Nutricalc - Instructions 

It is important to know and to check the quality of the fertilizers used. Columns C & D in the recipe calculator contain data on the percent nutrient in each fertilizer. Note that the nutrients are percent element (%K, %P) not percent oxide (%K2O, %P2O5).Click on the red triangles for more information. These columns are not locked, and if your fertilizer has a different composition to that shown then you will need to alter the percentages.

The recipe cost calculator has been set up with fertiliser prices that are typical for buying less than half tonne lots in New Zealand as at September 2002. The prices you are currently paying will need to be inserted in column D.

An old and new recipe must be loaded in the mix adjuster before it can be used. Select the new recipe in the recipe data base and press Command +x to load the new recipe, and then select the old recipe and press Command+o to load old recipe. Enter the volume of the old recipe remaining in the stock tanks in cell C4 of the mix adjuster and the volume you want to make of the new recipe in cell F9 and press return for the weights of fertilizer required for the adjustment to be calculated automatically. Print the work sheet and use it as your check list.

The check list printer is automatically loaded whenever you select a recipe in the data base and press Command +x. All you need to do then is enter the volume of the stock solution to be made in cell C4 and press return and then click on cell C4 for automatic calculation. Since the recipe is overwritten each time Command +x is pressed you should check and ensure that the sheet is calculating the recipe you want and not some other recipe. Print the list and tick off item by item as you are doing the weighing.

A recipe calculator is included on the workbook with the tab "Sonneveld's method". It is an ordinary Excel spreadsheet.

Row 5 already contains your water analysis, or your water analysis can be pasted directly into this row from the water analysis data base.

Enter the molar specifications of the recipe you want in row 7, for example if you want a write recipe for 15 mmol nitrogen per litre, 1 mmol phosphorus , 1.5 mmol sulphate and 8 mmol potassium, 4 mmol calcium and 1.5 mm magnesium, simply enter these numbers in the appropriate columns of row 7, together with the micronutrient (trace element) concentrations in micromols/litre (µmol/l). All solutions must be ionically balanced and so cells T7 and U7 keep an automatic check on the sum of cation and sum of anion equivalents as you enter the numbers. T7 must equal U7 for any possible solution except those containing acids or alkalis (they are balanced too but the calculator does not add hydrogen ions into the sum of equivalents).

Note also that T7 will be the approximate CF of the solution with this molar composition.

Line 8 shows the water analysis, but with the nutrient concentrations automatically converted to mmol/litre. Line 9 is the millimol concentration of each nutrient required in the stock solutions, that is the specified concentration for each nutrient less the concentration of that nutrient in the water supply. Iron in the water supply is usually not available and its concentration is ignored with the required iron concentration being supplied entirely from iron chelate.

This calculator is not automatic as there as any number of recipes that could fit the specification.

Column A in rows 11 to 22 contains the chemical formula of the principle fertiliser components. If you are not familiar with the chemical formulas then row 3 shows names and formulas.  Work down the spreadsheet deciding which fertiliser you wish to use, and filling the empty box with the molar contribution you want from that fertiliser. For example, if the phosphorus source in your recipe is to be from monopotassium phosphate put the required phosphorus concentration, that is 1 mmol in the empty box in the KH2PO4 line. When you do that potassium contribution from KH2PO4will be automatically entered in the K+ column. Choose next the calcium fertiliser to be used and enter the molar calcium concentration in the proper box. This will usually be calcium nitrate so enter 4 in the Ca++ column of the Ca(NO3)2 row. Since there are 2 N atoms in the chemical formula Ca(NO3)2 , the NO3- column will automatically now show 8. This recipe requires 8 mmols of K+ , which could be supplied by potassium nitrate, phosphate, sulphate or chloride. You have already included 1 mmol K+ from monopotassium phosphate only 7 mmol more K is needed from which ever source you choose. The recipe does not include any chloride and only 1.5 mmol sulphate, so the choice has to be potassium nitrate, so enter 7 in the K+ column of the KNO3 row. The recipe calls for magnesium and sulphate so go to theMgSO4 row and insert 1.5 in the Mg++ column.

Now check the totals in row 23. In the nitrate column it shows 15 mmol, that is the sum of 8 mmol from calcium nitrate and 7 mmol from potassium nitrate. Make sure each major nutrient is showing the correct required total. There are two lines of totals, one is the stock solution and the other includes the nutrients from the water.

Below the line of major nutrient totals is a column listing the most likely micronutrient sources. Each source only provides one micronutrient, and so the calculations are automatic but the user has too choose which alternatives to use, do this by inserting y (yes, use this one) or n in the next column.

Line 38 at the bottom of the worksheet is the stock solution recipe which meets the requirements of the recipe given in molar terms. The line shows the amount of each fertiliser in kg (or litres for acids) and for micronutrient in grams to be used to make 100 litres of each stock solution for dilution at about 1 in 200.

When you are sure it is all correct add the details of recipe number etc in the blanks at the start of the line and then cut and paste into your recipe data base. When that has been done this recipe can be automatically pasted into the feed calculator for a print out of dilution v nutrient concentrations in ppm, and into the cost calculator and check list printer using Command +x. The calculator will have calculated fertiliser rates to the nearest gram, and this is probably much more precise than necessary, so it may be easiest to paste into the recipe line of the recipe calculator and work along the line rounding the quantities to the whatever precision you require, then check the dilution x CF table to be sure that no errors have been made before saving the file line with Command+r. Once it has been saved Command+x will paste the new recipe into the cost calculator, and check list printer.

An original paper by Sonneveld et al on this subject can be obtained at http://www.actahort.org/. The paper is in Acta Horticulturae 481, 1999:331-339.