Where’s the water? What will be the yield?

With the recent lack of rain in our area and around the state many are wondering where is the water. At the Franklin County Extension office we haven't had a rain give us more than a tenth of an inch since June 9^th. During this same period our estimated evapo-transpiration has averaged about two tenths of an inch per day. This has left us with dry soils and corn that is showing signs of stress. The real question that comes up though is what does any of this mean for yield? For this we need to go back to the physiology of corn and look at what is happening currently and how stress will affect that. In general, when talking strictly about grain yield, our younger corn will weather a dry period without yield losses much better than our older crop. These younger crops are typically developing roots which may be limited due to drought but can recover if good moisture follows. The only real critical time for this young corn is the V-4 to V-5 stage where the number of kernel rows is determined by the plant.

Typically the corn that has not reached V-12 will have little yield loss. At the V12 to V14 stage the corn plant is initiating multiple processes which will set in stone what the maximum yield will be. These include; ear number determination (only on prolific hybrids), ear size, and number of kernels per row. Once these variables are in place we head into the critical time around silking. From R1 to maturity we have to have good conditions for the ear to silk in time for pollen shed as well as pollinated kernels to fill. Drought conditions around the silking time may lead to unfertilized kernels, thus decreasing yields. Once fertilization has occurred moisture and nutrients are still required to push fill.

This may seem like an effort in futility since we have little to no control on the amount of water our crop receives. However, if you are looking to make management decisions based on yield projections now is a good time to make sure you adjust yields if you feel your corn has been stressed to that point.