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.

Corn Residue Breakdown as Affected by Tillage and N Application

November 5, 2019
Rate of CO2-C released as an indicator of residue breakdown/decomposition from control (bare soil) and Bt and non-Bt corn residue mixed into the soil or un-mixed with soil (left on soil surface).

Crop residue serves an important role in physically protecting soil from erosion during rain events or high winds, as well as enhancing the soil biological activity by providing sources of organic carbon and nitrogen for its energy needs. In order to understand how residue decomposes, we need to understand how the degradation processes are influenced by environmental and soil conditions; namely, air and soil temperatures, soil moisture availability, soil pH, oxygen, and type of microbial community.

Managing SCN for 2020 Should Begin Now

November 5, 2019
sampling map

A critically important fall activity that can pay large dividends for next year’s soybean crop is sampling fields for the soybean cyst nematode (SCN). Also, some farmers might consider sampling fields in which soybeans were grown in 2019 if disappointing yields occurred for no apparent reason. This article discusses how to collect a meaningful SCN soil sample, where to send the sample to get it processed, and how to interpret SCN soil sample results from Iowa State University.

Fall Fertilizer Nitrogen Application

October 30, 2019

Fall nitrogen (N) fertilizer application continues to be popular for several reasons, including lower cost, time for application, equipment availability, often better soil conditions, and competing springtime field activities.

Crop Quality in 2019: Another Unusual Year

October 10, 2019
Fusarium on an ear of corn (left) and Pennicillium on an ear of corn (right). 

This year continues the chain of growing seasons with extremes and rapid changes beyond our long-term experiences. This made for periods of both stress and favorable crop growth despite the planting dates. Frost, potentially killing in the northern half of Iowa, is expected between October 11-13. USDA data indicate a wide range of maturity due to planting date, but the periods of hot weather scattered through September and early October may have reduced the potential for very high moisture corn and soybean. Variability will be the key issue to manage in 2019 corn and soybeans.

Phosphorus and Potassium Management for 2020 after a Year with Highly Variable Yields

October 1, 2019
Net returns to P or K fertilization of corn and soybean for different soil-test levels in many Iowa soils for shown prices

Very variable weather this season will result in variable corn and soybean yield within and between fields. Entire fields or portions of fields were planted later than usual or were not planted. This will result in variable removal of phosphorus (P) and potassium (K) with harvest. Reduced yields combined with continued low market values create uncertainty about P and K fertilization decisions for the 2020 season.

Fall Burndown Treatments for Winter Annual Weeds

October 1, 2019

The plentiful rain in September has provided ideal conditions for establishment of winter annual weeds, thus many no-till fields will have dense stands of these weeds going into winter (Fig. 1). The wetter springs we have encountered recently complicate getting spring burndown applications made in a timely matter. 

Verifying Combine Adjustments During Crop Harvest

September 26, 2019

Taking time to verify combine adjustments made in the shop match with the field conditions may seem time consuming but can minimize harvest loss as well as profit loss. This article discusses how to evaluate for pre-harvest loss and losses during harvest, and the types of in-field adjustments that can be made to minimize harvest losses.

To determine what types of adjustments may be warranted, assess if losses are due to pre-harvest loss or due to the harvesting process i.e. from the combine head or the threshing cylinder and the separation sieves.  

Fall Weed Control in Pastures

September 26, 2019

Fall is one of the best times for managing perennial and biennial weeds found in pastures or other areas maintained in perennial grass. As perennials prepare for the upcoming winter they move energy reserves from shoots to their perennial vegetative reproductive structures (e.g. rhizomes, perennial rootstocks). Systemic herbicides applied at this time are translocated along with the energy reserves to the reproductive structures, therefore providing more consistent control than applications made at most other times of the year.  

Corn Earworm Picks up Activity in Iowa

September 23, 2019
Corn earworm.

Corn earworm  (Photo 1) is common in Iowa corn. It is a migratory pest, migrating from the southern and southeastern U.S. every summer. There are two general fights to the Midwest every summer, but the first flight is not of economic concern. Iowa’s corn is more vulnerable to infestation of the second flight, arriving in late July. Yield losses can occur in late-planted cornfields, where caterpillars can infest >50% of plants. It is more common to see corn earworm issues in sweet corn, white corn, popcorn, and seed fields.

Survey of Herbicide-Resistant Waterhemp in Iowa Corn and Soybean Fields

September 20, 2019
Waterhemp infestation in a soybean field in Iowa. September 2019.

The escalating spread of herbicide-resistant weed populations has become a production challenge in the corn-soybean based cropping system of the Midwest. With the evolution of weed resistance to major herbicide groups used in corn and soybean, we have a limited number of herbicide options left, which is even more disconcerting as no new herbicide site of action has been discovered in the past three decades. A new site of action coming to the marketplace in the next 5-8 years would also be a rare event.