for introduction of beneficial insects and mites. Daily humidity maps are among the products offered by weather information suppliers.

Many management factors associated with harvest affect both the quality and quantity of marketable product. Precision agriculture harvesting techniques have been focused on quantitative measurements (yield and moisture content). The yield data obtained during the harvest operation are a critical input to any precision management system. However, data sets that describe subfield variation of crop development also have other implications. Producers must be concerned with the quality aspects of their products. Product quality can be as important a determinant of profitability as quantity.

In the future it may be possible to map product quality as well as yield. Real-time quality sensors do not exist, but predictive crop models may be a substitute. If crop growth models can use subfield-scale data to predict product quality, a producer may be able to avoid harvesting a portion of the field, for example, that has a high probability of containing aflatoxin. If a cotton field has areas with significant differences in lint quality, the producer may choose to operate the pickers so that the cotton would be placed in modules with more uniform qualities. With sufficient knowledge of the product quality, GIS and differential global positioning system technologies could be used to schedule harvest operations to optimize marketing opportunities.

Marketing is often considered to be the most important factor in the profitability of agricultural production. Precision agriculture techniques have not yet been developed to the point of significantly affecting crop marketing decisions. However, the availability of a detailed data set that describes the growing conditions and all chemical applications used in the production of a crop can have economic value. Product identity and documentation can be particularly important for products intended for human consumption. The use of detailed data sets to predict yields several weeks in advance of harvest would be of great value in a marketing plan that uses forward contracting or options. The communication technologies associated with precision agriculture could potentially provide marketers of agronomic products more complete information on market trends.

The previous sections have described the various ways in which precision agriculture will affect crop management. Some of the practices described are based on documented experiences with these new technologies. Others are the