Electronic control, monitoring, information sensing and information display systems for use in agriculture, comprising computer hardware, electrical controllers, electrical and optical sensors; vehicle mounted electronic crop analysis systems comprising computer hardware, computer software for analyzing volumes of crops collected and dynamically controlling amounts and types of fertilizer and other chemical compounds to be applied to specific geographic areas; electronic control, monitoring, information sensing and information display systems comprising a computer for mounting to vehicles, combine harvesters, agricultural tractors, agricultural implements, agricultural machines, and harvesting machinery; field data communication systems comprising communications servers and communications software for connecting computer network users to the communications servers; software for the presentation, management, and analysis of agricultural data, variable-rate irrigation control systems and GPS guidance and autosteering systems, for use by farmers