HOW to measure fertilizer?

[Gary350]

If you need to fertilize a certain plant how do you know if 1 teaspoon is too much or too little?

My soil test shows, Nitrogen 0, Phosphorous 100, Potassium 98. This year my garden needs NO P&K. It only needs N nitrogen.

I have already learned that nitrogen does not stay in soil very long and hot dry 100° temperatures makes nitrogen be gone sooner than 4 months. After winter next summer soil will be very near 0 nitrogen.

After having 36" of rain another soil test might show lower P&K numbers. I am shooting in the dark unless I get another $15 soil test after having 36' of rain. Soil test says, rain will lower P&K and remove N.

This year my garden gets NO P&K all summer.

I bet commercial farmers do soil tests once a month and probably know from experience what NPK will be all summer with no soil test.

Plants need P&K but no information can be found on how much P&K plants remove from the soil?

I am trying to learn how much fertilizer each plant really need. At the moment in my garden my guess is plants need NPK = 5-0-0 and corn will need 30-0-0.

FFA online shows corn only needs nitrogen. Many farmers plant 2000 acres of corn, they recommend row spacing = 32" and seed spacing = 5" and a certain number of lbs. of nitrogen per acre. FFA nation wide maps recommend nitrogen according to geographical location. air temperature and rain fall.






FFA for farmers have recommendations for farmers, example, 5 lbs per acre for corn, row spacing 32", seed spacing 5".

[applestar]

This may or may not apply, but your question reminded me that I followed this youtuber’s example over the winter for container plant feeding —



… in the description, he posted link to this table for variety of fertilizer formulations:

Here is a spreadsheet to use for other fertilizers:
https://docs.google.com/spreadsheets/u/ ... c/htmlview

[Gary350]

That makes no sense to me?

1%=4.7tsp
20%=.24tsp

.24 tsp is not more than 4.7 tsp

Is that for a 3" tall tomato plant or a 6 ft tall tomato plant.

[imafan26]

You can use your soil test recommendations to figure out your nitrogen requirement. 1 lb of nitrogen fertilizer ( sulfate of ammonia 21-0-0) = 2 cups.

https://rutherford.tennessee.edu/wp-con ... rition.pdf

[Gary350]

My soil test says nitrogen is 0. I expected my soil N to be 0 I know when we have 100° temperatures and soil is dry as desert for 4 months N evaporates away.

I threw about 40 lbs. of bent nails all over my garden about 4 years ago and soil test shows NO iron in my soil.

Last summer I learned if I give each tomato plant wood ash tomatoes grew larger and get ripe sooner. Wood ash is about 30% calcium plus potassium.

[imafan26]

I use the formula for nitrogen. I only use sulfate of ammonia (21-0-0). 20 lbs lasts 5 years. 2 cups sulfate of ammonia = 1 lb of nitrogen

The low nitrogen formula 1 tablespoon per 100 sf ( Use this when you have a lot of nitrogen in the soil. I can tell by looking at the size of my plant leaves)

High nitrogen formula 2 tablespoons per 100 sf.

Soil test will tell you how much nitrogen to add 1/2 preplant, 25% at flowering 25% at fruit set, and monthly thereafter

How I do it. 1 tablespoon of sulfate of ammonia over 100 sf after transplant or after seeds germinate and have true leaves.
For leafy greens I use the high formula 2 tablespoons per 100 sf. after transplant or seedlings have true leaves. Too much nitrogen at the start is not needed. Leafy greens are about 50-70 days so unless they live longer like chard or kale they only get one feeding. Longer lived plants get additional nitrogen and k-mag ( 1 tablespoon each for npk = 11-0-11) every 3-4 weeks. My soil is extremely high in phosphorus so I need a zero phosphorus fertilizer.

My soil test called for more nitrogen, but if you look at my plants, this is all I really need.

[Gary350]

I use the formula for nitrogen. I only use sulfate of ammonia (21-0-0). 20 lbs lasts 5 years. 2 cups sulfate of ammonia = 1 lb of nitrogen

The low nitrogen formula 1 tablespoon per 100 sf ( Use this when you have a lot of nitrogen in the soil. I can tell by looking at the size of my plant leaves)

High nitrogen formula 2 tablespoons per 100 sf.

Soil test will tell you how much nitrogen to add 1/2 preplant, 25% at flowering 25% at fruit set, and monthly thereafter

How I do it. 1 tablespoon of sulfate of ammonia over 100 sf after transplant or after seeds germinate and have true leaves.
For leafy greens I use the high formula 2 tablespoons per 100 sf. after transplant or seedlings have true leaves. Too much nitrogen at the start is not needed. Leafy greens are about 50-70 days so unless they live longer like chard or kale they only get one feeding. Longer lived plants get additional nitrogen and k-mag ( 1 tablespoon each for npk = 11-0-11) every 3-4 weeks. My soil is extremely high in phosphorus so I need a zero phosphorus fertilizer.

My soil test called for my nitrogen, but if you look at my plants, this is all I really need.

My soil has too much phosphorus and I have not yet learned how to lower it. We had 5 ft of rain this year and last week we had a few days of no rain and 87° temperatures that caused my garden soil to turn green color with algae. Some where online I found the name of the toxic condition of having green algae soil. So far rain has not lowered phosphorus in my soil.

Google says. Excess phosphorus fertilizer in hot, wet soil can lead to several problems. These include nutrient deficiencies in plants, soil compaction, and water contamination. Specifically, excess phosphorus can interfere with plant uptake of other essential micronutrients like zinc and iron, causing yellowing or dwarfing in plants. It can also contribute to soil compaction, reducing crop yields. Moreover, excess phosphorus in runoff can contaminate waterways, causing eutrophication and harmful algal blooms.

So far I have not found a cover crop that will remove phosphorus from soil. Phosphorus is mined rock ground into powder for fertilizer. Google says, it takes lots of rain and 5 years to lower phosphorus in soil.

I am not putting anymore phosphorus in my garden for 5 years. Until now I have never read anywhere that said soil can over dose with too much phosphorus. I want to find a way to lower phosphorus. Online says, mix low phosphorus soil with high phosphorus to lower phosphorus. I never learned in college that phosphorus can become toxic in soil.

[imafan26]

My soil phosphorus has been excessive for over 10 years. Basically, it does not move well through the soil. I just cannot add any more phosphorus. I had only been adding sulfate of ammonia and nothing else. Then during covid, I tried organic fertilizers, that made things worse and I could not find good compost so, I was doing no till and added 4 inches of potting soil every planting. The phosphorus went up instead of down. because while I was adding sulfate of ammonia, the potting soil and compost was fortified with either synthetic or organic animal manures that were high in phosphorus. My soil test then recommended only maintenance compost 3/4 of an inch of plant based compost. It is actually hard to find compost without any fertilizer. No organic fertilizers, manure or vermicast. My Potassium was a little below about 20 ppm but it did recommend more potassium and the pH was around 6.0 which is good for my soil, but I did not want it to go lower. I added a little bit of lime with the sulfate of ammonia and kmag.

The last soil test, I overshot the pH now it is 7.3, so I will stop adding lime. I don't have any nutrient issues with the plants. I did check my total carbon since I was adding organic matter. It had gone down a bit from 7.98 to 6.38 better but both were high. It means that organic matter is over 12%, Phosphorus is down from 483 to 355, still too high. Organic matter only needs to be about 3%. Over 10% can cause problems. My potassium was 339 (350 goal), Nitrogen 4.7 (norm 15-30) I was not worried about that because it is actually what I expected since it was at the end of the crop cycle and about time for another dose. I plant mainly brassicas Asian greens komatsuna, semposai, pak choy over winter. I also planted perpetual spinach, kale, and Swiss chard. I also had cilantro and a couple of tomatoes planted. With less than an inch of compost with not til, the weeds come up like crazy.

I do a modified no til. All of the green waste is taken out and put in the green bin. Cabbages, lettuce, tomatoes use a lot of phosphorus, but I don't want any to go back into the soil so it must be net negative to lose carbon and phosphorus. I cannot use any organic fertilizer or manures since almost all of them do have phosphorus. And organic fertilizers are not very pure and can vary from batch to batch and are inefficient fertilizers for my intensively planted garden. I actually don't do pure no til. I find that the clay soil compacts over time and nutrients on top don't always trickle down, so I do till once in a while. While I was raising the pH, lime does not really work that well unless it is worked in.

I finally found some plant based compost, but I am adding it to my containers instead of the garden in place of some of the peat moss. I did not test my containers this time. I am basically throwing the soil away when it has nutrient problems because it is just too hard to fix. My container soil had a pH of 5.5 and phosphorus over 400 ppm. I had calcium, magnesium, potassium and zinc deficiencies and the fertilizer is actually hard to get. I can reuse less than 1/3 of my container soil. I put in less fertilizer, and monitoring the pH in the containers, but I now have to supplement nitrogen, potassium and micros and minimize phosphorus and I haven't quite figured out the fertilizer interval, so I have to watch what the plants are doing stunting or showing signs of deficiency to figure out how often I need to supplement. I have been switching and combining different fertilizers trying to find the right mix and I haven't found it yet.
https://www.aces.edu/blog/topics/lawn-g ... den-soils/
https://valverde.agrilife.org/files/201 ... Suffer.pdf
https://news.oregonstate.edu/news/study ... nic-matter