What is in this article?:
- Moist Soil Sample Provides Precision, Better Accuracy in Estimating Potassium
- Rapid field analysis
- Five-minute nitrate field results
Five-minute nitrate field results
"The No-Wait Nitrate field lab gave us an accurate nitrate reading in five minutes," says Irwin Arndt, CVC agronomy sales manager. "We’d tried early season testing for N in the past, but it took too long to get results back. With Solum's system, we take the samples, run them and can apply that day."
Samples were taken according to productivity zones, which were then sidedressed for optimum yields. In some cases no need for sidedressing was indicated. Control strips were sidedressed according to traditional protocols. Sampling was carried out at stages V3 through V5 for application needs and again at V8 for verification.
"Where no need was indicated, yields were unaffected," says Arndt. "We also saw no yield advantage to standard sidedressing. Where a need for additional N was indicated, we saw the best yields ever, with 10-20-bu. increases over no application control strips. Our growers ended up putting on less N than they would have normally, but used it where it was needed. I think in most cases they used around 80% of what they had planned to use."
Arndt says growers were equally pleased with results from field moist sampling for K. Cooperators chosen for the comparison had good fertility programs. However when the field moist samples came back for highly productive areas in fields, K levels were lower than conventional tests indicated.
"We have really been trying to push yields in these fields, but with conventional soil sampling, we weren't getting the yields we wanted," he says. "When we applied potash VRT on 2.5-acre grids according to the moist samples, we were applying more in the areas where it was needed. We saw yields climb dramatically, up to 260-270 bu. in areas where we had never seen those yields before. It is tough to tell, but we expect a 5% yield increase with field-moist sampling over conventional dry."
Field moist sampling isn't a silver bullet, but Mallarino feels it is more precise and more accurate in estimating actually available K. He has seen no difference between wet and dry samples for P, calcium, magnesium, pH, buffer pH or other minerals. As a longtime advocate of moist sampling, he’s pleased to see other states gathering data for K recommendations on their soils, as well. While the original data used for fertilizer recommendations in the 1960s and 1970s used moist samples, fresh data needs to be gathered, he says.
"Soils, varieties and hybrids are different across states,” says Mallarino. "We need to do fresh field calibrations using field trials and gathering yield data."
Mallarino and Arndt agree that farmers maintaining high K levels in their fields may not see a difference in yield response. "If you maintain optimum or high levels, this test may not affect what you are doing. The issue is with a portion of fields or entire fields where levels are low," explains Mallarino. "The moist test is a better predictor. It may not be a problem when growers are making money and applying everything, whether needed or not. When crop prices drop and people need to really fine-tune their inputs, that's when even a minor difference in testing will really help."
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