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Soil Test Amendments & adding fertilizer

16 years ago

I amended my garden soil by adding N, K, and compost according to the recommendations resulting from a County Extension Office soil test from October. I then asked the county horticulturist (the guy who tested and reported on the soil) what I should do with the recommendations for fertilization for some of the melons and whatnot. I'm talking about where they say to add this or that fertilizer at such a rate 2-wks before planting, for example. The horticulturist said to not add anything in preparation once his soil test recommendations have been completed. Is that right?

I'm thinking that is not right. Seems the soil is now nominal; at a "baseline". Seems additions should be made according to whatever it is I'm planting. I'm set to ignore his latest instructions so maybe the forum can set me straight.

Comments (5)

  • 16 years ago

    It seems as if he is right but I too have a problem when you get a general vegetable fertilizer recommendation without giving guidelines for specific crops. If you were to idicate that your only crop to plant was sweet corn you would get a different recommendation. That's just the way they do it. In your case the guy reporting back to should be the one taking the test results to the next level in his recommendations.

    Unless your P2O5(phosphate) lavel is off the charts I would always still include it in a starter fertilizer. And for most crops, especially corn, you benefit from incorporating minimal N(nitrogen) at planting time and applyng more at various growth stages throughout the season. I'd be very surprised if the lab even tested for N. The computer generated printout is usually based on soil type and crop.

  • 16 years ago

    Personally, I don't change any amendments past the general for any crops but corn. Few vegetables need any special nutrients at long as N-P-k is reasonble.. Grasses like corn, do need or at least can use more nitrogen than other vegetables. Overdoing the amendments can be much worse than underdoing.

  • 16 years ago

    Ok, I'll buy in. Even if maybe not the absolute best possible for each vegetable, the amended silty clay loam will be some great soil.

    As it is, the P is off the chart at 78ppm so that nails it down.

    Thanks for the comments.

  • 16 years ago

    A soil test is usually done specific to one crop. Below are some soil tests for some giant pumpkins. While these levels will work for giant pumpkins they would probably cause all sorts of problems with other vegetables.

    {{gwi:34500}}

    This is my soil sample taken in October of 09 for my giant pumpkin patch. I have been steadily adding amendments to it and am going to have it tested again in about a week. I grew a 309.5 pound pumpkin in this dirt.

    {{gwi:34501}}

    Here is a link that might be useful: 2010 giant Pumpkin Diary

  • 16 years ago

    Adding according to the soil test recommendations will give you a good, general level of nutrients which will start your plants off well. Most of the nutrients are fairly stable in the soil and won't disappear over the summer, other than uptake by the plants. Nitrogen, however, is fairly easy to leach out of the ground with excess moisture and can gasify under some conditions.

    Your recommendations for a general garden may need some adjustments depending on the favorite nutrients of the plants you are growing. As mentioned, corn loves nitrogen, and you would likely want to side dress with some additional nitrogen when the corn is about 2 feet high. Corn, however, isn't the only nitrogen lover although it is extremely transparent in telegraphing its nutrient status so shortages become quickly and easily visible. Pretty much everything other than legumes (which use bacteria to make their own) love nitrogen too, and even legumes can respond to nitrogen.

    Watch your plants around 6-8 weeks after planting and if there are any signs of potential shortage or weaker/slower growth, then side dress with some additional nitrogen. After mid summer, let the plants use up what is available in the soil. You don't want to fertilize so heavily that you leave a lot of available nitrogen in the soil at the end of the season where it can leach to groundwater or anywhere else.

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