C A L I F O R N I A
FieldCrops A SPECIAL GROWERS’ REPORT OF AG ALERT ®
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Water decisions for corn get new urgency in drought
ByKathyCoatney California’s third consecutive year of drought means continued challenges for growing corn. Konrad Mathesius, a Universi ty of Cal i fornia Cooperat i ve Ex t ens ion agronomy adv i sor for Sacramento, Solano andYolo counties, has some advice. Mathesius suggests two strategies for successful irrigation management in corn. First, determine how much water will actually be available during the growing season and at what time, he said. Second, it is important to manage the environment around the corn. Growers should know that any reduction in water will reduce yields, Mathesius said. He offers this strong caution: There are times during the growth cycle when irrigation should never be reduced. “The twoweeks leading up to and the twoweeks after silking is the most critical time, and that’s when you’re not going to reduce anything,”Mathesius said. “No defi- cit irrigation. Keep watering with crop evapotranspira- tive demand, and avoidmoisture stress.” The time to consider reducing irrigation is after all the pollination has occurred and the kernels have set, he said. Then, it is possible to slightly reduce water during this period, but only if the soil has enough moisture. “At that point, you’re coasting to the finish line, right? In silage corn, you’re coasting to 50%milk line; in grain corn, you’re coasting to black line,” Mathesius said. “In both cases, you still need to make sure that your crop has the water that it needs. But you can monitor your soil moisture and scale back if it seems like the corn will have enough as it’s approaching its maturity.” He said the corn crop “is going to be able tomine that soil moisture, continue to create carbohydrates, push those carbohydrates into the seed, and fill up the actual kernels.” But he said growers are “going to take a hit” no matter when irrigation is reduced. “The question is howmuch of a hit (growers will face), and stress in the final stages of maturity is relatively less of a hit,” Mathesius said. He warned against skimping on water at the begin- ning, and he said tomake sure that roots have a place to explore, because they don’t go where there is no water. “People think that roots will go down and will push through dry areas to hone in on water,” Mathesius said. “That’s not actually what happens. What happens with roots is that they continue to explore wet areas and die off if they run into dry areas. They’re like probes being sent out in deep space, and the ones that send signals back like, ‘Oh, there’s water here,’ they’re the ones that get maintained and continue to explore.” In short, according toMathesius, the cropdoesn’t have a sixth sense. It doesn’t know where water is before it encounters it, so it just continues to explorewherewater has been found. “So, if you have water in your profile, at a reasonable depth, the roots are going to be able to follow that as
With another drought year, farmers who grow corn may need to focus on varieties that require a shorter season and less water.
See CORN, Page 8
March 16, 2022 Ag Alert 7
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