A system for detecting and analyzing fast neutron activity to determine soil moisture levels and to direct the actions of an irrigation machine, wherein the system comprises: a GPS location detector; a machine orientation detector; an accelerometer; a fast neutron detector, wherein the fast neutron detector is comprised of: a 4-He based noble gas detector; a power source; a signal processing circuit, wherein the signal processing circuit is comprised of a resistor in series with a preamplifier and a shaping amplifier to produce a processed signal; a signal channel analyzer, wherein the signal channel analyzer receives the processed signal from the fast neutron detector and isolates signal data from the processed signal; and a pulse counter/rate meter, wherein the pulse counter/rate meter provides a count of the detected fast neutrons from the signal data of the processed signal; and an irrigation system controller, wherein the irrigation system controller receives the count of the detected fast neutrons;; further wherein the irrigation system controller further receives GPS coordinates corresponding to the location of the detected fast neutrons; further wherein the irrigation system controller further receives accelerometer data and machine orientation data; wherein the irrigation system controller translates the detected number of fast neutrons into moisture level data for a given field; further wherein the irrigation system controller combines the moisture level data with the detected GPS coordinates for the detected fast neutrons to create an irrigation map indicating the required levels of irrigation needed for selected areas of the given field based on the detected moisture levels. a GPS location detector; a machine orientation detector; an accelerometer; a fast neutron detector, wherein the fast neutron detector is comprised of: a 4-He based noble gas detector; a power source; a signal processing circuit, wherein the signal processing circuit is comprised of a resistor in series with a preamplifier and a shaping amplifier to produce a processed signal; a signal channel analyzer, wherein the signal channel analyzer receives the processed signal from the fast neutron detector and isolates signal data from the processed signal; and a pulse counter/rate meter, wherein the pulse counter/rate meter provides a count of the detected fast neutrons from the signal data of the processed signal; and a 4-He based noble gas detector; a power source; a signal processing circuit, wherein the signal processing circuit is comprised of a resistor in series with a preamplifier and a shaping amplifier to produce a processed signal; a signal channel analyzer, wherein the signal channel analyzer receives the processed signal from the fast neutron detector and isolates signal data from the processed signal; and a pulse counter/rate meter, wherein the pulse counter/rate meter provides a count of the detected fast neutrons from the signal data of the processed signal; and an irrigation system controller, wherein the irrigation system controller receives the count of the detected fast neutrons;; further wherein the irrigation system controller further receives GPS coordinates corresponding to the location of the detected fast neutrons; further wherein the irrigation system controller further receives accelerometer data and machine orientation data; wherein the irrigation system controller translates the detected number of fast neutrons into moisture level data for a given field; further wherein the irrigation system controller combines the moisture level data with the detected GPS coordinates for the detected fast neutrons to create an irrigation map indicating the required levels of irrigation needed for selected areas of the given field based on the detected moisture levels.