Introduction
The warm, gentle shower we are receiving today is well received as it will help to recharge surface soil moistures and warm the soil.  There has been a lot of field activity in the area over the last week, farmers are applying anhydrous ammonia, field cultivating and planting oats in some fields.  As we look forward to planting corn and soybeans, request from your seedsman the seed germ test so that you can match seed quality with field conditions.  The alfalfa is starting to green up; you should be out inspecting those fields for any winter kill or injury.  If you find less than 40 healthy stems per square foot you should consider replanting.

 Weather update – Comments from Dr. Elwynn Taylor
A Drought is a Drought - There are U.S. population centers with limited water supplies for human use and for generation of power.  This condition is known as a “Water supply drought."  Meteorological drought is below normal precipitation.  Fire drought is very dry litter in a forest.  Agricultural drought is an insufficiency of subsoil moisture.  All are related but all do not usually develop at the same time nor exist at the same place and time.  We remember that the extensive agricultural drought of 1988 began as a serious drought in South Carolina.  The reported drought in South Carolina this year has many farmers concerned.  At this time there is no agricultural drought in South Carolina, and very little in the U.S. There is extensive “Water Supply Drought."  We will watch that, but, a water supply drought does not often develop into Agricultural drought, it is usually the other way around.

     -Elwynn Taylor, Iowa State University Extension Climatologist; April 2, 2002

Planting and Crop Development
Soil temperature has been in the mid to upper 30’s but is forecasted over the next three days to move into the low to mid 40’s.  Obtain the most recent soil temperatures at ISU’s NPKnowlege webpage http://extension.agron.iastate.edu/NPKnowledge/

Interpreting your seed lab results
Seed germination results from the ISU Seed Testing Lab indicate that seed quality is very good this year.  Yet it is important to understand and interpret the seed germ results and plant the seed according to the seed quality and soil conditions.  When planting into a harsh soil environment (cool, wet soils) use high quality seed.  The information presented here was taken from the ISU Seed lab web site http://www.seeds.iastate.edu/seedtest/ .

 ISU Seed Lab Frequently Asked Questions…

 ·         How do soybean warm germ results typically compare with sand germ results?
Typically sand germ results are the same or slightly higher than warm germ results.  In the instances of fungal problems or extremely dry seed, the sand germ can be markedly higher.  We find that the higher the germination of the seed lot, the less positive effect the sand has on the results.

 ·         What do cold test results in corn tell me about my seed lot?
Vigor tests are used two ways:  1) To “predict” field emergence and /or to rank seed lots.  Since field conditions vary greatly from field to field and from year to year, no test can predict how a lot will do in all situations.  However, cold test results typically correlate well most years with field emergence for most lots.  2) To rank seed lots into categories.  Many brokers consider an 82% cold test result to be the minimum acceptable for marketing a corn seed lot.

 ·         Is the cold test the preferred method for determining soybean vigor?
No, we recommend using the accelerated aging (AA) test as the vigor test of choice for soybeans.  The main reason for this is typically the cold test doesn’t stress soybean seed all that much.  Even though you would expect soybeans to be more sensitive to cold than corn, they don’t actually seem to be.  Some years, there are a few lots that experience decayed unifoliate leaves in the cold test which actually gives lower than expected results.  The AA test gives a good indication of the vigor of soybean lots, except that some lots that have extremely low seed moisture have lower than expected AA results.

 ·         Why do I sometimes get high warm results and low cold results?
In general, carryover corn seed that is stored in cool, dry conditions maintains its viability and vigor well.  Seed that is of low vigor or stored in less favorable conditions should be expected to experience a drop in vigor from year to year (or even month to month in the case of low vigor seed).  It is not surprising to have a 92% warm germ and a 65% cold test in a carryover lot.  However a warm germ in the high 90’s and a low cold test is surprising for many people.  Remember a warm germ exposes the seed to “ideal” conditions.  A seed lot without any mechanical damage or dead seed shortly after harvest would be expected to maintain its viability fairly well when stored correctly.  But when the seed is stored in less favorable conditions, the seed ages more quickly and cannot tolerate the stressful conditions of most vigor tests.

 ·         What is an acceptable soybean accelerated aging (AA) result?
In general, we advise that an AA result should be within 15% of an acceptable warm germ.  Acceptable varies from person to person, but most consider a 90% to be the minimum acceptable soybean germ in most years.  In a year like last year, for many varieties, even results in the 80’s were acceptable.  But again, in a normal year, a 75% AA would be at the low end of a desirable AA result.

 ·         Why do I sometimes get higher soybean AA results than warm germ results?
There are at least two possible explanations.  1) In lots where much of the seed has a light amount of Phomopsis infection of the cotyledons, the AA test reduces the harmful effects of the Phomopsis because it does not stand up well to the hot, humid conditions of the AA chamber.  Seed with a heavier amount of Phomopsis has already had the damage done, but light infections can be kept from becoming heavier infections.  2) Some lots (especially large-seeded edible soybean lots) can have problems taking up moisture on Kimpakâ.  The gradual uptake of water during the aging period of the AA test and covering the seed with moist sand following the aging period can help some lots. 

Check Alfalfa Fields for Winter Injury
Although northwest IA has experienced one of the mildest winters on record, winter injury could still be a problem in alfalfa fields.  A major factor to winter survival for alfalfa is to have a good insulative cover from snow.  As we all know, snow has been hard to come by this last winter.  In addition to cold stress, plants may be injured from heaving of plants from the soil and mid-winter de-hardening of plants.  Now is the time to inspect alfalfa fields for killed or injured areas.  Refer to the most recent ISU Extension Field and Feedlot newsletter for more information or go to http://extension.iastate.edu/carroll/crops/newsletters/2002/alfalfa%20stand%20evaluation.doc

Newsletters and Websites
Several excellent articles have written in the ISU IPM newsletter, check them out here:
http://www.ipm.iastate.edu/ipm/icm/default.html

 Subscribe to these newsletters for more agricultural information.

·         Acreage Living http://www.extension.iastate.edu/Pages/communications/acreage/

·         AnCy News http://www.ans.iastate.edu/current/ancy.html

·         Horticulture and Home Pest News http://www.ipm.iastate.edu/ipm/hortnews/

Todd Vagts
Iowa State University Extension
Field Crops Specialist
1240 D. Heires Avenue 
Carroll, IA 51401 
Office: 712-792-2364; Cell: 712-249-6025;  Fax: 712-792-2366
Email: vagts@iastate.edu  

For questions or comments please respond to vagts@iastate.edu

This page last updated on 02/03/04