User friendly model July 2005 Password Protected

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					            Welcome to Texas A&M University - University of Illinois User Friendly Corn Yield
            Forecasting Model (Copyright by TAES of Texas A&M University) by E. C. A. (Ed)
            Runge with computational assistance from John F. Benci
************ First step is to save this spreadsheet on your computer (Microsoft excel or compatible software ) ****************************************
             Save it under a name that is easy for you to remember e.g.. John Farmer 2005 corn yield field A.
             If you have more than one field you can save the spreadsheet more than once (different name for each field) and run the model for each field.
             Multiple model runs are only required if weather conditions, irrigation, or plant available stored soil moisture (PASSM) vary from field to field.
             Once you have saved the spreadsheet under your name, work with that copy.

Requirements to run this forecasting tool are outlined below:
       1) Ten weeks of weather information from a previous year for which you have corn yield results (no more than 5 years prior to the current year).
       2) Week 1 is six weeks before your tasseling/silking (anthesis) date. It occurs about 4 or 5 weeks after the planting date. If you have delayed
          emergence due to cold weather, or delayed crop development due to cold weather you may need to readjust the 10 weeks of weather you have
          used in the model.
       3) Ten weeks of weekly average daily maximum temperature, ten weeks of weekly total precipitation and any irrigation applied for the same year
          as #1 above.
       4) Weather for the current year (10 weeks of maximum temperature, precipitation and any irrigation).
       5) Determine your specific Plant Available Stored Soil Moisture (PASSM).
                      Click on PASSM at the bottom of your worksheet for assistance in determining this value

To Begin
       1) Click on "data input" at the bottom of your worksheet and enter your specific field information.
       2) Enter the previous year's weather (previous year and current year weather data will be identical until you begin replacing the previous year with
          the weather for this year).
                       ( The use of the term previous year does not necessarily mean last year but rather the year [Can use multiple
                       years by repeating the process] for which you have the required data)
       3) At this point hit enter and the "yield forecast results".
       4) The forecast yield will be identical to your previous year corn yield until you begin replacing the weather data with this year's data.
       5) Click on "data input" to enter the current year's weekly weather as the season progresses (beginning with week 1 and ending with week 10).
       6) Enter weather up to the current week and then click on "yield forecast results.
       7) As each week of current weather is entered a comparison of this year's corn yield to the previous year's yield is made.
       8) The model is completed after 10 weeks of this year's weather has been entered in "data input".
       9) The assumed tasseling date should be adjusted if it is determined to be different from the assumed date.
          (If the tasseling date is different you will have to adjust the 10 weeks of weather data so that week 1 is six weeks prior to tasseling.
          Tasseling is assumed to occur instantly between the 6th and 7th week. Since pollen shed occurs over several days put most of the
          pollen shedding period in the 7th week rather than the 6th week.)
  Results
            Results are calculated based on the historic yield provided and are reported as a percent of that year's yield.
            Better growing conditions in the current year (better weather, more PASSM, more irrigation)
            will result in percentages being more than 100% of the previous year's yield. Poorer growing conditions
            in the current year will result in percentages of less than 100% of the previous year's yield.
            The assumption is fertilizer, hybrid, insect and disease control, and other management is relatively constant for the two years.

Assumptions made in using The Corn Yield Calculator
         1) Farmers grow corn the same way this year as they did last year.
         2) Corn yields are not predicted absolutely. To use the Corn Yield Calculator you must provide data from a prior year, including -
                     a) Corn yield in bushels per acre.
                     b) 10 weeks of average daily maximum temperature, in degrees Fahrenheit (with 6 weeks before and 4 weeks after anthesis/silking)
                     c) 10 weeks of total precipitation, in inches (with 6 weeks before and 4 weeks after anthesis/silking, irrigation is added to the rainfall)
                     d) Anthesis date.
                     e) Plant available stored soil moisture (between 4 and 11 inches) at planting or just after planting time-
                                 reported as inches of water available in the root zone.
                     f) Corn yield for the year of interest is given in bu/acre (15.91 bu/a = 1 t/ha) and as a percentage of the historical year of data
         3) Unusual situations (flooded spots in fields, frost, insect or disease damage, poor stand, poor weed control, etc.) are assumed to
           be the same as they were in the historical year of data.
         4) The model assumes that corn yield and weather relationships are the same as they were for the experimental data from which the
           model was derived. This does not appear to be a serious limitation in using the model.
         5) Yield increases since the model was derived may be a concern to you. Experimental data indicate that most of the 1.2 to 2+ bu/acre
           annual increase in corn yield for the past several decades is due to increases in plant population for new hybrids - particularly the
           single cross hybrids of the past 35 years. The model was derived using data from one of the first widely adapted high-population
           single cross hybrids and that often achieved yields in excess of 200 bu/a under favorable conditions..
GUIDELINES FOR SELECTING PASSM FOR YOUR FIELD OR PARTS OF YOUR FIELD

Corn is generally planted on soils that hold large amounts of plant available stored soil moisture (PASSM). PASSM supplies water to the plant
when rainfall is less than evapotranspiration from the soil and corn plants during the gowing season. In most areas of the corn belt in
most years PASSM is gradually reduced during the corn growing season. Consequently, the soil is often quite dry when corn is mature.

PASSM for most corn belt soils is usually at field capacity at planting or the beginning of the growing season. In the Western Corn Belt fall
and winter rainfall may be insufficient to bring PASSM to field capacity. PASSM below field capacity may occur in the Central and Eastern
corn belt in some areas in some years. It is critical that you correctly assess PASSM to make best use of the model to predict corn yield for
your field or plot during the current growing season. Please consult the Soil Survey Report for your county to assess the PASSM for your field.
Personnel with the Natural Resources Conservation Service-USDA and your County Extension Service with your State Land Grant University
can also assist you.

The best corn belt soils hold 10 to 12 inches of PASSM if they are at field capacity. Soils like Muscatine, Tama, Sable, Flanigan, Drummer,
Proctor, Nicollet, Webster, Sharpsbug, Marshall, Pawnee, Brookston are among the most productive corn belt soils because they hold 10 or more
inches of PASSM. Other soils like Cisne, Mexico, Putnam, Edina, Elliott, Miami, hold some 8-10 inches of PASSM. Soils in the fair category
that hold 6 to 8 inches of PASSM are soils like Swygert, Clarence and sloping or eroded phases of many glacial till soils as well as soils like
Vigo, Hosmer, Bluford and Wynoose. Smaller soil inclusions occur in many fields that hold less water than the most prevalent soil. It is not
unusual for such soils to have PASSM's of 4 to 6 inches or even less. These soils will have reduced corn yields in most years. Corn yields in the
northern corn belt are higher for soils holding less PASSM than they are in the southern corn belt. In years when rainfall is above
normal, soils with low PASSM's can yield nearly as much as soils holding considreably more PASSM. Examples of such
soils are - "slick spots" like Huey and Darmstadt in Cisne soil areas; sandy areas; soils shallow to till in glaciated areas; eroded hillslopes in
many fields; soils shallow to bedrock in a few areas; areas where infiltration is slow and much of the rainfall runs off, etc. If you have farmed the
area for some time you will be aware of low yielding spots in your fields. These low yielding spots are generally low in PASSM compared to
other parts of the field.

In the Western corn belt, soils may not receive sufficient rainfall for PASSM to reach field capacity. If irrigation is used to bring soils to
field capacity and irrigation done on demand during the growing season the difference in yield between years will be small, however if irrigation
is not available corn yield can vary by year because of lower amounts of PASSM in drier years.

Table - Index for Plant Available Stored Soil Moisture for Corn Belt Soils

1. Best soils 10 to 11 inches of PASSM with adequate rainfall to reach field capacity.
2. Good Soils 7 to 9 inches of PASSM with adequate rainfall to reach field capacity.
3. Fair Soils 6 to 7 inches of PASSM or better soils with inadequate rainfall to reach field capacity.
4. Soils with restricted rooting depths - shallow to till or rock, "slick" spots, eroded spots, sandy areas, etc. - 3 to 6 inches of PASSM.
             Such soils are often inclusions and are not the major soil in most corn fields.
DATA ENTRY AND YIELD FORECAST PAGE

Week 1 is six weeks prior to tasselling (to be determined separately for previous and current year). It usually occurs some 3 to 5
           weeks after planting depending on temperature.
Enter previous year weather for 10 weeks ---average of daily maximum temperature (F) for week and total precipitation (inches) for week.
Enter weekly irrigation if any, PASSM and corn yield for previous year.

        PREVIOUS YEAR'S WEATHER                                                                    PASSM = 10        inches
         average week     week                    week            week
 week #   maximum     precipitation            irrigation     total water                       Corn Yield = 165 bu/acre
              (F)       (inches)                (inches)        (inches)
    1        83.0         0.85                    0.00            0.85
    2        82.7         1.22                    0.00            1.22
    3        84.3         0.82                    0.00            0.82
    4        85.1         1.12                    0.00            1.12
    5        84.7         1.18                    0.00            1.18
    6        83.0         1.04                    0.00            1.04          Corn
                                                                            <<<<<<< Tasseling week for previous year
    7        85.0         0.76                    0.00            0.76
    8        82.4         0.75                    0.00            0.75
    9        82.5         0.93                    0.00            0.93
   10        81.6         0.69                    0.00            0.69

For this year's forecast replace each week of weather with current weather as the growing season progresses.
           THIS YEAR'S WEATHER
              maximum        total weekly    applied                              PASSM =               10 inches
 week #     temperature      precipitation  irrigation     total water
    1            83.0            0.85          0.00           0.85
    2            82.7            1.22          0.00           1.22
    3            84.3            0.82          0.00           0.82
    4            85.1            1.12          0.00           1.12
    5            84.7            1.18          0.00           1.18
    6            83.0            1.04          0.00           1.04          Corn
                                                                       <<<<<<< Tasseling week for this year
    7            85.0            0.76          0.00           0.76
    8            82.4            0.75          0.00           0.75
    9            82.5            0.93          0.00           0.93          Current Yield Forecast       =    165.0 Bu/acre
   10            81.6            0.69          0.00           0.69          Percent of Previous Year     =    100.0 %
state   county     week         cell        max        min    precip    w        wsq
                                        1
                      1                 2    83.00               0.85       10         100
                      2                 3    82.69               1.22
                      3                 4    84.32               0.82
                      4                 5    85.05               1.12
                      5                 6    84.72               1.18
                      6                 7    83.00               1.04
                      7                 8    85.00               0.76
                      8                 9    82.36               0.75
                      9                10    82.50               0.93
                     10                11    81.60               0.69


                 Now Calculate yield for this years weather

                   week         cell        max        min    precip    w        wsq
                                        1
                      1                 2    83.00               0.85       10         100
                      2                 3    82.69               1.22
                      3                 4    84.32               0.82
                      4                 5    85.10               1.12
                      5                 6    84.70               1.18
                      6                 7    83.00               1.04
                      7                 8    85.00               0.76
                      8                 9    82.36               0.75
                      9                10    82.50               0.93
                     10                11    81.60               0.69


                 farmer yield for previous year          165 bu/acre
                 yield as a percent of previous year is       99.98923 %
                 farmer forecast yield current year 164.9822 bu/acre
      sumr*t   sumr*tsq   sumth*t    sumth*tsq sumr*th*t sumr*th*tsqyield

628.79 48.92141 327.4175 4575.479 31917.82         4075.12 27180.18         156

                          This is for previous years weather.




      sumr*t   sumr*tsq   sumth*t    sumth*tsq sumr*th*t sumr*th*tsqyield

628.79 48.93227 327.4826 4575.591 31918.19         4076.14 27185.97         156

				
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posted:10/6/2012
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