Having good fertilizer records is important because it's important to know what you have done so that you can plan for the future. I've seen so many instances of fertilizer records that are descriptions of what you have done, but are formatted in a way that provides little information that is easily digested or that can be used to guide future decisions.
At the most basic level a fertilizer application record should contain the date, area applied, type of product, amount of product and your spreader setting and looks like this:
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| One of my first digital fertilizer records from 2008 |
While this is a good record of what you did at the most basic level, it is almost next to useless to actually help you understand how much of each nutrient was applied. Are you applying fertilizer for the name on the bag or are you applying fertilizer to alter the nutrient content of your soils?
Making these calculations easier was one of the main reasons I initially switched from paper records to a spreadsheet. Spreadsheets make doing multiple similar calculations extremely easy and automatic. The example below from my 2008 fertilizer records show this calculation done.
Wow, there is a lot to digest here and looking back I am surprised at how bad my fertilizer practices once were. I was applying massive quantities of nutrients that the plant couldn't even use. In 2008 I was spending 3x as much on fertilizer for 9 holes that I know spend on 18 holes!
Once you have your records organized in a similar fashion to the one shown above, you can summarize the data to compare year to year and month to month.
As I often apply fertilizer to more than one area at a time we can also reflect that with some advanced spreadsheet skills which I won't describe here but might do some other time.
Collars generally require more nitrogen than the other areas in order to tolerate the elevated traffic levels found on this part of the golf course. The table above shows how the nitrogen rates on collars are elevated even though I only specifically apply fertilizer to collars in rare occasions. The records pull data from greens apps where I also spray the collars and also data from fairway applications where I do a lap around my greens to supplement the fertilizer rates on my collars. A robust fertilizer record makes it easy to calculate the rates where you apply fertilizer to more than one specific area of the golf course in a single application.
You can also summarize costs if you include that data in your records.
So far I showed a few ways that you can improve your fertilizer records to help you better understand what you have done so far. What can we get from these records that will simplify future applications?
I like to show the most recent fertilizer application on my Maintenance HUD. I break these recent applications down even further to show the most recent application per macronutrient. The table below shows that area, macronutrient, rate and how many days ago the application was made. I don't have to go into my records to manually sift through the data to figure this information out. It's all automatic.
This sort of information is especially helpful when you shift your fertilizer application schedule away from a calendar or "program" based approach to a reactive approach which adapts to the actual conditions of the day.
I further add the estimated amount of nutrient used since the last application to this information display. This uses the daily growth potential figure multiplied by the maximum daily nitrogen use of 0.07g/m^2 which is derived from a maximum monthly nitrogen rate of 2g/m^2. The P and K are 0.13 and 0.5 of the n rate respectively.
We can compare the GP nutrient use since the last application to the application rate to see if we are over applying or underapplying fertilizer based on this model.
For our greens where we measure clipping removal, we can even calculate the estimated amount of nutrient removed through the clippings! To do this take the #clipvol in ml/m^2 and multiply it by 0.00252 to get the nitrogen removal rate. Again, the P and K are 0.13 and 0.5 of the n rate respectively.
On the table above, you can see that the estimated nutrient removal is exactly the same as the estimated nutrient use from the GP formula. We are comparing guesses to guesses here but it can be a tool to get a better understanding of you fertilizer practices. The most recent fertilizer application applied more than 3x of the total nitrogen use over that time period so far but almost 100% of the expected K use. Maybe I should include some K in the next fertilizer application.
Chris Tritabaugh described how he does something similar in a recent blog post of his.
With good fertilizer records we can do these comparisons for any time period, not just since the most recent fertilizer application.
With a supercharged fertilizer record sheet you can combine it with a tool such as my Growth Ratio to get even more control and understanding of how we are growing our grass.
It might seem complicated at first but it really isn't.
We have our most recent nutrient rates, the amount of expected nutrient use, the estimated nutrient removal and when combined with the growth ratio, an idea of how fast we are growing the grass relative to the current weather conditions.