33 Story Idea? Email Paul.Nolan@Farms.com Better Farming | May 2024 crops: yield matter$ and surface applications of nutrients. In this particular field, the top two inches have a soil test phosphorus of 42 ppm where the standard zero- to six-inch depth is 25 ppm. The fertility interpretation is based on zero- to six-inch sample depth; inconsistent sampling depth results in different values that lead to errors in nutrient recommendations. Soil test results, much like a balance sheet, indicate how effectively you manage nutrients on your farm. Just like you would not make financial decisions today from a balance sheet from 2010, you should not make nutrient plans from dated soil test results of that vintage either. For farmers who simply opt to apply nutrients at a crop removal rate each year, this approach is not without risk. If soil nutrient rates are low and producers are not aware of these deficiencies, simply fertilizing to replenish crop removal rate will not optimize yields. On the flip side, if soil nutrient rates are excessive – and without a soil test you would not know that – fertilizing at the crop removal rate means producers are increasing the size of their environmental footprint. In the process, farmers may not be optimizing harvested yield and most likely are not maximizing nutrient use efficiency. Most programs based on crop removal calculations tend to apply the same fertilizer to all fields. One thing I have learned over 45 years, however, is that not all fields are the same. A single soil report can provide good information. A series of reports over the years is better. We can look at multiple years’ worth of reports to find trends in soil fertility and allow for adjustments in amendments. If soil nutrient levels are increasing, then our applications of nutrients exceed what our crops are removing from the soil. If nutrient levels are declining, the opposite is true. If the values remain constant, we have a balance in our cropping system. In years when net returns of cropping are marginalized, we can prioritize our nutrient applications. In the fields with high fertility, we can reduce the amendment rates there in the short term. We can reallocate amendments to fields that will need the most help to maintain yields. When we face years with marginal returns, yield maintenance is vital. The higher our yields, the more yield we have available to sell at any price. The economic and agronomic risks of cutting back nutrients on all farms are unacceptably high. Without soil tests, we will not know which fields are in most need of amendments. With all the technology we have available today, including soil sampling, keeping records and sorting fields by productive capacity, it is easy to do custom-blended nutrient programs targeted to address specific field variability. What does it cost to soil sample? What does it cost if we don’t? Are we talking about the soil sampling activity by itself and what it costs? Or are we integrating soil sampling data into a comprehensive, forward-looking crop production system tied to farm profitability? Producers who soil-sample on a regular basis are better off managing their risks and helping to optimize profits. These farmers are also gaining competitive advantages with more efficient production systems. The photo on Page 32 is from an area of a field that the producer soil-tested in the fall ahead of planting wheat. The area had a pH of 5.3. The winter wheat in this area is performing poorly, as the crop grows best at a soil pH of 6.9 to 7.0. The soil test described an acidic condition, the result predicted poor crop performance, and the prescription was to apply lime. The only issue was that lime needed to be applied the year before, so that it had time to react and change the soil pH. Additional soil test values in this area were 35 ppm for phosphorus, 145 ppm for potassium, CEC at 12, SOM at three per cent, and base saturation of calcium at 40 per cent. The low pH value reduced the availability of phosphorus and potassium and would reduce the availability of any applied nutrients until such a time the pH was increased from the limestone application. Keeping soil tests current and deciding on nutrient use with soil tests no older than four years is a requirement of 4R nutrient stewardship. Reach out to your trusted certified crop advisor and review which of your fields needs to be brought into a current position with soil tests. It will be time well spent. Plan for good things to happen. BF DALE COWAN Dale is agronomy strategy manager and senior agronomist for AGRIS Co-operative. He has been a regular contributor to Better Farming since its launch in 1999. CCA-ON, 4R NMS.
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