- Where NIR is the near infrared band and Red is the red band within the digital data commonly measured by sensors borne by either aircraft or EOS platforms.

In its role as an estimator of canopy greenness, NDVI is beset with problems with accuracy that are due to soil background and atmospheric aerosol effects of scatter and attenuation. These influences combine to dilute the vegetation signal it is designed to portray. The accuracy for NDVI to portray hydrologic responses is enhanced by conversion to NDVI* that calibrates the canopy from zero to one to represent the full range of vegetation greenness from none to saturated. This index has been shown to outperform all other available vegetation indices in use in the field of remote sensing. The calculation of NDVI* corrects for the error-inducing effects from soil background and atmospheric aerosols (Equation 2),

\begin{matrix} N D V I^{*} = \frac{N D V I_{i} - N D V I_{0}}{N D V I_{S} - N D V I_{0}} & Equation 2 \end{matrix}

- Where NDVI_iis the measured NDVI for the ith pixel, NDVI_Sis the saturated value for NDVI, and NDVI₀is the NDVI value representing bare soil.

NDVI* is calibrated using scene statistics and hence, requires no specific ground target or ground-based measurements. For calculation of NDVI*, there are times of the year where a maximally verdant target suitable for setting NDVI_Swill be missing, for example, for periods outside of the main growing season, e.g., fall, winter and spring. Hence, the NDVI_Svalue is simply chosen as an empirical constant, since the peak value for non-cloudy scenes in an atmosphere relatively clear of non-gaseous aerosols occupies a known range that is determined empirically. The choice of the saturated NDVI value as a median for this range to represent NDVI_S, produces only insignificant influence upon the resulting NDVI* values. These relationships have been determined for use with Landsat™, however, calibrating other EOS sensors to be mathematically equivalent to Landsat™ is accurately accomplished using linear regression analysis of extracted pixel values.

For making amendment prescriptions, the relational information provided by virtually any vegetation index could be used, since it is the differences in production, expressed as greenness, that are of interest. NDVI* is specified here, specifically, because it is the index that will be used for guiding amendment application to meet crop needs and because it is calibrated in a such a manner that it permits comparison from year to year to cross check the efficacy of the treatments on any region of a field or fields. Thus, NDVI*, calculated in the manner described here, provides standardization.

For comparison of EOS data across seasons, the effect of variable solar angles and distance to the sun are corrected through the calculation of reflectance: the ratio of reflected light to the incident light. Reflectance is often calculated at the top of the atmosphere; such values are further corrected to at-ground reflectance by means known to those with ordinary skill in the art. NDVI* functions as an approximation of at-ground NDVI but also corrects for the influence of the soil background that generally raises NDVT for zero vegetation cover to some value greater than zero.

NDVI and NDVI* can also be calculated from the digital number (the uncorrected output) from the sensors, or from radiance which is the calculation of the relative light received by the sensor, irrespective of the incident light. Papers describing these calculations are available in the published literature. Some appropriate EOS data (having red and near infrared bands) are available at resolutions of several meters. However, EOS datasets covering large geographic areas (many tens of thousands of square miles), may only be available in moderate resolution (20-30 m/pixel). The spatial resolution of these data are enhanced by using kriging that can bring the spatial resolution down to several meters—a scale appropriate for controlling this application.

Spatial datasets in raster form permit the mathematical manipulation that is described here for prescribing amendments. The use of raster-based calculations enables serving the farming community across an immense geographical area.

The flowcharts,FIGS. 2 and 3, provide a means to track the embodiment through the various steps, from EOS data to the application of the amendment to the field. The conventions used inFIGS. 2 and 3 are

j_ithrefers to the jth day. The jth day for EOS data is the day of the overpass.

i_ithrefers to the ith pixel.

n_ithrefers to the nth field.

The process begins at Start (S100) when satellite data for any desired jth day is obtained and stored at block S102. Initial development of the crop is preferably required for the most advantageous application of the embodiment of the invention and so the crop first needs to develop over about the first month, or so, in order for it to express the limitations imposed by the soil environment. Amendments are applied as many times per season as is necessary, though one application is generally sufficient.

From block S102 the workflow passes to block S104 that calculates the NDVI* for each ith pixel using scene statistics as described in the literature (for example Baugh, W. M. and Groeneveld, D. P., “Broadband vegetation index performance evaluated for a low-cover environment,”International Journal of Remote Sensing,27:4715-4730 (2006)). From 5104, the workflow splits to block S106 that provides for the use of a geostatistical procedure that interpolates the NDVI* values (as pixel centroids) across cropped field n. Kriging will be used if the EOS data are of moderate resolution (20-30 m/pixel). The kriged values provide for metering amendments at a finer scale than the coarse blocks that would otherwise be defined by pixels. Fields of geo-referenced NDVI* values are sent to the controller at block5108 that meters the amendment onto the field.

From the split at S104, the other path proceeds to S110 to provide input for field sampling by identifying high and low values in the geo-referenced NDVI* for field n. These values are used to select sampling locations in field n at S112 to determine the amendments that are needed to make crop growth achieve the desired level of productivity. Although the sampled soil beneath the high crop expression may represent the high for field n, the crop may not be operating at the desired level of production and so, this peak value for field n may also require additional amendments. This is shown inFIG. 1, where the hypothetical peak NDVI* is 0.9 (defined zero amendment requirement), however, the measured high for field n is less than that. To achieve the 0.9 NDVI*,FIG. 1 indicates that an addition of about 0.1 (application scaled zero to one) would be needed for the field n high value to become optimal. This optimum is optimal only with regard to production, without taking into account efficiency.

TheFIG. 1 hypothetical presents an opportunity for the farmer to interact with the flow of information to choose the percent of optimality as a target and thereby influence the efficiency of the crop. The choice for percent of optimality is to either run close to optimal, in which case input costs for fertilization and water run high, or at some fraction below optimal that does not require such high input costs. These and other considerations are made at the sample analysis stage in block S114. The prescription is passed to the amendment mixing stage at S116.

FIG. 3 receives input fromFIG. 2 that enables the prescribed amendment to be delivered. The data that was prepared to enable metering application at fields of geo-referenced values of NDVI* enters at S120. The prescription for mixing the amendments is received at block S140. The prescribed amendment is mixed in a tank or similar vessel and then delivered to field n at S142 by the methods previously described.

Both the portions of the fields of NDVI* determined soil conditions and the amendment mixture are regulated by the controller at S122 that receives input for the geoposition within field n according to GPS data at S150. The controller as described within the example embodiment controls the prescription and mixture of amendments and subsequent application to the field, in one embodiment, in a diluted liquid form through individually controlled sprinklers. Alternatively, delivery may be in the form of a tractor with sprayer, or if in solid form as a spreader that is guided by GPS to distribute the amendments according to the prescription tied to NDVI*. This process precisely applies amendment to correct nutrient problems for less-green portions of field n at step S124. Once the application is complete the process ends at S126. Data from each of these steps, including soil sampling, NDVI*, amendment prescriptions, etc. are stored electronically and referenced by geoposition for future use.

Various preferred and other embodiments of the invention have been described but it will be understood by those of ordinary skill in the art that modifications may be made without departing from the spirit and scope of the invention of the system and method. For example, a wide variety of soil amendments and nutrients other than those mentioned above may be employed depending upon the soil and crop in the field. Various delivery methods and mechanical systems may be employed for delivery of the prescribed amendments as determined by the variety of data from various sources as described above. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated and described embodiments but only by the scope of the appended claims.

Claims

I claim:

1. A precision method for applying soils amendments to an agricultural field or portions thereof through a delivery system comprising the steps of:

obtaining EOS data including scene statistics and pixels for the field containing an existing crop;

calculating NDVI* per pixel satellite scene statistics;

identifying and ranking NDVI* values for selected portions of the field;

obtaining soil samples at the selected portions of the field based on the ranked NDVI* values;

analyzing the soil samples and prescribing soil amendments based on interpolation of requirements at high and low NDVI* values at the selected portions of the field;

preparing an amendment mixture based on the prescribed soil amendment; and

delivering the prescribed soil amendment mixture to the selected portions of the field based on the NDVI* sample analysis values.

2. The method ofclaim 1 wherein the delivery system comprises a water irrigation system and the soil amendments are water-soluble and distributed through sprinklers of the irrigation system.

3. The method ofclaim 2 wherein the water irrigation system is precisely controlled by a field located controller in communication with a central computer system that gathers the data and performs the calculations to prescribe the soil amendment mixture.

4. The method ofclaim 3 wherein the water irrigation system includes multiple sprinklers that are controllable individually or in blocks.

5. The method ofclaim 3 wherein the water irrigation system is a center-pivot mechanical irrigation system.

6. The method ofclaim 1 additionally including the step of geospatially interpolating the EOS data before calculating the NDVI* for a pixel.

7. The method ofclaim 1 wherein the EOS data is adjusted during the growing season to reflect the variable solar angle and the distance from the sun.

8. The method ofclaim 1 wherein GPS location is used to determine the portion of the field where the sampling takes place.

9. The method ofclaim 1 wherein the soil amendments are selected from the group comprising nitrogen phosphorous, potassium, and micronutrients, or chemical substances that change soil properties limiting to plant growth.

10. The method ofclaim 1 wherein the NDVI* corrects for the soil background and atmospheric scatter and attenuation.

11. A system for applying soil amendments to an agricultural field or portions comprising:

a. computer system for acquiring and storing EOS data including scene statistics and pixels for the field containing an existing crop;

an algorithm for calculating NDVI* per pixel based on said scene statistics;

identifying selected portions of the field by GPS;

an algorithm for ranking the NDVI* values for the selected portions of the field;

physically obtaining soil samples at the selected portions of the field based on the maximum and minimum NDVI* values;

an algorithm for analyzing the soil samples and prescribing soil amendments based on interpolation of the requirements at the high and low NDVI*values at the selected portions of the field;

a container for mixing an amendment based on the prescribed soil amendment; and

a mechanical apparatus for delivering the prescribed amendment mixture to the selected portions of the field based on the NDVI* sample analysis values.

12. The system for applying soil amendments to an agricultural field ofclaim 11 wherein the EOS data is adjusted during the growing season to reflect the variable solar angle and the distance from the sun.

13. The system for applying soil amendments to an agricultural field ofclaim 11 additionally including GPS location data to determine the portion of the field where the sample is taken.

14. A precision method for applying soils amendments to an agricultural field or portions thereof through a delivery system comprising the steps of:

calculating greenness utilizing the satellite scene statistics;

determining the maximum and minimum greenness values for selected portions of the field;

obtaining soil samples at the two selected portions of the field;

analyzing the soil samples and prescribing soil amendments based on interpolation of the greenness values for the selected portions of the field;

preparing soil amendment mixture based on the greenness values of the selected portions of the field;

delivering the prescribed soil amendment mixture to the selected portions of the field based on the sample greenness analysis.

15. The method ofclaim 14 wherein the delivery system is precisely controlled by a field located controller in communication with a central computer system that gathers the data and performs the calculations to prescribe the soil amendment mixture.

16. The method ofclaim 15 wherein the water irrigation system includes multiple sprinklers controllable individually or in blocks.

17. The method ofclaim 14 wherein the delivery system is a center-pivot mechanical irrigation system.

18. The method ofclaim 14 wherein the delivery system comprises travelling tricklers.

19. The method ofclaim 14 wherein the delivery system is a drip irrigation system.

20. The method ofclaim 18 wherein the delivery system comprises a mechanical tractor with a dry soil amendment spreader.