Winter wheat update: How recent rains will influence the wheat crop

Josh Lofton, Harrison, Stephen A.

Originally published June 1, 2014

A recent article discussed how much potential the current wheat crop had but we may be seeing that yield potential in jeopardy due to heavy rains for the past week. One of the greatest impacts this can have on wheat seed is in the final harvest test weight. Mature wheat kernels are smooth and have the highest test weight as soon as they initially reach harvest moisture (10 – 14%). Every time a heavy rain falls on a mature wheat field the dry kernels re-absorb moisture and swell up. Upon drying again the kernel shape changes slightly and test weight is lost. Test weight losses can reach several pounds per bushel, resulting in dockage at the elevator and decreased profitability. The article below, published by the Virginia Cooperative Extension Service, summarizes findings from NC State on the impact of delayed harvest of test weight. Hot weather during late grain fill can also negatively impact test weight, particularly for late-heading varieties. This is why some late-maturing varieties are not suitable for Louisiana, even if they do fully head out and have relatively good grain yields.

While decreased test weights may be the most common and damaging condition experienced across the state, others certainly exist. Seed diseases can also be a concern. One that has been identified in the southern part of the state by Dr. Steve Harrison is black point (Image 2).

This fungus develops when humidity and temperature in the canopy are high during grain fill. While this disease can be damaging, how wide-spread these conditions become are yet to be determined. Additionally, with frequent rainfalls the seed can lose sprouting resistance and germinate in the head prior to harvest (Image 3). This not only influences seed quality but may result in significant dockage at the mill and influence harvest moisture.

In addition the effect at the seed head level, these storms can also impact the crop at the field scale level. One common and easily identified impact is lodging in the crop. Lodging can occur when the seed head becomes too heavy and the straw deteriorates and snaps when storms occur. While most producers will be able to harvest, this high rate of lodging can increase seed deterioration and shattering prior to harvest.

While these problems may seem like a foreboding effect for the current wheat crop, there is still a large amount of potential for the crop. It will be essential to let the field and crop dry prior to recommencing harvest. However, as soon as these conditions exist, wheat harvest should be the upmost task and mechanical drying may be important. While this will not decrease damage that has already been done, it will decrease the potential of continued damage going forward.

For additionally questions or comments, feel free to contact:

Josh Lofton- LSU AgCenter, State Wheat Specialist, jlofton@agcenter.lsu.edu

Steve Harrison- LSU AgCenter, Small Grain Breeder, sharrison@agcenter.lsu.edu