Larry M. White

Carbohydrate reserves of grasses: a review.

Highlight: Carbohydrate reserves are nonstructural carbohydrates. Sucrose and fructosan are the predominant reserve constituents of temperate-origin grasses; sucrose and starch, of tropical-origin grasses. Nitrogenous compounds are used in respiration, but probably are not alternately stored and utilized as are carbohydrate reserves. Most carbohydrate reserves are stored in the lower regions of the stems-stem bases, stolons, corms, and rhizomes. Nonstructural carbohydrates in the roots of grasses are probably not used directly in herbage regrowth following herbage removal. Plant development stage, temperature, water stress, and nitrogen fertilization can drastically change the reserve level. The seasonal variation of carbohydrate reserves is often different for the same species when grown in different environments. The level of carbohydrate reserves in the lower regions of the stems apparently affects the regrowth rate for the first 2 to 7 days following herbage removal. Following the initial period, plant regrowth rate depends on other factors, such as leaf area and nutrient uptake. This initial effect from the level of carbohydrate reserves can be maintained during subsequent exponential growth. Grazing may be more detrimental than clipping if it removes herbage from some plants and not others. The ungrazed plants may take the available nutrients and water away from the grazed plants. However, grazing may be less detrimental than clipping if grazing leaves ungrazed tillers on a plant while removing others, thus allowing for the transfer of carbohydrates.

Yield and quality of WW-Iron Master and caucasian bluestem regrowth.

Old World bluestems (Bothriochloa spp.) have been seeded on over a million hectares of marginal farmland in Oklahoma and Texas, yet we know little about their regrowth yield and quality. The objective was to determine seasonal pattern of forage regrowth yield and quality of leaves and stems of WW-Iron Master (B. ischaemum [L.] Keng) and Caucasian (B. caucasica [Trin.] C.E. Hubb.) bluestem when 4-week regrowth was harvested at weekly intervals from early May through mid-September. Four plots of each bluestem were established in each of the 4 blocks (32 plots total). Harvesting was rotated so that 4-week regrowth of each bluestem was harvested weekly from 1 of the 4 plots in each block during 1988 and 1989 to determine regrowth yield, in vitro dry matter digestibility (IVDMD), and crude protein (CP) of leaves and stems. Forage regrowth of both species peaked in June both years. Regrowth during August averaged 10 and 35% of June regrowth in 1988 and 1989. WW-Iron Master produced 80 and 45 % greater 4-week regrowth than Caucasian in 1988 and 1989. WW-Iron Master produced 75 and 28% greater leaf regrowth than Caucasian in 1988 and 1989 and twice as many stems both years. Leaf and stem IVDMD of WW-Iron Master averaged 2 to 6 percentage units higher than Caucasian. Leaf CP of WW-Iron Master averaged 2 percentage units higher than Caucasian during May and June. However, stem CP of WW-Iron Master averaged 1 percentage unit lower than Caucasian. Grazing management plans need to consider that the majority of bluestem forage production was restricted to a 1 month period in June. This technique of sampling 4-week regrowth every week during the growing season was an effective method for determining the seasonal regrowth pattern.

Seasonal Changes in Yield, Digestibility, and Crude Protein of Vegetative and Floral Tillers of Two Grasses

The seasonal change ol dry matter (DM) yield, estimated in vivo dry matter digestibility (DMD), and crude protein content of the vegetative and floral tillers of ‘Rosana’ western wheatgrass (Agropyron smithii) and ‘Lodorm’green needlegrass (Stipa viridula) was determined on forage harvested April through October on 10 dates during 1973 and on 11 dates during 1974. Vegetative tillers on both grasses were comparable in seasonal DM yield, DMD, and crude protein for both years. Flora tillers of western wheatgrass produced only 20% as much forage as did floral tillers of green needlegrass; however, they contained on the average 2 and 4 percentage units more crude protein and DMD, respectively, than floral tillers of green needlegrass. On an average, floral tillers contained 4 and 8 percentage units fess crude protein and DMD, respectively, than companion vegetative tillers. When floral tillers are harvested before DMD decreases below 5090, they are most valuable for maintenance of mature animals. Preventing development of floral tillers would increase DMD but decrease DM yield. Range managers, planning their grazing management for native rangeland in the northern Great Plains, should consider more than dry matter (DM) yield and forage quality of whole plants. They should also consider DM yield and quality of floral and vegetative tillers. Their ratio can be manipulated by management (Lawrence 1973, Hyder and Sneva 1963, Field and Whitford 1980). Damage or removal of floral primordia prevents floral tiller development and the tiller remains vegetative. Lawrence (1973) showed that cutting Russian wildrye (Elymus junceus) during late May or early June prevented floral tiller development. Hyder and Sneva (1963) proposed heavy livestock grazing of crested wheatgrass (Agropyron desertorum) when the shoots were in the boot stage to remove flora primordia. Application of growth regulators can also change the ratio of floral to vegetative tillers (Field and Whitford 1980). Timing of management practices to prevent floral tiller development will depend on time of floral primordia initiation. Some species such as western wheatgrass (Agropyron smithii), prairie junegrass (Koeleria cristata), Russian wildrye, and other temperate-origin grasses initiate floral primordia in the fall (Lawrence and Ashford 1964, Johnston and MacDonald 1967, and Hodgson 1966). However, those species that require vernalization for floral induction initiate the floral primordia in the spring (Evans 1964). Preventing development of floral tillers could reduce forage yield, yet increase forage quality if the tillers remained culmless. Knowledge is needed of seasonal DM yield and quality of both vegetative and floral tillers of major forage species before management systems are formulated that will prevent development of floral tillers. The author is range scientist, USDA, Agricultural Research Service, Northern Plains Soil and Water Res. Center, P.O. Box 110!2, Sidney, Mont. 59270. This study is a contribution from USDA, Agricultural Research Service, in coopcration with Montana Agr. Exp. Sta., Sidney, Mont. Journal Series No. 1295. Manuscript received June I, 1982. 402 The in vitro digestibility of whole plants of western wheatgrass or green needlegrass (Stipa viridula) have been studied (Bezeau and Johnston 1962, Kamstra 1973, Lawrence 1978, White and Wight 1981). Still needed is information on the seasonal change of DM yield and DMD of vegetative and floral tillers of western wheatgrass and green needlegrass. The objective of this study was to determine the seasonal change of DM yield, DMD, and crude protein content of vegetative and floral tillers of western wheatgrass and green needlegrass. Materials and Methods The study was conducted on a Shambo soil (fine-silty, mixed Typic Haploborolls) 7 km southeast of Sidney, Mont., at an elevation of 610 m. Average annual precipitation at this site is 345 mm, with 21% received from October through March, 44% from April through June, and 35% from July through September. Precipitation from October 1972 through March 1973, April through June, and July through September 1973 was 73, 134, and 129% of normal, respectively. Precipitation from October 1973 through March 1974, April through June, and July through September 1974 was 103, 104, and 8 1% of normal, respectively. January and July long-term mean temperatures are -13 and 2O“C, respectively, and the average frost-free is 125 days. The study was conducted during 1973 and 1974 on adjacent fields of ‘Rosana’ western wheatgrass and ‘Lodorm’ green needlegrass seeded during early September 1971. The land had been summer-fallowed during 1970 and 1971. Both species were seeded at 30 live seeds per meter of row with a double disc drill with openers spaced 18 cm apart. Clipping plots were arranged in a randomized, complete-block design with 4 replications (each 6 by 20 m) per grass species. Forage was harvested from different 0.36-m by 4-m clipping plots with a 0.4-m border between plots in the western half of each replication on 10 dates during 1973 and from the eastern half on I I dates during 1974. Plants were sampled on a biweekly interval from April through July and then monthly through October. At each sampling date, plants on a previously unharvested plot were clipped 5 cm above ground and separated into vegetative and floral tillers. Plant material was dried at 700 C and ground to pass through a l-mm screen before analyses. A modified Tilley and Terry (1963) two-stage method was used to determine in vitro DMD as previously described by White et al. (198 1). To overcome random week-to-week variation, standard forage with a known high, medium, and low in vitro DMD were included in each run and their deviations from a long-term average were used to correct all values. The resulting in vitro DMD values were converted to estimated in vivo DMD by using a regression equation previously reported by White and Wight (1981): Estimated in vivo DMD = 10.78 -I0.767 (in vitro DMD); R = 0.87 This equation was previously determined as the regression of in JOURNAL OF RANGE MANAGEMENT 38(3). May 1983 vivo DMD of 8 forages, fed to sheep, upon the in vitro DMD of A two-way analysis of variance was performed on DM yield, these same forage samples determined by the above procedure. DMD, and crude protein of vegetative and floral tillers of each Nitrogen was determined with an auto analyzer (Schuman et al. species in each year. All differences discussed in this paper are 1973) after forage samples had been wet digested on a block significant (o-CO.05) unless otherwise stated. Linear regression digestor. Nitrogen concentration was multiplied by 6.25 to estianalysis was used on DMD and crude protein data for the period May-July, when values were declining linearly, to determine the mate crude protein. average decrease per day.

Predicting flowering of 130 plants at 8 locations with temperature and daylength.

An improved plant phenological method is needed to accurately predict flowering of a large array of plant species at locations with a wide range of latitude. Degree days or degree days times daylength cannot be used to accurately predict flowering of both early and late flowering species when grown at locations with wide range of latitude. Published flowering dates of 130 plant species from among 8 locations in central North America ranging in latitude from 39 to 50 degrees N and longitude 84 to 108 degrees W were used to develop a degree days times daylength factor to predict flowering dates. Plants flowering in late June flowered at the same time at all 8 locations regardless of latitude. Species flowering earlier than late June flowered earlier at southern locations than those at Treesbank, Manitoba. Species flowering after late June flowered later at southern locations than those at Treesbank. Flowering of 124 species divided among 8 locations was most accurately predicted by the accumulation of degree days (threshold = 2 degrees C) times daylength factor (1/(0.259-0.0140*daylength) from the first of December. This method slightly discounts daylength below 13 hours and greatly increased its weight for every hour over 13 hours. This method predicted flowering dates with a standard deviation of 0.1, 0.5, -1.7, 2.4, -0.1, 6.0, -1.8, and -1.1 days for Swift Current, Saskatchewan; Treesbank, Manitoba; Sidney, Mont.; Fargo, N.D.; Sauk and Dane Co., Wisc.; Wauseon, Ohio; and Manhattan, Kans.; respectively. Degree days or degree days times daylength had a standard deviation of 10 and 18 days in predicting flowering dates at Manhattan, Kans.

Stand age, precipitation, and temperature effects on forage yield.

The effects of seasonal distribution of precipitation on forage yield are often confounded by stand age. Forage yields of Russian wildrye (Psathyrostachys juncag), green needlegrass (S@MI vir*r), created whaQrassr(A@vpyrcm dsertorra), and hltermediate pubesctnt wheatgrass (Agropyron int mnedium-trichophorum) were determined from 6 separate studies, each of 6 years duration, from 4 locations in the northern Great Plains. Stepwise multiple regression showed that forage yield of all 4 species was significantly (PCO.01) related with April and May precipitation and stand age. Forage yield of Russian wildrye was significantly (KO.05) related with April mean monthly temperature and degree days (accumulation of daily mean air temperature above a given threshold temperature) accumulated until the end of May or June; however, yields of the other 3 species were not significantly related with April, May, or June mean monthly temperatures nor degree days accumulated until the end of May or June. The highest forage yield per centimeter of precipitation occurred either the second or third year after establishment; then yield decreased asymptotically and by year 5 or 6 was only 75% of maximum for green needlegrass and 40-50% for the other grasses. Economic evaluation of seeding forages must include the itiuence of stand age on forage yield.

Perenniality and development of shoots of 12 forage species in Montana.

A study was conducted to determine the perenniality and development of shoots of two sedges, four grass species of temperate origin, and six grass species of tropical origin. Floral shoots of sedges were at least 3 years old and had remained vegetative the first 2 years. Floral shoots of temperate-origin grasses varied between 2 and 3 years old, and those of tropical-origin, between 1 and 2 years old. By knowing the perenniality of floral shoots, it may be possible to develop management practices to change the ratio of floral to vegetative shoots.

Mefluidide effect on Caucasian bluestem leaves, stems, forage yield, and quality.

‘Caucasian’blucstpm [&A&c&e cuucawcu (Trin.) C.E. Hubb.] provides high quality forage during early summer but growth of floral stems causes a rapid decline in forage quality. In 1985 and 1986 mefluidide [N-(2,4-dimethyl-S-{[(trlfluromethyl)sulfonyl] amino)-phenyl)acetamidel, a growth regulator, was applied to Caucasian in late May, early June, aud mid June at 0.00,0.28,0.56, and 0.84 kg/ha to determine which combination of date and rate of application would effectively decrease number of floral stems and yet increase forage quality. Caucasian was grown on a Pratt fine sandy loam (Thermic Pasammentlc Haplustalfs) soil 6 km north of Fort Supply, Okla. Plots (1.5 by 5 m) were replicated 4 times in a randomized complete block design with a factorial treatment arrangement. Forage was harvested above a 6-cm stubble height in late July. On the control plots, the in vitro dry matter digestibility (IVDMD) and crude protein of leaves was 6.5 and 2.0 percentage units higher than stems. Leaves accounted for 40% of the forage yield the first year and 64% the second year. Mefluldide was most effective if applied late May. Response surface analysis showed that mefluidide (0.56 kg/ha) application in late May decreased number of floral stems 35 to 509&forage yields 20 to 251, and leaf yields 7 to 25%. In 1985, mefluidide had no effect on IVDMD and crude protein of leaves, stems, and whole plants. In 1986, application of 0.56 kg/ha mefluidide in late May increased leaf, stem, and whole plant IVDMD by 1.2, 2.7, and 2.0 percentage units and crude protein by 0.5 to 1 percentage units. Mefluidide did not decrease number of floral stems enough nor increase leaf yield and forage quality enough to be economically used on Caucasian to improve livestock gain during late July.

Growth regulators' effect on crested wheatgrass forage yield and quality.

If crested wheatgrass [Agropyron desertorum (Fisch.) Schult.] could be maintained in an immature growth stage, it would improve forage quality and thus extend the grazing season. In 1981 and 1982, plant growth regulators were applied to crested wheatgrass 0, 2, 4, and 6 weeks after first floral primordium initiation to determine which compound, date, and rate of application would maximize forage quality yet minimize reduction of forage yield when harvested at seed ripe stage. Mefluidide [N-(2,4-dimethyl-5{[(trifluoromethyl)-sulfonyllamino}phenyl)acetamidel at 4 rates [0.0, 0.28, 0.56, and 0.84 kg/ha active ingredient (a.i.)], maleic hydrazide (MH) (1,2-dihydro-3,6-pyridazinedione) at 4.5 kg/ha ai., and MH (3.36 kg/ha ai.) phl chlorflurenol (methyl-2-chloro-9-hydroxyfluorene-9-carboxylate) at 1.12 kg/ha a.i. were applied to crested wheatgrass growing on a Shambo loam (Typic Haploborolls) in northeast Montana. Application of MH or MH plus chlorflurenol generally gave a similar response in heading, forage yield, CP, and in vitro organic matter digestibility on a dry matter basis (IVDOMD) as did melfluidide at 0.56 kg/ha. Mefluidide (0.56 kg/ha) applied 2 weeks after first floral primordium initiation decreased heading 80 and 95%, decreased forage yield 20 and 30%, increased CP 1.7 and 2.3 percentage units, and increased IVDOMD 1.8 to 4.2 percentage units compared to untreated, depending upon

Long-term residual effects of nitrogen fertilization on western wheatgrass.

Nitrogen (N) fertilization can be an effective way of increasing forage production. The question is how much does N fertilization increase forage yield of western wheatgrass (Agropyron mnithti) when there is not a shift in species composition as occurs when N is applied to a native range site. The objectives of this research were to determine the residual effects of a single application of (1) 6 geometric rates of N and phosphorus (P) on forage yield, in vitro dry matter digestibility (IVDMD), crude protein (CP), and phosphorus (P) concentration (cone) of western wheatgrass grown near Sidney, Mont. during a lO-year period. Ammonium nitrate was applied at 0,40,80,160,320, and 640 kg N/ha in March 1973 and triple super phosphate at 45 kg P/ha on split plots during August 1975. A single application of N increased forage yield by 0.0, 0.0, 0.95, 0.35,0.0, 1.16, 0.52, and 1.41 kg/ha per kg of N applied the lst, 2nd, 3rd, 4th, Sth, 6th, 7th, and 10th year sampled, respectively, regardless of N rate. Nitrogen fertilization increased the accumulative forage (IYO.01) and CP (X0.01) yield over the 8 harvest-years by 4.35 and 0.87 kg/ha per kg of N applied. Nitrogen fertilization increased the average forage IVDMD by 0.1 percentage units (KO.05) and decreased P cone by 0.03 percentage units per 100 kg N/ha applied (KO.01). Application of 45 kg P/ha in 1975 increased the P cone of the forage an average of 0.04 percentage units each year, increased forage yield only the 10th year by 150 kg/ha, and had no effect on IVDMD or CP. This study also showed that long-term observations are necessary to measure the residual effects of fertilization.