|
|
C.O.R.N
Newsletter
2004-20
June 29, 2004 -
July 5, 2004
Back
to main issue
|
 |
 |
|
Will Poor Root Development Impact Corn Yield Potential in 2004?
by
Peter Thomison, Robert Mullen, Patrick Lipps
|
|
In early July, nearly all our attention is focused on corn canopy development - canopy closure, plant height, tasseling, etc. Unseen, but probably of greater importance to the crop’s long term success and productivity is the root development. The corn crop’s access to soil moisture and nutrients during the growing season depends on establishment of an effective root system. Understanding root development can help with diagnosis of various production problems, from nutrient deficiencies early in the season to stalk rots at maturity. Estimates of root growth and penetration are complicated by a number of factors because growth is dependent upon soil moisture, aeration, texture, structure, and fertility.
Research by Dr. Stan Barber at Purdue University indicated that corn will produced similar total amounts of roots each year. The difference between years is mainly where in the soil profile the roots predominate. Warm dry soils will promote deeper root development, whereas cold, dry soils promote shallower root development.
In a year such as 2004, when the surface soil moisture after planting was above optimum for an extended period in many fields, corn roots are usually confined to the surface eight or twelve inches of soil. Lateral roots are short and less abundant, very little branching, and essentially all of the root development is horizontal. In contrast, in a year where there is a period of three to four weeks with light rainfall after planting, a deeper root system is favored. Lateral roots are longer and more abundant, considerably more branching, and they likely “turn down” earlier. Such root systems generally enable the crop to tolerate late season water deficits much better than shallow root systems. Unfortunately, cool rainy weather conditions and wet soils are often the norm after planting in Ohio.
Well drained soils favor penetration of roots better than compacted soils with a hardpan and poor aeration. In one past study, a well drained soil was characterized by a general root distribution of 70% in the upper 10 inches, 19% in 10-30 inch depth, 8% in 30 to 48 inch depth and 3% in the 40 to 72 inch zone. However, for a poorly drained soil, the general root distribution was 56% in the upper 8 inches, 42% in the 8 to 28 inch depth, and 2% in the 28 to 48 inch depth.
Root development can be related to different stages of vegetative development. Under favorable growing conditions in a well drained soil the following rules of thumb would usually apply.
1. Up to the 7th or 8th leaf stage (knee high) the roots will be almost parallel to the soil surface with little penetration more than a foot deep.
2. Between knee-high and four feet, the roots may extend 2 to 3 feet from the base of the stalk, where they usually turn down abruptly. Penetration at this stage can range from 1 foot to over 4 feet in depth. Since roots have likely reached the row middles by about the V8 stage, they are more vulnerable to pruning by cultivation.
3. As maturity approaches, roots tend to branch and penetrate deeper. Maximum root spread from the stalk is often 3.5 feet in all directions. Maximum penetration of very fine roots may be from 4 to 8 feet.
4. Root mass reaches it’s maximum size at silking
5. Brace roots (above ground nodal roots) are initiated from the lowest 3 to 4 stalk nodes during late vegetative development and usually penetrate the soil surface by silking. Brace roots provide support to the stalk and are of considerable importance in “resurrecting” plants root lodged by strong winds.
How will root development impact this year’s corn crop? Although excessive rainfall this year has certainly limited root development in many corn fields, the relatively moderate to cool temperatures have been beneficial and probably promoted root growth. If we had experienced a prolonged period of high temperatures with little rainfall, root development would have been severely inhibited. Root growth declines at temperatures above 86 degrees F, and soil temperatures in corn fields, which have not yet canopied, often exceed this temperature on hot days with air temperatures in the 90 degree range.
Fortunately, cooler than normal temperatures after sidedressing have probably also reduced the nitrogen losses associated with denitrification. Although water-logged plants have a chlorotic appearance which is indicative of nitrogen stress, the problem is probably more attributed to the small root system than actual N deficiency of the soil (this is dependent upon N management). In fact, some fields that receive sidedress applications of N may not “green up” very quickly depending upon the placement of N. The root systems have not grown large enough to capture the N that has been applied, or the roots are not actively taking up N (depending upon how wet the soil actually is). This problem can be more prevalent in fields that are sidedressed with anhydrous ammonia. The primary form of N taken up by the corn crop is nitrate and anhydrous is strictly ammonia. The bacteria that convert ammonium to nitrate prefer aerobic (oxygen rich) conditions and excessive moisture can slow their activity dramatically.
Based on corn performance in past years, the impact of a wet spring on corn prospects is largely influenced by weather conditions later in the growing season especially during grain fill. Despite the adverse effects of saturated soil conditions on root development during vegetative growth, with moderate temperatures and frequent rainfall during grain fill, a corn crop still has the potential to generate excellent grain yields; this was the case in 2003 when a new, record high corn yield was achieved.
If frequent and heavy rains provide near continuous saturated conditions in fields during the first few weeks after silking, soil pathogens like Pythium and Fusarium will continue to reduce effective root systems. Under these conditions early deterioration of root systems will likely hasten premature ripening of the crop leading to lower yields and light weight kernels. The best situation we can hope for is sufficient moisture to eliminate any moisture stress on the plants with alternating soil drying to allow air to penetrate the soil profile. Continuous high moisture conditions or excessive drying will both limit the yield potential of the crop. The key to adequate yields from this point on is avoiding any additional stress on the crop.
References:Zublena, J.P. and C.L. Parks. 1980. Nutrient and volume of water available to the corn plant are influenced by volume and depth of root development. Coop. Ext. Serv. Clemson Univ. Soils & Plant Nutrition Information Sheet.
|
|
Readers can subscribe electronically to this newsletter by signing up at http://agcrops.osu.edu/services/email.html. E-mail labarge.1@osu.edu
if you have problems subscribing or no longer wish to receive this newsletter.
C.O.R.N. is a summary of crop observations, related
information, and appropriate recommendations for Ohio
Crop Producers and Industry. C.O.R.N. is produced by
the Ohio State University Extension Agronomy Team, State
Specialists at The Ohio State University and Ohio Agricultural
Research and Development Center. C.O.R.N. Questions
are directed to State Specialists, Extension Associates,
and Agents associated with Ohio State University Extension
and the Ohio Agricultural Research and Development Center
at The Ohio State University.
Information presented above and where
trade names are used, they are supplied with the understanding
that no discrimination is intended and no endorsement
by Ohio State University Extension is implied. Although
every attempt is made to produce information that is complete,
timely, and accurate, the pesticide user bears responsibility
of consulting the pesticide label and adhering to those
directions.
All educational programs conducted by
Ohio State University Extension are available to clientele
on a nondiscriminatory basis without regard to race,
color, creed, religion, sexual orientation, national
origin, gender, age, disability or Vietnam-era veteran
status.
Issued in furtherance of Cooperative
Extension work, Acts of May 8 and June 30, 1914, in
cooperation with the U.S. Department of Agriculture,
Keith L. Smith, Director, Ohio State University Extension.
TDD # 1 (800)
589-8292 (Ohio only) or (614) 292-1868
|
|
Email this story
