eupdate Extension Agronomy

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1 411 Extension Agronomy eupdate 07/02/2013 These e-updates are a regular weekly item from K-State Extension Agronomy and Steve Watson, Agronomy e-update Editor. All of the Research and Extension faculty in Agronomy will be involved as sources from time to time. If you have any questions or suggestions for topics you'd like to have us address in this weekly update, contact Steve Watson, swatson@ksu.edu, Jim Shroyer, Crop Production Specialist jshroyer@ksu.edu, or Curtis Thompson, Extension Agronomy State Leader and Weed Management Specialist cthompso@ksu.edu.

2 eupdate Table of Contents 07/02/2013 Issue Alfalfa management during drought Interseeding winter cereal crops in bermudagrass pastures can double land use efficiency Holiday schedule: Comparative Vegetation Condition Report

3 1. Alfalfa management during drought Due to severe drought three years in a row, managing alfalfa has become very challenging in western Kansas. Proper management will be critical to maintain long-term productivity and profitability under these conditions. Even irrigation isn t able to compensate when the crop is under severe heat stress, with temperatures more than 100 degrees. Since alfalfa is a cool-season forage legume, it has a lower level of heat tolerance and water-use efficiency than warm-season forages. Although alfalfa has one of the deepest tap roots of forage crops, alfalfa becomes dormant under very high temperatures and drought conditions. Alfalfa yield from the first cutting this year was percent lower than normal, largely due to damage from spring frost and insects such as alfalfa weevil, aphids, and thrips; high temperature; and spring drought. After the first cutting, drought-stressed alfalfa grows very slowly and looks almost stunted (6-8 inches tall), especially alfalfa fields that were seeded last fall. Most drought-stressed alfalfa may accelerate its maturity process while stem internode growth is suppressed. This will result in reduced dry matter yield for the second cutting. One of the biggest concerns about drought-stressed alfalfa might be losing both forage yield and quality resulting from leaf loss. Plants may become dormant if severe drought continues over a long period. One big debate is whether drought-stressed alfalfa should be harvested or not. If alfalfa stands are so stunted that they would not yield enough hay for the second cutting to be economical, it would be better off to leave it uncut until the drought breaks. By doing so, alfalfa stands may be able to store more root reserves, which would help it cope with drought and regrow. If the alfalfa is tall enough to make it economical to make a second cutting for hay, it should be cut before it drops its leaves from the stress. Producers might be tempted to limit nutrient additions to stressed fields since alfalfa stands slow down their nutrient uptake during drought periods. It is, however, recommended to test your soil in spring or fall. If soil nutrient levels are low, the alfalfa will not be able to withstand drought stress as well as if soil nutrients are in the optimum range. When water is limited, irrigation priority should be given to the alfalfa fields that offer the highest economic return or to newly seeded fields. Another thing to be considered during drought is to scout for insects. When drought is severe, some insects such as leafhoppers and aphids migrate from rangeland to alfalfa or other forage fields in search of food sources. Therefore, scouting insects helps alfalfa deal with drought and lengthen the stand longevity. 3

4 Stunted alfalfa growth in Garden City. Photo by Doo-Hong Min, K-State Research and Extension. --- Doo-Hong Min, Southwest Area Crops and Soils Specialist --- John Holman, Cropping Systems Agronomist, Southwest Research-Extension Center --- Jim Shroyer, Crop Production Specialist --- Stu Duncan, Northeast Area Crops and Soils Specialist ---Doug Shoup, Southeast Area Crops and Soils Specialist 4

5 2. Interseeding winter cereal crops in bermudagrass pastures can double land use efficiency Bermudagrass is a warm-season perennial forage that can be very productive in southern Kansas when intensively managed. However, it has a relatively long period of winter dormancy and is often invaded by annual, weedy species during this time. While these weedy species produce some forage, their production is sporadic and their quality short-lived. Winter cereal crops such as wheat, rye, and triticale produce high-quality forage during the time period that bermudagrass is dormant. Fall-established cereals grown in the dormant bermudagrass sod can be used to lengthen the grazing season of the pasture. Cattle gains from rye interseeded into bermudagrass sod compared favorably with gains from rye grown in clean-tilled conditions, despite less forage being produced, due to better utilization. Land use efficiency nearly doubled when rye was no-till seeded into bermudagrass sod compared to growing each crop on separate acres. Species Any fall-seeded winter-hardy forage species adapted to the area could be suitable for seeding in bermudagrass sod. However, the earliest, most productive species would likely produce the most desirable results. Rye, wheat, and winter barley have similar forage yields when interseeded into bermudagrass sod, but yields are generally less than where winter cereals are grown alone in cleantilled conditions. Rye will generally produce the most early growth in the fall. Rye, wheat, and triticale have each resulted in satisfactory pasture gains. Seeding The cereal crop must be seeded early enough in the fall to enable establishment and provide growth for early grazing, but late enough that bermudagrass will not compete with cereal crop seedlings for moisture and nutrients. Mid-September is an optimum time for cereal seeding in southern Kansas. By mid-september, shorter day length and cooler nights have typically slowed bermudagrass growth, and the likelihood of fall showers usually enables cereal seedings to become established. Prior to seeding, the bermudagrass cover needs to be reduced by mowing, or whatever method is most practical, to no more than a few inches in height. For consistency in interseeding, a drill suitable for no-till conditions is required. Broadcasting seed on the surface of the sod will rarely produce an acceptable stand. A grain drill designed for tilled seedbeds may produce good stands when soil conditions, particularly moisture, are nearly optimum. However, since bermudagrass is efficient at extracting the limited amount of soil moisture typically available in late summer, bermudagrass sods are usually dry. Therefore, a heavy no-till drill may be needed to place the seed at the optimal 1-inch depth. Seeding rates vary by species because of differences in seed size and establishment rate. Stands optimal for forage production of cereals require, as a rule, 1.5 to 2 times the seeding rate used for grain production. When seeded in early September, adequate stands have been obtained by seeding 90 5

6 pounds/acre of wheat and 100 pounds/acre of rye or triticale. Later seedings or less favorable conditions may require higher seeding rates. Fertilization Bermudagrass is efficient at extracting and immobilizing soil nitrogen (N) as well as soil moisture. Producers will need to apply additional N to get good forage production from the cereal grains. However, timing of the application is critical so that N is available when the cereal crop needs it. Nitrogen applied too early in the fall when soil temperatures exceed 50 degrees may be immobilized in bermudagrass sod. It s best to hold off on applying N in the early fall, although cereal seedlings will likely suffer some N deficiency at that time because of this. Despite that, N application prior to late fall will likely not benefit interseeded cereals much. Late fall/early winter is the best time to apply N for the cereal forage. The efficiency of N applications at that time is quite good. Application of 45 pounds/acre of N in January produced almost as much animal gain as 135 pounds N/acre. Thus, the application of more N than the cereal crop can use, or an amount that produces more forage than the animals can utilize, will not benefit animal gain and may not carry over to be used by the bermudagrass. Annual phosphorus and potassium applications should be made to meet soil test recommendations for bermudagrass pastures. These nutrients can be applied as a starter fertilizer. Forage use Forage produced by a cereal crop in bermudagrass will be primarily for pasture, with the possibility of harvesting forage that cannot be grazed out. However, the typical slower rate of development of interseeded cereals makes it inadvisable to plan to use them primarily for harvested forage or grain. Grazing should begin when adequate forage is available to carry the animals for a period of time. Cereals interseeded into bermudagrass pasture can withstand hoof traffic in wet conditions better than conventional wheat fields because of resiliency of soil under bermudagrass sod. This is especially helpful in areas where high rainfall may limit the opportunities to graze conventional wheat fields. Weed control is another benefit to grazing winter cereals interseeded in bermudagrass. Many coolseason species that invade bermudagrass are suppressed by winter cereals, and their production can be utilized by cattle in early spring. Fall grazing will likely be limited due to competition from the bermudagrass for moisture and nutrients which inhibits fall cereal production. Most grazing will occur during a 60-day period beginning in mid-march. During that time, cereals will support a stocking rate similar to the summer carrying capacity of the bermudagrass and provide a high level of animal performance. This would be especially true if the same cattle were grazed on the bermudagrass, since they would be smaller at placement on the cereal than when bermudagrass growth begins. This further simplifies management and allows placement when stocker prices may be lower. -- Joe Moyer, Forage Agronomist, Southeast Agricultural Research Center jmoyer@ksu.edu 6

7 -- Doug Shoup, Southeast Area Crops and Soils Specialist 3. Holiday schedule: Comparative Vegetation Condition Report Because of the July 4 holiday timing, the eupdate is coming out early this week, before the Comparative Vegetation Condition Report maps are available. As a result, there will be no VCR maps in this week s issue. They will resume as usual with next week s edition. -- Steve Watson, Agronomy eupdate Editor swatson@ksu.edu 7