Sustainable Soil Management Is More Than What and How Crops are Grown

Soil management in agricultural landscapes should deploy production practices that are in harmony with soil-mediated ecosystem functions if they are to deliver a broad range of ecosystem services. Such services include edible and nonedible biological products, clean drinking water, processes that decompose and transform organic matter, and cleansing processes that maintain air quality. Several categories of ecosystem services are recognized: provisioning, regulating, cultural, and supporting (Millennium Ecosystem Assessment [MEA] 2005). In agricultural landscapes, provisioning ecosystem services can be delivered effectively and efficiently when the linked regulatory and supporting services are allowed to operate normally. Ecosystem functions that protect and enhance regulatory and supporting ecosystem services in the soil and landscape in which crops are grown appear, in general, to offer an effective way of harnessing the best productivity, ecological, and economic performances. Thus, agricultural soil management can only be considered sustainable if field soil health and productive capacity are kept at an optimum to provide ecosystem services such as provision of clean water, hydrologic and nutrient cycling, habitats for microorganisms and mesofauna, carbon sequestration, and climate regulation. Across agricultural and mixed land use landscapes, such ecosystem services form the necessary conditions for society to be able to sustainably harness the biological potentials of the altered agroecosystems and the associated provisioning services of food, vegetation, water, etc. In general, over the past several millennia, agricultural land use globally has led to soil physical, chemical, biological, and hydrological degradation, and this state of affairs continues unabated in most farmlands (MEA 2005; Montgomery 2007; FAO 2011a). This is true on small and large farms, on farms using mechanized or manual farm power, in developing and in industrialized countries, in the tropics, and outside the tropics. The dominant farming systems paradigm globally is based on mechani- cal tillage of various types to control weeds (often along with herbicides), soften the seedbed for crop establishment, and loosen compacted subsoil. At the center of this paradigm, there are farming practices for crop, soil, nutrient, water, and pest management that are considered by most agricultural stakeholders to be “modern, good, and normal.” However, the same farming practices have also forced farmers to accept that, supposedly, any accompanying soil degradation and loss of ecosystem services are inevitable and “natural” consequences of farming—consequences that can be kept under control but not avoided altogether. This view is increasingly being challenged and considered to be outdated, and inherited farming practices are considered unable to deliver the multifunctional objectives of productivity with ecosystem services now being demanded from agricultural land and producers who use it for farming. In the past three decades, ideas and concepts, as well as an ecosystem approach to sustainable production intensification, have led to the emergence of an alternative approach to farming across all continents. The title of this chapter is “Sustainable Soil Management Is More Than What and How Crops Are Grown.” Not only how and what crops are grown matters but also the interactions of the two in space and time lead to effects and consequences that influence system performance and delivery of ecosystem services. Some ecosystem services involve processes such as hydrological, carbon, and nutrient cycling that operate at the level of the fields on farms, landscapes, watersheds, and beyond. In addition, agricultural soil management is undertaken within different farming systems for the purpose of producing biological products for markets, and a range of production inputs, equipment and machinery, and management skills are needed to operate successfully. Thus, the topic of sustainable soil management has a wide and complex scope as reflected in the list of 10 tenets proposed by Lal (2009). This chapter is about soil degradation in agricultural land, its root causes, and what solutions are being implemented in different parts of the world to integrate sustainable soil management into sustainable farming and landscape management. Section 14.2 describes what is meant by agricultural soil degradation and its extent. Section 14.3 provides an explanation of some of the major causes of soil degradation in agricultural land use and illustrates three cases of widespread soil degradation in contrasting environments. This is followed, in Section 14.4, by a discussion on the elements of sustainable soil management. Section 14.5 provides an elaboration of sustainable soil management based on the agroecological paradigm that is increasingly being promoted internation- ally, including how sustainable soil management has been able to restore degraded soils in different agricultural environments. Section 14.6 illustrates the kind of contributions crop management, intercropping, crop–livestock integration, and farm power that can make to sustainable soil management objective. Section 14.7 presents three examples of large-scale landscape level ecosystem service benefits that are being harnessed from sustainable soil management systems. This is followed by Section 14.8 on policy and institutional implications for sustainable soil management. Section 14.9 offers some concluding remarks regarding the current trend toward sustainable soil management and what policy makers can do to support the trend