Sustainability and Limitations

Sustaining Productivity

Successful forage and beef production in drier areas of the Prairies will involve the management of grass or grass-legume for the optimum use of soil water and nitrogen.

Soil water is the first limiting factor in forage production in the semiarid prairies. Many studies have reported the relationship of forage yields or carrying capacity to precipitation and other climate variables affecting soil water. Weather cannot be controlled but it is possible to make better use of available water.

Row spacing can be increased for more forage production in dry years. The disadvantages are that the fields become more uneven and erosion may increase . Weeds may invade the bare ground. Cross seeding of grass mixtures or grass alfalfa will reduce erosion and trap water in the square pattern. Kilcher (1982) demonstrated the benefits of cross seeding to alternate or mixed rows.

Standing seed stems or snow fence increased the forage production and carrying capacity of fertilized Russian wildrye at Swift Current by 15% compared to stands in which the standing litter was trimmed to the crown (Holt 1995). This advantage was attributed to snow trapping which increased spring soil water by an average 20(standing stems) or 25 mm (snow fence). On a commercial scale, snow fences would be replaced with tall wheatgrass or other biological barriers. Our preliminary grazing trials indicated that the cattle eat the seed stems and reduced the snow trapping. However, standing litter or mulch will reduce evaporation and increase forage production (Smoliak 1965).

Mixtures of grasses may be more water efficient than monocultures but more work is required on researching complementary grasses.

If a seeded grass produces 454 kg (1000 lb) forage per year containing 2% nitrogen (12.5% protein), then 9 kg(20 lb) of nitrogen was removed from the soil just to produce the above ground forage. Even in grazed pastures, most of this nitrogen is not re-cycled very efficiently because of concentration of excreted nitrogen in feces and urine spots or losses to the atmosphere. Some of the nitrogen is replaced through rainfall and some is contributed by free-living nitrogen fixing bacteria in the soil. It is estimated that this may contribute approximately, 3 kg (7 lb) per acre per year. In the absence of a legume, the remainder must be provided by soil organic matter.

If bloat is not a concern and it can be minimized by management, alfalfa is the legume of choice to grow with Russian wildrye. Since Russian wildrye is very competitive with alfalfa, then the rows should be separated. Other non-bloating legumes may be used with Russian wildrye but very little information is available about their use in pasture.

Nitrogen fertilizer is a more expensive method of returning nitrogen to the soil. As Russian wildrye has a high demand for nitrogen, it responds very well. However, fertilizer response is water dependent and results are disappointing in dry years. Lawrence and Heinrichs (1968) reported a return of 20 lb forage per lb nitrogen fertilizer for a 15 year period. Kilcher found a lesser response during a drier period. In general, utilization of nitrogen fertilizer will be greater in more favorable environments. The results of Lawrence and Heinrichs and a grazing study reported by Holt et al. (1991) suggest a return of about 12 to 15 animal unit grazing days/acre for the first 30 lb nitrogen applied per acre. The additional grazing capacity must pay for the cost of fertilizer and application. In most situations, fertilizing pasture is not profitable in this region. Nitrogen fertilizer may extend the grazing season at both ends, improve forage quality and reduce the variability of production. These may have some monetary value.

Manure or other mulches. Manure is a valuable source of nitrogen and other nutrients. When available, it may be spread on pastures providing spreading costs are not prohibitive.

Old stands of forages become low producing or 'root bound'. Many producers extend the lifetime of a Russian wildrye pasture by various means of renovation. Generally it involves thinning the stand by cultivation but herbicides may also be used. The usual implement is a cultivator with narrow 5 to 10 cm (2 to 4 inch) spikes. The field may be harrowed at the time of renovation and new forage introduced. Usually a legume is sown to take advantage of the input of nitrogen. At Miles City, Montana specialized equipment has been built for range renovation. These include a lister, a 'pitter' and a strip rotavator.

The extreme renovation is breaking and re-seeding. In a year of above normal rainfall, this was accomplished at the Research Centre in one year without a serious loss of grazing. The earmarked field was grazed heavily until June and then was broken with a double disc. The field was fallowed for the remainder of the year and 'set-up' for seeding by harrow-packing early the next year. The Russian wildrye was sown in one direction. Alfalfa and sweet clover was sown in alternate rows with Dahurian wildrye, across the Russian wildrye. Some grazing was available in the seeding year. Above average rainfall in summer made this work. Annuals may be used as 'break' crops to grow out weeds. If land is prone to erosion, then it is best to proceed cautiously, breaking small strips at a time.

Limitations of Russian Wildrye for Pasture

The main complaint about Russian wildrye is its lack of productivity in the long term, possibly due to its high demand for soil nitrogen which is related to the high protein (nitrogen) content of the forage. Reports by White (1985) and Holt et al. (1991b) have described the decline of yield of Russian wildrye as the stand ages. Pastures that contain alfalfa may not decline in yield as quickly as monoculture stands but eventually the alfalfa is also lost. Alfalfa has a relatively high requirement for phosphorus. Fertilizer or manure may extend the life of a Russian wildrye or Russian wildrye-alfalfa stand.

Russian wildrye is a bunch grass with an elevated crown, and results in rough fields. It also may be prone to erosion because of the elevated rows channelling water. Cross seeding of grass-grass or grass-alfalfa will reduce the erosion but will may the sward even more uneven. It may be possible to mix bunch and creeping rooted grasses but this has not been widely tested. The solid stand may defeat the purpose of wide row spacing.

Russian wildrye is very slow to establish but very competitive once in a stand. It may crowd out other forages in the mixtures such as the legume or other grass. Sowing in alternate rows or cross seeding is recommended to reduce the competition of the Russian wild rye.