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Crop Development Relative Maturity of Field Crops
Things You Might Not Know About Wheat Development
Wheat Growth Stages Still, the rate of growth development for any wheat variety is directly related to temperature (accumulated heat units), except under extremely dry conditions. Thus, by knowing the planting date for wheat, and by tracking weather data, one can predict growth development and plant stage. This helps growers make timely treatments to control weeds, topdress fertilizer, control diseases, and other management decisions. (The 2006 Hard Red Spring and Durum Wheat Management Calendar is in the hardcopy of Issue #78. Please call 1-800-242-6118 to receive a copy.) The North Dakota Agricultural Weather Network (NDAWN) can help growers keep track of weather and growing degree days. On NDAWN’s Internet home page (http://ndawn.ndsu.nodak.edu ) click on the “applications” link. There, you will find a number of applications for using NDAWN, including:
Consult with an agronomist, certified crop adviser, or county extension agent/educator for more background on growing staging crops, or about how to apply NDAWN information. NDSU has a publication online, “Identifying Leaf Stages in Small Grains,” at www.ext.nodak.edu/extpubs/plantsci/weeds/w564w.htm. The University of Minnesota publication “Growth and Development Guide for Spring Wheat” can be found online at www.extension.umn.edu/distribution/cropsystems/DC2547.html. Soybean Growth Stages The V stages following VC are numbered according to the uppermost fully developed leaf node. Start with the unifoliolate leaf node when counting the number of fully developed leaf nodes. A leaf node is fully developed when the leaf above it has leaflets which are fully unrolled. That is, the leaflet edges are no longer touching. Vegetative Stages
Reproductive Stages
Bloom Key Soybean Development Stage Soybeans are at 50% bloom when an open flower can be found on every other plant in a row. Flowering, unlike maturity on soybeans, begins toward the bottom of the plant (at the third to sixth node) and then progresses upward and back downward. Branches off of the main stem will flower a few days later than the main stem. While flowering begins at the base of the plant and proceeds to the top of the plant, physiological maturity of the beans will progress anywhere on the plant stem. Normally, soybean pods will be mature in the middle or top of the plant and down. Thus, remember to check pods toward the bottom of the plant when determining if harvest time has come. Flowering of soybeans is an important time in bean growth and development. At stage R2, full bloom, each plant has accumulated about 25% of its total dry weight and nutrients; it has attained about 50% of its mature height; and, it has produced 50% of its total mature node number. This later flowering stage begins the period of very rapid N-P-K and dry matter accumulation that will continue through R6. Also, during flowering, the soybean plant gears up on its nitrogen fixation in order to provide for the demands of the plant. Scout for disease and insect problems (aphids) during this critical early time period of flowering.
Soybean Maturity 101 Relative maturity ratings consist of a number for the maturity group designation such as: (000-early, 00- mid early, 0-mid or 1-late) and followed by a decimal and another number, ranging from .0 to .9, which indicates maturity rankings within each maturity group. Each 0.1 change in group rating represents approximately 0.75 to 1 day later maturity. For example, the variety ‘Jim’ is indicated as 00.6, making it a medium maturing variety in the 00 group. ‘Walsh’ would be a 0.0, making it one of the earliest varieties in the 0 group whereas ‘Sargent’ is a 0.8 making it one of the later varieties in the 0 group. Few if any group 1 soybeans are currently planted in N.D. except in the extreme southeast part of the state. Check Your Soybeans for Nodulation Check the health of your soybean nodules and check root proliferation (both of which may be a concern in continuous beans). Soybean roots should be dug up to check nodules and not pulled from the soil. The pulling action tends to slough off nodules and results in an inaccurate assessment. At V2, soybeans should be rooting down six inches into the soil and by V5 will completely reach between 30-inch rows, making any cultivation at V5 needing to be very shallow. Percent of Yield Produced By Various Soybean Growth Stages
Soybean Stand Compensation and Yields Soybean Stand Reduction Loss
Corn Growth Stages Each leaf stage is defined according to the uppermost leaf whose leaf collar is visible. Loss of the lower leaves will begin about V6 due to increased stalk size and nodal root growth. To determine the proper leaf stage after lower leaf loss, split the stalk lengthwise and inspect for internode elongation. The first node above the first elongated internode is generally the fifth leaf node. This fifth leaf node can be used as a reference point for counting the top leaf collar. Vegetative Stages
Reproductive Stages
Corn Growth Staging
At the five leaf stage, the corn plant switches from vegetative growth to reproductive growth as the growing point stops initiating leaves and begins initiating the tassel. At the 6 leaf stage, ear shoots begin to form. The number of kernel rows on the developing ear is determined relatively soon after it begins development and is largely determined by genetics, and less so by the environment. The length of the kernel row and therefore the total number of potential kernels, however, is determined during a longer period of time (6 leaf stage through one to two weeks before tasseling). Severe stress during this stage can shorten the length of the cob and reduce yield potential. Nevertheless, stress during ear development is far less damaging to yield potential than stress during and shortly after pollination, as the potential number of kernels developed typically exceeds the number that can be pollinated filled. Certain management practices are growth stage dependent; therefore, properly identifying the growth stage of your corn crop will be important to ensuring that management practices are applied at the appropriate time. This is particularly true of the application of herbicides. When growth staging a crop you should begin by obtaining a representative sample of plants from the field or part of the field of interest. Remove any soil attached to the plants so that you are able to observe the roots and crown. 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 when counting leaf numbers. 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. 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. Include all leaves, even those that have been damaged by hail or frost. The total number of leaves that a plant will develop is more or less fixed for a given hybrid; leaves that are stripped from the plant will not be replaced by additional new leaves. In order 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 ½ 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. In corn, management recommendations can also refer to the height of the plant, rather than leaf stage. For example, certain herbicides can only be applied to corn less than 12 inches tall. The plant height in this case is measure from the base of the plant to where the upper most leaf reaches without stretching it out. Canola Growth Stages Canola in the 5.3 to early 5.4 stage should be near or at swathing stage. These stages change very rapidly during the ripening period if temperatures are warm and under dry conditions.
How Saturated Soil Affects Cereal Crop Growth Effects on corn - The growing point of the corn plant remains below the surface of the soil until the 5-6 leaf stage and is quite sensitive to waterlogged conditions at this stage. Young corn plants can be killed if soils are saturated beyond 48 hours, particularly when soil temperatures are high (i.e. above 65F). Waterlogging also reduces root growth and predisposes the plant to root rots later in the season. To determine if plants have been killed by ponding, wait 3 to 5 days after the excessive moisture has drained through the soil and then check to see if there is any visible re-growth. Effects on small grains - Barley is reported to be more sensitive to temporary waterlogging than is wheat. Furthermore, varieties vary considerably in their response to waterlogging. Sensitivity to waterlogging generally decreases as crops mature, with spike size and tiller numbers being the yield components most affected. Though leaf yellowing is common in small grains after soils have been waterlogged, yield loss can occur, even if these visible symptoms are not observed. Effects on the soil - Waterlogging can also indirectly impact cereal crop growth by affecting the availability of nitrogen in the soil and by reducing root development. Excessive water can cause leaching of nitrate nitrogen beyond the rooting zone of the developing plant, particularly in lighter textured soils. Furthermore, when oxygen levels become depleted, nitrate nitrogen is converted to a gaseous form that is lost to the air. Research conducted in other states has found losses between 1 and 5% of the nitrate N lost for each day that the soil remains saturated. Corn responds to additions of N when N is limiting up to the beginning of grain filling. Consider sidedressing N to corn fields with good stands where excess water may have caused problems. In small grains, in order to impact yield, additional N should be applied prior to the 6 leaf stage. Additional N applied after this stage would be more likely to impact wheat protein levels rather than yield. Sunflower Development, Growing Degree Days
Check the NDSU NDAWN web site for the 2006 Growing Degree Units in various locations in N.D. (http://ndawn.ndsu.nodak.edu/sunflowerdd-form.html). Just enter in the planting date and the current date for your location. Evaluating Herbicide Injury Look for patterns of injury in the field. Herbicide injury is often in a pattern associated with soil types or movement of application or incorporation equipment. Observe other susceptible crops or weeds in the area for herbicide effects. For comparison, try to find a check area where no herbicide was applied in the same field. If you conclude that herbicides are the probable cause of crop injury, try to determine why the injury occurred. Limited crop tolerance to certain herbicides is sometimes a problem, especially under heavy rainfall or sandy soils or on dry, loose soil. Misuse of high rates, wrong chemical, contaminated spray tank, improper method of application, nonuniform application, overlaps, improper applicator adjustments and tillage operations that concentrate the chemical are some causes of herbicide injury. Some varieties/hybrids are more susceptible than others. Don’t be too hasty to evaluate the effects of herbicide injury. Give the plants a chance to recover. Check growing points to see if the plants have potential for recovery. Compare injury effects and weed control benefits. Stand counts and injured plant counts are important considerations. Consider digital photos of initial symptoms and to help gauge plant damage and possible recovery. Unbiased yield checks later in affected and unaffected similar areas of the same field are the best estimates in damage losses. Diagnosing plant problems IPM Surveys Track Growing Season Field Pests NDSU – Waldron Hall, Room 206, PO Box 5012, Fargo, ND, 58105, ph 701.231.7854, email: diaglab@ndsuext.nodak.edu , web site: www.ag.ndsu.noda.edu/diaglab . Fee-based services include insect, weed, disease identification and control recommendations, herbicide injury diagnosis, and soybean cyst nematode screening. UM - Plant Disease Clinic, St. Paul, ph. 612.625.1275. Web site: www.extension.umn .edu/distribution/cropsystems/DC3170.html. Fee-based services include plant disease, virus ID, nematode analysis, as well as seed quality testing. SDSU – Oscar E. Olson Biochemistry Labs, Brookings, ph 605.688.6172, web site: http://anserv.sdstate.edu. SDSU Plant Disease Clinic: http://plantsci.sdstate.edu/planthealth (click on Plant Disease Clinic). Ph 605.688.5157 Link to more private and public testing labs can be found online: www.ag.ndsu.nodak.edu/diaglab/diaglab_chemlabs.htm. These labs (as well as professional crop consultants/certified crop advisers) can help determine key factors that affect crop productivity, such as: Soil organic matter tests – Knowledge of the organic matter level will serve as a guide in selecting an effective herbicide and rate of application, as well as helping to assure crop safety. Testing once every five years should be adequate. Herbicide spray water analysis – High salt levels in spray water can reduce weed control in nearly all situations. Calcium, and to a lesser degree, magnesium, are antagonistic to 2,4 -D and MCPA amine , dicamba, and glyphosate. Plant tissue analysis – This indicates the nutrient status of plants at the time of sampling, serving as a monitoring tool for determining the adequacy of current fertilization practices. Plant tissue analysis will also detect unseen nutrient deficiencies and may confirm visual symptoms of deficiencies. Toxic levels also may be detected. Combined with soil test information, a plant analysis report can help a producer tailor fertilization practices to specific soil-plant needs. |
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