Verified FBN Member (OH)
Agronomy

How much lime do I need?

New farmer here. So after a really bad corn harvest I decided it was time for some soil samples. Unfortunately the coop I use is real crap and the attached photo is what I got for a report. It was only after I waited 6 weeks did they tell me the lab they use no longer gives recommendations for rates anymore. I’m pretty lost as to how to get how much lime I need to spread off of this information, even googling how to calculate it gives me few results with the information I’ve been given. Thanks for looking.

How much lime do I need?
Verified FBN Member (AL)

I would personally put out no less than 2 tons per acre and incorporate it. Where the ph is 4.5 I would bump it up to 2.5 or 3 and resample in the fall of 21.

Verified FBN Member (WI)

I would probably go with 3 ton per acre. From my experience 3 always spreads the best and it would not put you above 6.8-7.

Verified FBN Member (IL)

Is each sample from a different field? When were the samples taken? What method did you use to determine where to pull samples? (Grid, zone, composite?). Lots of variability for only 3 samples, the higher CEC soil will need the 3 tons incorporated and the other two will take much less because of the lower cec and higher starting ph.

Verified FBN Member (OH)
(edited)

Each sample is a different field, samples were taken on Nov 6, 2020, I pulled a plug out every 60’ to a depth of 6-8”, put all plugs into a bucket and then mixed the sample(per field). I’m not sure what method that would be called.

Verified FBN Member
Response deleted by author
Verified FBN Member (MD)

The lime index( buffer pH) tells you how much lime to apply. Without knowing what lab ran the tests it’s hard to give an accurate recommendation. I would encourage you to simply call the lab yourself and ask a staff member. Another option would be to take another sample and send to a lab that can give a more detailed report.

Verified FBN Member (IA)

I had a field a couple years ago with similar Ph numbers. My cec numbers were 12.7 to 23. Some of the ground with 4.7-4.9 ph was calling for 4-5K lbs/acre of lime. My agronomist and another area farmer told me that much would be a waste of money. It was grid sampled so I half rated the variable rate. Two years later I wanted to plant some of the worst ph areas to alfalfa so I retested. The ph had improved to the point I didn't need to do anything and I got an outstanding alfalfa stand. Now as to the sample method. It is obvious lime is needed and not seeing or being around the fields in question it is really hard to know what you are dealing with, but when you have someone grid sample the field and run each sample on its own, if your field are like most of mine, there is a wide variance in how much lime is needed across the field. One sample may call for two ton, the next .5 ton, and the next nothing. If you apply 2 ton of lime in an area that doesn't need any you will be doing more harm than good. I would encourage you to find someone to grid sample and then do a prescription for you. Getting the lime and other nutrients where they are needed will pay for the service when you fields are in bad shape.

Verified FBN Member (OH)

These are small fields, 3 acres for one and two and 7 acres for the third. If I can’t get the expected yield out of 13 acres I might as well not go any bigger.

Verified FBN Member (IA)

Our grid samples around here are 2.5 acres, and manure management requires one every 10 acres so there wouldnt be any advantage over what you did then.

Verified FBN Member (OK)

Would like to see the buffer PH to determine the amount of reserve acidity in the soil structure.

Verified FBN Member (TN)

2-3 tons an acre

Verified FBN Member (MO)
(edited)

I'm new to farming as well. I wanted to get a good idea of my land as it was coming out of CRP for the first time in 40 years. I had a company come in and do a 2.5 ac grid on my 80 acres. 32 samples at 12.50 an acre so it cost me $1000.00 but I know CEC, organic mater, P, K, Mg, Ca, Na, soil ph, S, Zn, Mn, Fe, Cu, B, and soluble salts from 32 spots across the 80 acres. I will get recommendations tomorrow and feel like it may be the best $1000.00 I will spend.

Verified FBN Member (OK)

It’s the best way to assure your fertility dollars are being well spent. Especially with the phosphate market in shambles.

Verified FBN Member (KS)
(edited)

Im not an expert, but we put TONS of lime on all of our farms. We grid sample 2.5 acres, and apply variable rate. When we first started a lot of our acres were requiring 4 tons an acre. That was over 10 years ago. There is a lot of variation throughout the field. The spots on the farms near gravel roads are often 6.7 or above so they don't require lime because the dust from the road carries over. But there are still areas that are 5.5. I agree that knowing your buffer PH helps, and the quality and fineness of the lime you spread is important as well. It should also be noted that we do a lot of continuous corn and apply anhydrous. Soil acidity means that there is a excessive amount of hydrogen ions in the soil. NH3 (anhydrous) makes the soild more acidic whenever the NH4 (NH3 reacts with H20 changing it to NH4 and OH) converts to NO3. When it converts to N03 it releases the 4 hydrogen ions into the soil causing more acidity.

Verified FBN Member (IL)

One other item to keep in mind is that Lime typically takes three years to fully break down and be seen in new soil samples. You could expect to see 1/3rd of the applied lime benefits each year for three years. Don't be tricked by resampling in one year after the application and thinking you need to apply a large amount immediately again.

Good luck

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