When is the best time to topdress winter wheat in Northeast Texas? We’ve been working with timing studies since the mid 1980s, and reviewed our research trials to try to make some sense out of the numbers.

We have data on 24 studies from 1987 to 2006. Over that period, we have compared an early application (early- to mid-February) to a late application (early- to mid-March) to measure the optimum timing for grain yield. After summarizing the data, we found in some years, timing did not make very much difference – the early February applications made almost as much as the early March applications.

In one study in 2005, the early application produced almost 15 more bushels of grain per acre than the late one. Rainfall records in 2005 showed a dry period from mid-March to mid-April. Evidently, there wasn’t enough rain to move the nitrogen into the soil profile in time for the wheat plants to use it for growth and development.

Other years, the late application made 8 or 9 bushels more than the early ones. We assembled rainfall data over the same period (courtesy of Maynard Cheek), and found a common denominator. Years with very wet conditions in March and April favored the March applications. Later applications during those years produced 8 or 9 bushels more than the early February applications. On the other hand, in years where March and April rainfall was less than normal, there was very little difference in grain yield between the early and late applications.