June 13, 2014
Striped Corn Leaves
During late May and early June, many corn fields along and south of Highway 34 began exhibiting striped leaves, characteristic of Sulfur deficiency. This phenomenon has worked its way north and is now showing up along and north of the Highway 20 corridor. I was along Highway 2 in southern Iowa earlier this week, and most corn there has shaped up nicely, and I expect this phenomenon will also work its way north.
Sulfur deficiency in corn is characterized by the new growth exhibiting green tissue along the leaf veins and chlorosis (yellowing) of the leaf material between the veins.
Sulfur deficiency in corn. (Courtesy of Brian Lang)
While it is possible for there to be an actual deficiency of sulfur in the soil, in the vast majority of cases there is adequate sulfur in the soil and it is simply a case of roots not taking in sufficient sulfur; as root function improves, the new growth quits exhibiting the striping and the field shapes up.
Organic matter is an excellent source of sulfur, so true sulfur deficiencies are confined to low organic matter soils without a recent application of animal manure. In fields that meet this description, it may be worth applying a sulfur fertilizer in some spots to see if the plants and yield respond; if they do, then consider applying manure or a sulfur fertilizer in future years prior to corn or alfalfa. Elemental sulfur needs to mineralize before it becomes available to plants, so a source that has sulfur in the sulfate form should be used in trials this year.
In most fields, the issue is one of root function, as stated earlier. Items I have run into limiting root function this year include:
Soil Firmness: I have been in several fields where the seminal / seed / primary roots are confined by sidewall compaction, and, in many cases, so are the secondary / nodal roots. I have been in fields where there is loose soil at the surface but severe compaction at and below where the seed was placed. At the other extreme, I have been in fields where the soil is so loose that I can actually just push my hand down into the soil. Soil needs to be firm enough for there to be good seed-soil contact for germination and good root-soil contact for good root function. However, the soils should not be so firm (compacted) that they prohibit the roots from exploring the soil to find water and nutrients.
Moisture: Rainfall has been very erratic so far this year. Some farmers are praying for a nice rain while others only a few miles away hope it stops raining for a while. Good root function requires adequate soil moisture but also requires adequate aeration for oxygen.
In addition to the above, seed placement in many fields has had an impact, with seeds planted more shallowly exhibiting more severe symptoms because of the difference in the soil environment to which the seedling is exposed, either soil firmness or moisture.
Tillage patterns and old traffic patterns are showing up frequently because of the variation in soil characteristics they have caused.
As stated earlier, this phenomenon is usually transient and new growth should soon quit exhibiting the striping unless there is a true sulfur deficiency or there are severe adverse soil conditions.
FOR YOUR CALENDAR
Cover Crops Field Day
12:30 p.m. 3:00 p.m., Thursday, June 19, 2014
Location: Dick Sloan farm, 3046 Harrison Ave., Rowley, IA.
Lunch: RSVP for lunch to Lauren at PFI at 515-232-5661.
Topics: Growing winter cereal rye for grain production and using cover crops after rye by Dick Sloan. Also presenting are ISU Extension nutrient specialist Chad Engels, Cedar River Coalition watershed coordinator Mary Beth Stevenson and NRCS State Soil Scientist Rick Bednarek
Directions: From Independence, go south on Hwy. 150 for 5 miles; turn west (right) onto D47 (290th St); go 2 miles. Turn south (left) onto Harrison Ave, go 1.5 miles. Farmstead will be on the left.
Spring Field Day Northeast Research and Demonstration Farm
1:00 p.m., Tuesday, June 24, 2014
Details are at: http://www.extension.iastate.edu/Pages/eccrops/meetnerf.html.
Spring Field Day Muscatine Island Research and Demonstration Farm
5:30 p.m., Tuesday, June 24, 2014
Details will appear at: http://www.extension.iastate.edu/Pages/eccrops/meetmusc.html.
Hay & Forage Expo
June 25 26, 2014
Spring Field Day Southeast Research and Demonstration Farm
1:00 p.m., Thursday, June 26, 2014
In addition, training for Certified Crop Advisors will be conducted, beginning at 9:00 a.m. Registration for the CCA training is now open at the website below.
Details are at: http://www.extension.iastate.edu/Pages/eccrops/meetserc.html.
Weed Science Field Day
8:30 a.m., Thursday, June 26, 2014
Details are at: http://www.extension.iastate.edu/CropNews/2014/0606owen.htm.
Mid-season Crop Management Clinic
9:00 a.m., Wednesday, July 9, 2014
Details are at: http://www.aep.iastate.edu/feel/mid.
Late-season Crop Management Clinic
9:00 a.m., Tuesday, August 19, 2014
Details are at: http://www.aep.iastate.edu/feel/late.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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