Every year, tissue samples unlock insights for the following season. Here’s a summary of 2020 tissue sampling trends from counties in southern Minnesota.

Corn: Build macronutrients, then micronutrients. In 2020, nitrogen deficiencies occurred early, remained throughout the season and were significant — more than double (82%) what they’ve been for the last three or four years. In some instances, weather conditions were such that soils either didn’t allow nitrogen to mineralize or didn’t have nitrogen available for plants in the first place.

As is typical, we also saw early micronutrient deficiencies — specifically zinc, manganese and boron — and farmers often perform foliar applications at specific times to correct those. But first, we should always capitalize on our corn seed investment by ensuring adequate levels of macronutrients. What we learned in 2020 is that we have to do a good job with potassium and phosphorus in order to optimize nitrogen and sulfur, and then achieve yield response when we apply zinc, manganese and boron following the rules of elemental prominence and nutrient hierarchy in corn.

Soybeans: Increased nutrient deficiencies. I concentrate on soybean tissue samples taken at the R1 and R4 growth stages. This is because, operationally, that’s the best time to make a nutrient application, and it’s when soybeans need the most attention to capitalize on increased yield.

The biggest micronutrient deficiency in soybeans across southern Minnesota in 2020 was manganese, with nearly 60% of sampled crops coming up deficient. Because manganese is the primary energy transfer source for photosynthesis, as we get higher soybean yields, our plants need to use more of it.

Figuring out sulfur applications. Sulfur is a key building block in both corn and soybeans. Recent tissue samples have indicated an increase in sulfur deficiencies during the early reproductive growth stages in both crops over the last several years. Sometimes this correlates with potassium and/or nitrogen deficiencies. Tissue sample trends may provide hints as to which of these macronutrients need to be finely tuned. But that’s not always the case. Some of this deficiency might be weather-related, which correlates to soil mobility and lack of applications of sulfur.

Ideally, we would apply sulfur in spring prior to planting because most sources are soil-mobile. Some farmers do a fall band and broadcast of sulfur, while others may have the ability to do an early sidedress, which is OK, too. Keep in mind that there are many ways to apply sulfur, depending on your source or product choice. Use tissue sample trends and past deficiency indicators to address your crops’ sulfur needs and adjust your strategy.

Look ahead to 2021 nutrient plans

As you review 2020 sampling data with your agronomist, look at the different ways your deficient nutrients are available to plants. Are they mobile or immobile in the soil? That’s going to dictate when you can apply them to ensure proper uptake for in-season plant needs.

If they’re immobile in the soil, that might mean you need to apply them foliarly, or use technologies such as chelation to slow tie-up. Also, pair 2020 tissue samples with soil samples and yield results to help formulate a sound nutrient plan for 2021.

Zuk is a regional agronomist with WinField United in southern Minnesota. Contact him at [email protected].

Source: WinField United, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all of its subsidiaries are not responsible for any of the content contained in this information asset.