ADMIXING ORGANIC OVERLAYS AND MINERAL SUBLAYERS OF SHALLOW PEAT SOILS FOR IMPROVING SOIL PRODUCTIVITY

Abstract

This growth room and greenhouse study with 13 subsoils and organic overlays was aimed at developing crop choices and strategies for continued land use of shallow organic soils and at refining the criteria used for assessing the long-term agricultural capability of deep organic soils. Soil materials from four geoprovinces in Canada were mixed in various volume/volume proportions to provide 25 different soil media. Root, leafy vegetable and grass crops were grown on each soil. All pots were adequately fertilized and watered. A gyttja-layer of marine-fecal origin that acidifies rapidly on exposure to air was rendered productive on admixing with an adjacent layer rich in Ca-containing molluscan-shells. Generally, all clay, sand and silt sublayers improved on admixing with organic overlays. At the same time, the organic overlays did not become markedly less productive on being mixed with mineral sublayers in 1:1 volume proportions except when the sublayers were clays. Yields decreased when clays formed more than 25% of the mixture by volume, particularly when the crops grown were vegetables. Key words: Peat soils, soil management, soil productivity