Agronomy and Crop Sciences Commons^™

Photosynthesis And Dry-Matter Distribution In Altitudinal Ecotypes Of White Clover, J Noseberger, F Machler, B C. Boller

IGC Proceedings (1977-2023)

Productivity of white clover (Trifolium repens L.) is limited by plant characteristics that prevent efficient use of environmen­tal inputs. In the temperate zone, low temperature often limits growth. Comparisons of ecotypes originating from sites with cool or warm climatic conditions (low or high altitudes) can show, when plants are grown in a common environment, the degree of adaptation of processes related to net photosynthesis and the distribution of dry matter. Our objectives were to determine the photosynthetic responses to temperature in relation to the thermal regime during growth and the effects of temperature and daylength on partitioning of dry matter …

Photosynthesis Of Grass Swards Under Rotational And Continuous Grazing, B Deinum, M L. 'T Hart, E Lantinga

IGC Proceedings (1977-2023)

First-year results are presented on the photosynthesis of grass swards under intensive rotational or continuous grazing. In rotational grazing, crop photosynthesis was high in spring, declining during grazing but recovering rapidly during regrowth, possibly because of the high photosynthetic capacity of individual leaves and of the great area of active leaves left in the sward. In autumn, crop photosynthesis was rather high initially, declined rapidly during grazing, and recovered slowly during regrowth, possibly because photosynthetic capacity of the leaves was low, the decline with age was great, and the active leaf area in the stubble was small. Crop photosynthesis under …

Physiology Of Growth Of A Grazed Sward, E L. Leafe, A J. Parsons

IGC Proceedings (1977-2023)

To improve our understanding of grassland utilization under grazing, the physiology of a grazed sward was investigated. An enclosure method, infrared gas analysis, and radiocarbon were used to measure sward and single-leaf photosynthesis and assimilate utilization. Intake by sheep was also measured. Expanding and recently expanded leaves had high rates of net photosynthesis but leaf sheaths, whose projected area in a "hard" grazed sward equaled that of the lamina, had low efficiency and contributed little to canopy photosynthesis. But because high leaf efficiency did not compensate for the small leaf area, canopy photosynthesis decreased markedly as grazing intensity increased. Twice …

Leaf Growth And Grain Yield Of Wheat In North-South And East-West Rows, M B. Kirkham

IGC Proceedings (1977-2023)

Few experiments report the effect of row direction on growth of wheat in windy areas. The objective of this research was to determine the optimal row direction for winter wheat (Triticum aestivum L. em. Thell;) in the southern Great Plains of the U.S.A. for minimizing stress from wind, optimizing leaf growth (forage yield), and maximizing grain yield. During a 3-year period (1976-1979), Osage wheat was grown in north-south (NS) and east-west (EW) rows. Wind, soil water content, stomata! resistance, leaf water potential, leaf osmotic potential, elemental concentration of straw and grain, height, leaf area, and grain yield were measured. Prevailing …

Plant-Water Relationships Of Crested, Pubescent, Slender, And Western Wheatgrass, A B. Frank

IGC Proceedings (1977-2023)

Objectives were to characterize development of water stress in the field and in controlled environments; to determine stress ef­fects on transpit"ation (E), stomata} conductance (C), leaf water potential (LWP), leaf osmotic potential (LOP), and photosyn­thesis (P); and to relate measured changes to drought tolerance in crested wheatgrass (Agropyron desertorom [Fisch.] Schult.), slender wheatgrass (A. trachycaulum [Link] Malte.), pubescent wheatgrass (A. intermedium var. trichophorum [Link] Haloc), and western wheatg:rass (A. smithii Rydb. ). Both L WP and LOP decreased for all species as soil water potential decreased, but not in a 1: 1 ratio indicative of maximum osmotic adjustment. The LWP …

Responses Of Siratro (Macroptilium Atropurpureum) To Water Stress, M J. Fisher, M M. Ludlow

IGC Proceedings (1977-2023)

Experiments were conducted to seek understanding of the adaptive characters that contribute to the success of the twining tropical legume siratro (Macroptilium atropurpureum) as a component of sown pastures in the seasonally dry tropics and sub­tropics of northeastern Australia. Siratro was grown both in the field and in controlled environments and was subjected to se­quences of water stress. Measurements were made of tissue-water relations, leaf gas exchange, leaf movement, and leaf energy balance. Siratro avoids the effects of stress by maintaining its leaf-water potential greater than -20 bar, while grasses grown in associa­tion with it are about -60 to -80 …

Comparative Flooding Tolerance Of Tropical Pasture Legumes, P C. Whiteman, M Seitlheko, M E. Siregar

IGC Proceedings (1977-2023)

Growth and persistence of many tropical pasture legumes can be limited by flooding or waterlogging. Selection of tolerant species is important for pasture development in the humid lowland tropics. The aim of this project was to compare flooding tolerance of seven tropical pasture legumes and to determine whether the pot technique we developed was reproducible and rele­vant to the field situation. Plants were grown in pots and at the start of flowering were flooded to 15 cm above soil level. Water temperature and oxygen content were monitored regularly. Sets of four uniform pots were removed from flooding after 7, 14, …

Responses Of Alfalfa To A Simulated Midwinter Thaw, M Suzuki

IGC Proceedings (1977-2023)

Effects of a freezing-waterlogging-freezing treatment, under controlled environmental conditions, on the viability and chemical components of alfalfa (Medicago sativa L.) were determined to assess physiological responses to midwinter thaw. Alfalfa plants grown in a field were more resistant to freezing but less resistant to waterlogging than those grown in a greenhouse. Both types of plants sustained severe damage from the second freezing treatment. An accumulation of ethanol and methanol, a solubilization of proteins, and a decrease in carbohydrates occurred during the waterlogging. Two important physiological characteristics for surviving a midwinter thaw appear to be an ability to maintain freezing resistance …

Seombadi (Dystaenia Takesimana [Nakai] Kitagawa), A New Forage Plant: Its Germination And Early Growth Characteristics, D A. Kim, S H. Hur, Y J. Kim, C M. Park

IGC Proceedings (1977-2023)

Seombadi (Dystaenia takesimana [Nakai} Kitagawa) is a member of the Apiaceae (Umbelliferae) family and is ecologically adapted to the island of Ulneung, situated 160 km off the east coast of the Korean peninsula. The plant is an important forage for livestock on the island; but because of lack of knowledge about its germination, and its slow establishment characteristics, its use on mainland Korea has been limited. Objectives of our study were to examine the seed characteristics and factors affecting germination of seombadi and to evaluate depletion of seed food reserves and elongation of organs of seedlings during germination and …

Climatic Influences During Flowering On Seed Dormancy And Seed Formation Of Stylosanthes Hamata Cv. Verano, P J. Argel, L R. Humphreys

IGC Proceedings (1977-2023)

Effects of variation in temperature, soil moisture supply, and illuminance on seed dormancy and seed formation of Srylosan­thes hamata cv. Verano were studied. Plants were grown in the open in successive seasons, in controlled-temperature cabinets, and in the greenhouse where shading and watering treatments were varied after the onset of flowering. Hardseededness was strongly developed and was positively related to temperature during seed formation. After seed matura­tion, seed moisture content was the main factor governing hardseededness, and this quality was negatively associated with temperature during seed formation. High levels of hardseededness developed in all seeds when seed moisture content was …

Strategies Of Seedling Development In Warm-Season Grass, L E. Moster, C J. Nelson

IGC Proceedings (1977-2023)

Establishment of warm-season prairie grasses is often difficult because of slow seedling growth and weed competition. Seed­

ling development of four perennial warm-season grasses was compared with that of a vigorous annual grass, giant foxtail (Setaria faberi Herrm.) Big bluestem (Andropogon gerardii Vitman), switchgrass (Panicum virgatum L.), indiangrass (Sorghrutrum nutans [L. J Nash), caucasian bluestem (Bothn'ochloa caucasica [Prin.] C .E. Hubb. ), and giant foxtail were grown in a greenhouse. Leaf elongation rate, collaring date, and leaf length were measured daily. Carbon-exchange rate (CER) was determined. Plants were harvested at the sixth and eighth leaf …

Phenology And Culm-Weight Variation Between Two Wheatgrass Species: Agropyron Smithii And A. Spicatum, M K. Owens, H G. Fisser

IGC Proceedings (1977-2023)

Knowledge of plant phenology and live weight dynamics is necessary for intensive management of semiarid rangelands. Thir­teen sites in Wyoming were sampled for plant phenological development and culm weights of western wheatgrass (AgroP.,ron smithii) and bluebunch wheatgrass (A. spicatum). These species are sympatric and allopatric within these rangelands. Such a distribution allows site comparisons between these species. Environmental data were collected for use in differentiating sites. Data on all variables were collected at 14-day intervals throughout the growing seasons of 1979 and 1980. Permanently marked plants were sampled for phenology, and plants of similar development were collected for culm-weight estimates. …

Simple Mixtures For Dry Mountain Regions: Relations Between Tall Fescue And Birdsfoot Trefoil During Five Years, G Haussmann, P Paoletti, C Locatelli

IGC Proceedings (1977-2023)

Grass-legume mixtures are of great interest, especially in central and northern Appennine regions with a summer dry season .. Birdsfoot trefoil (Lotus comiculatus L.) cv. Franco and tall fescue (Festuca anmdinaceaSchreb.) cv. Manade were grown in mixture and in pure stand at the experimental farm of the Institute. Our objectives were to determine the seeding rates in the mixtures and the most suitable method of sowing. The two species were seeded in mixture and alone to 20 seeding treatments: (a) 16 mixtures in alternate rows 12 cm apart, in factorial combinations of four seeding rates (5-10-12-15 kg/ha …

Utilization Of Hydromorphic And Alkaline Hydromorphic Soils In Sap Vojvodina By Establishing Cultivated Grassland, B Miskovic, P Eric

IGC Proceedings (1977-2023)

Hydromorphic and alkaline hydromorphic soils are heavy and unsuitable for the growing of row crops. Their poor structure and water and air properties make cultivation expensive. The establishment of cultivated grassland for production of fodder for 4 or 5 years requires less expenditure than that necessary for the production of row crops. Four years of experiments, conducted on hydromorphic and alkaline hydromorphic soils, included four grass cultivars and three legume cultivars. Yields, chemical composition and physical properties of hay, and soil properties were examined. The results indicated that cultivating grasses for the production of fodder is a good use of …

Interception Of Rainfall By Creosotebush (Larrea Tridentata), J M. Tromble

IGC Proceedings (1977-2023)

The objective of this study was to examine interception by creosotebush (Larrea tridentata [DC.] Cov.) of artificially applied rainfall for improved understanding of this phenomenon in hydrologic processes. This research was conducted near Las Cruces in southern New Mexico. Forty-four creosotebush shrubs were collected to obtain a representative sample of shrub size classes. Simulated rainfall was applied at the rate of 6 cm/hr. Measurements taken for each shrub were: (1) shrub height, (2) canopy area, (3) shrub volume, (4) number of stems, (5) leaf area, (6) green weight of stems, (7) oven-dry weight of stems, (8) green weight of …

Grassland Development In The Southern Highlands Of Peru, E J. Stevens, P Villalta

IGC Proceedings (1977-2023)

This paper describes grassland development in Peru. Vegetation of the high alpine region of Peru, which occupies some 4 million ha, is dominated by native grasses normally producing less than 2,000 kg/ha dry matter annually. On land with ade­quate soil moisture, pastures based on perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) were established successfully, but on drier sites alfalfa proved superior, producing over 12,000 kg/ha/yr in some trials. Alfalfa and clovers were also successfully introduced into improved native pastures by mechanical direct seeding and by hand sowing. With direct seeding, dry-matter production increased from about …

Pasture Evaluation In The Desertic Zone Of Venezuela For The Development Of Goat Production, A Gallardo, A Leone

IGC Proceedings (1977-2023)

The desertic zone of Venezuela is an area of approximately 4.1 million ha that represents 4.8 % of the total national territory, on which there are two million goats. Goats represent the main, if not the only, income source for 60,000 rural families. According to UNESCO (1973), the desertic zone of the country comprises two vegetation types, evergreen scrub and deciduous scrub. In each of these zones the plant species consumed by goats were collected and, for those plant parts consumed by the animals, chemically analyzed to determine nutritive value. Forage plants from other tropical countries were also in­troduced and …

Evaluation Of Biological Components In Decision-Making In Forage Allocation, J E. Skiles, G M. Van Dyne

IGC Proceedings (1977-2023)

Forage allocation to mixtures of large herbivores is accomplished by minimizing the difference between the available herbage and the required forage for animals on rangeland. Availability is determined in part by the plant's physiological tolerance to grazing or its allowable-use factor and the animal preference for that plant, measured in part by the proper-use factor. The mix of large herbivores on the rangeland must also be considered. The grazing requirements for animals are dependent on animal preference for plant species and on the total forage intake rates. This paper presents an analysis of these concepts and published information. The concept …

Nutritional Quality Of Leaf Proteins Prepared From Crops Containing Phenolic Compounds And Polyphenolase, T Horigome, S Uchida

IGC Proceedings (1977-2023)

Many studies have indicated that leaf protein prepared by green crop fractionation affords good potential as a protein supple­ment. It has been noted, however, that there were some marked differences between crops in the nutritional quality ofleaf pro­tein in spite of a similarity in amino-acid composition between leaf proteins made from different crops. We previously showed that brown casein, which was produced by the interaction of milk casein with phenolics undergoing enzymic oxidation, had lower nutritional value than original casein. In addition, it has been suggested that leaf proteins prepared from crops containing phenolics and polyphenolase were brown after extraction …

Hail As An Ecological Factor In The Increase Of Pricklypear Cactus, W A. Laycock

IGC Proceedings (1977-2023)

Detached joints or pads of plains pricklypear cactus (Opuntia pov,acantha) can root and form new plants. However, few data exist to quantify this phenomenon or to describe conditions under which rooting takes place. A severe hailstorm at the Central Plains Experimental Range in northeastern Colorado on 31 July 1978 broke segments from plants of plains pricklypear. This oc­currence provided an opportunity to determine the amount of joint dispersal and rooting from a natural destructive event. Cactus joints detached and scattered by the force of the hail were counted on permanent belt transects established in two pastures having different pricklypear populations. …