Smallfarmtn
Newly Registered
Posts: 4
Joined: Sun Mar 19, 2017 11:30 pm

Help improving my vegetable garden

Hello, I recently joined and I could use a little help improving my gardens soil. I had my soil tested for the first time and I am now wondering whats best to optimize it. I am a little confused reading the results I got in the mail hoping maybe you guys could help me out. I understand near the bottom it says to add 20lbs of lime per 1000sqft and I assume 3lb of N, 4lb of Phosphorus, 4lb of Potassium and .2lb of Magnesium?
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bri80
Senior Member
Posts: 282
Joined: Sat Nov 19, 2016 10:12 pm
Location: Portland, OR

Re: Help improving my vegetable garden

Soil fertility is a complicated topic that even seasoned, smart gardeners can have trouble understanding all the subtleties of. You're going to have to do some math. The simplest thing for you to do is take the recommendations at the bottom and calculate additions based on your garden size. The most in-depth thin for you to do is go pick up a copy of the book "The Intelligent Gardener" by Steve Solomon and do what I did, rereading it like 6 times to try and understand, then use the worksheets he provides to calculate every single thing you can for your particular garden.

Here is a good place to start, it contains some primers and and copies of some worksheets.
https://soilanalyst.org/wp-content/uploa ... ion-03.pdf

I'd like to be able to tell you what to do, but honestly, you kinda gotta figure it out for yourself for your specific garden. When I moved to a new house I did a soil test and all these worksheets for both the front and back yard gardens. It took me a looooooong time to come up with specific amounts of soil amendments. It was a pain in the butt. It's been 4 years and I haven't repeated the process, adding amendments based on my knowledge of my garden/past soil test/gut/experience, but I will probably do it again in another year or two.

Smallfarmtn
Newly Registered
Posts: 4
Joined: Sun Mar 19, 2017 11:30 pm

Re: Help improving my vegetable garden

Thank you, I will check and see if I can find that book at the library. From what I'm guessing on the results they recommend I add a 3-4-4 fertilizer? What throws me off is they used a graph instead of numbers. I don't know how much 12lbs of P is per acre other than low...

bri80
Senior Member
Posts: 282
Joined: Sat Nov 19, 2016 10:12 pm
Location: Portland, OR

Re: Help improving my vegetable garden

If you can start to make sense of the info at the link I provided you'll be able to calculate how much of each nutrient your soil needs, then how much of what amendments to raise the levels towards the targets provided on the worksheets. It takes some time to get your head around but it's doable.

j3707
Green Thumb
Posts: 306
Joined: Mon Jul 13, 2009 2:11 am
Location: Pacific Northwest, Zone 8, 48" annual rainfall, dry summers.

Re: Help improving my vegetable garden

I second bri80's suggestion. I'm doing the same this year.

Can you post better picture of the report? I'd like to see all the lab notes and recommendations.
Avoid predictable disaster caused by unpredictable events, keep yourself open to positive outcomes from improbable events. -Aaron C. Brown

imafan26
Mod
Posts: 11272
Joined: Tue Jan 01, 2013 1:32 pm
Location: hawaii, zone 12a 587 ft elev.

Re: Help improving my vegetable garden

What it is saying is per 1000 square feet you need: (Get a digital scale, it is the best way to do this)
You need 3lbs of Nitrogen (nitrogen will always be a recommendation since it is a volatile element that is easily lost. You want to give nitrogen in divided doses. I usually put in 1/4 of the requirement in the starter mix. 0.75 lbs/1000 sq ft. give half the requirement or 1.5 lbs (it helps to have a scale) of actual nitrogen after the true leaves come out (seeds started in garden or when you transplant. This is assuming you transplant by the time the second set of leaves come out, and the remainder 6 weeks later.
How to calculate actual nitrogen. Since your pH is 6.2. I would use Urea 46-0-0. It has 46 lbs of actual nitrogen per 100 lbs.
Set up your equasion 46/100 = 0.75/x = 0.46 lbs of nitrogen in 1 lb, 0.75/0.46 = 1.63 lbs of ureal per 1000 square ft. or 0.163 lbs per 100 square feet. (1 cup urea = 0.33 lb, 0.163 lbs/0.33 = approx 1/2 cup per 100 sq feet total. 1/8 cup would be in the starter mix per 100 square feet. You would side dress with 1/4 cup in the first side dressing and give the remaining 1/8 cup in the second side dressing.

You would need to know the analysis of your bag of fertilizer to figure out the other elements in similar fashion. You would use something like superphosphate for the phosphorus, and potash for the potassium or K mag. There may be other elements in these fertilizers but they are primarily one element and while they are not balanced they are easier to calculate as single elements.

Or you can fudge it. You need a fertilizer that comes close to 3 parts nitrogen, 4 parts phos and 4 parts potassium
Around here what comes closest is 10-20-20 plus micros. 2 parts nitrogen, 4 parts phos and 4parts potassium. I would calculate based on 100 lbs because it is easier but use 1/5 the amount because I don't need 10lbs only 2lbs. I can make up the remaining lb of nitrogen with urea as a side dressing.

Find what fertilizer you have available that comes closest to your ratio of 3-4-4. If the numbers are larger you would use proportionately less. This works with organic except you have to multiply your result by 2. The thing with organic fertilizers is that the bag indicates the total Nitrogen, phosphorus, and potassium and not the available nitrogen.

If a bag contains 3lbs Nitrogen, 4 lbs phos, 4 pounds potassium per 100 lbs. Divide 3-4-4 by 100 = 0.03lbs N, 0.04 lbs P ,0.04lbs K per lb. Divide pounds you need by lbs available = lbs of fert you need. I only calculate for Nitrogen on complete fertilizers. I convert lbs to cups but it is easier to use a scale at this point to get the amount you need to apply per 100 square feet. I also try to find a fertilizer lower in nitrogen since I want to give the rest as a side dressing. Ideally in your example instead of 3-4-4, I would be looking for a ratio of 1.5-4-4 or slow N fertilizer.

For most organic fertilizers less than half is in available form Slow N isn't bad but it means that all of the nitrogen will slowly be released over time for up to two years. You have to choose your organic nitrogen carefully or supplement with a faster releasing nitrogen like fish emulsion or blood meal.

Some synthetic fertilizers now have slow release nitrogen. The total nitrogen is higher and you have to do some sleuthing reading the label to find out how much of the nitrogen is ammoniacal nitrogen which is the one that will be available faster. It will still be more available over the course of the crop than organic. Always add compost even if you use synthetics. The soil web does not care what nitrogen the source comes from, but they also need carbon which the synthetic fertilizer does not provide. Young seedlings need nitrogen available at the right time or the plants will not get as big. It is why organics take about 2 years of constantly adding compost and organic matter to build up more consistently available nutrient levels.

I repeat my soil tests every three years just to make sure I am in line. It is not necessary to do it yearly unless you are making a lot of changes or your soil test is way out of whack. Yours is not, and so once you figure it out it. You can fertilize the same way for a couple of years. It will be important to balance your crops so they don't take out too much of any one nutrient.

Your pH is fine for most crops. As long as you are not growing anything that likes very alkaline conditions it will work. Tomatoes, eggplant, leafy greens will do fine. Root crops like beets, carrots, potatoes might do better with a pH that is slightly higher or by adding less nitrogen and boosting with some bone meal when the plants start to get ready to bulb up. Cabbages tend to alkalinize the soil around them.

In most situations with synthetic fertilizer with numbers under 15, you would use 1/2-1 cup of fertilizer per 100 square feet
Organic fertilizers would be 15-20 times the synthetic amounts since with the exception of blood meal, bone meal, and potash, most organic fertilizers have a ratio of 1-0.5-0.5 so you have to use 5-10 times as much to deliver same NPK.
Happy gardening in Hawaii. Gardens are where people grow.

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