Agronomy Notes

March, 2003

RICE
FORAGES AND PASTURES
SOIL TESTING
COTTON

 

 

 

 

RICE

Dr. Joe Street

Burndown herbicides: With the wet conditions we have had, many fields are still relatively free of weeds. Now is a good time to check fields and apply a burndown herbicide during the next few weeks if needed. An application of 2,4-D now, especially if you have curly dock, will reduce herbicide requirements later. If ryegrass is a problem, mix glyphosate with the 2,4-D. Harmony Extra is a good tank-mix partner with glyphosate for dock control, or Valor can be mixed with glyphosate to provide residual activity. Harmony Extra must be applied 45 days prior to planting and Valor must be applied 30 days prior to planting rice.

Planting Rates: With the introduction of new drills with more precise seed placement, it is time to try reducing seeding rates. We have always recommended planting 40 seed per square foot hoping to get 15 to 20 rice plants to emerge. With better seed placement, especially on good seedbeds, seeding rates can be reduced to about 30 seed per square foot. Rolling the field with a flat roller will increase seed to soil contact and increase emergence. Several growers are using wider drill spacing so they can drill soybean and rice with the same drill. With a 10-inch spacing, forty seeds per square foot are too many. See the table below for seeding rates

Seed per sq. ft.

30

40
Row Spacing (in.)

Seed per foot of row
6
15
20
8
20
27
10
25
33
In research plots, seeding rates as low as 20 seed per square foot produced the same yield as 40 seed per square foot. I am not yet ready to recommend planting 20 seed per square foot for conventional varieties, but I am confident that in a relatively good seedbed, planting 30 seed per square foot will work well. Hybrid rice should be planted at 30 pounds per acre, which is about 14 seed per square foot, which usually provides 8 to 10 plants per square foot. If you plan to reduce seeding rates, apply gibberellic acid and a good fungicide seed treatment as discussed below.

Seed Treatment: Fungicide seed treatments may increase emergence if you plant early in cool weather. Fungicides may not improve emergence if rice is planted when temperatures are favorable for rapid germination. Seed borne diseases such as Brown Spot can be controlled with Thiram. Pythium can be controlled with Apron XL or Aliegence. Maxim or Vitavax controls rhizoctonia but that is generally not a problem. Vitavax also has some activity on pythium.

Zinc seed treatment may help on soils with a pH greater than 7.5, a light silt loam soil, or newly land formed fields. We have generally seen little response to zinc on clay soils.

Icon seed treatment is very effective in controlling rice water weevil. It offers partial control of chinch bug but will not control a heavy infestation. Icon also offers control of some stem borers.

FORAGES AND PASTURES

Dr. David Lang

Coming Out from a Cold Winter -March is here and it's been a heavy hay feeding season due to the cold wet winter. It hasn't been this cold since 1996 so there are differences you'll need to watch for that we haven't seen in a few years. The wet fall caused a lot of ryegrass to be infected with gray leaf spot or 'Blast'. Plants which survived an encounter with this plant disease are still showing some lingering effects into February. It's a combination of the cold weather in December and January and a weakness due to the disease itself. A lot of ryegrass hasn't grown well this winter because of the cold weather, but if it was affected by Blast, it's had a double dose of difficulty. It's best to fertilize your ryegrass now with 50 to 80 lbs. of actual N per acre. March is a time when you may see a lot of yellow flowers in your ryegrass and other pastures. This is Yellowtop or Ranuculus. By the time you see the yellow flower it's too late to control it for this year with a herbicide. A pint of 2,4-D in December or January is the treatment you should plan for next year. Right now about all you can do, is clip it off. Yellowtop is slightly poisonous and it can cause an off-flavor in milk. Your cattle generally won't eat too much of it unless it's about all they have to consume.

Bermudagrass, dallisgrass, and bahiagrass are our subtropical summer grasses in most permanent pastures. They have good cold tolerance down to about 10o F, but they can suffer winter injury below this temperature which can result in some stand loss. Our cold snaps came following generally cool weather so most plants should have been ready to stand the single degree nights we experienced in January. Maintaining high to medium levels of soil test potassium (K or potash) is very important for winter survival of these summer grasses. Look for slow growth and some stand loss on summer grass fields where you've let the soil test K get too low. Hay production removes a tremendous amount of K from the soil. A ton of bermudagrass hay, for example, can contain 35 to 50 lbs. of potash per acre. If you have a three to 5 ton/acre hay harvest, it removes 100 to 150 lbs. of potash/acre! Most of our soils are not able to supply this much K for more than a couple of years, so if you are removing hay, plan on adding back potash. It comes as 0-0-60 fertilizer so it takes about 300 lbs. 0-0-60/ acre to replace the yearly removal of K in a 5-ton hay harvest. Check the soil fertility of a hay field with a soil test at least every two years. Pastures also need medium levels of K and P in the soil test to stay productive with long lasting, persistent stands of desirable forages, but the K removal is much less in a pasture situation. You can maintain adequate soil fertility levels in a pasture if you fertilize with P and K according to a soil test every 3-4 years.

Nitrogen fertilizer, however, is not determined by the soil test! Improved summer grass varieties grown for hay need 60 to 80 lbs. N/acre per cutting. Grass pastures will not be productive unless you provide about 1 lb. of N per day of growth or 50-60 lbs. N/acre every couple of months beginning in April. If you have legumes, they will provide about 50 lbs. N/acre for annuals such as crimson clover or up to 150 lbs. N/acre for a perennial like white clover. It takes a couple of years of legume growth to really see a benefit. Summer legumes which can be over-sown into summer grasses in March and April include annual lespedeza and alyceclover. They will add protein and improve digestibility of a summer pasture, but don't expect them to provide much nitrogen fertilizer for the summer grass. Their nitrogen will be released in the fall throughout the winter, and will benefit winter grasses. Likewise, nitrogen from the winter legumes is released in the spring and early summer, and will benefit the summer grass.

SOIL TESTING

Dr. Keith Crouse

We are still receiving samples with insufficient payment or without MSU customer identification form being completed. Even though the clientele may have an account with MSU-ES Soil Testing Laboratory they need an account with MSU Accounting Department in order to process samples as an account receivable. We are holding samples for processing until payment or MSU Account form is received for a period of time. Kept in mind we are separate from the nematodes and plant disease laboratory, therefore; we need separate payments for analysis. We appreciate your assistance with this matter.

Knowing the residual nitrate nitrogen of the soil may be useful, the test is only good for the nitrate nitrogen that is present when the sample is collected and has very little value unless the following items are considered.

  • Since nitrate nitrogen is lost throughout the year in Mississippi, take samples before nitrogen fertilizer application.
  • Samples must be collected deeper than 6 inches and to depths of 36 inches depending on the crop being grown. Samples need to be taken in 6-inch increment and need to be representatively collected in the field with the appropriate number subsample in order to make up one soil sample.
  • Research in Mississippi showed that nitrate nitrogen samples need immediately air-drying after taken. This can be accomplished by spreading the samples out in metal or plastic trays.

Soil testing laboratory at Mississippi State University can provide the results of nitrate nitrogen analysis if the appropriate information sheet is filled out and accompanies the sample(s). If you have a clientele that is interested in this service is $ 15 per sample.

COTTON

Dr. Will McCarty

Stale Seed-beds: Cool temperatures in January and February have, to some degree, delayed growth of many winter annuals. However, as day length begins to lengthen and average daily temperatures increase, expect to see a rapid explosion of vegetation where you may have thought none existed. In-fact, I expect to see additional emergence as soil temperatures slightly increase. It is a good idea to make burn-down applications before natural vegetation grows excessively large. This is especially true on heavy textured soils. There are several reasons for this which includes: 1) smaller vegetation is easier to cover and control with lower use rates of material. 2) Plants are perhaps the most efficient moisture pumps in existence and rapidly growing vegetation can dry seed-beds tremendously fast. If spring vegetation is allowed to dry out seed-beds, additional rain will be required before planting. This is especially true for narrow rows. A narrow row bed (30 -32 inches) contains less soil volume than a 38-40 inch row. The key is to let the vegetation get large enough to provide some soil cover but not large enough to be hard to control.

In many cases the use of a tank-mix including a residual herbicide may be advantageous. To assist in getting good burn down activity - the use of tank mixes is recommended. Seek good advice for each situation.

Planting Date: Determining when to plant is one of those situations where a little knowledge must be tempered with a lot of common sense. A general recommendation for planting date is when the soil temperature, at the two inch depth, is 68F and the five to seven day forecast calls for an accumulation of 50 to 60 DD60s. When does this occur? You won't know until after it happens, right? This date changes considerably depending upon yearly weather conditions. The following table will give you some "average" information regarding when those conditions may occur.

Thirty Year Average DD60
Accumulation
Stoneville, MS

April 9 - 15

28.7

April 16 - 22

45.6

April 23 - 29

48.4

April 30 - May 6

53.8

May 7 - 13

71.0

May 14 - 20

85.2
Common sense must apply but the long term average indicates that the last two weeks of April and the first two weeks of May are perhaps the most favorable for planting. Never set a calender date and start planting. Use soil temperature, soil moisture saturation and weather conditions as a guide. The first 24 to 36 hours a seed is in the soil is the most critical. If a cotton seed imbibes cold water (in the low 50'sF) root damage may occur and emergence will be significantly reduced. An emerged cotton seedling has a better chance of surviving adverse weather (cool front with an associated shower) than a sprouting seed. Remember - common sense must apply - look at the soil and weather and not be handcuffed to a particular calendar date.

Seeding Rates: Monitor seeding rates closely. Recent tendency has been to plant as thin as possible in an attempt to reduce per acre technology fee cost. To do this you will need to have a very firm understanding as to the quality of the seed you are planting. Be sure you know the actual germination and the cool germination of your selected seed lots.

This information is available upon request and can be useful. Good quality seed should have a standard germ of 80% or better and a cool test of 65% or better. The standard germ will reflect expected field emergence under favorable conditions while the cool germ is a better indication of expected field emergence under cooler and wetter conditions.

Consider soil conditions and seed quality and plant for a final stand of 3.0 to 4.0 plants per foot of row in 38 to 40 inch rows and 2.0 to 3.0 plants per row foot in narrow rows (30 to 32 inches). This usually translates to dropping about 4 to 5 seed as long as spacing is uniform.

Some tips for setting a planter are:

1. Use manufacture suggested settings only as a guide.

2. After settings are made by the use guide run the planter on a hard surface such as a turn row. Measure 20 feet and count the number of seeds and divide by 20. Check several of the units, not just one. Make any necessary changes for the planter to deliver the desired number of seed per row foot. Forget about pounds of seed per acre, concentrate on number of seed per linear foot of row.

3. Forget about running the planter in the field and digging up seed for the purpose of setting plant population. You will never find all of them and the cotton will be too thick. Only use the digging method to set planting depth.

Below is a table that converts plants per row foot to plant population per acre.

To determine seeding rates you will need to adjust this number by an emergence factor. For example: if you are planting in a 40 inch row and want a final stand of about 45,000 plants acre, from the table you will need an average of about 3.5 living plants per row foot. Adjust this number by actual germination and what you expect to get up. If that number is, for example 85%, you would divide 3.5 by .85 which would equal 4.l seed per foot. In other words, for that lot of seed, drop and average of 4.l seed per row foot for a final stand of 3.5 plants per foot, etc.

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

Will McCarty, Ph.D.
Extension Leader

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