Method and Apparatus to Improve Crop Yields and Increase Irrigation Efficiency in Agriculture

Abstract

An irrigation control system is described for optimizing water used for growing crops. The irrigation control system uses a moisture sensor to measure soil moisture by measuring directly the relative phase velocities of different modes of propagation along a metallic structure mounted to a dielectric substrate. The average phase velocity is a function of the water content of the soil. The water content measurement is then transmitted to a central controller which then, through a set of heuristic algorithms, regulates the water distributed to the soil in a spatial and temporal manner.

What is claimed, is: 
     
         1 . A moisture sensor, comprising:
 a dielectric substrate;   an embedded coupled metallic line structure mounted to the dielectric substrate;   a power source;   a processor that is programmed to determine even and odd mode of phase velocities by measuring the transit time along the metallic line; and wherein the phase velocity is a function of the water content in the soil.   
     
     
         2 . The moisture sensor of  claim 1  wherein the metallic line structure comprises a plurality of broadside coupled transmission lines 
     
     
         3 . The moisture sensor of  claim 1  further comprising an oscillator and a high frequency counter, wherein the transit time is measured using the oscillator and the high frequency counter. 
     
     
         4 . The moisture sensor of  claim 3  wherein the high frequency counter comprises a low power low frequency oscillator and a pre-scaler circuit to extend the range of the frequencies that can be measured by a low power low frequency oscillator. 
     
     
         5 . The moisture sensor of  claim 1 , further comprising a wireless communication circuit for sending data indicative of the water content to a receiver. 
     
     
         6 . The moisture sensor of  claim 5 , wherein the wireless communication circuit is constructed to implement a Bluetooth compliant communication transmitter. 
     
     
         7 . The moisture sensor of  claim 6 , wherein the data indicative of the water content of the soil is transmitted in an advertising payload section of a Bluetooth Low Energy packet. 
     
     
         8 . The moisture sensor of  claim 1  further comprising a radio frequency circuit to measure a dielectric constant of the soil by measuring the ratio of even mode and odd mode impedances or phase velocities and the metallic line structure is embedded in the substrate. 
     
     
         9 . The moisture sensor of  claim 8  wherein the transmission line structure comprises a plurality of structures at different lengths, and switching elements coupled to the structures that are constructed to enable water content measurements at multiple frequencies to improve overall measurement accuracy. 
     
     
         10 . The moisture sensor of  claim 8  wherein the transmission line structure is a microstripline structure. 
     
     
         11 . The moisture sensor of  claim 8  wherein the transmission line structure is a set of broadside coupled lines that have phase velocity variation based on the water content of the soil. 
     
     
         12 . The moisture sensor of  claim 1  wherein the processor is programmed to compare a frequency of oscillation to the rate of oscillation in free space to determine the water content in the soil. 
     
     
         13 . The moisture sensor of  claim 1  wherein the metallic line structure forms a low pass filter. 
     
     
         14 . The moisture sensor of  claim 1  wherein the metallic line structure forms a high pass filter. 
     
     
         15 . The moisture sensor of  claim 1  wherein the metallic line structure forms a transmission line. 
     
     
         16 . An irrigation control system, comprising:
 a moisture sensor, further comprising:
 a dielectric substrate; 
 an embedded coupled metallic line structure mounted to the dielectric substrate; 
 a power source; 
 a processor that is programmed to determine even and odd mode of phase velocities by measuring the transit time along the metallic line; and wherein the phase velocity is a function of the water content in the soil; and 
 a transmitter; 
   a receiver;   a valve controller coupled to the receiver.   
     
     
         17 . The irrigation control system of  claim 16 , wherein the valve controller executes algorithms to optimize the use of water for the purpose of enabling optimized growth of crops or other plants. 
     
     
         18 . The irrigation control system of  claim 17 , wherein the algorithms are heuristic in nature. 
     
     
         19 . The irrigation control system of  claim 18 , wherein the valve controller is constructed to receive temperature and light history information and to use this information in the heuristic algorithm as a prediction from current water cycle to next water cycle to implement a watering program including duration and/or start time. 
     
     
         20 . The irrigation control system of  claim 16  further including a wide-area network radio constructed to receive environmental data such as insolation, precipitation, temperature and humidity, and the algorithms use moisture content data from the sensor and the environment data to to adjust watering times and durations.