Agronomy Notes

May, 2002

Contents:

RICE
CORN
GRAIN SORGHUM
RECOGNIZING THE VALUE OF QUALITY FORAGE
SOIL AND NUTRIENT MANAGEMENT
COTTON
SOYBEANS

 

 

RICE

Dr. Joe Street

The rice crop is in various stages of development from tillering to unplanted. Acreage predictions are more uncertain now than ever with some growers trying to decide which crop to plant based on the uncertainty of the farm bill and now trying to sort through the new farm bill.

Thin Stands. Although we seldom replant rice, there are many situations where fields will have a thin stand on a portion of the field. The desired plant population is 12 to 20 plants per square foot. Six to 10 plants per square foot will make a satisfactory yield in most cases. When the stand is four to five plants per square foot, it should be managed carefully. Replanting small spots in the field can cause harvesting delays and reduced milling yield. If clay soils are cracked, seed may be flown on and the field kept moist for germination and then flooded at the normal time for the field. These later planted plants will gain about 10 days in maturity.

In thin stands, apply about 50 pounds of urea or 100 pounds of ammonium sulfate when the rice is in the two to three leaf stage. Aquatic weeds will be worse in the thin areas so an application of Bolero pre-flood or Londax immediately after flooding should be considered. Establish a shallow flood to allow maximum tillering. Water weevils will be more prevalent in the thin areas. If Icon seed treatment was not used, then a foliar insecticide should be used within five days after flooding.

If managed properly, thin stands will produce a good crop of rice. We always make a good crop in seed increase fields planted at 30 to 40 pounds of seed per acre.

Grape Colaspis. As rice emerges, it is a good time to check for grape colaspis, which is sometimes called lespedeza weevil. If you have reduced stands or areas that appear to be seedling disease, it could be grape colaspis. The small rice plants will look sick, stunted and yellow and with any stress the plants may die. Grape colaspis larvae girdle the stem (mesocotyl) between the seed and the soil surface. It is normally worse on silt loam soils than on heavy clay but it can be a problem on clay, especially following irrigated soybeans. If you see symptoms, check the plants just above the seed for the girdling. There is no treatment for the larvae other than avoiding stress on the plants. However, next year, consider using Icon treated seed to control this pest.

Weed Control. Expect about three to four weeks of residual barnyardgrass control from Command. Residual control of broadleaf signalgrass will be about two to three weeks. With Facet, you can expect about one week of residual activity per one-tenth of pound active ingredient. Newpath is a good grass herbicide but water management is critical with this herbicide. It must be moved into the root zone to maximize activity. Regiment will be available this year. Regiment is very good on barnyardgrass and johnsongrass but has no sprangletop activity. It also has good activity on several broadleaf weeds including hemp sesbania and smartweed. Ricestar will also be available and is very good on sprangletop and small barnyardgrass. Clincher has not received a label as this is written.

Fertilizer application. With the price of rice and the cost of nitrogen, efficient nitrogen management is a must. With Cocodrie, Priscilla and Clearfield, apply two-thirds to three-fourths of the fertilizer prior to flooding and the remaining fertilizer at midseason. For Wells and Lemont, apply half of the fertilizer preflood and the other half at midseason. Apply 180 pounds of nitrogen to Clearfield, Cocodrie, Lemont and Priscilla. For Wells, fertility data show no yield increase above 150 pounds of nitrogen. These rates are assuming that the flood can be established in five to seven days. If it takes more than seven days to flood, you may want to apply 200 pounds of urea preflood and then apply 100 pounds when the flood is established. This is not based on research data but it concerns me to have 300 pounds of urea on the soil surface for more than a week. Research is underway to evaluate this fertilizer system. If it takes longer than seven days to flood and your pH is above 7.5, you may want to consider ammonium sulfate to decrease the amount of loss through volatilization.

Hybrid rice has different fertilization recommendations. For XL7 and XL8 on silt loam soils, apply 90 pounds of nitrogen preflood and 60 pounds at late boot to five percent heading. On heavy clay, apply 120 pounds of nitrogen preflood and 60 pounds at boot to five percent heading. Apply a minimum of 50 pounds of potassium to hybrid rice unless the soil test recommends more.

CORN

Dr. Erick Larson

Replanting/Late Planting suggestions - Late-planted corn significantly reduces yield potential because plant development is delayed, which increases the chance of late-season water and heat stress, and insect and disease pressure. Corn planted during the optimum time frame spaced uniformly at about one to one and a half plant per foot of row will still have around 80-90% of optimum yield potential depending on the yield level. Late planting can reduce yield potential similarly or substantially more even with an optimum stand. Thus, planting corn in May is generally only recommended if the initial stand is a disaster and other crop options are not available or not economically feasible.

Kill an unacceptable stand - When replanting corn, destroy the existing stand with herbicides or tillage before replanting. Surviving plants will have a huge disparity in plant development, causing severe competition with the adjacent replanted plants. This results in significant yield loss because of a high percentage of barren plants.

Rootless corn - Several fields have recently had young corn plants falling over because they do not have their nodal root system developed. The nodal roots develop from the crown of the stem. This condition is often referred to as rootless corn syndrome. There are several reasons why nodal roots may not develop, including shallow planting, poor seed-furrow closure and soil erosion. Corn planted less than one inch deep will move the nodal root origination point up to or above the soil surface, subjecting these roots to many factors that can retard growth (hot, dry and/or compacted soil, herbicide injury or carryover, and surface-feeding insects). Corn planted at the recommended seeding depth (one and a half to two inches deep) will develop the nodal roots below the soil surface, avoiding these potential problems. Corn planted in fairly moist soil may also compact the soil around the seed-furrow, especially on heavy clay soils, causing the furrow to open and present the same problems as shallow planting. Heavy rainfall or wind erosion may also move soil away from the crown of emerged corn plants, especially on light textured soils with raised beds, exposing the nodal root system as well. The ability of corn plants to recover from this condition depends upon favorable environmental conditions and why the nodal roots are failing to develop. Corn should likely recover if rainfall or irrigation water is received, which should promote nodal root development. However, dry land fields could sustain considerable stand loss, if rainfall doesn't promote root growth soon. Cultivation may also promote root development, if soil can be moved around the base of plants without knocking them down.

Purple/Stunted corn - Corn often appears stunted and lower corn leaves turn purple during the first couple weeks of May as a result of phosphorus deficiency. This deficiency is especially prevalent when corn is grown following a rice crop. New leaves emerging from the whorl are usually green, but may turn purple shortly thereafter. Phosphorus deficiency symptoms often occur as young plants are exposed to good growing conditions following cool and often wet conditions. This results in a lag phase where vegetative growth exceeds the roots' ability to supply phosphorus. Young plants are especially vulnerable because their root systems are small and phosphorus is immobile in the soil solution. Any cultural or environmental factors which limit root growth will aggravate deficiency symptoms. Examples of such conditions include: cool temperatures, too wet or dry soil, compacted soil, herbicide damage, insect damage, and root pruning by side-dressing knives or cultivators. Acidic soil can also intensify phosphorus deficiency symptoms. Low soil pH severely limits phosphorus availability to plants, which may cause deficiency symptoms even where high soil test phosphorus levels exist. Plants normally recover when favorable growing conditions allow root expansion. However, phosphorus deficiency will likely reduce yield by delaying maturity, decreasing root and stalk development, and reducing energy transfer and storage. Treatment options to quickly remedy phosphorus deficiency have limited effectiveness, since phosphorus is immobile in the soil solution. Surface application of phosphorus fertilizer will limit availability to the top couple inches of soil. Phosphorus injected as a side-dress treatment would increase availability to roots, however, be careful not to prune roots.

Irrigation Initiation - Drought stress can potentially reduce corn yield anytime during corn's developmental stages. Therefore, irrigation should commence whenever soil moisture becomes limiting. Since corn's water requirement increases with plant size during vegetative stages (from emergence until tassel), plant growth stage does play a determining role, but there is not a definitive growth stage when irrigation should commence. This time is normally highly dependent upon seasonal rainfall. Corn's most critical and largest moisture requirement time interval is from tasseling through milk stages.

GRAIN SORGHUM

Dr. Erick Larson

Sorghum establishment - Scout sorghum fields diligently during establishment for stand, insect and weed problems. Sorghum seedlings have considerably less vigor than corn which often translates to more difficult stand establishment. Chinch bugs also prefer sorghum compared to corn and since chinch bug populations tend to thrive during warm, dry conditions which are normal in May, they can cause major sorghum establishment problems. Postemergence herbicide options for sorghum are quite limited, so timely identification and response also is imperative to control weed problems. Scout sorghum fields every two days until sorghum exceeds six inches tall and then gradually decrease scouting frequency.

Minimum Stand - Grain sorghum has tremendous ability to compensate for low stands by producing tillers, especially if plants are spaced uniformly. Thus, the optimum plant population for sorghum is very broad, ranging from 40,000 to 70,000 plants per acre for dry land production. Replanting would be required only if stands were reduced to less than two plants per foot of row or skips larger than five feet occur in adjacent rows.

RECOGNIZING THE VALUE OF QUALITY FORAGE

Dr. Malcolm Broome

In my travel about the state, it is apparent that much of the forage grown is not of sufficient quality. Quality forage is a valuable resource and all producers or purchasers need to recognize its value. Quality forage is high in total digestible nutrients (TDN), protein, and energy. It will have a high leaf to stem ratio, making it low in fiber.

Many factors affect the quality of a forage, but the four most easily understood and managed are: 1) maturity; 2) species; 3) time of the year; 4) and fertility. From the maturity standpoint, all forage plants are higher in quality when young than when mature. Young plants have thinner cell walls, which means higher digestibility. They will usually contain more nitrogen, resulting in an increased protein content. Even though maximum yields are obtained as the plant approaches maturity, much of the quality and thus value has been lost. Some sacrifice in total yield must be forfeited to get higher quality forage which gives more beef or milk production per acre of forage. To get maximum TDN and protein per acre, you should graze or harvest for hay generally every 30 days if weather permits sufficient growth.

Time of the year is more pronounced for our warm season forages. Summer grasses lose quality as the season progresses, even with harvesting at the proper stage. This is caused by shorter days, higher temperatures and lower available soil moisture. Therefore, the first grazing of hay in early summer will be higher in quality than that harvested the remainder of the summer, making the value greater.

Fertility may be the most critical of these factors since the amount of available plant food, especially nitrogen, determines the yield and, to some extent, the quality of a forage. The crude protein content of a forage is determined by the amount of nitrogen in the plant tissue. Research has shown that nitrogen fertilization also increases animal preference, the amount consumed and to some degree, the digestibility. Common bermudagrass without nitrogen has been shown to have only 40 percent utilization by cattle compared to 57 percent where the equivalent of 100 pounds of ammonium nitrate was used.

The last of our quality factors, plant species, will impact forage quality, however, it is not so critical that you would totally destroy a good persistent stand of one grass to plant another. Be sure of one thing from the specie standpoint, there is no "silver bullet" forage that can be planted to solve both yield and quality. The rule is normally cool-season grasses are higher in quality than warm-season grasses, and annual grasses have higher quality than perennial grasses. Legumes will be of a higher quality than grasses. So from the specie selected, if management practices are used a valuable forage can be grown, but differences in yield per acre will be common depending on the specie.

As you can see by now, management will play the major role in forage quality. To keep a forage grass producing a good quality, controlled grazing is a must. This is best done by cross-fencing and rotational grazing. Ideally, at least three pastures per herd are needed, and the pastures should be small enough to allow a grazing pressure of three cows per acre. Hybrid bermudagrass, the exception, will require up to five cows per acre. Rotational grazing based on these assumptions will involve moving the cattle from one pasture to another every 7 to 14 days, depending on moisture, fertilizer, and forage height. The value is this will increase forage quality and reduce forage loss to the point of increasing production by 20 to 30 percent without additional fertilizer. Hay can be harvested from excess forage and will only decease in quality with age. It costs very little more to produce quality hay and grazing than it does to produce fair to poor quality. As costs of production inputs continue to increase, it should be obvious the value of quality forage is not a difficult task to achieve.

SOIL AND NUTRIENT MANAGEMENT

Dr. Larry Oldham

Publication news:

MSU Extension Service Information Sheet 1635 "Using Poultry By-Products in Forage Production" is now available in hard copy, and will be on MSUcares.com in the near future. It has an example of the calculations necessary to determine the nutrient content of broiler litter per ton. Best management practices associated with land application of broiler litter are also included.

Dr. Cliff Synder of the Potash and Phosphate Institute and Dr. Nathan Slaton, Director of Soil Testing at the University of Arkansas recently published "Effects of soil flooding and drying on phosphorus reaction" in the regional News and Views of PPI. This subject is very timely in the Delta. The newsletter is available at http//www.ppi-ppic.org/.

Events:

The 25th Annual Conservation Tillage Conference for Sustainable Agriculture will be held June 24-26 in Auburn, AL. The associated field day is on June 26 at the E.V. Smith Research Center in Shorter, AL. Program details and registration information are available at http//www.ag.auburn.edu/nsdl/sctcsa/.

The Milan, Tennessee No-Till Field Day on July 25 will feature precision technologies. The field day is moving to an every other year schedule with the next one occurring in 2004. A press release is available at http//www.agriculture.utk.edu/news/0311PrecTech.htm.

COTTON

Dr. Will McCarty

2002 Start - Thus far, weather has not been terrible, but it has been far from perfect. Some areas got cold rains while other areas remained too dry to plant. The Mississippi River has threatened, or is is threatening, some low lying areas. However, thus far, I have seen worse stats - but it is not over.

According to the Mississippi Agricultural Statistics Service, as of April 29, Mississippi's cotton crop was 19 percent planted, compared to 25 percent on that date last year and 14 percent for the 5-year average. It is not late! The first of May is really the ideal time to plant cotton. Year in and year out - cotton planted the first two weeks of May will catch and surpass cotton planted earlier, mature with a few days of earlier planted cotton, and often out yield earlier planted cotton. And, generally will produce fewer sleepless nights when cold rains are in the weather forecast.

Regardless of the start, there will be problems. Here are a few thoughts on some potential problems:

Replanting: Let's hope we don't have to make a decision to replant; but if we do, it is often a difficult one to make. In fields with questionable stands, you must consider several things before making a replant decision.

1. What is the calendar date?

2. What is the population of plants that will survive?

3. What is the health of those plants, especially their roots?

4. Are there large skips and frequent skips?

5. What is the productive capability of the soil, and is the field irrigated?

6. What variety is planted in this field, the surrounding fields, the rest of the farm and what seed are available at the critical time?

A big consideration is soil type and moisture. If the soil type is one that dries quickly, replanting decisions must be made ASAP and carried out before moisture falls out of the beds. Replanting on these type soils (generally mixed textured to heavy soils) may necessitate returning to replant before first planting is complete. To do other wise is to gamble that rain will recharge the beds or that the limited stand may actually survive.

If plant distribution is fairly uniform in fields on productive soils, good yields can be made with low plant populations in the low 20,000 range, or as low as one per row-foot with no or few skips. If the stands are broken with numerous skips, replanting is in order at populations below 30,000 plants per acre, depending on the size and frequency of skips. In some cases a grower may "spot-in" areas of the field with his planter. Calendar date is significant; a stand you would plow up on May 1 would probably be kept on May 25. Bt cotton and boll weevil eradication have really made the late replant decision easier.

If replanting is necessary, continue to use fungicides as appropriate. That decision needs to be made on a field-by-field basis. If your replant is on the stale row, use a burn-down herbicide to kill the old stand and weeds that may have emerged on the row. In some cases the bed may need to be "freshened" before planting. This decision will need to be made on a field by field basis.

Other replant tips:

Make replant decision quickly and act quickly before moisture limits your options.

McCarty's Rule of Thumb: If you have enough cotton in the field to really make the decision difficult - KEEP IT!

SOYBEANS

Dr. Alan Blaine

As of late April, the state soybean crop was over 50 percent planted. Two weeks prior to this many felt we were getting behind. However, as you look at planting progress it is obvious that a lot of acreage was planted in a relatively short period of time.

Several areas scattered around the state were in much need of a rain prior to planting. Once again (even though it was April) we saw it go from too wet to too dry in an extremely short period. The delay in making a burndown decision put many in a deficit moisture situation. Hopefully, many will reflect on this situation and attempt to avoid this scenario next year.

It does not matter whether you are going to plant no-till or use some form of tillage, an early burndown can make both scenarios easier to handle. The key to success is "being early". Make yourself adhere to a calendar schedule (prior to trees greening up and corn emerging). If mother nature has not afforded you the opportunity to put out a burndown or perform necessary tillage, call the airplane and get something out. Do not wait until right before planting. Lack of vegetation gives you better control over planting dates. Do not take this lightly. There are growers who have planted and have a stand compared to those who have let green vegetation or excessive tillage deplete moisture supplies. It is one thing if you can continue to knock down rows, but with most of our acreage planted flat, we do not have that luxury.

Seed Treatments

Up to this point, we have not had the kind of weather we usually experience in April. Emergence has been excellent, and it probably would not have mattered what materials we used unless you happened to plant right before a rain.

Many feel that once temperatures begin to warm, we can stop using an Apron type material. While this is true, it is the uncertainty of when rain events will occur that makes me continue to utilize seed treatments effective against pythium.

I looked at a field of beans planted on June 8, 2001 that was lost to pythium. The grower commented that since it was early June he thought a seed treatment was no longer needed. Most of the time he would have been correct, but this reminded me of the uncertainty of timely rains. If you want to take a chance, use an Apron type material to protect you from the uncertainty of rain and back off on other materials (only if you have high quality seed). We have a hot weather pythium, one that thrives under hot, wet conditions that will make our cool weather pythium look like a wimp, but it all depends on rain events.

Seeding Rates

Emergence thus far has been excellent. In the majority of our SMART fields, we are getting far more soybeans up than growers thought they planted. This is a typical scenario that is prevalent for more times than not. Adequate plant populations are within a range of 75,000-125,000 plants per acre for row plantings and 125,000-175,000 plants per acre for drills. We are observing excellent emergence thus far, so do not overplant. As you change varieties, recalibrate planters. I know this can be a inconvenience, but at $25 per bag for Roundup Ready seed, it is worth the trouble.

Recently, I made the comment about how the savings would add up if you fine tuned your planter. A couple of growers have asked me some questions regarding my comments, and I thought I would take just a moment to do the math and let you figure it out for yourself.

If you bought a Roundup Ready variety for $25 per bag (that is a 50 pound bag), seed cost would be .50 cents per pound. On 20 inch rows, if you wanted to plant a little extra, many might consider 6.5 seed per foot of row as sufficient. At 3000 seed per pound, that is slightly over a bag per acre. It figures out to be 56.6 pounds per acre. We normally recommend 5 seed per foot of row, and 6.5 seed per foot represents a 24% increase. If you were to plant 4 seed foot of row, that is 34.8 pounds per acre or 104,544 plants per acre with 100% emergence. Keep in mind, seed dropped in the field is often higher than when calibrated on the turn row. An exception to this is the server vacuum type planter.

At 104,544 plants per acre you would be right in the midrange of our recommended plant population. This reduction would be a savings of 21.8 pounds per acre at .50 cents per pound. On 1500 acres of beans going from 6.5 seed per foot of row to 4.0 seed per foot of row would translate into a savings of $16,350.

Seed are a vital input, but costly. The industry is changing and I encourage you to stay on top of this input. It will not surprise me if in the future we do not start getting charged by seed count like corn and cotton. While I hope this does not occur, as fast as we are allowing this crop to move to Roundup Ready do not be surprised. Instead, get comfortable with fine tuning planters.

Weed Control

Early emerged weeds are not usually growing as actively as those that emerge after mid-May. Pay attention to weed size, growth rate, and populations. Watch emerged weeds. Every day you delay a post application is to your advantage.

If moisture is short, weed growth is going to be affected. Once adequate moisture is received, a new flush will occur. Try to time your first application for your largest flush even if you let early emerged weeds grow freely.

No-Till Fields

Scout fields. We are beginning to see populations of bean leaf beetles, grasshoppers and slugs, none of which are at treatable levels. Over the last few years, no-till fields have continued to be the problem fields or the ones with the most obscure problems.

 

 

Department of Plant and Soil Sciences
Box 9555
Mississippi State, MS 39762

Will McCarty, Ph.D.
Extension Leader

A black line that separates the body text from footer information