It's common for farmers to talk about the many hats they wear. I think it's one of the reasons that farming is an attractive profession for me. Not only do I get to grow crops but I also need to know how to manage employees, prioritize tasks, fix equipment (like the walk-in cooler from last weeks farm update), manage finances, market crops, and so, so much more. Today I'm going to share a new and recent fun intersection of growing crops, fertilizing crops and how chemistry plays a role in all of it. By the way, I'm no chemist - I took chemistry in high school and college and I was just ok at it.
We've seen a pretty big drop in tomato production in the last few weeks on the farm and there's probably several issues happening all at once. One of those issues is soil pH and the plants ability to utilize nutrients as soil pH increases. I tested our soil pH with a handy pH meter I bought earlier this season and go a reading of over 8! That's really high and not what we want. Most plants prefer a pH closer to 6.5. At pH readings over 7-7.5 the plants ability to utilize nutrients goes down significantly.
A couple questions emerged. First, why is my soil pH so high? Second, how do I lower my soil pH in a cost-effective way? Luckily, I had a pretty good inkling why our soil pH was increasing. This particular soil is inside our tomato tunnel where it doesn't rain (it does flood however) and our irrigation water is pH 7. Over time, soil pH can increase because of irrigation water leading to the pH reading we took. This tidbit of knowledge came from a conference session I attended last winter and is the work of Natalie Hoidal from the Unniversity of Minnesota.
The second question I don't have an answer to yet. It's a bit of an ongoing experiment on our farm. The only organic approved amendment to lower soil pH is citric acid. There isn't a lot of good information out in the world yet about how much citric acid you need to lower the soil pH. I figured if I lower the pH of my irrigation water that over time I should be able to lower my soil pH to a more acceptable pH reading. I needed to do a bit of testing to determine how much citric acid to add to my fertilizer injector but after a couple of trials I found that .1oz of citric acid per gallon of irrigation water reduced the pH from 7.3 to 4.82.
So our experiment is adding enough citric acid to our irrigation water to reduce the pH as described above. We'll do that once a week for a month and take a new soil pH reading and see where we land. If the reading is unchanged we'll try adding the citric acid every day or perhaps every other day with an end goal of reduce the soil pH to somewhere around 6.5
The ultimate goal is to give the tomatoes what they need to keep producing until frost and to develop the acid and fertilization plan to maintain a plethora of tomatoes all season long.
Farming is indeed a profession of many hats.
