha-1 produced the highest marketable potato tuber yield with (34 Mg ha-1) or without (27 Mg ha-1) fertilizer supplement, whereas the highest wheat grain yield was obtained with the 23 Mg PHC ha-1 level in the following season. When PHC was added at 11.5 Mg ha-1 it markedly improved soil biochemical properties and potato crop yield whereas the 34.5 Mg ha-1 level was excessive.