C.O.R.N. Newsletter 2013-07

Dates Covered: 
April 2, 2013 - April 8, 2013
Glen Arnold

A Big Change is on the Way for the Second Week of April!

A Big Change is on the Way for the Second Week of April! A big warm-up that is!

However, in the meantime, after a cold March, it will also start colder than normal for the first week of April. Temperatures will average 5-10 degrees below normal while rainfall will be below normal. A warming trend will begin later in the week though.

The outlook for the second week of April is for above normal temperatures and near normal rainfall.

Videos of Slug Management on Soybean and Corn

Presentations done by Ron Hammond that discusses slug management on soybean and corn were recently uploaded onto the Plant Management Network News (PMN Update) website last Friday.

The addresses for the two sites are, respectively, http://www.plantmanagementnetwork.org/edcenter/seminars/soybean/SlugManagementSoybean/ and http://www.plantmanagementnetwork.org/edcenter/seminars/corn/slugmanagementcorn/.

These presentations are similar to the field crop slug talks that we have done over the past few years, and provide current information on how to best manage your slug problems.  It is too early to know if we will have problems this spring, but as always, we advise growers with previous histories to keep monitoring the situation in their fields.


Taking a Second Look at Planting Depths for Corn

Planting depth recommendations for corn in Ohio are 1.5 to 2 inches deep to ensure adequate moisture uptake and seed-soil contact. Shallower planting depths increase the potential for injury from certain preemergent herbicides although widespread use of safer herbicides (e.g. glyphosate) has probably decreased this effect. Deeper planting may be recommended as the season progresses and soils become warmer and drier. Planting shallower than 1.5 inches is generally not recommended at any planting date or in any soil type.

When corn is planted 1.5 to 2 inches deep, the nodal roots develop about 0.5 to 0.75 inches below the soil surface. However at planting depths less than 1 inch, the nodal roots develop at or just below the soil surface. Excessively shallow planting can cause slow, uneven emergence due to soil moisture variation, and rootless corn (“floppy corn syndrome”) when hot, dry weather inhibits nodal root development.  This latter situation has led some field agronomists to speculate that shallow plantings increase stress and result in less developed roots, smaller stalk diameters, smaller ears and reduced yields. Nevertheless, many corn growers plant at depths less than 1.5 inches.  The rationale for this shallow planting is that seed will emerge more rapidly due to warmer soil temperatures closer to the surface. This is an important consideration as corn growers across the Corn Belt are planting earlier so they can complete planting before yield potential begins to decrease after the first week of May. Particularly in soils that crust, speed of emergence is critical in order to establish plant stands before heavy rainfalls “seal” the soil surface.  While previous research has generally documented faster emergence rates with shallower planting depths, the comparisons have often included deeper planting depths than the recommended ranges and results are highly influenced by temperature and rainfall in the given season.

Recent studies comparing planting depths that are within the depth ranges commonly used by growers are limited, and none have attempted to compare hybrid differences to varying planting depths. Hybrids with higher levels of drought tolerance may provide improved yield stability in shallow planted situations while also providing improved performance at normal planting depths, though this has not been documented.

In 2011 and 2012 we a conducted a study supported in part by a Pioneer Crop Management Award to determine the response of hybrids with different drought tolerance ratings to varying planting depths.  Plots were established at the ten Ohio State University Ohio Corn Performance Test locations (Hebron, Washington Court House, S. Charleston, Greensville, Van Wert, Hoytville, Upper Sandusky, Bucyrus, Wooster, and Beloit). Three Pioneer brand hybrids with relative maturities of 109 CRM, 108 CRM and 107 CRM were planted at three planting depths (0.5, 1.5, and 2.5 inches).  The drought tolerance ratings for the three hybrids were 7, 8, and 6, respectively; based on scale where 1 is poor and 9 is excellent.

Did planting depth affect corn yields?

In 2011 at eight of the 10 sites, yields of the 2.5-inch planting depth treatment exceeded those of the 0.5-inch planting depth treatment. At five of the 10 sites, yields of the 1.5 and 2.5-inch treatment were similar. The 1.5-inch treatment out yielded the 2.5- inch treatment at one site.  Grain yields, averaged across locations and hybrids, were 13% and 15% greater for the 1.5- and 3-inch planting depths, respectively, than the 0.5 inch planting depth. The lower yield of the shallow planting treatment was associated with a reduced final stand (27,200 plants/A for the 0.5-in. depth vs. 34,180 and 34,000 plants/A for the 1.5- in. and 2.5-in planting depths, respectively) and a greater % of late emerging plants or “runts” (28% for the 0.5-in. depth vs. 5% and 4% for the 1.5- in. and 2.5-in planting depths, respectively).

In 2012, a much hotter and drier growing season than 2011, at 9 of the 10 sites, yields of the 1.5 inch and 3-inch planting depth treatment were greater than those of the 0.5 inch planting depth. At six of the 10 sites, yields of the 1.5 and 2.5-inch treatment were similar. Grain yields, averaged across locations and hybrids, were 40% greater for the 1.5- and 2.5-inch planting depths than the 0.5 inch planting depth. The lower yield of the shallow planting treatment was associated with a lower final stand (19,460 plants/A for the 0.5-in. depth vs. 32,000 and 31,000 plants/A for the 1.5- in. and 2.5-in planting depths, respectively) and a greater % of runts (31% for the 0.5-in. depth vs. 6% and 3% for the 1.5- in. and 2.5-in planting depths, respectively).

Did yield response to planting depth differ among hybrids?

Although differences in yield were present among hybrids, the three hybrids exhibited similar yield responses to varying planting depth. In 2011, yields of the  109 day hybrid which had the highest drought tolerance score, averaged across locations and planting depth treatments, were greater than 107 day hybrid (which had the lowest drought score)  at four of the 10 sites in 2011.  In 2012, yields of the 109 day hybrid, averaged across locations and planting depth treatments, were greater than 107 day hybrid at seven of the 10 sites.

Results of the evaluation support current recommendations to avoid planting shallower than 1.5 inches. There was no evidence that yield response to planting depth was affected by hybrid.

There is Time for Final Checks While Waiting to Plant

Soil temperatures from around the state are on the cold side and are not favorable for planting much of anything at the moment.  From the weather stations at the branches, these are the soil temperatures at 2.5 inches.

County                 Research Branch              Temperature (F)

Jackson                Jackson                                    44.0

Noble                   Eastern                                    43.2

Huron                   Muck Crops                             41.5

Ashtabula             Ashtabula                                 37.8

Sandusky             North Central                           40.5

Wood                   Northwest                                37.3

Clark                    Western                                   42.3

Now is a good time to take a second look at the varieties and hybrids that you are about to plant.  The reason why I bring this is up is that even in a drought we did have some losses last season and most could be tied to the lack the resistance to key Ohio pathogens.

Soybeans:  Do your varieties have the right package for Ohio.  Rps genes are fine, but they will not be effective to every strain of Phytophthora sojae that is in a field.  Especially for those fields which can get saturated very quickly – does the variety have high levels of partial resistance (field resistance or tolerance).  Every company uses a different scoring system so get out the reading glasses to read the fine print so you are sure that you are reading it correctly.

During the last 2 seasons, in studies at the Northwest Branch – the variety with a 2-gene stack combined with partial resistance had significantly greater stands each season than those with a no partial resistance or high partial resistance alone.

Continuing with soybean – is it weak on frogeye leaf spot?  Then a key will be to avoid planting this in a field that had frogeye the year before.  This past winter is very much like the winter where we identified that the this fungus can now overwinter here in Ohio and while March was cold, temperatures did not go below 10 to 15 degrees F for a sustained period of time.  We have inoculum ready for this year.

What is the SCN rating?   Iowa State (http://www.plantpath.iastate.edu/tylkalab/research-efforts/variety-trials) has published their ratings for SCN resistance.  Check the company listing as well for what the source of resistance is:  PI88788, Peking, or CystX.  We have documented yield losses to SCN of 25 to 35% with no above ground symptoms – when a Susceptible variety is planted in fields with SCN populations greater than 500 eggs/100 cc (approximately a cup) of soil.  Have you tested any time recently?  Is the field where that variety is targeted continuous soybean?  Were your yields 10 bushels off of your neighbors and the county average?  Check the Ohio Agriculture Statistics (http://www.nass.usda.gov/Statistics_by_State/Ohio/index.asp) to see where your yields stack against others in your area.  If you are lower than you neighbors, I am betting that one of the prime issues could be soybean cyst nematode.

Keep a record of the variety and notes on the resistance packages.  If they don’t perform as expected this year then you will be armed with a tool to make a better variety selection for 2014.

Drought Tolerant Corn Hybrids

Several major seed companies have recently introduced corn hybrids that specifically target enhanced drought tolerance. Optimum® AQUAmaxTM hybrids from DuPont Pioneer and Agrisure ArtesianTM hybrids from Syngenta were commercially available last year. In 2013, Monsanto is conducting a “stewarded” commercial introduction of Genuity® DroughtGardTM hybrids in several Western Corn Belt states.

Most  seed companies generally provide drought tolerance ratings for the hybrids they market (e.g. 1= poor; 9= excellent) but the recently introduced AQUAmax, Artesian, and DroughtGard hybrids represent an effort to develop hybrids with traits affecting  response to water stress. DuPont Pioneer and Syngenta drought tolerant hybrids involve native traits and those from Monsanto involve a transgenic trait. The companies marketing these hybrids emphasize that the enhanced drought tolerance associated with these hybrids is not associated with “yield drag”.

The hybrids are primarily targeted for use in the Western Corn Belt especially in areas where corn growers are looking for ways to reduce irrigation and conserve water supplied by aquifers. Nevertheless AQUAmax and Artesian hybrids adapted to Eastern Corn Belt conditions are available and Ohio growers had an opportunity to assess the performance of these hybrids during the 2013 drought.

Unlike Bt insect or herbicide resistant traits which involve single gene qualitative traits, drought tolerance is more complex and involves many genes. Some of the physiological traits associated with improved drought tolerance include a short anthesis silking interval (ASI, the time between the onset of pollen shed and silk emergence), delayed leaf rolling and senescence (leaf greenness), reduced barren and nubbin ears, better ear fill (greater kernel set and reduced abortion under stress), improved root development and architecture and photosynthetic/transpiration rates under stress.

A corn crop may be subjected to different types of drought stress -  droughts may be protracted and  season long in duration, or they may be limited to one or more developmental stages ( early to late vegetative growth, early and late grain fill). High temperatures in conjunction with drought during one or more of these stages can magnify the impact of stress. Hybrids may react differently to the varied types of drought stresses. Moreover drought tolerance may be strongly influenced by management practices. Greater corn plant populations promote more stressful conditions, and delayed and late planting dates often result in drier and hotter weather during critical development stages (i.e., flowering, grain fill).

In 2012 we initiated a study to determine if drought tolerant AQUAmax and conventional (non-AQUAmax hybrids) differ in their response to plant population and planting date.   Various physiological traits associated with drought tolerance were also evaluated. 2012 was the warmest year on record in Ohio and the summer one of hottest and driest. However the impact of drought and heat varied considerably across the state. These conditions provided us with an opportunity to assess the response of the new drought tolerant hybrids to varying levels of stress.

The study compared four hybrids (two drought susceptible and two drought-tolerant AQUAmax hybrids) at five plant populations (24,000, 30,000, 36,000, 42,000 and 50,000 plants/A) at two planting dates (early May vs. early June). The susceptible and tolerant hybrids were characterized by drought tolerance ratings of 7 and 9, respectively, on a scale of 1-9 where 1 is poor and 9 is excellent. The study was conducted at three OSU-OARDC research stations in southwest, northwest, and northeast Ohio.

Preliminary results indicated that the grain yield of each hybrid had a similar response to plant population at each site but differed due to planting date at each location. At the NW Ohio location for the early planting date (May 3), which was subjected to the greatest drought stress, the drought tolerant hybrids out yielded the drought susceptible hybrids by 8 to 10 bu/A (about 5% averaged across plant populations). At the other locations, where drought stress was limited or absent, the drought tolerant hybrids generally yielded more or about the same as the drought susceptible hybrids.

Drought stress can delay silking and increase ASI.  This “asynchronous” flowering can result in poor kernel set and inn extreme situations barren plants. In the 2012 study, measurements of flowering synchrony at the NW Ohio location for the May 3 planting date indicated that the anthesis silking interval was 1 to 3 days greater for the drought susceptible hybrids than the drought tolerant hybrids but no consistent effect of plant population on flowering synchrony was evident. On the later planting date (June 7), no difference in flowering synchrony between hybrids was present but ASI increased as plant population increased.

The preliminary results suggest that under the water stress conditions of the type  experienced at the NW Ohio location in 2012, drought tolerant hybrids offered a yield advantage over drought susceptible hybrids (w/ lower drought ratings). Under more favorable conditions, the drought tolerant hybrids showed yields that were similar or slightly higher those of the drought susceptible hybrids.



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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.