Abstract:
The invention concerns a method of predicting rainfall and crop production in regions of substantially varying rainfall in which run-up rainfall for a season is correlated with the growth season rainfall predicted from a pattern of growth season rainfall derived from historical records.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a method of obtaining crop production by the controlled use of natural water supplies.  
         [0002]     The invention also relates to novel methods of obtaining foreknowledge of crop growth season rainfall prior to planting time. This allows timely cultivation planning for better utilization of the rainfall to obtain more economical crop production.  
       BACKGROUND TO THE INVENTION  
       [0003]     In areas of substantially variable rainfall seasonal crops can be liable to serious periodic average harvest failures. These failed crops impact severely on farming activities and profitability. The basic reason for such failures is the incorrect crop planting procedures adopted against the rainfall pattern during the growth season. This is due mainly to lack of any reliable foreknowledge of the good or poor order of growth season rainfall and most importantly the component of rainfall coinciding with crop pollination and maturation.  
         [0004]     Efforts to avoid the losses which occur have been limited to farmers relying on experience in order to try to program their procedures. Such efforts have shown no more than a seventy five percent reliability which is not generally satisfactory for viable long term farming operations.  
       OBJECT OF THE INVENTION  
       [0005]     It is an object of the invention to provide a method of obtaining more economically viable crop production than is presently obtained. This is to be achieved by the farmer more confidently pursuing crop cultivation planning than heretofore. It makes optimum use of growth season rainfall possible over many growth seasons of different rainfalls.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with this invention there is provided a method of crop production in regions of substantially varying rainfall comprising the planting of the crop at a time determined by the correlation of the run-up rainfall for the season with a growth season rainfall predicted from a pattern of growth season rainfall derived from rainfall records for the region of planting.  
         [0007]     Further features of the invention provide for the prediction to be obtained from a categorization derived from the pattern of the historical regional rainfall and the selection of cultivation program to be determined from the categorization.  
         [0008]     In the specification “run-up rainfall” means the rainfall which occurs during a selected period prior to the usual planting period of a crop in a particular year. “growth season rainfall” is the rainfall from planting to harvesting of a crop “late rainfall” is rainfall during crop pollination and maturation.  
         [0009]     The invention also provides for the categorization to be obtained by a comparison of crop yields against similar growth season rainfall patterns over an extended period of years. (In South Africa such records are available over a period of seventy-five years). The comparison may further be made by choosing historical years having similar run-up and early growth season rainfall to the year of planting and correlating the growth season rainfall against crop yield to select a cultivation program for the specific planting season crop.  
         [0010]     The invention further provides patterns and categories of information derived from historical rainfall and crop productions for use in the invention defined above.  
         [0011]     Generally therefore in this way crop production can be effected inter alia by planting at a time which is indicated to give adequate growth period rainfall. Further the cultivation program can be determined to give best results for predicted rainfall and thus avoid loss. The cultivation program refers to determination not only of planting time but includes all other aspects such as choice of variety of crop, fertilizer application and density of planting for example. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0012]     By way of example only and without limitation to the scope of this invention the method of crop planting was effected on the basis of the following description of preliminary determination of expected growth period rainfall specifically for the Sandveld region of the Western Cape Province in South Africa.  
         [0013]     To obtain a pattern and categorization for predictability of rainfall to achieve crop success it is necessary that access be had to historical rainfalls over consecutive periods to enable categories of norms of high consistency to be extracted over as long a period as possible. Six such categories have been identified in 75 years extending from 1925 for the Sandveld region. Four cover less than 9 years each, one 4 years and the remaining one 32 years.  
         [0014]     To use a category as a platform for working towards complete predictability one needs to derive one category that is dominant as either a “good” G or “poor” P crop yield year. Where a separation of years with G and P ratings is such that a category is not very dominant in any of them, subcategorisation is obtained by using finer variations on the usual run-up rainfall norms or by using norms applying to designated periods in the overall run-up rainfall period. This has been found to be a highly successful technique to get separation of rainfall patterns into G or P categories in summer rainfall regions.  
         [0015]     The rainfalls of all past years were first individually rated as G- or P- based on their “late” rainfalls for successful crop production on experienced norms of what rainfall must be to pass as G or otherwise be P.  
         [0016]     This selection of rainfalls into patterns already gives, for purposes of rainfall projection, a good separation of good and poor year indicators. Two of the smaller Sandveld patterns thrown up by this process contain about half of the 25 P years experienced since 1925 in their combined total of 15 years with a consistency of some 90% therein.  
         [0017]     Three other, also smaller ones, are one 100% and two 85% G and a fairly big one (32 years) 70% G. All this makes the year specific rainfall prediction much simpler.  
         [0018]     The invention also provides that some auxiliary fully consistent categories can be indirectly deduced from rainfall patterns, e.g. unbroken sequences of two years composed of any couple or combination of good G-rainfall patterns (85% to 100% G) always being followed up by a P-year. The correlation is referred to in this specification as a “rule” and could by itself have irrefutably indicated or confirmed the P-status of 12 of the 25 P-years since 1925. Another similarly derived category indication, enabled a further 4 P-years to be pinpointed.  
         [0019]     The absolutely consistent kind of pattern-based correlations and their connection with P-year outcomes, augmented by a few natural, mostly rainfall structure, correlations could in fact, it was found, have been used to project all the Sandveld P-years since 1925 year specifically. Therefore by difference also all G-years could be so predicted allowing one to submit that Sandveld rainfalls were unquestionably practically all predictable on the G and P of their late rainfall and will also be found to be so in future.  
         [0020]     The invention of course provides through the historical typical average monthly rainfalls of each pattern, useful information on full growth season period rainfall in general. This also is of considerable value for the utility of the invention itself.  
         [0021]     For example a “wet” April pattern is a year typically good in general rainfall except that 30% of the time its late rainfall is poor. Knowing however beforehand when it would be G, which it is 70% of the time, would support confident planning for top harvests in such years. Knowing which 30% of years would be poor in late rainfall could help to retrieve some of them as good harvest years by merely ensuring that planting was completed early in April.  
         [0022]     Generally the requirements for a good crop may be set out as follows:  
         [0023]     Region: Sandveld—Marginal dry land cultivation  
         [0024]     Typical Rainfall: Winter  
         [0025]     Crop: Wheat—growth period 3½ to 4 months  
         [0026]     Crop Growth Season: April-October  
         [0027]     Planting time: April (ideal)-Mid June (Depending on adequate rainfall for seed bed preparation (ploughing)  
         [0028]     Critical Rainfall for Good Crop Yields: i.e. “late” Rainfall—August&gt;37 mm. and/or August/September&gt;45 mm or on very late plantings August/October&gt;58 mm  
         [0029]     Poor Critical Rainfall that can result in Poor Crop Yields: August/September&lt;45 mm. or on late plantings August/October&lt;58 mm.  
         [0030]     Note: All good and poor year ratings hereunder relate to the foregoing Good (G) and Poor (P) norms on basically August/September (late) rainfalls in the Sandveld. Past Rainfall Records—75 years, monthly intervals  
         [0031]     Some categorization results extracted from the historical records are set out below.  
                                         (Predominant G or P indication on crop prospects 75%-90%)                                (1) April &gt;9 mm. but &lt;22.5 mm.   Generally unfavourable for planting.       May &gt;30 mm. (Planting can   Note: needs sub-categorisation -       commence)   itself not used as a pattern.       (2) (γ) A subcategorisation of (1)   Always good in late rainfall and       April &gt;9 mm. and May &lt;30 mm. and   yields       June &gt;30 mm.       (3) (α) A subcatergorisation of (1)   Predominantly poor (85%).       May &gt;30 mm. and June &lt;30 mm   Exceptions all predictable       (4) (Σ) A subcatecorisation of (1)   Predominantly poor or unplantable.       May &lt;25 mm. June &lt;30 mm.       (5) (θ)Selected category of April &gt;22.5 mm.   Predominantly good in late rainfall           and yields (±70%). Exceptions all           predictable       (6) Apr. &lt;9 mm.   Predominantly good; but needs           subcategorisation (- itself not used           as a pattern)       (7) (φ) Subcategory of 6   Predominantly good       April &lt;9 mm.; May &gt;30 mm.       (8) (φ 1 )Subcategory of 6   Predominantly good       April &lt;9 mm.; May &lt;25 mm.;       June &gt;25 mm.       (9) A loose correlation on 20% of years   Predominantly good yields (±66%).       February &gt;15 mm. (Preplanting time -   Exceptions all predictable       Direct correlation but very inconsistent       at 66%)       (10) A loose correlation   Always poor - except if April &lt;9 mm.       March &gt;30 mm. (Preplanting time)   (Has preplanting time availability)       Note: One of the few consistent direct       correlations - occurrence only 5%.       (11) A loose correlation   Poor but could be good if planting is       April &gt;65 mm. (One of the few consistent direct   completed before end April. (Has       correlations - occurrences 4%)   preplanting time availability)       (12) A loose correlation   Follow-up year predominantly poor.       Two consecutive yearly rainfalls &gt;550 mm.                  
 
         [0032]     The following is one of the typical correlations on rainfall structures that leads to finally defined preplanting projections of winter rainfall in Sandveld.  
         [0033]     There is never in poor year occurrences more than 3 single poor late rainfall years that is not subsequently followed by double poor late rainfall years. If 3 single poor crop years have been experienced over an unbroken period, the next poor crop year can be assumed as being the first of two successive poor crop years i.e. the first leg of a double poor year cycle.  
         [0034]     There is never more than 2 successive poor late rainfall years in a row. During the second year of such a cycle (occurrence about every 10 years) it is certain that it would be followed by a good late rainfall year.  
         [0035]     A cycle of 4 good late rainfall years in a row will always be followed by a P-year.  
         [0036]     The following is typical of a consistent rainfall pattern:  
         [0037]     A poor year will always follow year combinations of the 3 good late rainfall grouping of years within the developed categories. As explained above this pertains to an absolutely dominant correlation, consistent and fairly frequently occurring, and overriding any good year indication for e.g. a good rainfall pattern or a natural correlation. This “rule” is identifiable solely because a method of splitting up records of rainfall into patterns and categories is used. It is supplemented though in coverage in this respect by the consistent drought pattern cycle P-year indications and a few other such consistent and dominant natural correlations to predict poor years. This ensures that nearly all poor (P) late rainfall years in the Sandveld can be predicted a year beforehand.  
         [0038]     With all the poor year exceptions on the good (G) year patterns and categories and vice versa thus predictable, the overall net result is that virtually total year specific predictability of G and P of late rainfalls for virtually all years in the patterns categories could be attained. Very important to note here is that it means the farmer can now also use knowledge of general typical rainfall of the identified category concerned to pursue least risk optimization planning on crop cultivation.  
         [0039]     One need not stop with such findings with the effort of confirming or double confirming principal indications because there are still some further indications which can be determined.  
         [0040]     One is to be found in a two multiple rule derivable from the fact that good (G) years invariably come in cycles of two or four years.  
         [0041]     An in-depth analysis shows that by this latter rule alone virtually all good and poor years in a historical sample of Sandveld years could have been predicted by bringing less than half of the dominant poor year indications into play. Without use of the new methodology set out above, it could not provide more than say 75% predictability.  
         [0042]     Year specific prediction of G/P late rainfalls of Sandveld&#39;s years of April&gt;22.5 mm.  
         [0043]     This example of 32 Sandveld years since 1925 with wet April pattern and category selection was picked to illustrate here how this kind of prediction as defined was achieved in practice for this winter rainfall wheat producing region. For this purpose Table A of wet April pattern rain records in the region&#39;s last covering report on its rainfall predictability (October 2001) is given hereunder with the G and P ratings of their rainfalls in the second last vertical column. G for above 45-48 mm. range August/September rainfall and P for below that range. Where there is no prior P year indicator, as for example β, χ 1  in the following table, a cut-off point for G of 45 mm is to be accepted.  
                                                                                                                                             TABLE A                                                                           Aug/   G   P-       Year   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov/Dec   Tot   Sept   or P   Indication                                1929   0   3.8   2.8   22.6   37.3   49.8   24.6   24.4   23.1   4.3   18   210.8   47.5   G           1931   0   3.8   0.5   63.2   19.6   10.9   25.9   56.1   15.5   15.5   10   221.2   71.6   G       1935   4.1   0   5.3   38.1   40.1   19.1   26.7   64   35.6   8.1   11   252.0   99.6   G       1938   6.6   3   0   34.8   30.2   13.2   13.2   8.1   23.9   10.4   11   154.1   32.0   P   β       1940   0.3   3.5   10   23.1   17.6   41.1   12.2   18.5   27.1   12.7   22   188.0   45.6   P   α 1         1941   19.8   0.5   0.8   54.9   81   70.6   46   55.9   43.2   24.9   3   400.5   99.1   G       1942   1   0   0   31   23.4   72.6   12.7   58.7   7.1   6.1   47   259.8   65.8   G       1945   0.3   2.5   2   24.9   43.7   71.4   45.7   26.2   2.5   17.3   5   241.9   28.7   P   β       1946   0.8   1.3   10.4   31   20.1   19.8   14.2   18.5   89.9   10.7   3   219.6   108.4   G       1949   0.3   0   3.6   26.9   36.3   15.6   30.2   42.4   36.8   27.4   17   236.0   79.2   G       1950   0   1.3   4.8   34   7.6   16   72.8   2   43.7   15.7   19   216.4   45.7   P   α 1         1953   0   2   3   93.7   46.7   12.2   77.7   28.7   2.5   3.5   17   286.6   31.2   P   B       1954   5.1   1.5   8.1   37.6   40.7   52.1   83.3   56.4   7.1   20.1   13   324.9   63.5   G       1955   0   34.3   1.8   25.1   1.3   78.7   53.8   72.8   7.9   22.4   21   318.9   80.7   G       1959   1.8   6.1   6.6   23.9   106.7   10.2   29.2   48.8   16   17.3   8   274.5   64.8   G       1961   3.6   2.3   2   48.8   33.3   56.9   39.9   39.6   29.7   6.1   6   267.8   69.3   G       1962   2   9.9   1   23.1   17.5   24   44.7   95.8   14.5   25.1   23   281.0   110.3   G       1965   11   15   24   29   12.7   18.8   19.3   32.3   14.7   8.4   21   206.8   47   P   B       1967   1   21   2   56.4   37.1   88.1   18.8   27.2   24.9   13   19   308.9   52.1   G       1968   0   0.3   22   22.9   51.3   44.2   24.9   37.3   2.5   30.5   6   242.6   39.8   G       1976   6   2.7   3   91.2   12.3   94.5   71.6   22   11   7   82   403.3   33.0   P   χ 1         1977   8.7   18   5.5   33   98.5   71.2   59.4   50.7   22.6   7.5   30   404.8   73.3   G       1980   2   4.8   0   28.1   43.8   55.5   10   51   4.2   6.5   43   249.3   52.2   G       1982   20   2   24   33.1   19   48.1   38.4   20.2   4   22.2   24   254.9   24.2   P   δ 4+         1985   13   5.5   45   27.7   47.5   31.1   51.4   26.7   21.2   4.7   46   318.7   47.9   P   B       1987   0   1.7   1.6   35   23.6   42.5   67.7   51.1   51.5   5.5   22   302.2   102.6   G       1988   0   1.2   11   51.2   33.4   41   23.8   31.9   28.5   1   13   235.5   60.4   G       1989   2.5   7.5   20   33.2   18.3   43.5   53.4   76   34.7   22.6   15   326.9   110.7   G       1990   1.5   9.7   0   55.1   60   55.1   63.9   18.3   6.5   3.2   8   281.6   24.8   P   δ 4+         1993   0   12   6   75.1   115.3   23   63.9   28.3   9.5   0   19   352.1   37.8   P   B       1994   0   0   0   23.8   17   112   34.8   3.2   25.4   27   4   247.1   28.6   P   X       1999   0.3   6   0   26   19.2   31.3   26.9   50   62.3   1.3   15   238   112.3   G       Ave.   3   6   7   39   38   45   40   39   23   13   19   273   62       75-   3   5.5   11   23   35   44   37   37   21   14   19   249   58       yr       Ave                 Note that this table as well as those for other rainfall patterns was obtained by the technique of categorization of rainfalls. This table illustrates incidentally the point that even a good (G) and large rainfall grouping generated by categorization could have less than 70% consistency in its G-indication.             
 
         [0044]     The last vertical column of the table is added to reflect where “late” P rainfall indicators were available (of course now so identifiable in hindsight from rain records and for this reason also identifiable in run-up rainfalls of future years) to going out a year beforehand whether a year&#39;s late rainfall would be G or P. And this was all that was needed to declare all P years in the table, and hence by difference, all its G-years, as year specifically predictable.  
         [0045]     It is believed that this table reflects very much the outcome of a historical first effort to prove full year specific predictability of rainfall, confirming this work on using basically the cyclical nature of rainfall to determine crop planting and why the principle of projecting forward rainfall by deductions made from past rainfalls is valid and validates the whole underlying hypothesis proceeded from in the relevant research that this is so.  
         [0046]     The use of the method set out above show that G and P predictions for G and P years in the Sandveld over a period of three years prior to the date of writing would have been accurate.  
         [0047]     From the above it will be appreciated that other correlations from the historical records of rainfall patterns and crop production can be developed in other regions for use in the production of crops according to the invention which are also location and time specific and will result in satisfactory or simply more profitable crop production under previously adverse conditions.