Soil Organic Matter and its Role in Crop Production

Soil organic matter - the product of on-site biological decomposition - affects the chemical and physical properties of the soil and its overall health. Its composition and breakdown rate affect: the soil structure and porosity; the water infiltration rate and moisture holding capacity of soils; the diversity and biological activity of soil organisms; and plant nutrient availability. This document concentrates on the organic matter dynamics of cropping soils and discusses the circumstances that deplete organic matter and their negative outcomes. It then moves on to more proactive solutions. It reviews a "basket" of practices in order to show how they can increase organic matter content and discusses the land and cropping benefits that then accrue.--Publisher's description.

Soil Carbon Storage: Modulators, Mechanisms and Modeling takes a novel approach to the issue of soil carbon storage by considering soil C sequestration as a function of the interaction between biotic (e.g. microbes and plants) and abiotic (climate, soil types, management practices) modulators as a key driver of soil C. These modulators are central to C balance through their processing of C from both plant inputs and native soil organic matter. This book considers this concept in the light of state-of-the-art methodologies that elucidate these interactions and increase our understanding of a vitally important, but poorly characterized component of the global C cycle. The book provides soil scientists with a comprehensive, mechanistic, quantitative and predictive understanding of soil carbon storage. It presents a new framework that can be included in predictive models and management practices for better prediction and enhanced C storage in soils. - Identifies management practices to enhance storage of soil C under different agro-ecosystems, soil types and climatic conditions - Provides novel conceptual frameworks of biotic (especially microbial) and abiotic data to improve prediction of simulation model at plot to global scale - Advances the conceptual framework needed to support robust predictive models and sustainable land management practices

Recognition of the importance of soil organic matter (SOM) in soil health and quality is a major part of fostering a holistic, preventive approach to agricultural management. Students in agronomy, horticulture, and soil science need a textbook that emphasizes strategies for using SOM management in the prevention of chemical, biological, and physical problems. Soil Organic Matter in Sustainable Agriculture gathers key scientific reviews concerning issues that are critical for successful SOM management. This textbook contains evaluations of the types of organic soil constituents—organisms, fresh residues, and well-decomposed substances. It explores the beneficial effects of organic matter on soil and the various practices that enhance SOM. Chapters include an examination of the results of crop management practices on soil organisms, organic matter gains and losses, the significance of various SOM fractions, and the contributions of fungi and earthworms to soil quality and crop growth. Emphasizing the prevention of imbalances that lead to soil and crop problems, the text also explores the development of soils suppressive to plant diseases and pests, and relates SOM management to the supply of nutrients to crops. This book provides the essential scientific background and poses the challenging questions that students need to better understand SOM and develop improved soil and crop management systems.

The presence - or absence - of soil organic matter (SOM) has important implications for agricultural productivity. It could also have significant implications for global climate due to its role as a source/sink of carbon. Therefore, it is important to understand the issues related to the accumulation or loss of SOM, to use what we have learned from experiments to make sound decisions about soil and crop management, and to test models and future concepts concerning SOM management. A database is included with the book, presenting tabular data for 34 sites in North America. Soil Organic Matter in Temperate Agroecosystems discusses all of these issues and more, answering such questions as:

The use of organic residues as a means of maintaining and increasing soil fertility is of long-standing. This tradition has been somewhat neglected since the introduc tion of mineral fertilizers at low cost. More and more farmers and scientists are now showing renewed interest in the proper and effective use of org~tnic residues, composts and other recycled organic additives. The role and function of organic amendments in modern agricultural systems have become topics of major interest in the scientific and agricultural communities. Research work on residue disposal has provided new concepts on the interaction between organic components and soils as well as new handling technologies (e. g. pelletizing of organic residues). The trend to conserve energy has led scientists to study the minimal tillage system, to find ways of replacing conventional inorganic fertilizers with natural organic prod ucts or microbial preparations, and to develop new composting methods. The drive to achieve higher yields in commercial greenhouse farming has led to a search for optimum substrates as growth media and for improved management techniques. This has led to the introduction of organic substitutes for peat, nota bly those originating from agricultural wastes. Another important aspect is the current interest in organic farming, where use of synthetic chemicals is avoided or prohibited. An increasing percentage of the population in highly developed countries is willing to pay premium prices for food produced on soils where inorganic fertilizers and other agricultural chemicals have not been used.

Soil organic matter (SOM) is the primary determinant of soil functionality. Soil organic carbon (SOC) accounts for 50% of the SOM content, accompanied by nitrogen, phosphorus, and a range of macro and micro elements. As a dynamic component, SOM is a source of numerous ecosystem services critical to human well-being and nature conservancy. Important among these goods and services generated by SOM include moderation of climate as a source or sink of atmospheric CO2 and other greenhouse gases, storage and purification of water, a source of energy and habitat for biota (macro, meso, and micro-organisms), a medium for plant growth, cycling of elements (N, P, S, etc.), and generation of net primary productivity (NPP). The quality and quantity of NPP has direct impacts on the food and nutritional security of the growing and increasingly affluent human population. Soils of agroecosystems are depleted of their SOC reserves in comparison with those of natural ecosystems. The magnitude of depletion depends on land use and the type and severity of degradation. Soils prone to accelerated erosion can be strongly depleted of their SOC reserves, especially those in the surface layer. Therefore, conservation through restorative land use and adoption of recommended management practices to create a positive soil-ecosystem carbon budget can increase carbon stock and soil health. This volume of Advances in Soil Sciences aims to accomplish the following: Present impacts of land use and soil management on SOC dynamics Discuss effects of SOC levels on agronomic productivity and use efficiency of inputs Detail potential of soil management on the rate and cumulative amount of carbon sequestration in relation to land use and soil/crop management Deliberate the cause-effect relationship between SOC content and provisioning of some ecosystem services Relate soil organic carbon stock to soil properties and processes Establish the relationship between soil organic carbon stock with land and climate Identify controls of making soil organic carbon stock as a source or sink of CO2 Connect soil organic carbon and carbon sequestration for climate mitigation and adaptation