Method and apparatus using soil conductivity thresholds to control irrigating plants

1. A method, comprising the step of:

operating an irrigation system delivering water to at least one plant, comprising the steps of:

determining a water absorption gradient based upon the difference of a present value and a past value, with both said present value and said past value as measured functions of soil conductance between at least two probes each separately located in soil near said plant; and

controlling said irrigation system based upon said water absorption gradients, further comprising of the step:

controlling at least one electric valve directing said water to said at least one plant based upon said water absorption gradient, further comprising one of the steps:

turning-off said electric valve when said difference is less than or equal to said first threshold multiplied by said present value; and

turning-off said electric valve when said difference is less than said first threshold multiplied by said present value.

2. The method of claim 1 , where said plant includes at least one of a grass, a clover, an alfalfa, and a ground cover.

3. The method of claim 1 , wherein the step determining said water absorption gradient, comprises the steps:

determining said water absorption gradient between two of said probes located in said soil near said plant.

4. The method of claim 1 , wherein the step determining said water absorption gradient, comprises the steps:

establishing a present value of the electrical conductivity between said probes; and

calculating said water absorption gradient based upon said present value and said past value.

5. The method of claim 4 , wherein the step determining said water absorption gradient further comprises the step:

setting a state in at least one member of a state group of said past value to said present value, wherein said state group consists of the members of a memory, a store and a latch.

6. The method of claim 5 wherein the step setting said past value, comprises the step: writing said present value to a non-volatile memory to create a stored value of said past value.

7. The method of claim 6 , wherein the step creating said conductivity difference, comprises the step: reading said stored value from said non-volatile memory to retrieve said past value.

8. The method of claim 1 , wherein the step controlling said electric valve, further comprises the step:

turning-on said electric valve when said water absorption gradient is below a second threshold.

9. The method of claim 8 , wherein the step determining said water absorption gradient further comprises the step:

creating a soil conductivity scale ratio from said difference divided by said present value; and

wherein the step turning-off said electric valve, further comprises one of the steps:

turning-off said electric valve when said soil conductivity scale ratio is less than or equal to said first threshold; and

turning-off said electric valve when said soil conductivity scale ratio is less than said first threshold.

10. The method of claim 8 , wherein the step turning-on said electric valve, further comprises one of the steps:

turning-on said electric valve when said difference is less than or equal to said negative of said second threshold multiplied by said present value; and

turning-on said electric valve when said difference is less than said negative of said second threshold multiplied by said present value.

11. The method of claim 8 , further comprising the step: creating a soil conductivity scale ratio as said difference divided by said present value; and

wherein the step turning-on said electric valve, further comprises one of the steps:

turning-on said electric valve when said soil conductivity scale ratio is less than or equal to said negative of said second threshold; and

turning-on said electric valve when said soil conductivity scale ratio is less than said negative of said second threshold.

12. A method, comprising the step of:

operating an irrigation system delivering water to at least one plant, comprising the steps of:

determining a water absorption gradient based upon the difference of a present value and a past value, with both said present value and said past value as measured functions of soil conductance between at least two probes each separately located in soil near said plant, further comprises the step:

creating a soil conductivity scale ratio from said difference divided by said present value; and

controlling said irrigation system based upon said water absorption gradient, further comprising the step:

controlling at least one electric valve directing said water to said at least one plant based upon said water absorption gradient, further comprising one of the steps:

turning-off said electric valve when said soil conductivity scale ratio is less than or equal to said first threshold; and

turning-off said electric valve when said soil conductivity scale ratio is less than said first threshold.

13. The method of claim 12 , where said plant includes at least one of a grass, a clover, an alfalfa, and a ground cover.

14. The method of claim 12 , wherein the step determining said water absorption gradient, comprises the steps:

determining said water absorption gradient between two of said probes located in said soil near said plant.

15. The method of claim 12 , wherein the step determining said water absorption gradient, comprises the steps:

establishing a present value of the electrical conductivity between said probes; and

calculating said water absorption gradient based upon said present value and said past value.

16. The method of claim 15 , wherein the step determining said water absorption gradient further comprises the step:

setting a state in at least one member of a state group of said past value to said present value, wherein said state group consists of the members of a memory, a store and a latch.

17. The method of claim 16 , wherein the step setting said past value, comprises the step: writing said present value to a non-volatile memory to create a stored value of said past value.

18. The method of claim 17 , wherein the step creating said conductivity difference, comprises the step: reading said stored value from said non-volatile memory to retrieve said past value.

19. The method of claim 12 , wherein the step controlling said electric valve, further comprises the step:

turning-on said electric valve when said water absorption gradient is below a second threshold.

20. The method of claim 19 , wherein the step turning-on said electric valve, further comprises one of the steps:

turning-on said electric valve when said difference is less than or equal to said negative of said second threshold multiplied by said present value; and

turning-on said electric valve when said difference is less than said negative of said second threshold multiplied by said present value.

21. The method of claim 19 , wherein the step turning-on said electric valve, further comprises one of the steps:

turning-on said electric valve when said soil conductivity scale ratio is less than or equal to said negative of said second threshold; and

turning-on said electric valve when said soil conductivity scale ratio is less than said negative of said second threshold.

22. A method, comprising the step of:

operating an irrigation system delivering water to at least one plant, comprising the steps of:

determining a water absorption gradient based upon a present value and a past value, with both said present value and said past value as measured functions of soil conductance between at least two probes each separately located in soil near said plant; and

controlling said irrigation system based upon said water absorption gradient, comprising the step:

controlling at least one electric valve directing said water to said at least one plant based upon said water absorption gradient, comprising one of the steps:

turning-on said electric valve when said difference is less than or equal to said negative of said second threshold multiplied by said present value; and

turning-on said electric valve when said difference is less than said negative of said second threshold multiplied by said present value.

23. The method of claim 22 , where said plant includes at least one of a grass, a clover, an alfalfa, and a ground cover.

24. The method of claim 22 , wherein the step determining said water absorption gradient, comprises the steps:

determining said water absorption gradient between two of said probes located in said soil near said plant.

25. The method of claim 22 , wherein the step determining said water absorption gradient, comprises the steps:

establishing a present value of the electrical conductivity between said probes; and

calculating said water absorption gradient based upon said present value and said past value.

26. The method of claim 25 , wherein the step determining said water absorption gradient further comprises the step:

setting a state in at least one member of a state group of said past value to said present value, wherein said state group consists of the members of a memory, a store and a latch.

27. The method of claim 26 , wherein the step setting said past value, comprises the step: writing said present value to a non-volatile memory to create a stored value of said past value.

28. The method of claim 27 , wherein the step creating said conductivity difference, comprises the step: reading said stored value from said non-volatile memory to retrieve said past value.

29. The method of claim 22 , wherein the step controlling said electric valve, further comprises the step:

turning-on said electric valve when said water absorption gradient is below a second threshold.

30. The method of claim 29 , further comprising the step: creating a soil conductivity scale ratio as said difference divided by said present value; and

wherein the step turning-on said electric valve, further comprises one of the steps:

turning-on said electric valve when said soil conductivity scale ratio is less than or equal to said negative of said second threshold; and

turning-on said electric valve when said soil conductivity scale ratio is less than said negative of said second threshold.

31. A method, comprising the step of:

operating an irrigation system delivering water to at least one plant, comprising the steps of:

determining a water absorption gradient based upon a difference of a present value and a past value, with both said present value and said past value as measured functions of soil conductance between at least two probes each separately located in soil near said plant;

creating a soil conductivity scale ratio as said difference divided by said present value; and

controlling said irrigation system based upon said water absorption gradient, further comprising the step:

controlling at least one electric valve directing said water to said at least one plant based upon said water absorption gradient, comprising one of the steps:

turning-on said electric valve when said soil conductivity scale ratio is less than or equal to said negative of said second threshold; and

turning-on said electric valve when said soil conductivity scale ratio is less than said negative of said second threshold.

32. The method of claim 31 , where said plant includes at least one of a grass, a clover, an alfalfa, and a ground cover.

33. The method of claim 31 , wherein the step determining said water absorption gradient, comprises the steps:

determining said water absorption gradient between two of said probes located in said soil near said plant.

34. The method of claim 31 , wherein the step determining said water absorption gradient, comprises the steps:

establishing a present value of the electrical conductivity between said probes; and

calculating said water absorption gradient based upon said present value and said past value.

35. The method of claim 34 , wherein the step determining said water absorption gradient further comprises the step:

setting a state in at least one member of a state group of said past value to said present value, wherein said state group consists of the members of a memory, a store and a latch.

36. The method of claim 35 , wherein the step setting said past value, comprises the step: writing said present value to a non-volatile memory to create a stored value of said past value.

37. The method of claim 36 , wherein the step creating said conductivity difference, comprises the step: reading said stored value from said non-volatile memory to retrieve said past value.