Crop Scene Investigation - 27 Solved: What happened to Larry's wheat?

Monday, November 1, 2010

by BERNARD TOBIN

The poor-performing wheat in Larry's field suffered from nutrient deficiency after he mistakenly adjusted the fertilizer rate rather than the seeding rate.

Agronomist Paul Sullivan explains that Larry had intended to increase the seeding rate on his drill as he finished up planting, but in his haste he somehow managed to change the fertilizer setting, reducing the flow of in-furrow starter fertilizer.

In his investigation, Sullivan ruled out many potential explanations – from spray injury to planting depth and seed performance. When he discovered that the plant population had not actually increased in the block of the poor-performing wheat, despite Larry apparently increasing the seeding rate, the pieces of the puzzle fit together.

"There are only two things being applied at seeding – seed and fertilizer," explains Sullivan. And if Larry did not adjust the seeding rate, he must have mistakenly changed the fertilizer rate. This conclusion was also supported by other evidence, including the backward growing conditions which make nutrients less available to plants and the soil tests which revealed poorer fertility in the affected area.

"It just goes to show the impact the starter fertilizer can have. You do see over time a delay or difference in heading where one field has had starter fertilizer seed placed versus another field that hasn't had any, or it has been broadcast, especially in a no-till situation," says Sullivan.

In this case, yield results revealed a 5.8-bushel-per-acre yield reduction in the block that did not receive the intended starter fertilizer application.

Sullivan also notes that uniform fertilizer application plays a key role in effectively using fungicides to control fusarium in wheat. "You always seem to have much more uniformity of heading when you have seed-placed starter fertilizer. It's much easier to make a call on the timing of a fungicide application when it's growing uniformly."

Congratulations to Tom MacGregor, Crysler for his correct answer. BF