Notes from the UW Agronomy field day session with Joe Lauer

Corn likes to have a “mini-drought” in June to develop roots, followed by 1” of rain per week. In most of southwest Wisconsin our rainfall is equal to if not slightly higher than 2016. The main difference in 2017 has been that the rainfalls have not been consistent. There have been multiple 2-3 week periods without rain that have created some plant stress. We’re expecting to see a greater advantage to fungicide applications that help reduce the impact of stress on the crop.

Usually corn reaches maturity and normal dry down if kernels are dented by Labor Day. There was some concern about how cooler temperatures might affect corn maturity. Much of the corn was dented by Labor Day in southwest Wisconsin. Something else to consider is how much yield are we shorting ourselves by planting hybrids that dent early and don’t utilize the full growing season?

 Length of daylight has a greater effect on corn maturity than temperature does during kernel fill. Again, photosynthesis and chlorophyll production are key to finishing the corn crop. This year most ears are averaging 16 kernels around compared to many times we see 18-20 kernels. We need the plant to fill out those kernels to achieve yield, and the more sunlight we can give these plants, the better they will be able to do the job of filling the kernel.

 Late season nitrogen availability and growing full season hybrids is important to reaching the top yield potential. There are several ways of feeding nitrogen to the corn crop, and many products claim to help keep nitrogen available later in season. A majority of corn fields are showing stress from running low on Nitrogen this year. There was a very visible difference where growers used anhydrous ammonia with N-serve as a pre-emerge source of N versus using pre-emerge urea or 28%. We also see a large benefit to sidedress nitrogen, especially where Y-drops were used to place the nitrogen directly over the root zone.  Later season hybrids are showing less stress as the plants have been able to more efficiently use the water that’s been more sporadic than consistent.

 There’s typically a 1.9 bushel advantage per day of maturity for corn. Ex: 109 day hybrids typically have 19 bushel higher potential than 99 day hybrids. According to the University of Wisconsin, the climate and soils across Grant, LaFayette, Green, and some of Iowa County favor corn maturities in the 110-115 day range. Many producers grow shorter maturity corn to be able to have drier corn at harvest. And we all have seen that current 100 day  hybrids are capable of producing the yield we used to see with 110 day hybrids. Losing out on 20 bushels of corn is a much higher cost than an extra couple percentage points in   moisture, especially given the fact that 20-24% moisture is recommended for combining corn.

Agronomic improvements and advancing genetics go hand-in-glove for increasing yields. Just like there’s a 1.9 bushel yield gain for each day longer maturity of corn, there’s also about the same gain made each year with advanced genetics. Without implementing  better farming practices however, we won’t see those increases. This is shown in the UW study at Lancaster, where the  no-nitrogen plot shows no yield difference between the newest genetics and 60 year-old hybrids. Without plant nutrients, both old and new hybrids are yielding 50-60 bushel. If we want to get the most out of the new genetics, then we need to follow modern agronomic practices for planting, feeding, and protecting these genetics.

Questions or Comments? Call me at 608-780-8116 or email

Andrew Tucker


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