ABSTRACT

Often the first step in producing a crop or planning a landscape is site selection. Considerations may include selecting crops adapted to your region. If you are at the limit of latitude or environment for a crop or landscape plant, these plants will grow poorly. A plant under stress is often more susceptible to disease. Within an area adapted for a crop, considerations for a site include soil texture. For example, soils with high clay content do not allow water to percolate easily into the soil and thus may result in standing water or saturated conditions. This creates an anaerobic environment that limits oxygen for root growth. In addition, these sites are often more prone to problems from diseases caused by the oomycetes Phytophthora and Pythium (Chapter 8 and Figure 25.1). Sites that have very sandy soils may drain rapidly and increase the risk of limited water for growth. A number of diseases are associated with drought stress including diseases caused by many Fusarium spp. and Macrophomina phaseolina, the causal agent of charcoal rot. In addition, nematode damage (Chapter 6) may increase with soils having greater sand content. Site preparation may be done to alter site characteristics or soil properties. Organic amendments may be added to improve water retention and aeration. Sand may be added to clay soils to improve drainage and aeration. Other considerations for site selection may be shading or hours of direct sunlight or topography. Sites may also be selected

Concept Box

to avoid inoculum of specific pathogens or the presence of vectors, which may introduce a pathogen into a crop.