Weed Science Commons^™

Some Effects Of Nitrogen Supply On Grass Growth, David Wilman

IGC Proceedings (1977-2023)

The paper summarizes some recent evidence from the Department of Agriculture, Aberyst­wyth, on changes brought about by applied N in field swards of grass. The aspects referred to are the number of tillers; weight per tiller; weights and dimensions of parts of tillers; initiation, appearance and longevity of leaves; and senescence and death of tissue relative to yield.

Relations Between Nitrogen Supply, Nitrogen Content Of Plants, Internal Efficiency Of Nitrogen, And Yield With Forage Grasses, Herbert Kaltofen

IGC Proceedings (1977-2023)

There exists the relation y = y(x) = w(x) [N0 + q(x) x] , where x = nitrogen dose, q = apparent re­covery of fertilizer nitrogen, N0 = amount of nitrogen present in the harvested plant matter in case of x = 0, w = internal efficiency of nitrogen taken up, and y = dry matter yield. The possibilities for improving q by way of plant breeding are rather limited because cul­tivated grasses usually take up almost the entire amount of available nitrogen. On the contrary, improvement of the internal efficiency w by breeding procedures offers much better opportunities. It …

Variation In Transpiration Rate In Dactylis, D Wilson, I B. Abdullah, S A. Trickey

IGC Proceedings (1977-2023)

Rates of water use, photosynthesis, leaf con­ductances, leaf growth, and epidermal and sto­mata! characteristics were examined in Dactylis glomerata L. and D. marina Borrill. Maximum leaf conductances were negatively correlated with epidermal papilla cell height which was greatest in D. marina and least in glomerata. Apparently because of this relationship, marina was able to maintain leaf growth rates longer during a drying pl:riod than was glomerata. D. marina plants were more efficient water users than were glomerata - growth rates of marina plants were greater for a given amount of water than were those of glomerata. Whole plant transpiration rates …

Evaluation Of Environmental Conditions And Physiological Processes Limiting Alfalfa Production Using Simed, R J. Bula, G E. Miles, M M. Schreiber, D A. Holt

IGC Proceedings (1977-2023)

Alfalfa (Medicago sativa L.) herbage accumula­tion, photosynthetic rate, and respiration rate were simulated over a 6-week period under three temperature regimes. The simulations were based on SIMED, a model of the growth and development of alfalfa. Highest herbage yields were noted under the 15 °C regime and lowest under the 25 °C regime. Herbage yields under the 20 °C regime were slightly less than under the 15 °C regime. These yield differences were due to higher photosynthetic rates, lower respiration rates, and a slower maturation rate under the 15 and 20 °C regimes compared to the 25 °C regime.

Formation Of The Biomass Of Long Established Meadow Plants After Sowing, Barbara Rutkowska, Barbara Stanko-Brodkowa, Elizabieta Lewicka, Zofia Debska

IGC Proceedings (1977-2023)

The formation of biomass was investigated in the period from 1971 to 1975 on a productive pasture newly sown up and on an intensively fertilized long-established pasture grazed five times during the growing season. The following layers were taken into consideration: in the above-ground biomass - the stubble (0-5 cm) and the productive crop (above 5 cm); in the underground biomass - the sod (0-5 cm) and the root biomass (5-35 cm). The structure and weight of the biomass, and particularly that of the underground bio­mass, of the newly sown pasture as early as in the third year became similar …

Investigations About The Reserve Carbohydrate Status Of Agropyron Repens Beauv. At Different Levels Of Nitrogen Fertilization Of Grassland, W Seyfarth, O Knade, W Kreil

IGC Proceedings (1977-2023)

Stolons of Agropyron repens were sampled at different dates in a trial fertilized with 0, 60, 120, 240, 480, and 720 kg N/ha for many years. From the carbohydrate fractions determii,ed by means of gas chromatography, the fructosan content, the degree of polymerization, and the content of structural substances are discussed. After heavy nitrogen fertilization the carbo­hydrate requirements of the plants could not be met for some time. Nevertheless, the vitality of plants did not decrease. When controlling Agropyron repens by way of mechanical and crop husbandry techniques, it is necessary to take into consideration the quantity of stolons increasing …

Features Of Regrowth Of Paniculate And Eragrostoid Perennial Grasses, I S. Belyuchenko

IGC Proceedings (1977-2023)

The regrowth of paniculate and eragrostoid grasses is conditioned by their peculiarities of tiller and bud formation. According to their arrangement and role in sward renewal, all vegetative buds of grasses are divided into five groups:

Apical buds of above-ground apogeotropic tillers; Lateral buds of above-ground diageotropic tillers; Lateral buds of above-ground apogeotropic tillers; Buds of tillering zone; Buds of rhizomatic tillers.

These groups of buds differ significantly in their stage of development. The major peculiarity of paniculate and eragrostoid grasses is their ability to regrow from lateral buds of above-ground apogeotropic and diageotropic tillers. The ecological conditions have a …

Tillering In Irrigated Smooth Bromegrass (Bromus Inermis Leyss.) As Affected By Elongated Tiller Removal, James W. Krause, Lowell E. Moser

IGC Proceedings (1977-2023)

A two-year field study at Mead, Nebraska, USA, showed that subsequent tillering was generally increased when 33, 67, and 100% of the elongated tillers were removed in Lincoln smooth bromegrass (Bromus inermis Leyss.). Apical dominance was apparently reduced when elongated tillers were removed and as a con­sequence new tillers elongated. If irrigated smooth bromegrass is grazed in the spring so about 67 % or more of the elongated tillers are removed and subsequent tillering will be in­creased. By removing only 67 % or slightly more of the tillers, remaining leaf area could supply carbohydrates to the small developing tillers.

Net Assimilation And Longevity Of Alfalfa Stands, R A. Moore

IGC Proceedings (1977-2023)

Stand reduction in established fields of alfalfa (Medicago sativa L.) has often been observed. This may be related to an increase in non­photosynthetically active tissue, causing respi­ration to exceed photosynthesis. Net carbon dioxide exchange rate (NCE) per unit leaf area and rate of respiration per gram of forage were determined from plants grown under field conditions. The uptake and evolution of carbon dioxide per plant were measured. The data suggest that the greater root mass of 2-year-old plants does add considerably to the evolution of carbon dioxide by the plant.

Some Results Of Studies On Correlations Between The Size Of The Assimilating Area And The Biomass Production In Medicago Sativa L. And Trifolium Pratense L., F Hrabe

IGC Proceedings (1977-2023)

The dependence of the biomass production upon the size of the assimilating area of Medicago sativa L. and Trifolium pratense L. was confirmed. However, this dependence was not linear in all the cuttings; in Medicago sativa and tetraploid Trifolium pratense the opti­mum values of the leaf area index (LAI) were 5 to 6 m2/m2 and 4 to 5 m2 /m2, respectively. In the second cutting, the highest production of both species was obtained when LAI was smaller by 1 m2/m2 than that of the first cutting. In M. sativa and tetraploid T. pratense the maximum assimilating area (leaves and stems) …

Morphological Characters Associated With Productivity Of Tall Fescue, C J. Nelson, D A. Sleper

IGC Proceedings (1977-2023)

Number of tillers and yield/tiller of tall fescue were similar in their association with forage yield, but were negatively correlated (r = -0.21 **) with each other. Area ofli:3f 6, which was correlated with leaf area expansion rate (r = 0.81 **), was correlated higher with yield/tiller (r = 0.58**) than with tiller number (r = -0.16*). Seeding characters were not strongly associated with number of tillers. In continental climates cool-season forage grasses produce most of their yield during the reproductive growth phase. In order to improve summer and fall productivity we are investi­gating development of the vegetative canopy. RHODES …

The Effect Of Changes In Crop Structure On Photosynthesis, Dry Matter Production, And Chemical Composition Of Lolium Perenne, L Sibma, W Louwerse

IGC Proceedings (1977-2023)

To study the effect of changes in leaf position in perennial ryegrass during the growing season, the leaf position was changed with wide­meshed wire netting in field and greenhouse experiments. CO2 measurements with a mobile unit showed that changing the leaf position from erecto­phile to planophile decreased the carbohydrate production by 30 %, and that proportional recovery of the production occurred when the leaves were replaced in the original erecto­phile position. Throughout a single growing period the nega­tive effect of a planophile leaf position on dry matter production above ground was 10% at the highest. This was associated with lower …

Influence Of Cutting Frequency On Quantity And Quality Of Root Matter Of Different Grasses After Two Years Of Utilization, J Stuczynska, S Jakubowski

IGC Proceedings (1977-2023)

The effect of cutting date and cutting frequency on the formation of the root system of several forage grasses was investigated in experiments over several years. The grass species differed in their response. Best tolerance of cutting was found in Festuca arundinacea, with Dactylis glomerata and Phalaris arundinacea ranking second and third, respectively. Bromus unio­loides was the most susceptible species. The amount of nitrogen contained in the dry matter decreased, for example in Dactylis, as the number of cuts increased. The mineral content of stubble and roots tends to increase as the cutting frequency goes up.

Trends Of Development In The Production Of Artificially Dried Feeds, M A. Smurygin

IGC Proceedings (1977-2023)

In recent years, many countries have seen trends towards specialization and enlargement of pro­duction units and transition to industrialized livestock farming technologies. New techno­logies are being prepared for feeding and industrialized feed production. The production of artificially dried feeds, including pellets and wafers, is going up continuously. The produc­tion of such feeds allows to cut nutrient losses to half and even one third as well as to accomplish mechanization and automation of feed production and feed distribution. Wider use of finished feeds in pelleted and wafered form, hence, will be instrumental to more requirement-oriented feeding and to maximiz­ing livestock production. …

Problems Of Modern Management Of Mountain Grassland, Jan Caputa

IGC Proceedings (1977-2023)

The importance of grassland does increase with the progression of latitude towards the polar circles, and with rising altitude. The potential of grass production is estimated to about 55 kg dry matter or 4 kg meat (live weight)/ha per day of growth. The develop­ment of management in mountain grassland does not keep the same rhythm as in the lowland. The modernization of mountain grass­land utilization should especially take into consideration the following points :

-Separation of lands being suitable or unsuit­able for agricultural purposes;

-Careful preservation for agricultural use of grassland areas suited for mechanized harvest of forage for winter …

Grazing Values Of The Boreal Forest And Tundra Regions, William L. Pringle

IGC Proceedings (1977-2023)

Grazing values of the Boreal forest and tundra regions of our world offer a tremendous future potential for the production of red meat. One of the only means we have of efficiently utilizing our northern lands is by grazing animals -that are able to forage over extensive areas. The Boreal forest and tundra biomes of the world occupy about 2. 3 billion ha. This area is equal to 85 % of the total potential arable area of the earth's surface. By far the largest portion occurs in the U.S.S.R. which has 1.2 billion ha of forest and 321 million ha …

The Intensification Off Forage And Livestock Production In Sub-Tropical Areas, L R. Humphreys

IGC Proceedings (1977-2023)

Options available for the intensification of forage production in sub-tropical areas are contrasted. Research on the removal of inedible species, the provision of stock-drinking water, the control of stocking rate and the incor­poration of well-adapted pasture legumes should receive priority. Approaches to maintaining continuity of forage supply and legume per­sistence are discussed.

The Importance Of Ley Farming For Improving The Forage Basis Of Tropical Africa, V A. Oyenuga

IGC Proceedings (1977-2023)

The concept and practice of including short­duration pasture mixtures or leys in agricultural rotations, particularly for intensive livestock production, are of recent development in tropical Africa. Although mixed farming -the keeping of animals for farm work, producing farmyard manure for the maintenance of soil fertility, and rearing of dairy cows to produce milk for household use - was first introduced as an organized system of settled farming in Nigeria in 1922, intensive animal husbandry, based on intensively maintained pasture mix­tures, be it on a small or large scale, is still in the process of widespread development in many parts of …

The Grassland Of Africa: Classification, Production Evolution And Development Outlook, H N. Le Houerou

IGC Proceedings (1977-2023)

Grasslands in the broader meaning, i.e. grazing lands, occupy huge areas in Africa, prob­ably in the vicinity of 10 million km2 (1000 million hectares), of which some 800 million hectares of permanent pastures and 200 mil­lion hectares of grazed woodland and open forest. There are also some 210 million hectares of crops and fallows most of which are grazed for part of the annual cycle. These African grasslands thus represent 7.5 % of the world's total land surface and 1/3 of its total acreage of grassland; they also corre­spond to 33 % of the surface of the continent, the remainder …

Pasture Possibilities In The Tropics, Fernando Perez Infante

IGC Proceedings (1977-2023)

Frnm an academic viewpoint, only biological aspects of pasture possibilities in the Tropics are considered in this paper. In spite of being an important . part of these possibilities, no mention would be made of a fundamental aspect, i.e. the one related to the people living in the Tropics and the ways in which they could make use of the potentials offered by their pastures to improve their living conditions. Thus when we come to consider "possibilities", it is not only a question of solving technical problems, but there are also economic and cultural factors which must be kept in …