Comparative Winterhardiness of Cultivated and Native Alaskan Grasses, and Forage Yield and Quality as Influenced by Harvest Schedules and Frequencies, and Rates of Applied Nitrogen

Leslie J. Klebesadel, Emeritus Professor of Agronomy

Agricultural and Forestry Experiment Station; Palmer, Alaska

Bulletin 99; August 1994 (22 pages)

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SUMMARY

Objectives of this investigation were to compare certain traditional forage grasses with several native Alaskan grass species for forage yield, forage quality as measured by percent crude protein and digestibility (in vitro dry-matter disappearance or percent IVDMD), and comparative winterhardiness in three separate experiments. Management variables included different harvest frequencies (2, 3, and 4 times per year), and five different rates of applied nitrogen (N). Experiments were conducted at the University of Alaska's Matanuska Research Farm (61.6oN) near Palmer in southcentral Alaska.

All species were tall-growing, cool-season perennials. Traditional forage grasses included 'Polar' hybrid bromegrass (predominantly Bromus inermis x B. pumpellianus), 'Engmo' timothy (Phleum pratense), 'Garrison' creeping foxtail (Alopecurus arundinaceus), and a non-cultivar, commercial meadow foxtail (A. pratensis). Native Alaskan species were Siberian wildrye (Elymus sibiricus), slender wheatgrass (Agropyron trachycaulum), arctic wheatgrass (A. sericeum), bluejoint (Calamagrostis canadensis), and polargrass (Arctagrostis arundinacea).

· The least winterhardy of the nine grasses were Engmo timothy and meadow foxtail (Exps. I and II). The other two cultivated grasses, Garrison creeping foxtail and Polar bromegrass, were much more winterhardy; however, even they sustained considerable injury during the severe winter of 1970-71, but both recovered well during the 1971 growing season (Exp. II). In contrast, the native grasses showed no evidence of winter injury in any of the experiments.

· Total annual forage dry-matter yields of all grasses generally were highest with two cuttings per year and became progressively less as the number of cuttings per year increased (Exps. I and II).

· When six grasses were cut 2, 3, and 4 times per year, meadow foxtail and native slender and arctic wheatgrasses and Siberian wildrye tended to be more injured by 3 cuttings per year than were Polar bromegrass and Engmo timothy. All grasses showed evidence of tolerat

ing two cuts per year better than three or four except Engmo which tended to produce better in the third year where it had been harvested most frequently (Exps. I and II).

· With two cuttings per year, total annual forage yields were highest with the latest of three first-cutting dates (7 July vs. 23 June or 8 June) (Exp. II).

· Engmo timothy invariably was significantly higher in percent IVDMD than six other grasses in the final (23 Sep.) harvest under all of five different harvest schedules. Moreover, Engmo forage yields in the 23 September harvest always were equivalent to, and sometimes significantly surpassed, the other highest yielders (Exp. II).

· The native grasses tended to be lower in forage yield in the final (23 Sep.) harvest than the traditional forage grasses, regardless of previous harvest schedule (Exp. II). Increased rates of N application up to 216 lb/A (1/3 at midseason), however, tended to increase second-cut yields of all grasses over yields at lower N rates (Exp. III).

· With three or four cuttings per year, digestibility (percent IVDMD) generally remained high with all grasses, and higher than in the herbage in either harvest with two cuttings per year (the only exception with two cuttings was high percent IVDMD in the very early 8 June first cutting) (Exp. II).

· With two cuttings per year, digestibility in the second cutting increased with shorter growth periods before the second harvest (= later first cuttings) (Exp. II).

· Bluejoint was often significantly lower in digestibility than the other grasses (Exps. II and III); arctic wheatgrass also tended to be lower in digestibility than other grasses in the second of two cuttings (Exp. III).

· At the lowest rate of N application, traditional forage grasses (bromegrass and creeping foxtail) and native Siberian wildrye were significantly higher in digestibility in the first (29 June) of two cuttings than the other native Alaskan grasses (bluejoint, polargrass, slen

der and arctic wheatgrasses). However, at higher rates of N (over 100 lb/A in spring), the latter four native grasses increased significantly in digestibility to equal the other grasses while, in contrast, the first-mentioned three grasses changed little (Exp. III).

· With two cuttings per year and the first cutting prior to July, digestibility in the first harvest generally surpassed that in the second cutting (Exps. II and III), especially with higher rates of applied N (Exp. III). However, with a late first cutting (7 July), digestibility in the second cutting (23 Sep.) tended to be higher than in the first cutting with all grasses except the wheatgrasses (Exp. II).

· Grasses differed considerably in yields of digestible dry matter; mean range in yield between highest and lowest yielder at five N rates was 0.71 T/A (Exp. III).

· Yields of digestible dry matter of all grasses were increased with increasing rates of applied N up to 216 lb/A. The increases generally were due to the combined effect of higher forage yields and enhanced digestibility with increasing rates of N (Exp. III).

· Native polargrass was generally highest in yield of digestible dry matter at all N rates; at the highest N rates bluejoint was second to polargrass and surpassed other grasses (Exp. III).

· Percent crude protein in grass herbage generally increased with increasing rates of applied N, more so in the first cutting than in the second; this may be at least in part a result of 2/3 of N being applied in spring and 1/3 at mid-season (Exp. III).

· With two cuttings per year on 29 June and 18 September, percent crude protein generally was higher in first-cutting forage than in the second harvest; those differences were greatest in the native grasses at the highest rates of applied N (Exp. III).

· Relatively high rates of applied N (with adequacy of other major nutrients) generally stimulated increases in dry-matter production, percent IVDMD, and percent crude protein of all grasses; those responses tended to be

of greater magnitude in first-cutting forage than in the second cutting (Exp. III).

· Percent dry matter in first-cutting herbage of all grasses decreased with increasing rates of N application, with the most rapid decline between 36 and 108 lb of N/A (spring applied); decline in percent dry matter at higher rates (144 and 180 lb/A) was less pronounced in all grasses except Garrison foxtail. Polargrass herbage was much lower in percent dry matter than all other grasses.

· Except for Engmo timothy which winterkilled totally, the seven other grasses compared in Exps. II and III persisted well, continuing to produce good yields of forage in their sixth year of growth.

· The reputation of native bluejoint of being intolerant of annual utilization is again shown to be due to conditions inherent in native stands of this grass and not a characteristic of the grass itself. When seeded on mineral soil (as with cultivated grasses) and grown divorced from the accumulated, undecomposed organic debris present in native stands, bluejoint responded well to fertilizers and tolerated regular harvesting well, producing forage yields equivalent to cultivated forage grasses (Exps. II, III, and follow-up harvests).

· The very markedly improved digestibility of bluejoint when supplied with about 200 lb N per acre may represent a key to not only producing high forage yields but, perhaps more importantly, enhancing the nutritional value of this species that grows native in vast acreages of strongly acidic soils but has been burdened with a reputation of poor forage quality. The added cost of fertilizer for that improved nutritional status could circumvent expensive liming that would be needed in those areas to grow other forage species (Exp. III).

· Only very minor residual effects of the different N rates were apparent in first-cutting forage yields of four of the seven grasses in the year after the several rates had been applied in Exp. III (a uniform application of fertilizer was applied to all plots that year). No residual effects were apparent in second-cut forage yields that year, or in first-cut yields the following year.