ISSUE 5 June 1, 2006
EARLY CORN GROWTH AND DEVELOPMENT
With the recent warmer weather, corn growth is starting to accelerate. After planting corn requires about 120 corn growing degree days (GDDs) to emerge and early in the season about 85 GDDs between the appearance of each new leaf. GDD accumulations averaged between 8 and 10 per day in May depending on the area of the state. Much of the corn planted in early May, therefore, should now be in the 2 to 3-leaf stage using the leaf collar method of staging.
Early corn development after emergence
Nodal roots initiate at the crown shortly after emergence and become visible at the first leaf stage. Nodal roots will be the dominant root system by the 6th leaf stage and may fail to form if the seed is planted too shallow and the soil surface dries out before nodal roots are able to establish. Plants with limited or no nodal roots will lodge at the base of the plant and will not have sufficient root mass to develop properly. By the 6th leaf stage the growing point has emerged from below the surface of ths soil and begins forming the tassel. Ears shoots develop during the 4-5 leaf stages at nodes on the stalk (only one or two will actually develop in to viable ears). Shortly after the 6-leaf stage, the number of rows per ear is determine. This trait is largely controlled by the genetics of the hybrid, and less so by the environment. From the 6-leaf stage to about 2 weeks prior to tasseling the number of kernels in a row is established. This number is determined more by the environment than by genetics. The corn plant is fairly tolerant to stress during these early growth stages; far more potential kernels develop in an ear than the plant will ultimately be able to fill.
Early grow staging corn
There are several grow staging methods that are used for corn. I will describe the leaf collar method which is commonly used in publications and in recommendations related to the timing of herbicides. When growth staging your crop you should begin by obtaining a representative sample of plants from the field or part of the field of interest. Ten plants should be selected at random. If emergence has been uniform, you can probably get by with fewer plants. Vegetative growth stages of corn are defined by the number of leaves. Counting leaves in corn is fairly straight forward as the process is not encumbered with tillers and leaves on tillers as is the case in small grains. However, care must be taken to ensure that the earliest leaves are included. The first leaf is small and often dies and is torn from the plant early in the growth of the plant. The first leaf has a blunt tip (see following picture). Look for sheath remnants at the crown of the plant if you suspect that the first leaf (or second for that matter) is missing. Include only those leaves that have a collar. In the following picture, the collar of the first leaf is present, but not for the second leaf. Count all leaves, even those that have been damaged by hail or frost. The total number of leaves that a plant will developed is more or less fixed for a given hybrid; leaves that are stripped from the plant will not be replaced by additional new leaves. To determine the growth stage of older plants that have lost their lower leaves, uproot the plant and split the stem with a knife through the root ball. At the very base of the stem, identify the first visible internode. Internodes are the white area between the more yellow bands of the nodes. The first obviously visible internode should about ˝ to 3/4 inch in length. The node directly above this internode will be the fifth node, and the leaf arising from this node will be the 5th leaf. Find that leaf and continuing counting leaves from that point.
Early corn growth
Extension Agronomist - Cereal Crops
SUNFLOWER OPTION ON FAILED ACRES
In 2006 like in most years one hears about fields planted with poor stands that fail to establish for one reason or another. Flooding, drought, soil insects and root rots, soil crusting and deep planting can all be involved with poor stands.
Producers who have planted crops that are likely to fail can consider a late planted crop like sunflower if the first crop is ‘zeroed out’. The USDA Risk Management Agency will allow a second crop to be planted and insured on ‘zeroed’ or ‘failed’ acres. Producers who choose to plant a second crop would receive 35% of their indemnity payment with the remaining 65% withheld until the second crop is harvested. If a loss occurs with the second crop; the producer is eligible to choose between taking the remaining indemnity payment for the first crop loss or take the indemnity for the second crop loss. Growers should contact their local insurance agent to check out this option.
Source: Sunflower Week in Review: May 22, 2006. National Sunflower Association.
BUCKWHEAT PLANTING TIME
Buckwheat is planted later than small grain, corn, beans and sunflower. It is very sensitive to spring and fall frosts and any seeding should be delayed until all danger of frost is past. Best planting dates are from May 25 to June 10 in most years. Research on the date of planting at Langdon during 3 years indicated significant buckwheat yield reductions when seeding was delayed to June 22 or later.
Buckwheat requires about 10-12 weeks after emergence to reach maturity. It also is very sensitive to high temperatures and drying winds during blooming time in July and early August. Seedbed preparation is similar to flax. By delaying sowing this permits killing several weed seedling flushes prior to seeding the buckwheat. Presently, no herbicides are labeled for use in buckwheat for weed control.
Under good moisture and temperature conditions, buckwheat shades the ground rapidly. A seeding rate of 40 to 50 lb A is recommended. Seeding depth of 1 to 2 inches is desirable in moist soil. Shallow seeding is desirable for rapid emergence. A conventional grain drill can be used and seed treatment is not necessary. Buckwheat has limited response to fertilizers. It’s a heavy user of phosphate with needs similar to wheat. Nitrogen application should remain low because of problems with lodging and delayed maturity. Buckwheat should be swathed when most of the seeds are ripe. In the event of frost, its highly recommended to swath promptly to reduce seed shattering losses.
For more information on buckwheat production request NDSU Extension Circular A-687 (Revised in 2003) available from your local county extension office. On the NDSU web site it can be found at:
Heavy rains on fields not yet emerged can lead to questions of whether soil crusting will be a problem. My best answer is it’s always best to wait at least 5 days after a crop is beginning to emerge to determine what percentage of the stand will be established. If a heavy crust does occur, a harrow or rotary hoe will be the best option once the soil starts to dry. Before deciding to rotary hoe or harrow, be sure that seedlings are unable to emerge through the crust. Harrowing can break off an emerging coleoptile or hypocotyl resulting in more damage than good. It is not advised to harrow canola, flax, mustard, or buckwheat seedlings which can be small and near the soil surface. If the plant is leafing out under the crust layer and the stand is poor, then breaking the crust layer is recommended. A harrow, rotary hoe or any empty press drill with disc openers has been used successfully to break up a crust. Light, spring tooth harrows should be set shallow (˝ inch deep) and angled back to reduce the potential of going too deep. Harrowing at a right angle to the rows and driving as slow as possible will also reduce the injury potential to the crop that has emerged.
Duane R. Berglund
NDSU Extension Agronomist