seed mix and cover crop growth calculator

by SoilYoga


Plan your cover crop seed mix to achieve your soil improvement Goals
  • Select up to 3 soil improvement goals for your next cover crop mix.
  • Calculator takes into account:
    • Benefits of different species.
    • Seeding rates, C:N ratios and total seeds needed for mix.
  • Enter your local prices to calculate total cost.
  • Suggests distribution to seeder boxes based on seeding depth.
Find your optimal cover crop seeding date and predict your results
  • Our calculator uses real historic weather data from a weather station near you.
  • Predict likelihood of frost in spring and autumn.
  • Find your earliest and latest safe seeding dates.
  • Cross check climate and plant characteristics to predict total biomass gain.
  • Receive warnings if vulnerable plants selected will likely be in danger of freezing.
  • Estimate bloom and ripeness dates considering climate and seeding dates.
  • Compare total growing degree days (GDD) needed vs available.
Calculate seeds per seeder box and how many times mixing is needed
  • The calculator will assign different species with similar seeding depths together.
  • Fully customizable with your own number of seeder boxes.
  • Calculate how many mixer loads per seed box needed.
Calculate your savings and gains
  • Estimate your gain in nitrogen in cash value (compared to buying fertilizer).
  • Estimate your top soil and humus thickness and organic soil matter increase.
  • Estimate water holding capacity of your soil.

Quick guide

Our cover crop seed mix calculator-Simulator consists of two tabs in Google Spreadsheet as shown below.

“Plant DATA” sheet is fully user-customizable to Your custom local information by Yourself (except list of Crops). For desirable input information: change seeding depths, rates and update Your local cover crop seed prices. However, we have put in the Default information for a quick use of the calculator which will be always in front of Your eyes.

All the cells with white background consist of user-changeable information, all the other cells are locked, therefore unintended changes in other cells that can affect any technical issues are excluded.

If You want additional information or something remains unclear, there are many ‘question-marks’ around the Cover Crop seed mix Calculator, which help You on the run. Simply hover Your mouse over question marks for notes to pop-up.

1. “Smart MIX CALC” – The Calculator-Simulator
2. “Plant DATA” – Personally customizable input data

Customizable Plant DATA sheet with default input data

A. Basic information

A. Basic Information

Mix name – Optional to give Your mix a name so it is easier later to orient in different PDFs or paperwork

Weather Region – Select a country/state and region closest to You. To find information about the frost probability in Your climate – scroll into the Section ‘F. Growth Simulator’. Information is based on last 15-20 years real climate.

Planable Cover Crop:

  • Seeding Date – Enter day and choose month for when You want to seed Your cover crop. By entering unrealistic seeding dates due to high frost possibility, You will be informed.
  • Termination Date – Enter the day You plan to kill Your cover crop or let the frost kill the annuals. You have to choose one (Termination date OR Frost-kill) for simulator to calculate the growth. In warmer climates where frost-killing is not likely, the simulator will let You know.
  • Planable area – Enter the area You would like current mix on. That affects total quantities and mixer advice.

Following Cash Crop & Soil Description – Cover crop effect on following cash crop and soil humus balance are topics we consider adding in next Cover Crop Calculator-Simulator version.

Priorities for mix: Select and track up to three priorities You want that cover crop mix to be helpful at.

Seeder Setup & Mixing: Calculator is able to divide Your selected crops and fertilizers in the mix into up to 3 different seeder boxes. Helpful for mixing up the seeds in right proportions. ‘Mixer capacity’ is also needed for that.

B. Mix Setup & Overview

B. Mix Setup & Overview


Crop selection: Below of this Crop selection section is a small guideline on which crops do well in Your particular priority goals You chose above.

Seeding rates are automatically calculated in equal proportions of each nominal seeding rate. In ‘Desired Seeding Rate’ it is possible to change each crop individually to make uneven mixes. By leaving the cell blank calc returns to automatic logic.

Desired seeding rate – There is 1 small white (changeable) box in Desired Seeding Rate title – Main seeding rate multiplier. As a rule of thumb through real life practices mixes should be sown with 125% of their nominal seeding rate.

Distribution into seeder boxes is done automatically depending on No. of boxes selection above using seeding depth logic: similar seeding depths are compounded. However this can be changed manually by selecting box number suggestion. By leaving the cell blank calc returns to automatic logic.

Informational results of your mix, suggestions and cautions on different aspects

Cover crops to consider for selected goals – Calculator highlights different crops from crops list which thrive in selected goals. Please be noted, that these recommendations in this case do not take into account seeding time and selected climate.

Advices and suggestions are informational based on selected climate and seeding and termination dates.

C. Other MIX Properties

C. Other MIX Properties

D. Suggestions for Mixing up & Seeding

Mixing and seeding suggestions

E. Inputs Calculation and Distribution Into Boxes

E. Inputs Calculation and Distribution Into Boxes

In this section You can add seed treatment inputs and fertilizers into Your mix and divide them between the suitable seeder boxes. Least information needed to add these into Your mixing up plan (Section D.) is to give a Product name, correct usage rate quantities with units and select box You want to add them to.


  1. Select whether it is inoculant or fertilizer in drop-down menu.
  2. Type in Product name
  3. Enter usage rate of the product and select units!
  4. Optional: enter price to see total quantities and price
  5. Select seeder box You want calc to automatically add it to the mixer equation
  6. Clarify the density of the product for accurate proportions in the mixer

Bulk density is set by default to water density – it is important for Calculator to understand the quantities in the mixer as mixer’s volume is fixed, but weight differs on products used in it.

All the other cells in right end of the table are just for Your information to acknowledge the quantities needed and money spent on.

F. Growth Simulator

F. Growth Simulator

Growth graph

Growth Simulator is fully dependent on Your input data and no other inputs needed in this section. Simulator calculates depending on Your seeding date and termination date, what growing stages crops will be developing based on Your average 15-20 years climate data.

In first version of Cover Crop Calculator there are approximate ‘Blooming’ and ‘Ripeness’ stages defined:

  • blooming indicates that plants are decreasing sugars into above and below biomass growth and start sending sugars into fruit, which means that there is not a huge biomass growth anymore.
  • ripeness stage indicates that plants are about to form first germinative seeds, which means there is possibility that these crops could reproduce and/or get invasive. Also at this point biomass starts to dry, which gives more room and light for another crops, e.g. weeds among others.

Estimated dates and percentages are based on Your climate’s and between seeding-termination dates gained GDD (Growing degree days) information.

Notes at right are informational on historically last frost probability in spring and first frost in autumn for Your information to plan seeding and termination dates better inline with climate.

The Growth graphic is visual illustration of plant growth stages mentioned above where green column’s end shows approximate blooming start throughout Your mix. Yellow column’s end shows start of ripeness and red line is gained GDD according to termination date.

G. Other Calculable Benefits

G. Other Calculable Benefits

In this section there is possibility to evaluate Your Nitrogen tying and scavenging depending on growth stages. This can be compared to Your local mostly used N fertilizer’s properties and price. Therefore You can evaluate what these cover crops produced in moneywise in this particular time. Your fertilizer information here needs Your update.

The other possibility is to evaluate how much of the biomass of Your grown cover crop turns into Soil Organic Matter (SOM) by describing Your humus layer thickness. Calculation also gives a hint on increase of the SOM and water holding capacity.

These are the possibilities and benefits of the very first version of Cover Crop Calculator-Simulator. We are already collecting information and developing to form new topics into approximately calculable terms to help biology more easily understandable and to give farmers cognition they need to make quick and effective decisions in a timely manner.

Hop on the ship and start calculating Your possible natural benefits and also leave us feedback!

Sincerely Yours

Indrek @SoilYoga