Agronomy Notes

August 1, 2000

Contents

FORAGES AND PASTURES

Dr. Malcolm Broome

Cool Season Annual Grasses for Grazing - Beef and dairy producers depend heavily on cool season annual grasses (rye, wheat, oats and ryegrass). With the current dry, hot weather causing hay supplies to be short and grazing limited, these grasses will be essential to this fall and winter's forage program. However, depending on rainfall, these too could be late getting started thus delaying grazing into winter. Additionally, there are other factors to keep in mind when planting annual grasses as early as possible. These are: Planting dates - Oats, rye, wheat (in that order) are best adapted to tolerate heat following early planting. For very early planting (September 1), oats usually grow best south of Highway 84 in Mississippi. Ryegrass will contribute the least grazing in the fall unless ideal fall growing conditions exist. The reverse of this is that oats are the least cold-tolerant, followed by wheat and rye. Rye would be a good choice for cold, wet clay soils, but will mature early in April. Summer fallow - If some acreage is not needed for grazing, tilling the soil by early August will destroy weeds, help tilled-under vegetation decompose, and allow the soil to take in moisture when it comes. This practice will greatly increase the chances of early grazing. Seeding Rates - Early planting is not the time to reduce seeding rate per acre. Using wheat, oats or rye plus ryegrass will probably be the best combination to help insure earlier grazing. In this case, use 30 pounds of ryegrass plus 90 pounds of the wheat, oats or rye. If a grain drill is used, seeding rate can be reduced for ryegrass. Sometimes under dry conditions, drilled seed provides earlier grazing because less soil is disturbed and moisture is conserved. Pest Control - At times, both weeds and insects can be problems when planting early. Many times even with limited moisture, pigweed or other broadleaf weeds can be a problem; these can be controlled should the need arise. Fall armyworms will likely be a problem and can very quickly destroy a stand of young grass seedlings. Scout your planted fields regularly and be alert for signs of infestation. Grazing Management - Don't graze the grass too early (less than 6 inches) because the stand can be damaged and forage production reduced for the winter. High quality cool season grasses can provide much needed livestock feed, but don't overlook what's needed to ensure a successful planting. It can fill a void in your forage program to compensate for lack of hay. For information on management of a livestock program, contact your county Extension agent.

COTTON

Dr. Will McCarty

Crop Situation: Cotton went into July with a very high percent fruit retention. High temperatures and lack of moisture really took a toll on the crop. Depending on moisture through August, we will be picking an early crop in 2000. Vascular Wilts: I am seeing significant evidence of these diseases in fields this year. While none of our varieties are resistant to the diseases, some are more tolerant than others. How do we prevent the problem next year? Plant tolerant varieties, implement a sound fertility program and try to prevent as much stress to the plant as you can. No magic cures exist. If you see the problem this season, take note of the field where it occurs and what variety it is occurring in. Nematodes: Remember to have your fields tested for the presence of nematodes. This is an excellent time to take soil samples for nematode analysis. Keep in mind that dry soils may give misleading information. If soil conditions are dry, I suggest waiting for moisture before sampling. A new wrinkle is that I also suggest you take subsoil samples. There may be some indication that nematodes move downward in the soil profile as it dries. A sound nematode analysis program is as important as a sound soil fertility testing program. Defoliation - The time to apply a defoliant is often a tough decision to make. Above all else, it should be based on the maturity of the plants and field. Harvest schedules and prevailing weather conditions and forecast also are prominent considerations. The maturation processes stop when the leaves are taken off a cotton plant. Anytime the decision is made to apply a defoliant or harvest-aid chemical, there will probably be some immature bolls on the plant. However, a grower cannot wait until 100 percent of the bolls are mature; some will have to be sacrificed. As a general rule of thumb, the last boll to be consistently picked will probably be the first position boll on the fourth or fifth node down from the terminal. The maturity of this boll should be used as the key for timing an application of defoliant. The yield and quality of the bottom crop and middle crop are far more important than those last two or three tiny bolls in the terminal. This decision is often hard to make. It is generally safe to apply a harvest-aid chemical when the crop is 50 to 60 percent open, and the last boll expected to be picked is mature. To determine maturity of this boll, a visual field check is recommended. With a sharp knife, cut in a cross-section bolls from the last fruiting position desired to be picked (usually the first position boll on the fourth or fifth node below the terminal). A mature boll is difficult to cut, but the real test is done by looking at the seed. The seed cavity should be filled, there should be no jelly present, and the seed coat should be dark in color. When the seed is mature, the boll is mature enough not to be adversely affected by a harvest-aid chemical treatment. Generally, the boll is mature enough to be defoliated at about 38 days of age, depending on the growing season. Cutout + DD 60's - Where a plant monitoring program is employed, growers might want to look at heat unit accumulation after what is considered "cutout" has occurred. Depending on location, cutout is generally defined as that point when the crop has progressed to a point of development where the first position white flower is within four or five nodes of the terminal. The technique to make these counts is described in the Plant Monitoring booklets available from your local Extension office or the National Cotton Council. "Nodes above white flower" (NAWF) is a powerful tool that can help crop managers make or verify several decisions. Potential timing of defoliation is one of those. Count heat unit accumulation after NAWF 5 and when 750 to 800 DD 60's are accumulated, the field may be ready for defoliation. Before any treatments are made, the fields should be physically examined to determine maturity. If long-term weather records are available, you may be able to use this data to predict defoliation date several weeks in advance. This is just another tool. Nodes Above Cracked Boll - This technique is valuable in verifying field maturity or other techniques you may have used to determine readiness for defoliation. It has been found in research that boll maturity extends four nodes above the uppermost first position cracked boll (NACB). To use this technique, select plants that represent the majority of the field; these plants must have a cracked boll (one where lint is visible through a cracked suture) on a first position site. When this is done, determine how many nodes are between the cracked boll and the youngest boll to be harvested. The crop will be mature four nodes above that cracked boll. At defoliation time, the NACB should be within four of the youngest bolls you want to harvest. When you are counting heat units or cutting bolls, the NACB technique can be valuable for confirmation. If you are not sure the boll you cut is mature, count down the plant, and if you find a first position cracked boll within four nodes, the bolls are mature enough to not be adversely affected by a defoliant. For more information, ask your county agent for a copy of the latest Cotton Defoliation Information Sheet.

SOYBEANS

Dr. Alan Blaine

At this stage of crop development, the major concern is need for water. Even with an early planted crop, there is a dire need of additional moisture. Only about 25 percent of our state soybean crop is irrigated, so a major portion is at extreme risk from a lack of moisture availability. If you have irrigation, use it effectively. Unfortunately many irrigated fields are not watered as needed, thus limiting yields. This is the third year in a row that we have had a fairly early crop, but water needs have been great due to extremely abnormally dry and hot conditions in May and June. This has brought increased need for early season irrigation. Watering on a 14 day schedule in furrow and an inch a week in pivot irrigated fields has not been enough. Early season production coupled with early maturing varieties has created a need for a shift in management practices. If your irrigated yields are not averaging 55 bushels per acre, you need to reevaluate your irrigation strategies. Do not settle for yield levels less than this. Don't be afraid to readjust your thoughts regarding irrigation. Just because that is the way you have always irrigated your crop, or that was how it was done before you, doesn't mean it is absolute. Attempt to push your crop to the maximum, and don't hesitate to ask for some help if you are uncertain about irrigation strategies. As I write this (7/23/00), we have watered some April-planted furrow irrigated soybeans 4 times and some pivot beans 7 times. Continuing to supply water as needed should produce in excess of 60 bushels per acre. Insect pressure from worms is beginning to show up, particularly in the South Delta. In our SMART program, spraying, thus far, has been for grasshoppers, three cornered alfalfa hoppers, and snails. This first flush of worms is very light and appears to be cycling out. However, by August 10, populations should start building. We are once again attempting to utilize Dimilin in as many of our SMART fields as we feel the need. Dimilin is an insect growth regulator that will provide about 3 to 4 weeks residual. Although not active on all pests, we are impressed with what it can do as a management tool for controlling worms. We are currently applying it to beans that we feel have a good yield potential (mainly V's). We will consider its use on IV's if later planted and irrigated. Dimilin appears to make good beans better. Yield responses have averaged approximately 3 bushels per acre on dryland and 5.6 bushels per acre on irrigated. These figures represent yield averages on data taken since 1983 (30+ tests over a 17-year period). Yield responses such as these are impossible to see visually, but from a management standpoint this option has proven beneficial. In the presence of heavy worm pressure and areas of high incidence of cotton, instead of spraying loopers twice, spraying is often limited to one application. Dimilin will not control loopers; it only suppresses them. However, the cost of Dimilin versus Larvin translates into a savings of $8-10 per acre. Under heavy looper pressure, Dimilin will buy you 7-10 days relief before needing to spray. When used as a preventative treatment, use no more than 2 ounces per acre. The label lists 4 ounces per acre for looper control, but if loopers are already present, you should use something other than Dimilin for satisfactory control. In the hill area of the state, worm populations that often develop are more readily controlled with Dimilin. When Dimilin is put out prior to heavy egg hatches, velvet bean caterpillar, green clover worms, and cabbage looper populations will be controlled. These much more readily infest the hill crops, and Dimilin is an excellent option for hill producers to consider. I often have growers tell me that they cannot afford to spend money on worm control. If that is the case, you should never have planted the crop because it is a shame to watch it grow all year long and then have worms eat it up in one week. When prices are low, we need to become more focused on increasing yields and improving management practices because it is in this situation that maximum yields must be obtained If considering any new late season management tool, do not spray the entire crop. Leave some areas untreated so you can see exactly what a tool such as Dimilin has to offer. If you have questions concerning any aspect of soybean production, do not hesitate to contact your nearest county Extension office for information.

RICE

Dr. Joe Street

The rice crop continues to look good in most areas. Rice was somewhat behind normal at first but with the heat in mid-July, rice is only slightly behind our five-year average maturity. Much of the early-planted rice headed during the 100-degree days of mid-July, which is not good for rice production. Temperatures above 95 degrees during flowering can reduce pollination and increase the number of blank grains. High nighttime temperatures may reduce grain weight and reduce milling quality. The cooler weather during late July will benefit the rice heading during that time. The county acreage survey is nearly complete and preliminary results indicate that we planted about 243,000 acres of rice this year. This survey has historically been a little low but there is no way to know how much. The USDA acreage predictions have historically been a little high and the true acreage normally falls between the two surveys. The initial USDA prediction was 280,000 acres so the final acreage should be somewhere between the two. We are still growing primarily Lemont. The variety distribution is as follows: Lemont ñ 61%, Priscilla ñ 25 %, Cypress ñ 5%, Cocodrie ñ 4%, Jefferson ñ 1 %, and Wells ñ 0.8 %. Other varieties planted include Drew, Kaybonnet, Dixiebelle, Jackson, Clearfield and the hybrid XL6. So far, diseases have been light to moderate. Some fields have been treated for sheath blight but the hot dry temperatures of mid-July seemed to decrease the disease activity. Sheath blight scouting should continue during weather favorable for disease development. With Lemont, Cypress, and Cocodrie, treat when sheath blight infestation level is greater than 35 percent if the disease appears to be moving up the plant and weather predictions are favorable for disease development. Based on research data with Priscilla and Wells, except in severe cases, you will not get a good return on investment with a sheath blight treatment. If rice has not yet headed, it is probably good insurance to treat for kernel smut if you are growing Priscilla, Cocodrie, or Cypress under high nitrogen conditions. Tilt appears to be the most active fungicide for kernel smut. Wells and Lemont are rated resistant to kernel smut and treatment is not generally necessary except under very high nitrogen fertilization. Bacterial panicle blight and false smut have received a lot of press lately. Data are not available to recommend wholesale application of Kocide or Kop-Hydroxide for control of these diseases. These materials do have activity on these diseases so you might want to evaluate them on a small acreage to become familiar with them. We have several tests on grower fields this year and will be able to provide more information this fall. I have received numerous calls concerning fall armyworms. These insects feed primarily on grass but they will feed on rice if it is the only thing around them that is green. It is a judgment call on when or if treatment is necessary. If the worms are destroying the crop or clipping the heads as they emerge from the boot, treatment may be necessary. Extension Service recommendations are to treat when you find an average of five or more worms per ten sweeps. Rice stink bugs are always a threat to rice at the heading stage. Both adults and nymphs feed by sucking fluids from the developing kernels. Feeding during the milk stage causes blank grains. Feeding during the soft dough stage causes pecky rice. Treat when you find an average of 3 stink bugs in 10 sweeps during the first two weeks of heading. When the field is completely headed and the grain is in the milk stage, treat when you find 5 stink bugs in 10 sweeps. Plan to attend the rice and soybean field day at Stoneville on August 16, 2000. This will be a good opportunity to see the latest research results and new promising breeding lines.

SOIL TESTING

Dr. Keith Crouse As harvest begins, we need to start thinking about soil sampling. Mississippi State University Extension Service (MSU-ES) Soil Testing Laboratory analyzed many fertility related problem soil samples this past fiscal year. These problems could have been avoided by sampling the field prior to planting. A low soil pH is still a major fertility problem. For most crops, lime should be incorporated into the top 5 to 6 inches of the soil, preferably at least 3 months in advance of planting. MSU-ES Soil Testing Laboratory's lime recommendations assume that limestone being used has a calcium carbonate equivalent (CCE) of 100 %. Remember, that Mississippi has two limestone grades: A and B, which also determine the amount of lime needed.

CORN

Dr. Erick Larson

Deciding when to harvest - Corn may be harvested any time after grain reaches physiological maturity, which occurs at around 30% moisture. However, corn may not be safely stored until considerable moisture loss occurs. Thus, grain elevators discount wet corn to account for drying expenses and moisture weight loss during drying. Moisture dockage schedules between elevators may vary significantly, so thoroughly compare rates. Most schedules discount about 2.5% per each percent moisture above the standard, and may increase as moisture content rises. Water evaporated during drying (shrinkage) accounts for 1.18% of the dockage per each percent moisture. The producer loses this weight regardless of whether they sell wet grain to the elevator, dry it personally or let the grain field dry. Thus, this value should be subtracted from the dockage rate to show "actual" dockage. Don't Give Away Corn - Producers selling corn at less than 15% moisture are giving away profit. A producer harvesting 100 Bu./A. corn at 14% moisture is losing $2.35 per acre or $4.71 per acre at 13% moisture (at $2.00/Bu.). This loss is solely from reduced grain weight due to lower moisture content. This moisture weight loss closely approximates the "actual" dockage most elevators charge for high moisture corn. Thus, growers seeking maximum profitability should always strive to finish harvest before grain moisture falls below 15% (because harvest losses accumulate as grain dries below 20%). Since corn loses approximately 0.6% per day during the harvest season, begin harvest early enough to guarantee all corn is harvested before it reaches 15%. Harvest losses - Harvest losses normally increase when grain dries in the field, due to increased shattering by the combine, stalk lodging, dropped ears, weathering and predation. Two corn kernels per square foot or one dropped ear per 100 feet of row equals about 1 bushel per acre yield loss. Research generally indicates combine efficiency is best (harvest losses are low) when corn grain moisture is about 20-22%. Aflatoxin tips: Don't delay harvest - Delaying harvest until grain moisture drops below 15% moisture will not reduce aflatoxin level. Conversely, harvest timing directly influences the duration corn is subjected to warm (above 80 F), humid (60-70% relative humidity) conditions which are likely to promote aflatoxin development. Thus, prompt harvest will help avoid continued aflatoxin development, despite moisture dockage incurred. However, aflatoxin levels may escalate within a few hours if high moisture grain is not handled properly. Wet grain should be immediately dried to below 15% moisture or hauled to an elevator (which will dry the grain). Wet grain should not be stored in trucks, combines, bins or any non-aerated site more than 4-6 hours before beginning drying. These conditions are critical to grain quality because, the fungal growth which causes aflatoxin will escalate to excessive levels very quickly under these conditions. Conversely, fungal growth becomes dormant when grain moisture drops below 15%. Avoid bad areas - Separately harvest obviously stressed, stunted or damaged areas and field edges, if you suspect any aflatoxin problem. These areas are much more likely to contain high levels of aflatoxin. Clean grain - Fungal infection is more likely in shriveled, cracked kernels and foreign material. Thus, grain quality may be significantly improved by reducing the combine ground speed, increasing fan speed and opening sieves. A post-harvest mechanical cleaner or gravity separator may also help reduce moderate aflatoxin levels (50 to 100 ppb) below the FDA standard (20 ppb). Sanitize equipment - Fungal infection can occur during storage as well as in the field. Thus, sanitation of handling and storage facilities is very important. Spores from fungi on infected grain readily disperse during handling and contaminate unaffected grain. Remove corn and debris remaining in combines, trucks, grain carts, pits, augers, bins, elevators, etc... on a daily basis. Chlorine cleaning solution (3/4 cup bleach per gallon of water) kills fungal growth when cleaning handling facilities. However, since chlorine solution is very corrosive, thoroughly wash with water after cleaning.

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