Five Steps To Useful Soil Test Results

If you’re like many this year and have unseeded acres, drowned-out areas, had excessive moisture or yes, even too little rain, soil testing and analysis is even more critical when planning next year’s crop. Excess moisture can cause nitrogen losses through leaching or denitrification, and the amount of mineralization that occurred during the growing season will be hard to estimate if fields were unseeded or grew poor crops.

We all hear it every year — fertilize according to your soil tests. But only a portion of fields are tested for nutrition requirements. Why is this? There are a couple of reasons: you’re busy harvesting in the fall; soil sampling costs money; results don’t always generate practical recommendations; and, most farmers have their own theory on what the crop needs based on what the previous crop took out of the soil.

Let’s face it, if you pay to have soil testing done or do it yourself only to have the results returned with no clear direction on what to do about them, you’re not likely to see a lot of benefit from the expense. Soil testing can also be finicky, and botched testing can lead to useless results. Soil testing must result in practical recommendations that make economic sense in order to be useful.

But first, why does soil testing matter? Soil sampling provides a snapshot of what’s happening in the soil and can help maximize your return from your fertilizer investment, for nitrogen and beyond. As important as it is to determine the amount of nitrogen required, it is also critical to apply the proper balance between all of the nutrient requirements. The proper balance between the nutrients is equally as important for yield potential as is concentrating on the level of nitrogen applied throughout the field.

There are many organizations and companies that are providing soil testing and fertility recommendations. Do your homework, ask around and find out what services are being offered by each. There’s a wide range in how the recommendations are derived, the lab methodology, as well as the quality of information sent back to you. Shop around and find a lab/company that suits your needs first. In the interest of full disclosure, we use Western Ag Labs for our soil sampling and analysis needs.

No matter which company or lab you use to get your soil sampling done by, there are five topics to address to ensure you that this information is useful to your farm.

PROPER SAMPLING TECHNIQUE

The sampling is where the process begins. If the sampling protocol is not correct, the results will not be meaningful to production. The gathered sample must be representative of the field (or an area of the field). It is imperative that the sampler takes the sample from areas of the field that are productive, staying away from areas that may throw off the results such as an old yard site, an area with a different history (i. e. remained in native grass longer) or problematic areas of the field such as solonetzic patches.

The sampler should ask you questions prior to taking the sample such as cropping history, where any unusual sites in the field are, where you are disappointed with production levels etc., to determine areas to ensure a proper sample is obtained. The sample sites should also be GPS benchmarked to remove sampling variability year to year as well as between people sampling. The sampler should take as many samples as needed to feel they captured a representative sample, remembering that more samples do not necessarily make it more accurate.

REPEATABLE RESULTS

Do you feel that the results that you receive can be repeated time after time? They should be to make them accurate. There are many different organizations that complete soil testing and recommendations to differing levels. It is important to be able to “back-cast” with a reasonable degree of repeatability. This is when, after harvest, you go back to the fertility recommendations provided by the soil analysis, input the fertilizer you actually applied to the field, add in the season-long amount of precipitation and compare how similar the actual yield in the field is, compared to what the target yield is from the recommendation model. When you back-cast a particular field you should see actual crop yields within 10 per cent of the target yield rec- ommendation. I consider these results to be repeatable which goes a long way to making the fertility recommendations accurate and proven in real life.

CUSTOMIZABLE RESULTS FOR YOUR FARM

Are the results that you are receiving made for your particular farm operation? All farms have limitations placed on them, whether it be the type of opener you use and your ability to seed place a certain amount of product, how many compartments you have in your air cart and what combination of blends and products you can reasonably apply, or if labour is limited during springtime the recommendations must work within your logistic capabilities to keep the drill moving in the field. All of these limitations are real, and when it gets down to go time in the spring if the recommendations you are receiving don’t work with your operation, most growers will simply revert back to applying the same fertilizer blends and rates as they normally have done in the past.

NUTRITION DECISIONS BASED ON NET RETURN PER ACRE

How do you decide if you are going to roll the dice and apply an extra 10 pounds of nitrogen? Is it a gut feel, or does it depend on what the soil and marketing outlook looks like at seeding time? Fertilizer is a big portion of our variable input costs and is perhaps the biggest investment we make into getting our crops off to the best start possible. It is important to know what incremental net return you will receive for each incremental pound of fertilizer you apply. This is an important exercise to go through, as there is a point with every nutrient that applying an incremental pound doesn’t make sense economically based on the amount of risk to reward.

A good fertility recommendation should be able to show you differing scenarios on risk and reward for your investment depending on your target yield as well as how aggressively you want to manage your crop. It is important that you choose the desired rate of return on your fertilizer investment for a particular field or farming operation. Everyone differs in the amount of risk that they want to take on — proper fertilizer recommendations and decision should allow the ability to run different scenarios showing different return rates on their fertilizer applied.

Of course, every farm has a different fertilizer budget to work with and for some, nitrogen-based recommendations may be more money than they’re worth. For farms with a lower fertilizer budget some analysis and recommendations may cost the farm upwards of 20 per cent of their budget — not necessarily a great use of resources. For example at current nitrogen pricing, farmers can apply at least 2.5 pounds of nitrogen per dollar spent. When you take that into consideration farmers could potentially apply a significant amount of nitrogen for the cost of some of the nitrogen-based recommendations.

ADAPTABLE RECOMMENDATIONS

We all know that many carefully made plans get altered and changed as you get into the seeding season. Cropping plans may change, or level of risk/ reward may change given the situation at seeding time. It is important that the fertilizer recommendations you receive can be changed at the drop of a hat to accommodate real-life plans. You should be able to take your soil analysis and evaluate differing scenarios such as crop to be planted, amount of precipitation received/expected and still come up with an economical recommendation for each major nutrient that is required.

These are five pillars to judge your soil analysis and resulting fertilizer recommendations on. All recommendations should be made to work to their best ability on your farm.

BobbieBratrudfarmswithherhusbandMark nearWeyburn,Sask.TheyalsorunBratrud AgAdvisoryServices( www.bratrudag.ca).

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A good fertility recommendation should be able to show you differing scenarios on risk and reward for your investment

depending on your target yield as well as how aggressively you want to manage your crop.

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