NDSU Crop and Pest Report

Plant Science


ISSUE 6  June 6, 2002

 

REPLANTING DECISION IS FUNCTION OF DATE AND STAND

The decision of whether to replant a row crop with a reduced stand is a function of the calendar date plus the stand that is available. Drought, wind, hail and cutworm activity have all taken their toll in reduction of row crop stands.

Reduction in stand is the major factor in deciding to replant row crops. As we move later in the season, the decision of how much stand to keep changes, because if we tear up the field and reseed, the late plantings have much less yield potential.

With corn, around June 10, with stands of only 12,000 plants per acre, we probably would want to tear it up and replant to a crop like sunflower, that can be planted at this date and still mature. By June 15. The decision may be to keep a stand of 12,000 to 14,000 plants per acre because it is too late to plant an alternative.

Uniformity of stand is the key to evaluating a poor stand. If there are no large skips in the field, fairly low populations of soybeans, dry beans and even sunflower can still maintain yields. These plants have the ability to branch or flex and fill in space. This is not true with corn and weeds become a bigger problem.

With 50 percent a stand of soybean, dry bean or sunflower, you may want to leave them. If less, you may want to replant to an earlier variety or switch to another crop. About the only choice in the 3rd week of June is flax, early-short season sunflower or proso millet. Also, one must take into consideration the herbicide used in the prior planted crop and will it create a problem with injury to a crop change.

Duane Berglund
NDSU Extension Agronomist
dberglun@ndsuext.nodak.edu

 

SUNFLOWER - HOW LATE CAN WE PLANT?

Most years in North Dakota, a number of sunflower fields are planted late or replanted. The many reasons for this include: extremely cold or dry conditions, wind erosion, insects (cutworm), diseases, hail and frost. This cold, dry year, 2002 will go down as one of the later planting of sunflower and several other crops.

Research on late planted sunflower has been conducted at various North Dakota NDSU Research Center sites. Results of these studies are shown below:

Table 1. Sunflower yields* (lb/A) as influenced by planting dates at Prosper and Carrington, ND.

Approximate
planting date

Hybrid

 

% oil

SW101**

894

June 1

2046

2087

43.9

June 15

2323

1891

44.1

June 30

1692

1076

40.5

July 15

312

123

33.9

* Average 3 years, 2 locations
** Sunwheat 101 - early semi-dwarf sunflower

Table 2. Sunflower oilseed yields* - Early vs. late planting

Planting time

 

Langdon

 

Minot

Mid May

1828

1632

Early June

1179

1368

 

diff.

649

diff.

264

* 5 year ave. Yields - lbs/A

When planting sunflower late (after June 10) itís suggested to plant early maturing hybrids. Selection of short season sunflowers will increase the chance of reaching maturity in the northern areas of North Dakota and Minnesota. Planting of non-oilseed or confectionary sunflowers is discouraged in June.

Duane Berglund
NDSU Extension Agronomist

dberglun@ndsuext.nodak.edu

 

FORAGE OPTIONS - WARM SEASON GRASSES

Hay and certain forage supply may be short in 2002 with the early cold and continued dry growing conditions. This first cutting of alfalfa and alfalfa-grass harvest appears to be much below average yield potential. Emergency hay crops to consider include sudangrass, sorghum, sorghum x sudan hybrids and millets.

Planting dates for crops such as hay millets, sundangrass, sorghum, sorghum x sudan is mid to late June. These crops are warm season grasses and develop rapidly under warm, moist conditions.

Foxtail Hay millets

Foxtail millets are grown primarily for shortseason emergency hay crops. Several landraces have been developed over time and are grown in North Dakota. Foxtail millet would be the best choices for emergency hay. Proso millets are slightly inferior to foxtail hay millets for hay.

Planting foxtail millets can be delayed until mid-June into the first week of July. When used for emergency hay production, late planting is usually encountered.

Plant into moist soil about 1 inch deep. Shallower seeding may be desirable on heavy textured soils with good moisture. Germination is fairly rapid but early seedling vigor is lacking.

Foxtail millets have low seedling vigor and in general are poor competitors with weeds. A seeding rate of 15 to 30 pounds per acre is recommended. The higher rates are recommended in eastern North Dakota with the higher rainfall potential. In western North Dakota, 15 pounds is adequate on weed free fields.

Harvest millets for hay in the late boot to early bloom growth stage. Any delay after full head emergence will reduce quality. Bristles become hard as maturity approaches and may cause sore mouth, lump jaw and eye infections when fed to livestock. Hay protein content is highest when the ratio of leaves to stems is high. Curing foxtail millet requires attention as light stands tend to sun dry rapidly after cutting, while heavy stands, especially of the German type, cure at a slower rate. If expected yield levels are greater than 1 Ĺ tons per acre, crimping will help the curing process. Potential yield of foxtail millet has is influenced by moisture relationships. Research trial yields from North Dakota Research Centers ranged from 2.1 to 3.2 tons/acre, with German millets having the most consistent yields for the hay millets.

Sundangrass and Sorghum - sudan crosses

The best time to plant sudangrass or sorghum - sudan crosses is late May or early June. If emergency forage is required, planting can be delayed until late June. Forage yields will be reduced with late planting.

The seeding rate varies considerably depending on the sorghum type. Sudangrass and sorghum-sudan crosses in 6 to 7 inch row spacings should be seeded at 25 to 30 pounds per acre. Forage sorghum varieties, hybrids and crosses in 30 inch or wider row spacings should be seeded at 5 to 8 pounds per acre. There has been some information from commercial sources suggesting much lower seeding rates. This may be true for some specific hybrids, but low seeding rates may result in thin stands and lower forage yields. A well prepared, firm, moist seedbed is best, although acceptable stands may be established with stubble-planting equipment. Plant 1 to 1.5 inches deep on medium and heavy textured soils and 1.5 to 2 inches deep on sandy soils.

Both Piper and Trudan are older traditional varieties of sudangrass. New sudangrass varieties with "BMR" (Brown Mid Rib leaf characteristic) are now available and have shown to be of better feeding value than the older traditional varieties. Seed may be difficult to locate but can be found with some searching.

A harvestable hay crop 50 to 72 inches tall can be anticipated in about 60 to 75 days after emergence depending on environmental conditions. Under good moisture conditions, sudangrass can grow to 6 to 8 feet tall, but forage quality decreases with advancing maturity. An early harvest (end of July or very early August) will normally permit a second harvest and maintain a higher forage quality.

Be careful when harvesting sudangrass for hay to make sure the forage is dry. The coarse stem will often retain enough moisture to cause the hay to mold even though it appears adequately dried. Always use a hay conditioner to crimp the sudangrass stem to enhance drying. When tall material is harvested, reduce the swather width by half to reduce the quantity of material in the windrow.

Sudangrass is also used as a warm-season pasture. When used as pasture, however, there is potential for HCN or prussic acid poisoning. Only graze once the crop is 20-24 inches or taller as a minimum for safety to livestock. Donít graze if sudangrass is under any moisture stress. HCN is not a problem in sudangrass hay.

 

Warm Season - Forage Trials - 2001

 

Yield (tons/acre DM basis)

Variety

Carrington*

Dickinson*

Langdon

Williston

Minot

German millet

4.0

1.9

3.4

2.7

3.0

Manta millet

2.2

1.9

2.4

2.6

3.3

Red proso millet

2.4

1.9

2.1

2.1

3.6

Siberian millet

2.1

1.9

2.5

2.6

3.1

Tifleaf pearl millet

2.3

1.9

2.9

1.6

4.9

Piper sudangrass

5.5

2.4

3.6

2.1

4.3

Forage sorghum

8.1

2.2

4.4

2.1

7.6

Sorghum x sudan

5.2

2.3

3.8

2.4

4.2

Mean

2.9

2.0

3.1

2.3

4.3

LSD 5%

0.4

--

0.7

NS

--

* two harvests.

Warm Season - Forage Trials - 2001 (continued)

 

Yield (tons/acre DM basis)

Variety

2001 average (all loc.)

3 year average (all loc.)

German millet

3.0

3.2**

Manta millet

2.5

--

Red proso millet

2.4

2.1

Siberian millet

2.4

2.3

Tifleaf pearl millet

2.7

2.8

Piper sudangrass

3.6

--

Forage sorghum

4.9

4.8

Sorghum x sudan

3.6

3.1

Mean

--

--

LSD 5%

--

--

** two year average.

Duane Berglund
NDSU Extension Agronomist

dberglun@ndsuext.nodak.edu

 

FROST VS. DROUGHT EFFECTS IN ALFALFA

Several callers have asked if frosted alfalfa, which occurred several times in May, should be clipped in order to enhance regrowth. No! This question is confusing frost and drought effects.

Spring growth of established stands of alfalfa can be killed with a spring frost in 15 to 20 degrees F range depending on how long the minimum temperature remained. When alfalfa is frosted at 6 to 8 inches of growth, the stem bends down so that the apex is facing the ground. If the stem straightens up when above-freezing temperatures return, the stem is alive and will continue active growth as the climate permits. If the stem does not straighten up, the stem has been killed and will die. If this case occurs, the decision is whether there is enough growth to warrant a harvest. If not, just let the plant recover from the crown tissue just as if it was the first growth in the spring or from any active bud on the lower stem.

Drought-stressed alfalfa is another story. If alfalfa basically stops growing at six inches or more due to drought, initiates a bud, and then a significant rain (say a 1 to 2 inches) occurs, the alfalfa plant will continue growth. But this growth is continuation of flowering and seed production, which will take several weeks to complete with only minimal additional dry matter laid down. In this case, harvest or clipping the stand (depending on how much forage is standing) will force the plant to initiate new growth and permit significant forage production if the climate permits.

Dwain W. Meyer
NDSU Professor, Forage Management

dmeyer@ndsuext.nodak.edu


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