20-0-20 Fertilizer - Ask Extension
My test report recommends a 22-0-22 fertilizer to be applied pre-plant and I have excessive amounts of magnesium and phosphorus. I'm having difficult...
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20-0-20 Fertilizer #865854
Asked April 25, 2024, 10:22 AM EDT
My test report recommends a 22-0-22 fertilizer to be applied pre-plant and I have excessive amounts of magnesium and phosphorus. I'm having difficulty finding that fertilizer that is not designated as a lawn fertilizer (such as Lesco). I use a drip irrigation system under Dewitt's landscape fabric. Can I use a two part soluble fertilizer, such as Master Blend 5-12-28 with Calcium Nitrate 15-0-0 and not use the Epson Salts (for hydroponics), that would give me a 20-12-28 blend and would be injectable through my system. I can also add Fish Emulsion to up the Nitrogen. As for quantities, how do you calculate liquid fertilizer rates as granulate is pounds per 1000 sq.ft. I use a Mazzei 384 injector with my well water system to inject, it uses about 2 1/2 gal of fertilizer solution in about 20 min of watering at about 4-5 gal per min.
Oakland County Michigan
Expert Response
I was able to look up your soil test results. Your soil has an above optimum Phosphorous (P) level. You should find a soluble fertilizer that does not contain any phosphorous because adding more phosphorous becomes a pollution risk and is also wasteful. You can probably use a 2 part solution (test for compatibility - meaning they don't separate out before using), but find a '0' P fertilizer.
Defining how much liquid fertilizer you should apply may be a challenge. You need to determine the quantity of Nitrogen (for example: 5#) in your liquid fertilizer container when it is full. Then determine the % you remove for each fertilization (let's say 5%). Thus you are applying 5# x 0.05 = 0.25# of Nitrogen in the 2 1/2 gallon of fertilizer solution you apply. You might need to contact the liquid fertilizer source to get the answer.
Fertilizer application recommendations I'm familiar with are # of element (N, P or K) per 1000 Sq Ft for lawns or # / acre for commercial agriculture. From a soil test, if potassium (K) is low they will recommend an additional application of a fertilizer containing extra K, but still at a # per 1000 Sq Ft rate. I am not aware of fertilization recommendations on an individual plant basis, except that some plants need more of certain macronutrients than others do, so you add a bit more fertilizer around those plants in their row(s).
Defining how much liquid fertilizer you should apply may be a challenge. You need to determine the quantity of Nitrogen (for example: 5#) in your liquid fertilizer container when it is full. Then determine the % you remove for each fertilization (let's say 5%). Thus you are applying 5# x 0.05 = 0.25# of Nitrogen in the 2 1/2 gallon of fertilizer solution you apply. You might need to contact the liquid fertilizer source to get the answer.
Fertilizer application recommendations I'm familiar with are # of element (N, P or K) per 1000 Sq Ft for lawns or # / acre for commercial agriculture. From a soil test, if potassium (K) is low they will recommend an additional application of a fertilizer containing extra K, but still at a # per 1000 Sq Ft rate. I am not aware of fertilization recommendations on an individual plant basis, except that some plants need more of certain macronutrients than others do, so you add a bit more fertilizer around those plants in their row(s).
Thank You for the response. I'll look around for a soluble Potassium fertilizer and use the Calcium nitrate for the Nitrogen or other High nitrogen component. I'm still trying new things in the garden.
Dick M. I was able to find a 12-0-12 fertilizer at Walmart. A 40 lb bag for under $20. Site one wants $80-100 for 50 lbs. I'm sure it's not the same quality but I don't want $2 tomatoes either.
Thanks
John Hoy
Thank You for the response. I'll look around for a soluble Potassium fertilizer and use the Calcium nitrate for the Nitrogen or other High nitrogen component. I'm still trying new things in the garden.
Your soul test results recommend 16# of 22-0-22 but also recommend 30# of 12-0-12, per 1000 Sq Ft which is what I would have recommended based on the ratio of nitrogen between the recommendation and what you purchased.
I plant in raised beds so I will add a small handful in the plant hole and then side dress in a month or so. I also grow in plastic buckets so I will do the same there and fertigate through the drip system with something else, maybe the triple 20 I have on hand.
I would recommend mixing the fertilizer with the soil around each planting hole or into the top 1/2" of soil around each planting hole (~6" diameter). Too much fertilizer concentrated in the planting hole risks burning the roots and killing the plant.