In recent weeks, nutrient deficiencies have been showing up with increasing regularity. This can be the result of many of the rice acres having been flooded and many others beginning reproductive growth.
Zinc (Zn) deficiency is one thing we are finding and it is not fun to deal with. It has shown up in a number of fields in the past week or so. Once a more severe deficiency is in place, lower leaf “bronzing” or purpling is present and the midrib has a bright yellow appearance.
The plants will generally be short and stunted, as well, with very little to no space between the leaf collars of plants. Those, in fact, should be elongating following the preflood N application. Moderate to severe Zn deficiency can lead to significant yield loss and plant death if not managed or corrected in a timely manner.
Unfortunately, moderate to severe Zn deficiencies show up soon after flood and the best method to correct the deficiency and recover as much yield potential as possible requires taking the flood off. Once the water is removed and muddy soil exposed, apply 1 lb of Zn/acre as a chelated Zn (typically 1 gallon/acre of a liquid Zn EDTA product, but this needs to be 1 lb of chelated Zn/acre regardless of product).
The use of a chelated Zn product for application at this growth stage is important to maximize plant uptake both through the foliage and also the rice root system. Zinc is an immobile nutrient in the soil and for early season or post-flood applications the rice typically has not fully canopied and much fo the soil surface remains exposed.
Using a chelated Zn source allows any of the Zn that does not contact rice leaves to be mobile in the soil and move downward towards the rice roots where it can also be actively taken up by the plant.
For a non-chelated Zn source, any of the Zn that does not hit the foliage will remain at the soil surface and rice plant uptake of this portion of the Zn application may be severely restricted and lower the ability of the application to correct the deficiency.
A few days following flood removal and Zn application, apply 100 lbs of ammonium sulfate/acre and reflood.