A collection of key scientific reviews concerning issues that are critical for successful SOM management, this book contains evaluations of the types of organic soil constituents-organisms, fresh residues, biologically active compounds and humic substances. It explores how organic matter benefits the function of soils in agroecosystems and practices that enhance SOM. Coverage includes impacts of crop management practices on soil organisms, organic matter gains and losses, the significance of various SOM fractions, the contributions of fungi and earthworms to soil quality and crop growth, and the development of soils suppressive to plant diseases and pests.