Integrated Crop Management News

Links to these articles are strongly encouraged. Articles may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If articles are used in any other manner, permission from the author is required.

Delayed PRE Herbicide Applications in Corn

By Mike Owen, Department of Agronomy

Given the way the season has developed, the best intentions to apply an Early Preplant (EPP) herbicide application prior to corn planting has gone out the window and it appears that applying a preemergence (PRE) application immediately after planting is also becoming a slim chance. Thus, many who intend to use a soil-applied residual herbicide treatment in corn may be forced to make the application of an early postemergence (EPOST) to the weeds and possibly the corn.

Planters are Rolling and Corn is Growing

Image of base 50 degree F degree days in regions of Iowa from May 1 to May 4, 2008

By Rich Pope, Department of Entomology

Today the first weekly report of base 50°F degree-day accumulations is posted for the 2008 Iowa crop season. Statewide, the first four days of May have accumulated degree days at the long-term average, but that follows a cooler-than-normal April.

Seeding Rates in Relation to Maximum Yield and Seed Costs

Graph of corn grain yield at varying seeding rates

By Roger Elmore and Lori Abendroth, Department of Agronomy

Increased seeding rates have ignited corn yield increases over the years. If seeding rates are the spark, hybrid genetics fuel the increase. It takes both high seeding rates and high-yielding hybrids that can tolerate increased plant-to-plant competition to maximize yields. If hybrids were not bred to tolerate increased seeding rates, we would have fields of flat corn at harvest. Older hybrids simply cannot tolerate today’s seeding rates without severe lodging and/or barrenness.

It’s a Late Spring: Should You Apply Nitrogen or Plant Corn?

By John Sawyer and Roger Elmore, Department of Agronomy

Our best information from planting date experiments show that corn yields are reduced as we plant into the second half of May. However, looking at planting progress and corn yields over the years, we see that although yields are increasing and in general we are planting earlier every year, above average yields can occur with delayed planting and below average yields can occur with early planting (see Sidebar article ‘Corn Planting Progress‘ from Wisconsin).

Surface Waters: Ammonium is Not Ammonia – Part 2

By John Sawyer, Department of Agronomy

A previous article explained the difference between ammonium and ammonia, the relationship between the two nitrogen forms and the implication of a combined (ammonium-N plus ammonia-N) analysis related to water quality criteria for aquatic life. This article focuses on the implication of ammonia and ammonium for chlorination of drinking water.

Field Testing of N-Hibit™ Seed Treatment in Iowa*

Map of the locations of experiments in 2007 where n-Hibit seed treatment was evaluated

By Greg Tylka and Chris Marett, Department of Plant Pathology

N-Hibit™ is a seed-treatment that contains harpin protein, a compound that can stimulate plant defense responses. N-Hibit™ is now being sold in the United States for management of the soybean cyst nematode (SCN). Iowa State University evaluated the effects of N-Hibit™ seed treatment on soybean yield and SCN population densities in experiments at nine locations throughout Iowa in 2007.

Don’t Use More Pressure than Needed on Wet Soils

Image of depth-gauge wheels adjacent to the seed opener

By Mark Hanna, Department of Agricultural and Biosystems Engineering

Many Iowa planter operators are faced with wet soil conditions this spring. Operators will want to wait for suitable conditions to avoid “mudding in” a crop with significant investments in seed, fertilizer, machinery and time.

Adapting to Alfalfa Winterkill and Winter Injury

By Stephen K. Barnhart, professor, Department of Agronomy

Significant areas of alfalfa winterkill are now evident in Iowa. The worst areas are along the Highway 20 corridor in eastern and northeast Iowa, with notable losses to the Minnesota border in Iowa and also in random fields in other parts of the state. Frozen alfalfa crown and upper taproot tissue is not able to recover. Evidence of the injury was delayed because some plants began to green-up and then died. Plants that still exhibit good taproot and crown tissue are likely unaffected.

When is it Too Late Plant Forages?

By Stephen K. Barnhart, Department of Agronomy

Spring hay and pasture seedings are normally done from late February through late April in Iowa. The extended period of wet weather in 2008 has many producers still waiting to get their forages planted.

Can they still successfully plant forage crops?

Managing 2,4-D for No-Till Burndown Treatments

By Bob Hartzler, Department of Agronomy

2,4-D is commonly added to glyphosate for burndown of existing vegetation in no-till fields. The advantages of including 2,4-D include:

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