Hello! Welcome back to another article of my Soil Series! This article is one of the last articles in this collection. We have covered a lot of information and now it is time to bring it to full circle on how to read a soil sample. Each soil testing lab has their own generated reports; please know that the information that has been collected by labs remain the same - it is just a different presentation of results as well as recommendations. My Garden Center uses Spectrum Analytic in Ohio. I feel they have an easy to read lab results as well as easy to follow application rates. Some lab reports have too much and complex information where it gets overwhelming. These difficult lab reports give the correct information however it maybe a little difficult for someone to process it.
I have chosen a recent soil testing report from one of my customers with their information cropped out. The background of the soil sample is that is it for a lawn that is 10,000 square feet.
We noticed automatically that everything is at a low point. We need to raise the pH levels, magnesium, calcium, phosphorus, and potash. We see the results and the optimum levels. Way at the bottom, we see the recommendation. For this sample, it is recommended to use 4 pounds of Nitrogen, 3.4 pounds of Phosphorus, and 3.8 pounds of Potash for every 1,000 square feet. Meeting these levels will put everything back at the optimal level.
This is where I come in - my role is to figure out HOW to get to that optimal level. Figuring out how to correct the pH is really easy. It is 50 pounds for every one thousand square feet to raise your pH up a half of a point for loamy soil; for clay soil it is 60 pounds for every one thousand square feet. The math is easy and it depends on how big of an area you have and how big of a bag your local Independent Garden Center stocks. For my garden center, the bag of pelletized lime is a 40 pound bag. For this customer’s soil sample, I have calculated four applications and using thirteen bags per application. This would bring the pH from 4.9 to 6.4.
My favorite documents are by Penn State Extension when it comes to figuring out how much fertilizer you need and how to calculate it. You can find the links at the bottom dj the page. We know that the lab suggests 4 pounds of Nitrogen, 3.4 pounds of Phosphorus, and 3.8 pounds of Potash for every 1,000 square feet. The question turns to WHAT fertilizer ratio we need to accomplish this. Looking at one of the articles from Penn State Extension. The best way to explain it is that you take each weight and divide it by the lowest weight:
Nitrogen: 4 divided by 3.4
Phosphorus: 3.4 divided by 3.4
Potash: 3.8 divided by 3.4
This will give you a fertilizer ratio of 1.17-1-1.1 for every one thousand square feet put down four times every six to eight weeks to correct problems.
We have our recommend ratio but how do we determine WHAT fertilizer we us. When you go into any garden center, there are so many product lines of fertilizers with different ratios and application rates. The way that I figure this out is by determining how many pounds of each nutrients is in a bag of fertilizer. For example, because the ratio of the nutrients is very similar, I would look at 10-10-10 first. So what I do is I make that fertilizer analysis and turn it into decimals and multiply it by the pounds of the bag:
Nitrogen: .10 x 50 = 5
Phosphorus: .10 x 50 = 5
Potash: .10 x 50 = 5
That means that there are five pounds of Nitrogen, five pounds of phosphorus, and five pounds of potassium in a fifty pound bag of 10-10-10. I feel with 10-10-10, this would match up with my customer’s needs to fix their lawn. Next, I take the pounds of the Nitrogen and I divide it by the ratio needed. This equals 4.2; I will round down to four to keep it all even. I will apply this fertilizer 4 pounds for every 1,000 sq ft so it receives the closest of the recommended ratio. Once I have this information, I am able to figure out the spreader settings on the a handy chart (link to chart on bottom) and give my customer what setting they need.
Sometimes when I am figuring out the fertilizer ratios and what fertilizer to recommend, it may take a lot longer to be able to create a recommendation with all the product lines my store offers to our customers. Everyone’s soil is different; with that being said when I get back into soil sampling season, we can circle back to looking at others soil sample results. This will allow me to walk you through when the numbers are not so equal, different needs for the soil, and the different products needed to correct soil problems!
Thank you so much for reading my blog post on reading and recommendations when it comes to soil sample results! Send those confusing soil sample results my way! Let me work with you to break it down your results and give you recommendations for your lawn and garden. Let me help you have nutritious and full of life soil. We know when our soil is healthy, our plants are healthy and happy too!