Northeastern Nevada Revegetation Guide: Planting Desirable Vegetation to Compete with Invasive Weeds in Upland Habitats

Transcription

1 Northeastern Nevada Revegetation Guide: Planting Desirable Vegetation to Compete with Invasive Weeds in Upland Habitats J. Kent McAdoo, Area Natural Resources Specialist Rod Davis, Lander County Extension Educator SP-03-14

2 PLANT COMPETITION IS THE CORNERSTONE OF A COMPLETE WEED CONTROL PROGRAM. You are about to kill or have just finished killing weeds. The job is done, right? Almost. Without a well thought out plan for revegetating the area, your time and money might well be wasted. Experience has taught us that we can spend a lifetime killing weeds with nothing to show for it but more weeds. Even under the harshest growing conditions, something will grow. Any landowner or manager with a weed infestation should ask the following question: If weed control and proper follow-up management are applied, are there enough desirable plants still present on the site to promote recovery without seeding the area? Without a revegetation plan you may face even more invasive, harder to control weeds next year. The elimination of weeds in an area that lacks sufficient desirable vegetation to colonize the site could result in a worse situation than the original weed infestation in just a few years. Without competition for soil moisture, sunlight, and nutrients, either the former weed infestation will return with a vengeance, or another weed species or combination of species will move in to occupy the void. This can leave the landowner with a problem worse than he or she originally encountered. Assuring a healthy and desirable plant community following a weed control program can be as simple as selecting the proper herbicide and/or choosing the right combination of species to reseed. This Guide will take you step by step through the appropriate revegetation techniques and vegetation maintenance practices that will help meet your land use objectives. Specifically, the topics addressed below include: The importance of soil conservation Weed control considerations Seedbed preparation Seed mixes When to plant How to plant Seed depths Fertilizing Other soil amendments Seeding success and maintenance Save Your Soil! Soil is the primary natural resource, and its conservation is the most important consideration. Therefore, the retention and enhancement of soil should be the primary consideration in all management decisions, including seedbed preparation, choice of a seed mixture, and weed control methods. If desired vegetation is not established rapidly, valuable topsoil may be lost through wind and/or water erosion, leaving the site suitable only for undesirable vegetation. When soils are mismanaged, desired vegetation becomes less productive, invasive weeds start replacing desirable plant species, recreation and scenic values decrease, and management options for the production of livestock forage and/or wildlife habitat become fewer. Weed Control Considerations The area to be seeded should be cleared of actively growing weeds and any debris. The specific method of weed control should be tailored for the weed species present. In addition to herbicides, some weeds can be controlled by repeated pulling, mowing, or grazing by livestock. Lightly tilling an area just prior to seeding can also be used to help control weeds before planting. Extensive cultivation is inappropriate if perennial species are present, unless the cultivation can be repeated and/or combined with herbicide treatments. Most perennial invasive weed species spread by root sprouting, and

3 cultivation creates many small pieces of roots that can produce new plants. For specific information on controlling invasive weeds, contact a local office of the University of Nevada Cooperative Extension, or access weed control information on-line at: Please note that some herbicides may have inhibiting effects on seed germination for up to two years in certain soil types. Because residual effects vary with each chemical product, be sure to always read and follow the label instructions/warnings. Just as an example, a landowner could spray his/her property with a glyphosate-based herbicide (e.g., Roundup, Kleenup, etc.) to kill or severely impact undesirable existing vegetation. The area may be safely seeded within 10 days after chemical application without injury to the planted seeds. Seedbed Preparation Where possible, seedbeds should be prepared with as little soil disturbance as possible in order to retain soil moisture and organic matter. Keep in mind that any disturbance of the soil can bring more competitive weed seeds to the surface as well. This preparation can be initiated with combinations of weed control methods followed by a short fallow period to provide time for the soil moisture to begin recharging. Minimum till or no-till drill seeding are options. Undisturbed soil with reduced weed competition in sensitive areas creates an excellent environment for germination and establishment of seedlings. Care should be especially taken in heavy clay soil areas not to overwork the soils, resulting in bug-dust that tends to crust and severely compact. Before seeding, make sure that footprints in the soil are no greater than onehalf inch deep in the prepared soil. If necessary, pack the soils with a roller or irrigate before seeding. For small areas, preparing the soil surface may be as simple as raking to provide a roughened surface. In areas where deeper seedbed conditioning is deemed necessary, topsoil should be conditioned to a depth of approximately six inches. If the property includes steep terrain, tillage operations should be conducted on the contour to minimize erosion. The final seedbed will consist of a furrow-like configuration to help minimize erosion and increase available soil moisture. Seedbed preparation should be accomplished immediately prior to seeding to minimize the time that bare soil is subject to wind or water erosion. Seedbed preparation can loosen compacted soils, provide water catchments (for plants), and create good safe-sites for seed germination and seedling survival. Equipment for seedbed conditioning for small landowners is often limited, but could include rippers, disk plows, etc. Methods can be combined to provide desired results. The most practical and available equipment should be utilized to complete the seedbed preparation. Seed Mixes Emphasis should be placed on siteadapted rapidly establishing species, which hold the soil and compete vigorously with undesirable weeds. Long-term land-use goals (e.g., livestock production, wildlife habitat, esthetics, etc.) are less important initially than conserving soil and crowding out weeds. Nevertheless, landowners should always keep their long-term land-use goals in mind as they make decisions about seed mixes. The focus here is only on the major upland plant communities in northeastern Nevada that are being jeopardized by weed invasions. Landowners who are uncertain which of the following seeding tables apply to their soil conditions should contact the local office of the USDA Natural Resources Conservation Service or University of Nevada Cooperative

4 Extension. For best results, landowners should collect soil samples and have them analyzed at a commercial lab. Keeping in mind that rangeland communities are very diverse, the choice of species depends on numerous site-specific factors such as elevation, length of growing season, soil type, topographical exposure, annual precipitation, availability of irrigation water, etc. Landowners may also be concerned about fire resistance of seeded species. Certainly seed availability and price will affect final seed mix decisions. All species selected must be adapted to the site. Using several seed species (as opposed to single-species seeding) is best in most situations for several reasons. First, no single species meets all of the varied conditions of a site, and therefore a multiple-species mix enhances seeding success. For landowners with livestock production and/or wildlife habitat goals, mixtures provide a variety of forage and cover for livestock and various wildlife species. Mixtures also provide increased resistance to insects and parasites, extend the grazing period, and generally increase vegetation production and soil protection. Because many of the native range plant species are especially poor competitors with weeds, particularly in the initial phases of establishment, many of the species recommended in Tables 1 3 are introduced (non-native) species. This Guide recommends plant materials that are the most reliably established in order to stabilize soil and develop functional plant communities. Plant populations can be altered over time by changing the type, intensity, and timing of management actions. Soil cannot be replaced if it is lost. Therefore, soil protection is vital to the future integrity and sustained production of the site. Depending on the exact seed mix selected, seed may be purchased from local seed dealers, and farm and ranch supply stores. Commercial seed companies typically have more selection, but may also have minimum order requirements. Always buy certified seed to guarantee variety, purity, and certainty of germination. When to Plant Seeding should normally be limited to the fall in northern Nevada. Seeding at this time of year typically meets the cold-dormancy requirements of seeds and stimulates seedlings to rapid growth the following spring. There is also less chance for seed depredation by birds, rodents, and insects during this time, as well as the benefit of the long winter moisture period. Care should be taken not to seed too early in the fall in order to ensure that seed germination is delayed until the following spring when the seedlings can take advantage of cooler temperatures and moisture from winter snowfall. Most grass, forb (wildflower), legume, and shrub seeds will survive the winter in northern Nevada. Planting should normally be conducted from mid-october through the end of November. Temperatures at this time of year are cool enough to prevent seed germination, and the soils are dry enough for successful planting. How to Plant Because of variable terrain and shallow, rocky soils, range plantings are among the most difficult to accomplish successfully. For planting large areas, the use of specialized equipment capable of withstanding rugged conditions may be necessary. Traditional rangeland drills and variations of chaining and railing implements are commonly used to seed rangelands where rugged conditions limit the use of conventional drills. However, modern drills equipped with precision seed depth

5 placement and seed monitoring devices perform well on moderately difficult landscapes. For smaller areas and where sophisticated equipment is not available, landowners can still achieve excellent results by broadcasting the seed and covering lightly with soil. Spreading seed with a hand-held whirly-bird can be followed by raking. Some landowners have successfully seeded areas by using an electric broadcast seeder mounted on the front of an ATV, with a blanket harrow or even a piece of chain-link fence attached behind to cover the seeds with soil. Seed Depths Controlling seed depth is essential for a successful seeding. Although recommended planting depths vary with seed size, most grasses do best planted 1/4- to 1/2-inch deep. The general rule is that the smaller the seed, the shallower it should be placed in the soil. Therefore some very small grass, forb, and legume species should be seeded only 1/8 to 1/4 inches deep. Other forbs and some shrubs do best when broadcast on the surface of roughened soils. Optimum seeding depth also varies with soil texture; for example, on coarsetextured soils (sands) seeds should be planted deeper than on lighter textured (clay-silt) soils. Fertilizing Application of fertilizer on arid rangelands after seeding establishment is not usually recommended. Most annual weeds (e.g., cheatgrass) thrive on high nutrient availability. Nitrogen, often a significant component of fertilizer mixes, is not required for seed germination, but stimulates the growth of cheatgrass and other invasive weeds. Therefore, fertilizing the newly planted site at seeding time or in early spring can result in record-class weed infestations. Other Soil Amendments Mulching involves placing a layer of material on the soil surface to increase soil moisture, prevent erosion, moderate soil temperature, and increase seedling establishment. Although mulching may increase plant cover, density, and biomass in some instances, this same practice in other cases may have no significant influence on plant growth. Of the wide variety of mulching materials, hay and straw are the two most commonly used. When mulching with these materials, great care must be taken to ensure that the mulches are free of noxious weeds that could be unintentionally introduced to a planted site. To access information on sources for weed-free hay, try the following website: Although mulching may be beneficial in some areas, it is not typically necessary, and may be cost prohibitive. Where mulch is used, it should be applied in an appropriate manner, depending on slope, terrain, access, etc. Methods include manual application, special blowers, and mechanical spreaders. Mulch may be crimped into the topsoil using a straw crimper or the equivalent. Hydromulching or other specialized methods may be used on steeper slopes and/or in areas requiring rapid plant establishment for mitigation against potential erosion. Seeding Success and Maintenance Seedlings from fall-seeded plantings should begin establishment in early spring. If spring precipitation is lacking, irrigation (if available) applied several times during the first two months after germination is beneficial. Under normal conditions, dryland seedings should be given at least two or three years for complete establishment. The diverse species in a seed mix may have a wide range of germination and growth requirements that will not all be met in a given year. Patience is a

6 virtue when it comes to seeding establishment. If results are less than desirable after the first growing season, landowners are tempted to plow the site and try again. Repeated soil disturbance of this nature often sets the stage for a new weed infestation. If the seeded site is to be grazed by livestock, the area should be protected from grazing and trampling until the plants are established (i.e., the root systems are developed enough that grazing will not pull up the plants). On arid rangelands, this typically requires two growing seasons. However, depending on precipitation and site-specific factors, more or less growing time may be required. If perennial plants can be easily hand-pulled, they are not ready to be grazed. If sustainable livestock grazing of a seeded area is a long-term land-use goal, the land manager should implement a grazing strategy that allows sufficient vegetation recovery for site maintenance. Specialists with the USDA Natural Resources Conservation Service or University Nevada Cooperative Extension can be contacted for additional information. Table 1. Recommended Weed Competition Seed Mixes (pls 1 lbs/acre 2 ) for Salt Desert Shrub Areas (6 to 8 inches annual precipitation). Species Clay Soils Sandy or Well Drained Soils Shallow Water Table/Saline Soils (Greasewood Areas) Grasses P27 Siberian wheatgrass 9 9 Russian wildrye 6 6 tall wheatgrass 10 western wheatgrass 7 Shrubs fourwing saltbush 1 1 forage kochia 2 2 Other adapted species (mostly native) that can be added to increase vegetation diversity: Grasses: For deep water tables needle-and-thread grass, Indian ricegrass (sandy soils), bottlebrush squirreltail, basin wildrye. For shallow water tables alkali sacaton, thickspike wheatgrass, beardless wildrye, saltgrass. Forbs: Lewis flax, Palmer penstemon, desert globemallow. Shrubs: shadscale, spiny hopsage, Nevada ephedra, winterfat. 1 pls = pure live seed (% purity x % total germination). 2 Pure live seed pounds per acre suggested for broadcast seeding, followed by dragging with a light harrow or other equipment to cover seed. If drill seeding, cut rates by ½.

7 Table 2. Recommended Weed Competition Seed Mixes (pls 1 lbs/acre 2 ) for Sagebrush/Grass Areas (8 to 10 inches annual precipitation). Species Clay Soils Moderate to Deep Loamy Soils Shallow, Sandy or Gravelly Soils Grasses crested wheatgrass 7 P27 Siberian wheatgrass 8 7 Russian wildrye 4 4 thickspike wheatgrass 2 4 western wheatgrass 4 2 Indian ricegrass 4 Forbs (optional) Lewis flax 1 1 Palmer penstemon 1 1 Shrubs (optional) fourwing saltbush forage kochia Other adapted species (mostly native) that can be added to increase vegetation diversity: Grasses: Snake River wheatgrass, basin wildrye, streambank wheatgrass, bottlebrush squirreltail, needle-and-thread grass. For areas with at least 10 inches precipitation: intermediate wheatgrass, Sherman big bluegrass Forbs and legumes: small burnet, ladak alfalfa (higher precipitation areas), yellow sweetclover Shrubs: Wyoming big sagebrush, spiny hopsage, winterfat, bitterbrush (higher precipitation areas) 1 pls = pure live seed (% purity x % total germination). 2 Pure live seed pounds per acre suggested for broadcast seeding, followed by dragging with a light harrow or other equipment to cover seed. If drill seeding, cut rates by ½.

8 Table 3. Recommended Weed Competition Seed Mixes (pls 1 lbs/acre 2 ) for Pinyon/Juniper Areas (10 to 14 inches annual precipitation). Species Clay Soils Moderate to Deep Loamy Soils Grasses intermediate/pubescent Shallow, Sandy Soils to 6 wheatgrass crested wheatgrass 5 5 P27 Siberian wheatgrass 6 Russian wildrye 4 thickspike wheatgrass 4 4 sheep fescue 3 Forbs (optional) dryland alfalfa (e.g., ladak) 1 1 blue flax Shrubs forage kochia Other adapted species (mostly native) that can be added to increase vegetation diversity: Grasses: Indian ricegrass (sandy soils), slender wheatgrass, bluebunch wheatgrass, needle-and-thread grass, Sherman big bluegrass, NewHy wheatgrass (at least 14 inches precipitation) Forbs and legumes: Pacific aster, globemallow, small burnet Shrubs: Wyoming big sagebrush, mountain big sagebrush, bitterbrush, fourwing saltbush 1 pls = pure live seed (% purity x % total germination). 2 Pure live seed pounds per acre suggested for broadcast seeding, followed by dragging with a light harrow or other equipment to cover seed. If drill seeding, cut rates by ½.

9 References Horton, H. (Editor and Compiler) Interagency Forage and Conservation Planting Guide for Utah. Agric. Exper. Sta. And Coop. Ext. Serv., Utah State Univ., Logan, UT. Extension Circular EC 433. Jensen, K., H. Horton, R. Reed, and R. Whitesides, and USDA-ARS-FRRL Intermountain Planting Guide. Utah State Univ., Logan, UT. AG 510. McAdoo, J.K., G.A. Acordagoitia Reclamation Site and Seedbed Preparation for Nevada Hardrock Mines. Landman 45(6): Smith, E., J. Davison, and B. Carlos A Homeowner s Guide to Planting Crested Wheatgrass. Univ. Nev. Coop. Ext. Fact Sheet. FS Tueller, P.T., G.K. Brackley, J. Biggs, J.W. Doughty, G. Staidl, and S. Swanson Conservation Plantings for Natural Resources Management. Joint Recommendations by Univ. Nev. Coop. Ext. and USDA-NRCS. BE