Timing the Tap

July 25, 2014 08:35 PM
Timing the Tap

Properly irrigating corn seed requires staying ahead of schedule

Proper irrigation is vital for a high-value crop, and for seed corn—hybrid corn’s weak 
sister—timing rules the day. Turning on the tap at the right moment offers the best chance to sync emergence, silking and pollen shed. 

Seed corn doesn’t handle a lack of moisture well, and the crop must be kept at the same height throughout the season. Drought or stress will throw male and female plant development off. McKillip Seeds in Wabash, Ind., compensates by using irrigation for basic water needs and to cool down the field at tasseling and pollination.

In an average season, McKillip plants seed corn the last week of April through May, staggered accordingly to match up with harvest flow. If stress levels are strong the company throws a little water on at the six- to eight-leaf stage to keep the corn the same height. 

"Just before tasseling, it’ll be time to hit it hard with water so we know the corn is in optimal health right before pollination," says Mitch Snyder, a yield specialist for McKillip Seeds. "Irrigation helps us manage heat and drought stress at pollination, which is a critical period in determining yield, seed size and quality," he adds.

After pollination, irrigation continues until kernels are formed. The water is shut off when the corn is at 55% to 60% grain moisture, usually a month before harvest, he says. Harvest runs from Labor Day until mid-October.

Stress points. Seed corn is susceptible to stress during pollination, says Lyndon Kelley, Michigan State University and Purdue University Extension irrigation educator. With the majority of fields using every fifth row to pollinate, stress arrives just as farmers are clipping the female plants and pulling tassels, usually in early July. 

Within a two-hour drive of Middlebury, Ind., including southern Michigan, nearly 70% of 680,000 irrigated acres have seed corn in the rotation.

"The seed corn is here because the irrigation is here," Kelley says. It’s about taking advantage of the least amount of risk—not highest yield potential. The sandy soils only hold 3" of available water for the plant and allow farmers to get back on fields after heavy rains without delay issues.

Seed corn problems are often related to delayed emergence. "We’re looking for a quick, uniform emergence," Kelley says. "We do several operations where we’re clipping the top of the plant, and so any plant that comes up a day or two later causes the machinery to dip down in the row to find it. Just one or two plants can create huge yield devastation because you’re clipping the top of the shortest plant."

Early strategies involve uniform emergence and herbicide uptake. Some herbicides used on seed corn tend to be older, more predictable types that work best with rain falling within a day or two of application. 

On a schedule. Seed corn producers look for rainfall to supply moisture needs until mid-June. Early season irrigation is aimed to meet the immediate needs of herbicide incorporation and germination. Based on a 30-year average, Kelley says there is no need for irrigation until the last week of June, but some farmers turn on pivots in May, while others wait until July 1.

In most seed corn fields, farmers begin filling the water profile a week before tasseling, leaving 1" off capacity in case of rain. During pollination, seed corn can drink ¼" of water per day when temperatures average 85°F. 

At pollination, farmers lower water time due to the increase in field activity. "These fields are going to have kids coming in for detasseling, and most of the companies, for safety reasons, have protocols that reduce the amount of time irrigation equipment can be run," Kelley says. 

Preparation is crucial. "Producers have to be sure to water ahead of schedule," Kelley says. "Treat the profile like a checking account, and fill the bank so you have capacity to get by detasseling or equipment failures." 

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