Agronomy Notes

July, 2001

Contents

 

COTTON

Dr. Will McCarty

According to the June 29 Crop Report, Mississippi cotton growers have planted some 1.7 million acres of cotton, up 400,000 acres from the 1.3 million planted in 2000. The last time Mississippi cotton growers planted 1.7 million or more acres was in 1974, in response to the high prices of 1973. The 1974 crop got off to a cold wet start and a cool finish, resulting in a statewide average yield of only 448 pounds per acre. Prior to 1974, Mississippi growers had last planted 1.7 million or more acres in 1955, with an average yield of 570 pounds per acre. Prior to 1955 Mississippi growers planted over 2.0 million acres per year.

The 2001 cotton crop is in a wide range of growth stages for this time of year. Entering July, the crop ranges from pre-square to near mid-bloom, from clean and uniform to near grownup and irregular. Fruit retention is variable, but adequate in most fields. Overall fruit retention going into July is slightly lower than desired, but can be managed.

Irrigation-Implement cultural practices such as side-dress fertilizer application and layby herbicides promptly to clear the way for timely irrigation. Be prepared to begin watering at or about first bloom if needed, and water as needed until open boll stage. Take all measures to ensure you are ready to start on time. Always consider soil moisture as you time irrigation; checking the soil can help prevent your getting behind with limited output systems.

Plant Mapping/NAWF - Determining the number of nodes above the first position white flower (NAWF) can be an important management practice. To do this, count the terminal as zero and count down the plant until you find the node with a first-position white bloom. NAWF will generally be 8 to 9 at first flower, and will decrease as the bloom period progresses and boll load increases. As the plant reaches 5 NAWF, it is considered in cut-out.

NAWF greater than 9 at first bloom indicates that vegetative growth may be out of control. If this condition exists, find out why. Consider factors such as variety, square set, moisture, fertility and weather factors. If excessive vegetative growth looks like a potential problem, you may need to apply a PGR such as PIX Plus, PIX or other mepiquatchloride (MC) product.

Cotton should maintain a NAWF of about 7 through the first 2 weeks of bloom, and then decrease as it approaches cutout. Although changes in NAWF during this period may be related to weather or to changes in fruit retention, NAWF can be a good tool in PGR decisions.

Square retention - Square retention on first positions above the white bloom should be relatively high, in the range of 90 to 95 percent or more. At minimum, the square set above the WF should be above 80 percent. As the crop progresses, the white bloom will move up the plant and slowly catch up with the terminal until the crop reaches cut-out, which should occur when nodes above the white bloom reach about 4 to 5. As the bloom moves up the plant, keep up with boll retention on the first position of the branches below the white bloom.

Considerations in using mepiquatchloride (MC) PIX Plus, Pix, Mepix, Mepachlor, etc. Moisture supply and heat generally result in vigorous growing conditions early in the season. It is important to monitor and manage plant growth. Plant height may easily exceed 30 inches at early bloom in some fields. Herbicide injury and drainage problems may affect this in many fields. Plants need adequate vegetative growth to support the soon-to-develop boll load, but excessive growth can have a negative impact, especially on fruit retention. A history of vigorous early season growth and the current crop condition may be the major factors in helping select the proper program, if MC is needed at all.

Several components of a crop monitoring program can help with MC decisions. One of these is plant vigor, measured as inter-node lengths (height:node ratio, HNR). More information is needed to fine tune this system, but it has tremendous potential. HNR will vary, but should be in the 1.5 to 1.8 range during mid- to late square. If the HNR exceeds 1.8 and growing conditions are good, perhaps MC is in order. HNR above 2.0 at first bloom indicates the plant has tremendous vegetative power, and plant growth and fruit set must be closely monitored and managed.

Another measurement being developed is Length:Node Ratio-Top 5 (LNR-T5). This measurement, along with fruit set and NAWF, can be helpful in plant management. It is simple and can be measured quickly. The top five inter-nodes represent the area of the plant where vegetative expansion is occurring. To take this measurement, count the uppermost unfurled main-stem leaf as 0 (zero) and count downward, 1-2-3-4-5. Measure and divide the length by 5. The LNR-T5, often similar to the HNR, is unaffected by earlier growth, and is an accurate refection of current growth. At early bloom LNR-T5, should be from 1.5 to 1.8. If LNR-T5 is greater than 1.8, the potential for rapid vegetative growth exists; monitor NAWF and fruit set and make PIX decisions accordingly. As the NAWF progressively gets smaller, the LNR-T5 should also be getting shorter if the plant has an average boll load of about 50 percent retention of first position sites. As fruit retention goes down, the plant will want to grow more vegetatively. The LNR-T5 will therefore increase, and with it, the likelihood of a positive response to MC. If first position boll retention is around 55 to 60 percent and the LNR-T5 is less than 1.5, consider factors such as previous MC used, NAWF, soil moisture, etc., and then make a decision.

Monitor your fields. Of the measurements discussed, fruit retention and NAWF are the most significant. By carefully monitoring development, you can make informed decisions regarding production practices.

Across the Cotton Belt, the most consistent method of using MC is an "at-bloom" treatment, followed by another application 10 to 14 days later. Remember, though, to make all decisions on a field-by-field basis, based on the needs of the cotton in that field. Avoid automatic treatments.

RICE

Dr. Joe Street

Rice is a little earlier than normal and is progressing well. Early rice will probably be heading between July 10 and 15, about a week ahead of normal. Overall, the crop looks good without significant production problems.

This crop is somewhat more grassy than usual. Facet post-flood has performed well, especially in situations where a flood deep enough for Ordam cannot be maintained. Aim has been added to the mid-season weed control arsenal; Aim has good activity (similar to Blazer) on hemp sesbania and is rated fair to good on large morningglory. Grandstand will control larger morningglories than Aim but it sometimes misses hemp sesbania (coffee bean). The addition of one pound of propanil enhances Grandstand activity on hemp sesbania.

Blast Alert - So far, blast has not been observed in Mississippi, although blast has been reported in Arkansas on Wells and is suspected in Louisiana. Less than 10 percent of Mississippi's acreage is in Wells, but blast could become a problem on other varieties under heavy disease pressure. Mississippi rice crops have had some suspicious leaf spotting, but it was not blast. Watch your crop closely if you have Wells or Jefferson. No blast problems have been observed on Priscilla or Cocodrie, although they are rated moderately susceptible. If the weather is not hot and dry, blast could become a problem.

With hot and humid weather patterns, expect sheath blight problems to increase. With Lemont and Cocodrie, treat at 35 percent infestation level if the disease appears to be moving up the plant and weather predications are favorable for sheath blight. With current rice prices, sheath blight should be moving up the plant fairly rapidly before a fungicide is applied. Except in very severe cases, you will not get a good return on investment with a sheath blight treatment with Priscilla and Wells. With Priscilla, you can expect about half the response to a fungicide that would be seen in Lemont or Cocodrie.

With Priscilla , Cocodrie, and Cypress, it is good insurance to treat for kernel smut especially under high nitrogen fertilization. Wells and Lemont are rated resistant to kernel smut and treatment is not generally necessary except under very high fertilization. Tilt applied at late boot appears to be the most active against kernel smut.

Rice stinkbugs are always a threat to rice at the heading stage. The adults migrate to rice soon after it begins it head. Both the adults and nymphs feed by sucking juice from the developing kernels. Feeding during the soft dough stage can cause "pecky" rice. Start scouting fields when rice reaches 10 percent heading and continue scouting until rice is mature.

So far, Roundup (glyphosate) drift has not been a serious problem; only three fields have reported suspected drift. If you suspect glyphosate drift, especially around mid-season to early boot, take leaf samples and freeze them as soon as possible. At heading, if symptoms such as deformed heads occur, you will have the samples for analysis. Drift at mid-season may or may not produce symptoms until the rice heads, and even then it is sometimes difficult to see symptoms other than reduced yields.

SOIL AND NUTRIENT MANAGEMENT

Dr. Larry Oldham

(Writer's note: Once in a while I get to write about agronomy, but once more, not this month. LO)

Producers and farm supply outlets mention they are seeing a new type of unsavory activity concerning nitrogen fertilizers: use of these fertilizers in manufacturing crystal methamphetamine.

It is well known that certain individuals will go to great lengths to procure anhydrous ammonia fertilizer for making crystal methamphetamine. Horror stories abound from around the state; one such case in south Mississippi during 2000 snarled traffic on I-55 for hours.

Law enforcement officers indicate that the illegal chemists have derived other production methods that involve less dangerous nitrogen fertilizers. Incidents have been reported in both north and south Mississippi, but it does not appear to very widespread at this time. While the fertilizers themselves are not as dangerous to obtain and transport as anhydrous, the processing of these other fertilizers produces significant heat that may present a problem if not handled safely.

CORN

Dr. Erick Larson

Corn Borers - The peak flight of second generation corn borers was expected around July 1 for most of the Mississippi Delta. A relatively heavy infestation of first generation corn borers was also found during June in Alcorn county in northeast MS. Growers in northeast MS should also be scouting for this potential pest, despite their historically having been limited to the Delta region. Although pheromone traps are a good tool, do not rely just on pheromone trap counts or your neighbor to determine an insect threshold: you need to intensively scout your fields to quantify the infestation. Late-maturing corn will be more likely to sustain corn borer damage than early-maturing corn, because it is more attractive to corn borers (more succulent vegetation) and damage occurs when plants are more susceptible to physiological stress (early grain filling stages). Heavily infested fields should be harvested as early as possible so that harvest losses (lodging and ear drop) are minimized.

Irrigation termination -One common irrigation error is terminating irrigation before physiological maturity (black layer) occurs. Corn planted during the suggested planting dates normally reaches physiological maturity beginning about the last week in July. Early irrigation termination will accelerate maturity, prohibiting kernels from reaching their full potential size and weight. Although corn's water use will drop to about one inch per week at the dent stage and steadily decline until physiological maturity, this is not the time to terminate irrigation. Potential kernel weight is only about 75 percent complete at the dent stage, and termination of irrigation at this stage can reduce grain yields as much as 15-20 percent. Continue irrigating until physiological maturity occurs. Producers using center pivot irrigation systems can compensate for reduced demand by applying less water, rather than decreasing frequency. Producers using flood systems can only decrease irrigation frequency to compensate for lower water demand.

Kernel maturation -Corn kernels continue to accumulate seed weight until physiological maturity is reached. Physiological maturity normally occurs about 60 days after silking or 20 days after denting. Hard starch begins forming at the kernel tip when denting occurs. This hard starch layer gradually progresses to the kernel base over the next 20 days. This progression may be monitored by observing the "milk line" on kernels; this is very important for irrigation scheduling. An abscission layer forms when the hard starch layer reaches the kernel base. Physiological maturity is signified by this black or brown abscission layer which is referred to as the "black layer." This abscission layer stops water and dry matter transfer into the kernel. Kernels will have a moisture content of 28-35 percent at this stage. The black layer may be found by shelling kernels from an ear and gently scraping away the seed coat to expose the abscission layer. The black layer formation occurs progressively from kernels at the tip of the ear to the base.

Check the milk line: Corn producers can monitor kernel maturity by observing the progression of the milk line. The milk line is the borderline between the bright, clear yellow color of the hard seed coat outside the hard starch layer, compared to the milky, dull yellow color of the soft seed coat adjacent the dough layer. To observe the milk line, break a corn cob in half and observe the cross-section of the top half of the ear (which is the bottom side of the kernels, the side opposite the embryo). If the milk line is half-way down the kernels, it will take about another 10 days to reach physiological maturity, since it takes about 20 days for the milk line to progress from the kernel tip to the base. Therefore, the field needs to irrigated enough to supply moisture for 10 more days.

SORGHUM

Dr. Erick Larson

Sorghum black layer - Grain sorghum physiological maturity is characterized by formation of a black layer similar to corn. However, the abscission layer is visible without scraping the seed coat. The sorghum black layer can be found at the kernel base opposite the embryo. Kernels at the top of the head mature first, followed by kernels at the base of the head. Seed weight accumulation is complete and moisture typically ranges from 25-35 percent when physiological maturity occurs.

SOYBEANS

Dr. Alan Blaine

Mississippi's soybean crop is progressing quite well. Approximately 40 percent of this crop is 20-30 days ahead of last year's production schedule, with the entire crop rated above average. It is still too early to make any yield predictions since the crop has 45 to 90 days until maturity.

For that portion of the crop that has starting blooming, it reached peak water demand at that time. If you allow the crop to undergo any stress, you will delay the maturity; this stress will translate into lost yield. If you can irrigate, once irrigation begins, stay on schedule. Do not use visual crop stress as a sign that you need to irrigate. Furrow, border and flood systems will need to be on an 8-10 day schedule. Pivots need to operate based on crop use of 1/4 inch per day.

Several calls have come in regarding plant growth. There has been a reduction in growth in many no-till fields. Additionally, because it is early, this crop has set a fruit load that has slowed plant growth. Some new growth may occur, but with some of the fruit loads being seen, additional growth may be minimal.

Various worm populations have been observed for well over a month. Although in some fields populations have been close to threshold, foliage loss has been minimal. The predominant species observed has been green clover worms. Identification is vitally important because cost of control varies considerably. With the high numbers of beneficial insects the current populations of green clover worms are being kept under control. If you find worms present, watch them closely. Beneficial insects may keep them in check, and spraying with certain materials this early could contribute to future problems.

The bulk of this crop has reached the time frame for using Dimilin/foliar fungicides. Not all fields are candidates for an application; fields that may still be candidates are Group V's and later plantings. This decision should be based on the maturity group, date of planting, rotation sequence, disease pressure, area of the state, past history, etc.

FORAGES AND PASTURES

Dr. Malcolm Broome

New Tall Fescue for Beef Producers

With an estimated 600,000 acres in Mississippi, tall fescue is clearly the most important perennial, cool season grass, but it is not without problems. In the 1970's, Auburn University linked a disorder referred to as fescue toxicity with a fungus (endophyte) commonly present inside "Kentucky 31" tall fescue, the variety that comprises most of the Mississippi acreage. However, the crop's long term stand persistence, competitiveness, yield and summer survival are directly related to this fungal endophyte (Neotphodium coenophialum) living in the fescue plant.

New fungus-free varieties were developed that resulted in improved animal performance; these varieties did not adapt to the management given the fungus-infected fescue. This resulted in many acres of lost stands and a general disregard for use of the fungus-free fescues in the mid 1980's.

It now appears another breakthrough has occurred in the fescue fungus scenario. Scientists studying the fescue endophyte learned that it produces a number of different naturally occurring chemical compounds (alkaloids). The fescue-fungus alkaloid was found to have both helpful and harmful complexes. One alkaloid (ergovaline) resulted in fescue toxicity while another alkaloid (peramine) is thought to give the plant stress and pest resistance. Spurred by this data, further studies found there are different strains of the fungus, with some producing larger amounts of the particular alkaloids. This explains why different fields of tall fescue seem to be more harmful than others.

Researchers at Ag Research Grassland, New Zealand identified a group of non-toxic endophyte strains and were able to insert them into elite cultivars of fescue. Under an agreement with Pennington Seed Company, this non-toxic endophyte technology (trade named Max Q) was inserted into endophyte-free Jesup and Georgia 5 tall fescue varieties by Dr. Joe Bouton at the University of Georgia and Dr. Gary Latch at Ag Research. Max Q endophyte technology gives these two varieties stand persistence and improved animal performance. Jesup is the preferred variety for the north half of Mississippi.

The following data was collected this year from producers' fields in Smith, Jones, Marion, and Walthall Counties:

MAXQ FESCUE DEMO FIELDS - 2001
Variety - Georgia 5
Data by Dr. Malcolm Broome, MSU Extension Forage Spec.

Harvest Dates (lbs.DM)

Location

March 6-7

April 10

May 11

Total Yd

Jones

738.8

1693.3

785.8

3217.9

Marion

847.5

2092.3

1358.3

4298.1

Smith

1340.1

1238.7

2167.9

4746.7

Walthall

1477.8

1559.3

690.2

3727.3

Mean

1101.1

1645.9

1250.6

.

Total Mean

.

.

.

3997.5

Stand survival this fall (2001) will be the key to determining how well adapted this fescue is in the area of the state normally not considered for fescue production. After two years of grazing pregnant mares on MaxQ at MSU, research has also shown no problems for these mares in foaling. Therefore, MaxQ is now recommended for horse pastures, also. Survival from the 2000 drought was as good for MaxQ as for endophyte-infected fescue.

Contact your County Agent if you would like further information on establishment and management of fescue.

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

Will McCarty, Ph.D.
Extension Leader

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