It would not be unusual to recommend ammonium nitrate (34-0-0) with P and K readings like that. Because of its high capacity for leaching (and contaminating ground water as well as being unavailable for plant use), I'd take another soil sample the season prior to your planting in situ and see what the results are at that time.

You could use organic based materials to increase the nitrogen content of your soil for the long term, but ammonium nitrate will not last in the soil.

"My soil test results are in ... the P and K ratings, in ppm, were 667 and 523, respectively ... how do those P and K numbers look to you?" [seedsonshirt]

Are you sure those were the results in "parts per million?"

P at 15 - 22 ppm is considered moderate in some soils while greater than 31 ppm phosphorus is considered very high.

Two of the common methods of determining available phosphorus in soil are the Bray-1 and Olson methods. The upper reporting limit for the Bray-1 test is 100 ppm. The upper reporting limit for the Olson method (used on more alkaline soils with pH greater than 7.4) is 50 ppm.

Are you sure the test results you quote weren't maybe measurements in "pounds per acre?" For example, in medium textured silt loam, P at 125 - 150 pounds per acre is considered favorable for tomatoes.

Seeds,

The information regarding desirable P at 125 - 150 pounds per acre came from Missouri and was specific to tomatoes. I looked up some info in other states and found various ratings different from Mizzou extension. For example, University of New Hampshire would rate 60 to 100 pounds per acre phosphorus "optimum" generally for crops, and 100 - 150 pounds per acre "high." Maybe "high" is "desirable" for tomatoes.

And I found that 2lbs/ac = 1ppm = 1mg/kg. So, in any case, your reports of "667 P" rates very high whether for ppm or lbs/ac. Oh, and UNH rates K = 170 - 280 ppm "optimum" and 280 - 430 "high."

It's my understanding from the Purdue horticulturalist that a soil test for pH, P, K, and Ca ... if the samples were obtained and handled as recommended ... will be good for 3 years before another test is warranted.

And I think the recommendation you got for nitrogen application is based not on test results, since due to the unstable nature of N and variations due to climatic conditions, most labs don't test for N, rather they simply give a stock recommendation for an N application program based on the extant turf type or anticipated crop to be planted.

So, if you're going to containers in 2008, and leaving your tomato bed fallow 'til 2009, maybe just plant it in a legume cover crop and save the N application until your tomatoes need it.

And I found that 2lbs/ac = 1ppm = 1mg/kg...

hoosiercheroke, I do not know what proper concentrations of N-P-K are for tomatoes. But I do know that if one dumps a miscible liquid with another in containers of different volumes but with equal surface areas, the relative concentrations (ppm etc.) can change quite a bit. So one cannot maintain that "2lbs/ac = 1ppm."

Reg

Reg,

The equation "2lbs/ac = 1ppm" comes directly from a Cornell publication and there are other publications regarding how the soil samples are put into suspension and the data is arrived at.

The soils reports from various university extension services give the results in "pounds per acre" (see Alabama and Missouri) and others give it in parts per million (see New Hampshire) so I guess the equation "2lbs/ac = 1ppm" comes in handy for converting the data.

The equation "2lbs/ac = 1ppm" comes directly from a Cornell publication and there are other publications regarding how the soil samples are put into suspension and the data is arrived at...

hoosiercherokee, That is a measure of w/w concentration (how deep a soil horizon was extracted ?). The confusion here is twixt application rates vs concentration rates. They are not the same and can only be very roughly correlated.

Reg

Are the numbers 667 & 523 lbs per acre? A good spot in my yarden is 1855 & 1320 (lbs/a)... When you submitted the soiltest, did you specify you were growing tomatoes? And what do you mean you'll be growing in containers this year--was your soiltest in-ground or for what's in your containers?

Reg,

Pounds per acre is a widely accepted measurement of soil nutrients used by ag schools all over the country when advising farmers and gardeners with regard to fertilizer applications following standard soils tests. Perhaps we're trying to make this too complicated. It's really very simple.

The pounds per acre refers to the pounds of a nutrient found in the upper 6 to 7 inches of surface soil weighing 2,000,000 pounds. Therefore the pounds per acre equals parts per million multiplied by TWO.

Reg,

Okay, after just now rereading some of my posts, I see where maybe I'm not coming across clearly.

"Pounds per acre" refers to the pounds of a particular nutrient determined by the soils test to EXIST in the upper 6 - 7 inches of surface soil weighing 2,000,000 pounds ... NOT the pounds of chemical nutrient recommended as an application of fertilizer AFTER the test results are published.

So, if the soils test determines that there are 100 parts per million of potassium EXISTING in 2,000,000 pounds of surface soil, one can readily see there must be 200 pounds of potassium in that 2,000,000 pounds (and vice versa).

And looking at the equation (ppm x 2 = pounds per acre) and the other information given, I'm assuming that about 1/2 acre foot (6 inches x 43,560 square feet) of surface soil weighs about 2,000,000 pounds.

To cross check that figure let's determine the cubic yards in the top half foot of surface soil in one acre and check the resulting weight ...

0.5 foot depth x 43,560 square feet surface = 21,780 cubic feet / 27 cubic feet per cubic yard = 806.667 cubic yards

2,000,000 pounds / 806.667 cubic yards = 2479.34 pounds per cubic yard

Hmmm ... sounds reasonable since a standard measurement of soil is 2500 pounds per cubic yard.

The pounds per acre refers to the pounds of a nutrient found in the upper 6 to 7 inches of surface soil weighing 2,000,000 pounds. Therefore the pounds per acre equals parts per million multiplied by TWO...

hoosiercherokee, Actually in the above example, the w/w concentration in the mix would be the reciprocal of your calc. The proper calc is this (assuming 2^6 pounds per acre):
(poundsn/acre)/(acre/2,000,000 pounds)
where n = nutrient weight
This resolves to #n/acre.
So if n=1, ppm-n/acre = 0.5 w/w. If n=2, ppm-n/acre = 1.0 ppm w/w.

Reg

Those are ppm figures under the heading 'Nutrient Availability Index.' They are also given in pounds per acre: P 1334, K 1046. They used the Mehlich 3 method.

I will use manure of some sort, rather than ammonium nitrate. Lots of manure...

Korney 19, I just specified that this plot is for vegetables rather than orchard or pasture. I'm growing corn, beans, and squash there next year - I'm taking the tomatoes out of rotation (by growing them in containers in a different location,) hoping to let tomato diseases go hungry for a while - but the year after they'll be back in the garden. Since the fertilization recommendations are the same for the upcoming three years, the information you're providing will be germane when I put tomatoes back in this plot in 2009. (If anything, after growing corn there, I might deplete Nitrogen even worse.)

Thanks all for the help and interest!

Seeds,

You might be interested that Alabama publishes a chart of "nutrient removal by high-yielding Alabama crops" that shows feed corn removing 100 pounds per acre (50ppm) P, and 250 (125ppm) pounds per acre K.

Beans are shown removing 41 pound per acre (20.5ppm) P, and 74 pounds per acre (37ppm) K. No figure is given for squash or pumpkins. But looking at those projections and at your test results for P and K, it would appear you'd have plenty remaining for your tomatoes after only one year gardening other crops.

BTW, out of curiosity, who did your soils test, what kind of soil is your garden in, what was the calcium and the pH?

The University of Arkansas (Fayetteville) Agriclture Department, Cooperative Extension Service, provides 2 soil tests per year free of charge in Arkansas. They did this test. They allow 2 in case you want to test 2 different areas, say the orchad and the garden. They ask that one specifies what will be grown there, so they can tailor your rcommendations accordingly.

Clay soil. pH 6.9. Calcium 6994 lbs. per acre, or 3497 ppm.

Thanks for that nutrient removal info, Bill. Most helpful!

My tomatoes didn't produce very well in this plot this year, so before my test results came in, I thought perhaps I had a K deficiency or something. Apparently the rock phosphate and greensand took care of the P and K requirements just fine! It just seems like asking for trouble to put that much N in the soil before a tomato crop, but I guess numbers don't lie... The tomatoes didn't show signs of N deficiency that I could tell - the leaves were dark green.

Seeds,

How fortunate to have U-Ark provide the soil testing service. I checked out their Soil Test Page . Cool.

I think your apprehension about applying too much nitrogen is valid especially if your tomatoes showed no sign of N deficiency this season. You're doing the right thing adding copious amounts of organic material to your clay soil. That should improve drainage and support better root development.

There are many opinions about N requirement of tomatoes. Here is something I found today that may interest you. It's from the World Fertilizer Use Manual and says about nutrient demand/uptake/removal for tomatoes: "100-150 kg N, 20-40 kg P2O5, 150-300 kg K2O, 20-30 kg MgO per ha for outdoor crop yielding 40-50 t/ha; or, for greenhouse crop on natural soil yielding over 100 t/ha, about 200-600 kg N, 100-200 kg P2O5, 600-1000 kg K2O per ha. The greatest rates of uptake of the three major nutrients occur during flowering and when the first fruits ripen."

1 hectare = approximately 2.5 acres (2.47105381)
100 - 150 kg. = 220 - 330 lbs.
So, about 90 - 130 lbs. per acre N seems to be what they're saying in that manual.

If U-Ark recommended 3 lbs 34-0-0 per 1000 sq.ft., that would be approximately 1 pound N (.34 x 3.0) per 1000 sq.ft. or about 43.56 lbs. pure N per acre ... if I did the math right. But then I'm not really sure I understand what the IFA manual is advising :::shrug:::

A general # I have seen quite frequently is recommending 75lbs/acre of N on soiltests. Nitrogen changes frequently and even paying extra for N testing with your soiltest often doesn't get you much satisfaction (or accuracy) because the recommendation was made at the time the sample was sent in... that can be fall or spring or just about anytime really, and things can change rapidly.

Maybe more important than N recommendations are cation exchange and organic matter content. Also, organic matter content is usually much, much less than you think. I'd like to see organic matter numbers to get a better idea...

hoosiercherokee,

I have read that 200-300 ppm NO3- w/w is a good concentration of that ion in most soils for tomato plants. Very easy to adjust it to that level if the initial concentration is known and the additive's concentration (if needed) is known. Of course this assumes that this nutrient (and its additive) is easily distributed in an assumed fixed soil horizon.

Reg