Agronomy Notes

February 8, 1999

Contents

COTTON

Dr. Will McCarty

Seed quality should be a concern to all producers. Apparently ample supplies of high-quality seed of most common cotton varieties are available; this is good. Two tests commonly used to evaluate cotton planting seed are the standard germination test and the cool test or vigor test.

         
         First, the warm-germination value stated on the bag will be 80 percent.  This value is an industry standard and may not represent the actual germination of the bag.  The seed must germinate within  tolerance (7 percent) of this 80 percent label to be sold legally.    The seed companies label the seed 80 percent because the seed  potentially are conditioned and bagged several months before delivery to the farmer.  There is so much variation in storage conditions after the seed are shipped, the company would be at great risk labeling the seed at the actual germination level and then have them (the seed)  drop below tolerance while in storage (over which the seed person has no control).  This is justifiable and necessary for the seed dealers to conduct business.

The seed person, however, should provide the actual germination of each lot of seed it ships. Most cottonseed companies doing business in Mississippi do this. Before you take delivery of seed, ask your dealer to obtain the actual germination and cool test information for each low (cool test discussed later in this column). If the seedsman does not provide this information, you may wish to do business elsewhere.

As far as evaluating the strength of the seed lot in question, standard germination is a somewhat weak test, which is conducted in the laboratory under temperature and moisture conditions favorable for germination and development of seedlings. Seed are planted on moist towels. Towels are rolled to hold the seed in place and to reduce drying. Towels are placed in a germination to maintain favorable temperature and moisture during the test period. The temperature may alternate between 20 to 30 degrees Celsius (68 to 86 degrees Fahrenheit), 16 hours at 20 °C (68 °F) and 8 hours at 30 °C (86 °F), or tests may be conducted at a constant 30 °C (86 °F). The test consists of 4 replications of 100 seed each (or 4 replications of 50 seed each under some circumstances), meaning a germination test may be composed of 400 or 200 seed.

The first evaluation is made 4 days after planting. The towels are unrolled, and the seedlings developed enough to be considered normal are counted, removed from the towels, and recorded. The towels are rerolled and placed back in the germination. A second evaluation is made at 8 days after planting. As in the first evaluation, those seedlings that have developed enough to be considered normal (as prescribed by the rules for testing seed) are counted, removed, and recorded. If at this time it can be determined that no additional "normal" seedlings will develop, the test may be terminated. If the test is not terminated, towels are rerolled, returned to the germination, and a final evaluation is made 12 days after planting.

Vigor Test or Cool TestóThe cool test data for a lot of seed are not stated on the tag. Numerous reasons exist for this but variation between seed-testing labs is the most prominent reason. As with the actual germination, the cool test results for cotton seed lots are available from the seedsman. If for some reason the seedsman will not provide this information, you may wish to look elsewhere for seed.

The cool test is a demanding test requiring good laboratory equipment and techniques to be conducted in a repeatable fashion. In the cool test, seed are planted on moist germination towels and placed in a germination set at a constant 18 °C (64.4 °F). The test protocol requires equipment capable of maintaining this 18 oC by a margin of plus or minus 0.5 (one half) degree Celsius.

The seed remain at a constant 18 °C (64.4 °F) for 7 days after planting. After 7 days, only one evaluation is made. Only strong, vigorous seedlings that reach a length of 1 ½ inches (4 cm) long are counted. The combined root-hypocotyl length of the seedlings is measured, i.e., from the tip of the root to the base of the cotyledonary leaves. The percentage of strong or vigorous seedlings is computed and results reported as "percentage cool test germination." This value will most always be below the cool standard germination; however, do not let cool test values as low as 70 percent scare you.

What test results are acceptable? Experience has dictated 80 percent or better standard germination test results as the standard. Cool germination test results should be 60 percent or better. Of course, the higher the cool test the more desirable the seed. It is assumed that field survival will be similar to the cool test germination percentage if cool soil temperatures occur at or shortly after planting. Again, if soil temperatures are less than 70 degrees Fahrenheit, wait awhile before you plant.

The combined results of the standard germination test and the cool germination test will provide a better guide for determining the planting value of seed. When field conditions are favorable, i.e., soil temperatures are warm (near 86 °F or warmer) and when soil is moist, emergence should approach the standard germination. If soil conditions are cool (near 65 °F) at planting, or if temperatures drop near 60 to 65 °F after planting for a few days, then emergence should approach the results of the cool germination test.

If the soil becomes excessively wet and temperatures drop near 50 °F or lower, the resulting emergence might be well below the results of the cool germination test. Field conditions may possibly be so severe that, regardless of how good seed are, you cannot get an acceptable stand. Follow the recommended minimum 68 °F soil temperature for planting cotton no matter how high the cool germination test results. This minimum recommended soil temperature is near the temperature at which seed are germinated in the cool germination test. Performance of seed at lower temperatures should not be speculated or based upon the cool temperature germination test results.

Actual germination and cool test values can be of tremendous help to you in determining seed rates and deciding when to plant. Number one: Do not plant any seed, regardless of quality, when the soil is cooler than 68 degrees Fahrenheit and the 5-day weather forecast is not good. Common sense must apply. Weather and soil conditions can be such that a stand failure occurs regardless of seed quality. Use germination and cool test values to your advantage. Realize that all lots of seed are not going to germinate over 90 percent with cool test values over 85 percent. If you know the values for your seed, however, you can make better decisions about when to plant a particular lot and how many seed to drop.

Vigor IndexóSome people use the term "vigor index" as the sum of the warm germ and cool germ of a lot of seed. Example: If a seed lot has a cool test of 60 percent and a standard germ of 80 percent, the Vigor index is 140. A vigor index equal to or greater than 140 is preferred. I would rather use the actual values for cool germ and standard germ because a seed lot with a vigor index of 140 may have an 80 warm germ, and a 40 cool germ may have a 90 warm germ and a 50 cool germ (there is a difference). For more information, refer to Extension Information Sheet 1364,"Understanding and Using Results of Cottonseed Germination Test."

SOYBEANS

Dr. Alan Blaine

As in 1998, many of the more popular soybean varieties are in short supply. It is hoped we can overcome these supply problems; however it is becoming increasingly frustrating to producers as they attempt to select varieties. If you have producers who have not yet booked seed, impress upon them the importance of doing this as soon as possible.

Short supplies are due in part to the early maturity of the 1998 crop. Certainly unexpected, the 1998 crop matured earlier than the 97 crop because of the drought conditions experienced over most of the Midsouth. This early maturity scenario was not anticipated, but hopefully after 2 years of supply problems, companies will take an aggressive position regarding seed production of their better varieties. Although supply problems vary, I am concerned the supply of conventional varieties is going to get much tighter.

Roundup Ready is an excellent option for many soybean producers but it is not the only or best option in every situation. Although transgenic varieties will be a more prominent player in the future, I still hope we will have available adequate supplies of nontransgenic varieties.

Copies of the Mississippi Soybean Variety Trials are available in the county Extension offices. In addition, we have compiled a list of high-yielding soybean varieties. By the time you receive this newsletter, the 1998 Mississippi Soybean Variety Trials should also be available on the Internet.

This past fall many producers had the opportunity to get many acres prepared for planting. Given the erratic weather conditions this winter (cool/warm) and the rainfall most areas have received since the first of the year, producers need to highly consider the use of burndown materials. Many options are available but the most cost effective approach to burndown will be to start early to minimize rates and cost. Base your needs on species present and size. A situation we must avoid is waiting too late to start.

Every year I see delays get some producers in a "Catch 22" situation. By waiting late, vegetation can get extremely large. It is not the fact that producers cannot kill it, but the cost of killing vegetation and the question of how difficult it will be to plant through.

Spend some time scouting your fields. The main purpose of applying a burndown is to avoid planting delays in the spring. With the amount of fall land preparation many accomplished, Mississippians are in a prime situation to burndown and plant.

Keep in mind all you are doing is substituting a chemical burndown program for tillage. Cost savings are questionable, depending on which option accomplishes your objective, which should be to have everything dead or dying when the planter hits the field.

In many instances a reduced tillage program will work best using a two-step approach to burndown. At this time of the year, all winter vegetation is emerged. From this point on, it will just increase in size. Starting early accomplishes two objectives: 1) It will destroy this vegetation while it is small for less total dollars; and 2) It will bare up the soil allowing it to warm and dry faster. If you delay a burndown, two things can happen: 1) In a wet spring, the green cover will keep a field wet and colder; and 2) If it is a dry spring, the green cover can pump all the moisture out of the ground, (similar to disking in late spring).

If a two-step approach is needed, use your second shot by adding a burndown material to your preemerge to control escapes. An early burndown may allow your first flush of summer annuals to emerge and these can be controlled with the preemerge/burndown combination. Another option for those using Roundup Ready would be to combine the burndown and first postemergence application. This technology offers an additional viable option. If you consider this option, do not delay the postapplication. If the crop and weeds coexist for very long, yield will be lostó yield that cannot be compensated even with 100 percent control the rest of the season. Early season competition is real. Don't let it suppress yields.

CORN

Dr. Erick Larson

Early plantingóTimely planting is an essential part of producing maximum corn grain yields. Early planting results in better yields than late planting for numerous reasons related to crop development. Early planted corn's sensitive silking period, when grain yield is most susceptible, generally occurs before drought stress reaches its normal late summer peak. Early planted corn generally also has greater opportunity to develop a deeper and more extensive root system before droughty conditions arise. Early planted corn will undergo reproductive development during a time with more available solar energy due to longer day lengths, but with lower air temperatures. Early planting often helps reduce yield loss associated with late-season leaf diseases and insect pressure. Early planted corn will also mature during August, meaning increased likelihood of favorable conditions for field drying and greater harvest efficiency because of a quicker dry-down period.

Suggested planting datesóThe standard guideline for determining earliest planting date is when morning soil temperature at a 2-inch soil depth is 55 F or 50 F at a 6-inch soil depth. Planting before the soil temperature is warm enough for germination greatly increases the potential for stand failure. Soil temperature may vary, depending upon soil texture, slope, color and amount and type of crop residue. Rather than relying on a predetermined date to begin planting, randomly measuring soil temperature with a thermometer within a field should provide a more reliable indicator of desirable conditions for stand establishment. Suitable soil temperatures for corn germination generally begin occurring about February 25 - March 20 from the coastal to northern counties.

WHEAT

Dr. Erick Larson

Wheat fertilization: Timing of nitrogen application plays a large role in N use efficiency. Wheat requires about 2 pounds of N for each bushel of grain it produces. Apply approximately 25 percent of the total nitrogen in the fall. If wheat follows soybeans, you can reduce this amount; however, if wheat follows corn or sorghum, increase this amount to compensate for nitrogen tied up by decomposing residue. The remaining nitrogen should be applied in the spring after dormancy breaks, but before the second node is visible. This generally occurs from mid-February through mid-March. Split applications in the spring often produce better results due to high likelihood of denitrification and possibly volatization when conditions are wet and warm. Application of liquid UAN solution (32 percent) should be limited to around 50 pounds of N per application to prevent excessive leaf burning.

SOIL AND NUTRIENT MANAGEMENT

Dr. Larry Oldham

One of the first farm visits I made in this line of work was to see a corn field the farmer suspected had herbicide damage. It was a pretty sick-looking crop. It is necessary to determine all management inputs before offering a preliminary field diagnosis. In this case, the farmer had to call the local co-op to find out what his fertility program had been. In other words, they applied the fertilizer, he paid the bill, and kept no records.

We learned the field had received about 20 pounds of nitrogen per acre, much less than the crop required. We were not seeing any environmental symptom other than simple lack of plant nutrition.

Use of soil testing for lime requirements, phosphorus, and potassium, in combination with using nitrogen rates based on realistic yields for corn and cotton, will be more critical then ever in 1999. Soils testing in the upper medium to very high ranges for P and K will not require fertilization with these nutrients. Maintaining adequate pH levels will ensure the native soil nutrients will be adequately available for the crop. Low medium to very low soil test ranges will respond positively to fertilization with P or K if the pH levels are optimal.

Keeping records of how much and where you apply nutrients serves as a baseline in preparing nutrient management plans for the 2000 crop year. This will be particularly critical for soils in the medium range which we may not fertilize this year.

Some folks like to soil test in the spring to plan fall applications of P and K, and to determine liming programs. If you did this but decided not to fertilize or lime last fall because of economic and to try and get through this year without lime or fertilizer, it is imperative you sample when it dries out this spring to properly evaluate your 1999 nutrient management program and to plan for next fall.

WEED CONTROL

Dr. John Byrd

Wild garlic is a troublesome weed in wheat. This weed causes significant price dockage if the aerial bulblets are detected in the grain sample collected at the elevator. Producers, therefore, should attempt to control wild garlic to minimize monetary losses caused by dockage. In the distant past, 2,4-D was the treatment of choice to control wild garlic. Suggested rates were 1.5 to 2 pints of a 4-pound per gallon formulation for control. If 2,4-D is applied in liquid fertilizer, rates must be reduced to 0.5 to 0.75 pint per acre to avoid injury. These rates may not provide garlic control, but will suppress aerial bulblet suppression sufficiently to avoid price dockage. Apply 2,4-D after tillering but before jointing to avoid injury.

More recently, however, Harmony Extra has been the treatment of choice for control. Rates of 0.5 to 0.6 ounces per acre plus nonionic surfactant will control wild garlic in addition to curly dock, sowthistle, mustards, buttercups, and many of the other common winter annual broadleaf weeds. For best control, garlic should be less than 12 inches tall with 2 to 4 inches new growth. Recently, Peak was registered for application to wheat. Peak also controls wild garlic at rates as low as 0.38 to 0.5 ounces per acre. For optimum control, wild garlic should be 1 to 6 inches tall if the low rate is used or 1 to 8 inches tall if the high rate is used. Application timing is anytime after the 3-leaf until the second node is detectable. Nonionic surfactant should also be used with Peak.

A rating for aerial bulblet suppress would be 80 percent for 2,4-D versus 90 percent for Harmony Extra or Peak. Also, Harmony Extra or Peak will kill more garlic plants than will 2,4-D.

SUSTAINABLE AGRICULTURE

Dr. Malcolm Broome

Some Current ChallengesóAs this century approaches an end, agriculture faces some real challenges. Current population projections of 8.4 billion people by the year 2020 will put enormous pressure on agriculture to provide food and fiber. Today, with a sufficient quantity of food being produced in total, some 800 million people still do not get enough to eat. Many of the models constructed to investigate food production and security in the years ahead conclude that food production will have to increase substantially.

Yet, many of those who produce the food and fiber for Mississippi, the United States, and the World find themselves hard-pressed to continue due largely to weather, commodity prices, input costs, and financial resources. To meet these challenges, farmers are faced with a process of learning that is crucial to their sustainability. Learning new technology, or embracing other methods of growing a crop, must be come a participatory process. Policy or regulations that enforce or coerce farmers to adopt will only continue if their incomes depend on the technology. These only serve to restrict the future options of farmers, and as economic, social, and environmental conditions change, so must farmers and communities be encouraged and allowed to changeónot only to change but to adapt too. Sustainable agriculture is not a simple process to be widely used or fixed as time passes, but a process of learning.

Some challenges to learn in 1999 and beyond: * Develop a better awareness of information by participating in organizations, institutions, and decision-making processes. * Focus on doing things different than in the past (for example, less tillage, new varieties, more timely planting, and crop rotations). Find out about no-till corn, Group IV soybean, ideal planting time for the crops you grow, and importance of crop rotations. * Know what it costs to grow an acre of a crop; transfer that to cost per bushel, bale, etc. * Take the initiative to become more self-mobilized; time may not allow you to wait on others for answers.

Sustainable agriculture has never faced a stronger challenge to create more locally available resources, skills, and knowledge.

SOIL TESTING

Dr. Keith Crouse

Nitrate nitrogen in soils of Mississippi is lost through denitrification or leaching. Research shows that, under the state's warm and wet environmental conditions, the level of residual nitrate nitrogen is low. Knowing the residual nitrate nitrogen of the soil may be useful; the test is only good for the nitrate nitrogen present when a sample is collected and is no good unless the following items are considered: (1) Since nitrate nitrogen is lost throughout the year in Mississippi, samples should be taken before applying nitrogen fertilizer and as close as possible to planting. (2) Samples must be collected deeper than 6 inches and to a depth of 36 inches, depending on the crop (nitrate nitrogen is a mobile compound in the soil). Also, samples need to be representatively collected in the field, with appropriate subsamples, to make up one representative sample. (3) Research in Mississippi shows that air-drying samples immediately after taking was the correct procedure for handling nitrate nitrogen samples. This can be accomplished by spreading the samples out on metal or plastic trays.

The Soil Testing Laboratory at Mississippi State can provide the results of nitrate nitrogen analysis if the appropriate information sheet is fill out and is with the sample(s). You can get the nitrate nitrogen sheet(s) and box(es) at your county Extension office or from the lab at Mississippi State University.

FORAGES

Dr. Lamar Kimbrough

Two things that forage producers may need at this time include: (1) nitrogen fertilizer for cool-season grasses and (2) weed control for cool-season weeds. Without nitrogen, these forages may not produce the needed growth. Without weed control, weeds may rob desired forages of added fertilizer and greatly reduce pasture production and quality.

Nitrogen FertilizationóUsually, as the weather begins to warm, cool-season grasses are ready to grow following a somewhat slow-growth, cold weather period. If adequate phosphate and potash were applied at planting, nitrogen is the nutrient needed at this time to make these crops grow. If a good stand of clover is grown with the grass, the nitrogen rate may be reduced, depending on how much nitrogen the clover supplies. Common questions are how much and what source of nitrogen to use and how often depend on how much growth is desired and what source of nitrogen is available.

The most common sources of nitrogen for forages include solid ammonium nitrate, solid urea, and solutions of ammonium nitrate and urea. In general, when conditions are right for active growth, each of these sources produce good plant growth. However, a lot of dead inactive grass can contain considerable amounts of the urease enzyme, which can increase volatile losses from urea containing liquids. Dribbling or knifing in the urea containing liquid can reduce losses, but is not always possible on rough pasture land. Grazing off inactive growth before applying liquids may also be helpful. Whether solid or liquid, the main need is for enough rain to get the nitrogen into the soil so it can be taken up by the plants.

Efficiency and cost per unit of nitrogen are other factors to consider when determining nitrogen source; also take into consideration ease and cost of application. Where liquid nitrogen is available, some producers are also using it to carry weed control chemicals, thus saving a trip over their fields.

Weed ControlóProblem cool-season weeds include dock, wild turnips and mustards, thistles, and yellow flowered buttercup. Buttercup is the one that turns many pastures yellow with flowers each spring.

Clipping may help, but in many cases the most economical and practical way to control weeds is to use herbicides. When used according to label directions, herbicides have proven economically safe to humans, animals, and forage crops. Chemical weed control can effectively increase forage quality and quantity; however, you must use other management practices to maintain healthy growing forages.

You can use several herbicides and herbicide combinations to control forage weeds. Specific chemicals, rates, and timing are needed for any given situation, making it impractical here to give specific herbicide information. Such information is readily available from your local county Extension agent and other sources. Before applying any herbicide, read and follow the label instructions that come with the chemical.

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