Crop Scene Investigation - 20: What teamed up to damage Matthew's corn?

Monday, October 5, 2009

by DEAN SHANTZ

When a field is doing poorly, a quick investigation may uncover a problem, but you need to be thorough in your assessment. Your diligence may reveal that several things are teaming up to take the sting out of your crop's yield punch.

At the end of June, I received a call from Matthew, a Wellington county farmer who was puzzled by the unusual appearance of one of his corn fields. "The corn is much better along the roadway than the rest of the field," he said. "The first 12 rows in from the side road are already at the 10-leaf stage. The plants are dark green and uniform in size. The rest of the field is yellowish and only at the 6-to-8-leaf stage. I think there is some kind of bug damage, too."

I decided it would be a good idea to see the corn for myself and made an appointment to walk the field. May and June had been cool and wet, prompting lots of calls from growers like Matthew.

Driving down the road, I could easily see the pattern he described as I approached from the south. I met Matthew at the edge of the field and we walked in from the roadway. He practised minimum tillage, so it was evident the field was also in corn the year before.

Strangely, I noticed the amount of crop residue on the soil surface increased as we walked further into the field. Matthew was quick to explain that he had harvested the outer portion last fall in order to get some early silage. The remainder of the field had been harvested as grain corn.

Besides growing corn, alfalfa, soybeans and wheat, Matthew runs a successful dairy operation. "We applied a heavy application of liquid manure last fall," he said, admitting that the ground was quite wet at the time. The corn also received a starter fertilizer through the planter and a pre-plant application of bulk urea. I was beginning to understand why we were seeing some of the differences.

The planting depth appeared mostly uniform at two inches, but it was difficult digging my spade into the ground to observe the plant roots. As expected, many of the roots were shorter in length and non-branching.

Matthew was right about the presence of insects. Some of the corn leaves exhibited a ragged, shredded appearance, a telltale sign of insect feeding. The degree of injury was definitely worse on the poorer-looking corn and was particularly severe on the lower leaves. Upon closer inspection, I noticed the occasional silvery, shiny trail on the ground.

Several things contributed to Matthew's poor corn. Can you identify two of them? Send your solution to Better Farming at: rirwin@betterfarming.com or by fax to: 613-678-5993.

Correct answers will be pooled and one winner will be drawn for a chance to win a Wireless Weather Station. The correct answer, along with the reasoning followed to reach it, will appear in the next issue of Better Farming. BF

Dean Shantz, CCA, is a Sales and Agronomy Manager for NK® Brand, Syngenta Seeds. He is based near Tavistock.