Dry weather taking toll on forage crops

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Indiana's forage crop yields are down and won't likely improve without decent rainfall in the near future, prompting a need for growers to take precautions to avoid further crop loss, says a Purdue Extension forage specialist.

Forages initially were damaged during hard freezes in April and have struggled to yield amid the unrelenting hot, dry weather of May and June.

"Many producers have reported to me that their first cutting was reduced fairly substantially as compared with other years - down by 25 percent or more," Keith Johnson said. "So we're starting out in a deficit in terms of total-season hay production possibilities. Then we couple that with the dry weather and the next harvest doesn't look to be super high-yielding either."

The April freezes damaged alfalfa tillers and, as a result, not only was the first cutting reduced, but if harvested prematurely the crop could have been lacking in carbohydrate reserves needed for the next crop to regrow. Harvesting second and subsequent cuttings before the plants have time to rebuild vigor could cause stands to suffer into the future.

Johnson recommended waiting until just after late bud or on into some flowering before harvesting alfalfa.

"If we've harvested relatively early a couple of times, we really have put some stress on that plant," he said. "We probably should give it an opportunity to get beyond late bud and maybe into some flowering to give us more days to put carbohydrates into the reserves in the crown and taproot. Then there should be enough vigor for regrowth."

In addition to delaying harvest a bit, Johnson also said now is a good time to look at soil fertility. Soil tests can reveal any nutrient deficiencies and help producers know which fertilizers need to be applied.

But Johnson cautioned producers against applying nitrogen in hay and grass-dominant pastures until there is enough moisture.

"I think we have to recognize at this point moisture is the yield-limiting need," he said. "I would hold off on nitrogen fertilizer application until we return to the more timely and sufficient rains we need for grass production to occur."

The lack of rain also has created conditions that exaggerate potato leafhopper damage. The insect feeds on alfalfa and many other plants. During feeding, it injects the crops with toxins that stunt growth and limit yield.

Johnson encouraged growers to scout for the potato leafhopper with a sweep net intended for this pest. Insecticide treatments could be warranted when the average number of potato leafhopper in a single sweep of the net is 0.1 leafhoppers per inch of alfalfa height.

For example, an alfalfa crop 10 inches tall would need more than one leafhopper per sweep to warrant control. Those insecticides, however, also kill beneficial insects.

A better option, Johnson said, is for growers to plant a leafhopper-resistant variety the next time they seed the field.

Finally, growers need to pay attention to harvest dates to avoid harvesting forage crops too late in the season.

"If enough stresses occur, growers really need to be aware of when they harvest the last crop," Johnson said. "Traditionally, for those in the northern part of the state, somewhere around Sept. 5 should be the last growing-season harvest. For those in southern Indiana, we probably can stretch that to around Sept. 15.

"This allows enough time to build those carbohydrate reserves before a killing freeze comes along, so we have a plant with a full tank of energy through the course of winter. And then, as we break dormancy the following year, enough reserves are there for a vigorous break winter dormancy crop."


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