ISSUE 4   June 5, 2008

ALFALFA HARVEST IS NEARING

Alfalfa harvest is just around the corner for those lucky enough to have reasonable rainfall or for irrigated producers. The cool weather has delay the first harvest this year since we typically harvest the last days of May in warm early springs or the first days of June in average years. Alfalfa at Fargo on dryland is only 13 to 15 inches tall on May 30 when it typically would be 24 to 28 inches tall.

Use plant height to determine when to harvest the alfalfa if the weather cooperates. Plant height affects forage quality of alfalfa more than plant maturity (Table 1). As the plant grows taller, the relative feed value decreases within each maturity stage due to increasing fiber and lignin laid down to keep the plant erect. Likewise, as the maturity stage increases, forage quality decreases, but not as fast as with plant height. For example, alfalfa at the early bud stage decreases in relative feed value from 220 at 16 inches of growth to 156 at 35 inches of growth or 64 units. At 16 inches of height the relative feed value also decreases from 220 to 186 or only 34 units as the maturity increases from early bud to late flower.

Optimum harvest maturity is when prime hay of 150 to 170 relative feed value can be obtained in the bale. The values presented in Table 1 are for alfalfa standing in the field. Forage quality also decreased from harvesting losses, primarily leaf lost. It is estimated that 20 to 30 units of relative feed value are lost during harvesting with good technique; therefore, harvest must begin at 170 to 180 estimated relative feed value to get prime hay in the bale. If alfalfa reaches only 16 inches in height, optimum harvest maturity is late flower (defined as the most mature stem with two or more nodes having an open flower), which will likely be the case in drought affected areas this year. If alfalfa reaches about 28 inches common under irrigation or with good rainfall, the optimum harvest maturity is at the very-late vegetative stage.

Alfalfa growth has been delayed by the cold weather this year so the plant height is less than previous years, but the maturity stage is less affected by the cold weather. Forage yield increases with increasing maturity, so delaying harvest to a more advanced maturity will increase forage yield. Therefore, the optimum harvest maturity will be latter this year than previous years. Last year the first harvest was taken at medium-bud growth stage at Fargo, which was later than the previous three years when harvest occurred at the very-late vegetative to earliest-bud growth stage in order to harvest prime hay.

The PEAQ system described in the previous paragraphs works best on the first harvest when the maturity of stems is more uniform. The PEAQ system does not work well for the second and third harvest due to the most mature stem occurring much earlier than the average crop. But the same principal applies, the taller the alfalfa in general, the optimum harvest maturity occurs at an earlier growth stage.

The optimum harvest maturity for the second, third, and fourth harvests occurs at more advanced growth stages than the first harvest. The typical maturity at which we harvest alfalfa at Fargo has been late-bud, 20 to 30% bloom, and regrowth initiating at the bottom of the canopy in the second, third, and fourth harvests, respectively. In a dry year like 2006, the maturity at harvest was late flower (nearly 100% bloom) for the second and third harvests.

Table 1. Estimated forage quality of alfalfa by the PEAQ system

Plant height

Stage of most mature stem

Early bud

Early flower

Late flower

inches

relative feed value

16

220

208

186

20

213

191

171

25

191

172

155

30

173

156

141

35

156

150

129

 

WARM-SEASON ANNUAL FORAGES

Drought in central and western North Dakota has reduced the forage yield of perennial forages like alfalfa, alfalfa/grass mixtures, and pure grasses like brome and crested wheatgrass.

Conservation reserve program (CRP) acreage was recently released, which should help producers meet their forage needs. If there is inadequate CRP acreage in your area or a higher-quality forage is needed, consider warm-season annuals.

Common warm-season annuals are foxtail or proso millets, sudangrass or sudan/sorghum crosses, and pearl millet. Pearl milletís major advantage is the lack of HCN or prussic acid, but pearl millet is the poorest choice for North Dakota. Forage yields in southeastern North Dakota have been equal or maybe slightly greater than sudan/sorghums, but generally lower yielding than the sudan/sorghums in the rest of the state.

Forage yield of foxtail or proso millet, sudangrass, and sudan/sorghums under a one-cut systems have been fairly similar with maybe a slight advantage to the sudan/sorghums. Forage yield will be substantially greater with sudangrass and sudan/sorghums than foxtail or proso millets when rainfall permits a second harvest. The major disadvantage of sudangrass and the sudan/sorghums is the presences of HCN (hydrocyanic acid). Under drought conditions, HCN can build to potentially toxic levels when rainfall restricts growth to less than 20 inches. If the sorghums are hayed under these conditions, be sure to get the forage tested for potential problems. Rarely will HCN be a problem in a hay or silage crop if the plant height is greater than 20 inches since maturity and the drying for hay and handling the silage after fermentation reduces the HCN in the forage. Grazing sudangrass or sudan/sorghums less than 20 inches under drought is the major concern for possible HCN poisoning.

Piper sudangrass has been the standard sorghum used in North Dakota. Piper is an open-pollinated sudangrass known to be lower in HCN. Sudangrass hybrids and sudan/sorghums will be higher in HCN. In recent years, the BMR (brown midribbed) sudangrass, pearl millet, and sudan/sorghums have been released. The BMR character reduces the lignin content of the plant, which increases the digestibility and animal performance compared with non BMR species. The major rap on BMR sorghums or pearl millet has been that they are considered lower yielding, but preliminary data in North Dakota does not show this yield drag. If considering a sorghum, I suggest considering the BMR types.

A major problem with sorghums and pearl millet is getting good-quality hay. The sorghums should be hayed at 2.5 to 4 feet in height. The large stems at this height makes it very difficult to get proper drying to preserve the forage in the bale. Always use a hay conditioner to either crush or break the stem to speed drying and be careful to reduce the size of the window, especially when the crop is heavy, to facilitate drying. Pearl millet does dry better than the sorghums since it has a greater leaf to stem ratio compared to the sorghums.

Foxtail millet, both siberian and german, and occasionally proso millet are commonly grown in North Dakota as emergency forage crops. Manta siberian millet is the most common species grown due to its drought tolerance. German millet is slightly latter maturing and higher yielding under good rainfall. Forage quality of foxtail millets tends to be the poorest of the common warm-season annuals and they may cause a diuretic action in livestock. Foxtail millets should never be feed to horses. Proso millet, commonly used as a grain crop, sometimes is harvested for forage. Due to the grain, forage quality is higher in proso than foxtail millets.

Cool-season forages like oat, barley, and triticale probably should not be planted in June or July. The warm summer temperatures forces maturity and reduces tillering causing poor forage yields. If considering a cool-season forage, Paul oat has performed the best. Recent Wisconsin data indicates that a late seeding of oat (about August 1 to 15) produced 1 to 2 tons of hay with good quality. If rainfall is inadequate to seed warm-season annuals, consider this late seeding if soil moisture is adequate.

Dwain W. Meyer
Extension Forage Specialist
Dwain.Meyer@ndsu.edu

 

CROP SCOUTING

Most of the field crops have been seeded and the attention is shifting to in season crop management. Scouting is an important part of the crop production decision making process. It is essential to have a good understanding about the weeds, insects or diseases present in a field in order to take proper action. Driving by a field and observing from the road will not provide the correct information needed for the right management decision. When scouting enter the field at different points during the summer so the sampling locations will reflect the whole field. It is important to stop and inspect the crop at multiple locations in the field away from the head-lands.

In order to obtain a good record during the season write down the observations about weeds, insects and diseases found, preferably on a map or a drawing with the field boundaries. If problems only occur in small areas you can consider spot application of pesticides instead of applying over the whole field. As Global Positioning Systems become more affordable it may be a good idea to write down the global coordinates of problem areas. Later in the season a repeat visit to the exact same location can be made.

When scouting cover as much of the field as possible. Try to cover areas of the field where indications of a pest are likely. For instance grassy areas at field margins might be the place to find grasshoppers. Weed and insect management decisions are generally evaluated on a plant or insect per square yard basis. Know the density of the pest in order to determine if an economic threshold is reached.

It is important to evaluate the plant stand early in the season. To determine plant stand, select the area of the field with lowest plant stand, and make at least 10 random stand counts in an area where the stand is reasonably uniform. Also take plant stands at locations with normal stands. Use a tape measure and mark off 1/1,000 of an acre for each count. The lengths of rows equal 1/1,000 of an acre with different row widths is indicated in Table 1. Multiply stand count per length of row by 1,000 to obtain stand per acre.

Table 1. Length of row to equal approximately 1/1,000 of an acre

Row Width

Length of row to equal 1/1,000 of an acre

30 inches

17 feet and 5 inches

20 inches

26 feet and 2 inches

15 inches

34 feet and 10 inches

10 inches

52 feet and 3 inches

7 inches

74 feet and 9 inches

Another method used to evaluate plant stands in drilled or narrow row canola, soybean, or other crops is to use a hula hoop. Throw the hoop randomly into the field and count the number of plants inside the hoop. Multiply the number of plants by the multiplication factor found in table 2 to obtain the plant population. Use the average of at least five to ten observations per field to estimate the plant stand. For instance, if a 30 inch hoop is used and 17 plants are counted the stand per acre would be 17 x 8,900 = 151,300 plants per acre.

Table 2. Multiplication factor for different hoop diameters

Hoop diameter in inches

Multiplication factor

30

8,900

32

7,800

34

6,900

36

6,200

38

5,500

When the plant stand is low and uneven record the possible causes so next year corrective action can take place. It is very difficult to determine a cause for poor stands at the end of the season. The recorded plant stand will provide baseline information for the remaining of the season. Drought, disease, hail and other factors may reduce the plant stand during the season, but you would not be able to document these plant stand losses without an early season stand count number. Good scouting methods, proper identification of problems and diligent recording of the findings will greatly assist in making the correct management decisions.

Hans Kandel
NDSU Extension Agronomist Broadleaf Crops
hans.kandel@ndsu.edu

 

FROST DAMAGE IN CEREALS

There are reports of frost damage, some severe, after the cold weather that moved through the region last week. Frost is generally most problematic in low lying areas as cold air tends to flow towards the lowest elevations. When assessing frost damage, visit the lowest spots of your farm first. Many factors affect how sub-freezing temperatures impact a crop; temperature alone does not always accurately predict damage.

Some of the main factors that influence frost damage in cereal crops are: crop tolerance, growth stage, moisture content of the soil, duration of the sub-freezing temperature, location in the field, and environmental conditions before the occurrence of the sub-freezing temperature.

Cereal crops are generally considered to be frost tolerant early in their growth cycle. There is considerable variation for tolerance between crops, however. In general terms for cereals crops in a similar growth stage, winter rye is the most tolerant followed by winter wheat, oats, barley, spring wheat, and finally corn (least tolerant).

Cereals tolerate frost early in the season relative to broadleaf crops because their growing points remain below the surface of the soil for several weeks after emergence and are therefore protected from the extremes in the temperature of the air above. This does not mean that leaf tissue will not be burned or damaged, but that the potential for relatively normal regrowth is high. In small grains the growing point extends above the soilís surface at about the 6 leaf stage or just prior to jointing and in corn at about the 5 leaf stage. Fortunately, all of the spring sown cereals in the state were still relatively young and their growing points were below the soilís surface during last weekís cold weather. Winter wheat, however, has started to joint in parts of the state and is potentially more susceptible to frost damage than its spring sown counterpart. I would recommend that you carefully inspect growing points in your winter wheat if you had temperatures below 25 degrees for any extended period of time. The growing point is more susceptible to damage than leaf tissue during jointing. A damaged growing point will appear brownish or water soaked. A dead leaf may appear in the whorl if the growing point has been damaged. Prolonged (or very low) sub-freezing temperatures can kill growing points of cereal crops even if they are below the surface of the soil. Corn is the most sensitive and temperatures of less than 28 degrees can be lethal.

Temperatures change more slowly in wetter soils than in dryer soils. Therefore, there is more risk of low temperatures killing plants if your soils are also dry. Plants are capable of hardening themselves against freezing and plants that had previously been exposed to near freezing temperatures are more likely to tolerate lower sub-freezing temperatures than those that have not.

Inspecting for damage

Foliage that has been damaged by frost will initially appear yellow and within a few days turn black usually towards the tips of the leaf first. If the growing point was not damaged, after 3 to 5 days of reasonably warm weather, new growth should appear from the whorl. If this occurs, then you can be assured that the growing point was not killed. Loss of leaf tissue at this early stage will have little if any effect on yield. For corn that has not yet emerged, I would suggest that you dig up a few seeds to check for germination and to see if the emerging seedling is viable. Seeds that had not germinated will not be adversely affected, but emerging seedlings could be killed if soil temperatures were very cold. Nevertheless, corn seedlings that are still below ground are rarely killed by cold soil temperatures! If you have winter wheat that was beginning to joint, I would also advise you to check the health of its growing point if you had visible damage to emerged leaves.

Joel Ransom
Extension Agronomist - Cereal Crops
joel.ransom@ndsu.edu


NDSU Crop and Pest Report Home buttonTop of Page buttonTable of Contents buttonPrevious buttonNext button