Fertilizer Decisions Following a Year of Drought

When my son was younger, he was so obsessed with anything ‘Lion King’ it was annoying. While I’m busy trying to develop mathematical algorithms to solve the world’s greatest agricultural problems, my son, pretending to be Simba is dragging me off my desk to run around the house with him singing Hakuna Matata! He is a bit older now and we don’t get to play that game anymore, but I wish we could, especially in a year like this. Scouting dry and thirsty crops while my walking boots leave a cloud of dust above the severely parched land, I need someone to remind me – Hakuna Matata (no worries), next year will be better.

It has indeed been a difficult year for agriculture in the Prairies because of the extreme drought conditions during the growing season. With the low precipitation and poor yields, many farmers are asking about what their soil nutrient levels will look like next year, and how they should approach fertilizer decisions.

What happens to soil nutrients during a drought?

Dry conditions decrease downward movement of nutrients and reduce nutrient uptake by drought-stressed plants, so there might be residual nutrients left over for the next season. But for mobile nutrients like nitrogen, whether or not significant amounts of these nutrients are available in spring will depend on how much precipitation is received after harvest. Heavy precipitation can leach nutrients out of crop rooting depths.

Furthermore, dry and hot conditions inhibit soil microbial activity, so the organisms that convert organic matter to plant-available nutrients are impeded, leading to a lower nutrient turnover than would otherwise be expected during a wetter year. In addition, biological nitrogen fixation by legumes can decrease during a drought resulting in a reduction in the usual soil nitrogen credit for the next crop.

Management activities can also affect soil nutrients for the next year. For example, during a drought, crops originally planted for grain may be harvested for forage instead, thereby removing more nutrients from the field.

What should you do?

The importance of soil testing can hardly be overemphasized, especially in a year like this. Soil testing is the best way to analyze a drought’s impact on your field and determine what your fertilization decisions should be next season. Soil sampling may be done in the fall when soil temperature drops below 10° C, or in the Spring before seeding.  A knowledgeable agronomist can help you interpret your soil test results and take appropriate action. Your SynergyAG team will be happy to discuss your soil testing needs. We’ve got your back. Hakuna Matata!

-Ikenna Mbakwe, PhD, PAg
Head of Research
SynergyAG