Soil Science Commons^™

Effects Of Grazing Management On Seasonal Variation In Nitrogen Fixation, J L. Brock, J H. Hoglund, R H. Fletcher

IGC Proceedings (1977-2023)

Using the acetylene reduction assay, field studies in recent years have investigated the variation in N fixation in grazed systems, and some of the principles involved in the interaction with available soil N have been described. This experiment ex­tends this work to include the effect of grazing management on the factors influencing N fixation. Two self-contained sheep-grazed units, one a 10-paddock rotationally grazed system and the other set stocked, were estab­lished on a high-fertility ryegrass-white clover pasture, with a basic stocking rate of 22 sheep/ha. Over the 1975-1978 period, both units were monitored for pasture growth, N fixation, and associated …

Symbiotic Nitrogen Fixation Of Alfalfa, Birdsfoot Trefoil, And Red Clover, G H. Heichel, C P. Vance, D K. Barnes

IGC Proceedings (1977-2023)

Forage legumes such as alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus comiculatus L.), and red clover (Trifolium pratense L.), grown in crop rotations, can provide an inexpensive source of nitrogen (N) to succeeding crops. Few quantitative measurements of seasonal patterns of N fixation in managed communities of perennial forage legumes have been undertaken, chiefly because of the lack of satisfactory methods. Therefore, there is little knowledge of how N fixation varies with crop development, yielding ability, and weather patterns. Quantitative measurements of N fixation are important in choosing the appropriate legume for use in a crop rotation and for …

Photosynthate Supply And Nitrogen Fixation In Forage Legumes, P M. Murphy

IGC Proceedings (1977-2023)

Photosynthate supply is known to limit nitrogen fixation in legumes, and the resulting shortfall in energy supply necessary for maximum crop production may be aggravated by the energy-wasteful process of hydrogen (H2) evolution by the legume N2 fixing system. There is less information available on these aspects of the nitrogen-fixing process in forage legumes, such as white clover (Trifolium repens). The objectives of the present work were to determine how N2(C2H2) fixation and H2 production are in­fluenced by carbohydrate supply in forage legumes.

Plants were grown under controlled environmental conditions, and nodule energy supply was varied by adjusting …

Selection Of Rhizobium Strains For Enhanced Dinitrogen Fixation In Forage Legume Production, C Hagedorn, W E. Knight

IGC Proceedings (1977-2023)

A set of procedures for the selection of Rhizobium strains for enhanced dinitrogen fixation in forage legumes is presented. Although forage legumes are among the most efficient members of the Leguminosae regarding biological nitrogen fixation (BNF), they are generally neither productive nor persistent without effective nodulation by appropriate rhizobia. The following methods define a selection and evaluation process to obtain appropriate Rhizobium strains. These include (1) regional survey of the production area, (2) strain collection and soil analyses, (3) strain characterization, (4) strain selection and manipulation, and (5) field evaluation of strains. The initial procedure is to survey the region …

Interactions Between Grasses And Rhizosphere Nitrogen-Fixing Bacteria, M H. Gaskins, D H. Hubbell, S L. Albrecht

IGC Proceedings (1977-2023)

Sorghum and Digitaria cultivars grown in soil or nutrient solutions were inoculated with a strain of Azospirillum in short-term greenhouse experiments. Carbon compounds lost by roots in solution culture experiments were determined in order to estimate the quantity of energy substrates that might be obtained by rhizosphere organisms from growing plants. Other plants were treated with plant growth hormones, and responses were compared to those of plants treated with killed Azospirillum cells. The similarity of the responses suggests that growth-hormone production by the inoculant organism, rather than nitrogen (N) fixa­tion, is responsible for part or all of the increase in …

Simple Computer Simulation Models For Forage-Management Applications, G W. Fick, D Onstad

IGC Proceedings (1977-2023)

Dynamic computer simulation models of forage growth can be useful in interpreting physical and biological limitations on production and in designing management systems for testing in the field. The explanatory detail of such models makes them both more reliable and more expensive to use than simple empirical formulations. Simple simulation models reduce the expense. They can also serve as reference points for designing, evaluating, or selecting more complex versions and thus provide a more ra­tional basis for using models in grassland research and management. Our objectives were to develop and to test a simple dynamic simulation model of alfalfa (Medicago …

Energy Flow And Conversion Efficiency In Grazing Grassland, T Akiyama, S Takahashi, M Shiyomi, T Okubo

IGC Proceedings (1977-2023)

Measurable energy storage on grassland ecosystems was examined for 5 years at the Fujinita site under the same rotation pro­gram with two grazing intensities. Daily global solar radiation and photosynthetic active radiation were measured as the energy sources in the ecosystem. Primary production by pasture plants and amount grazed by cattle were estimated by the biomass dif­ferences inside and outside of protection cages. For the estimation of energy produced or stored by plants or cattle, calorific values were examined for dominant plant species at the Fujinita site. Seasonal changes in digestibility were investigated to ascertain the energy of herbage digested …

A System Approach To Swedish Ley Production, J F. Angus, A Kornher, B.W R. Torssell

IGC Proceedings (1977-2023)

A simulation model for estimating yield of leys from standard meteorological observations is described. It is based on an S-shaped growth curve also accounting for phasic development and regrowth depression. Effects of temperature, radiation, and soil moisture are accounted for by a growth index. Soil moisture is simulated with a standard water budget. The parameters in the model were estimated by comparing measured with calculated growth. The model then predicted final harvest with reasonable accuracy, but with underestimate of early season growth, presumably due to mobilization of car­bohydrate from storage organs. Observed ley yields from 49 Swedish parishes (1961-1978) were …

Age, Date Of Cutting, And Temperature As Factor Affecting Chemical Composition Of Berseem (Trifolium Alexandrinum L.), F Guessous

IGC Proceedings (1977-2023)

Chemical composition ofberseem (Trifolium alexandrinumL.), produced in winter and spring under irrigation in Morocco, was investigated in a 4-year study. Berseem was planted at various dates, and after the first cut had been harvested, samples were taken from each regrowth at weekly intervals. Total plant samples and leaf and stem samples were analyzed for dry matter

(DM), ash, crude protein (CP), and crude fiber (CF). A total of 172 samples of above-ground regrowth were analyzed and used to calculate multiple regressions of chemical composition on age and date of cutting. Date of cutting was defined as number of …

Forage Quantity And Quality Contributions From A Grass-Legume-Shrub Planting On A Semi-Arid Rangeleand, D A. Johnson, M D. Rumbaugh, G A. Van Epps

IGC Proceedings (1977-2023)

Poor grazing management has led to deterioration of vast expanses of the world's semiarid rangelands. Although contem­porary thought in range-management circles suggests that combinations of grasses, forbs, and shrubs are desirable in revegetating these areas, past revegetation mainly involved the establishment of monocultures of perennial grass. The objectives of this study were to determine the forage and protein yields of a grass-legume-shrub planting in a semiarid rangeland. The study was conducted in central Utah on a rangeland receiving 32 cm of annual precipitation. Crested wheatgrass (Agropyron cristatum) was established alone and in combination with fourwing saltbush (Atriplex canescens), alfalfa (Medicago …

Effects Of Water Stress On Herbage Quality, J R. Wilson

IGC Proceedings (1977-2023)

Uncertainty exists about whether drought is detrimental to the nutritive quality of herbage. This paper tries to resolve this uncertainty by examining the influence of soil moisture on some herbage-quality characteristics. Unpublished data from my own work and review of published literature are presented. Field plots of three tropical grasses, green panic (Panicum maximum var. trichoglume), buffelgrass (Cenchrus ciliaris), and speargrass (Heteropogon contortus), were subjected to perioqs of controlled drought, and herbage from these plots was compared with that from well-watered plots. Leaf and stem dry-matter ?igestibility of water-stressed herbage was either similar to or higher than that of unstressed …

Effects Of Climatic Zone, Topography, Land Utilization, And Soil Condition On Nutrient Composition Of Natural Grasses In Bali, I M. Nitis, K Lana

IGC Proceedings (1977-2023)

A survey based on climatic zone (zones B, C, D, E, and F), topography ( coast, hill, and higher altitude), land utilization (rice field, dry land, and plantation) and soil condition (moist and dry surface) was carried out during the wet (January to February 1979) and dry (August to September 1979) seasons in 15 districts of 8 regencies in Bali. The objective was to study the quality of the natural grass commonly fed to livestock in the mixed-farming system.

During the wet season, the crude-protein content ( on dry-matter basis) of the natural grass ranged from 7.4 % (in climatic …

Consumption Rates And Desert Grassland Herbivores, R D. Pieper

IGC Proceedings (1977-2023)

Studies were conducted on a desert grassland range in southern New Mexico for 3 years to determine relative consumption rates of the main herbivores utilizing these range areas. Consumption of some groups (cattle, pronghorn antelope, and rabbits) was determined from direct estimates of intake/individual, and density was determined from censusing procedures or known stock rates. Consumption by other groups (birds, rodents, and invertebrates) was determined from census information relating to age structure of the population and metabolic rate. Consumption by all herbivores averaged less than 5 % of the above-ground net primary productivity for the 3 years of the study. …

Pattern Of Defoliation By Cattle Grazing Crested Wheatgrass Pastures, B E. Norton, P S. Johnson

IGC Proceedings (1977-2023)

Summary Utilization of a monotypic stand of perennial grass by cattle is generally assumed to be a random process that can be ade­quately measured by counting the number of plants grazed or by comparing biomass on caged and grazed plots. At a similar level of approximation, grazing is often simulated experimentally by clipping down to a prescribed height. The purpose of our study was to examine defoliation in more detail, following grazing severity and frequency on an individual plant basis with an inter­val of only 48 hours between observations. The study was conducted on two 28-ha pastures of crested wheatgrass …

Performance Of A Subtropical Legume-Grass Pasture Under Different Grazing Management Systems, G E. Maraschin, S C. Mella, G S. Irulegui, J Riboldi

IGC Proceedings (1977-2023)

Agronomic evaluation of the dynamics of tropical legume-based pastures is relevant in assessing the response of their com­ponents within systems of grazing management. The response of tropical legume-grass mixtures to periods of rest and grazing pressure and the combinations that result in meaningful legume content in the mixture need to be known. A central composite design was used to study the performance of a Desmodium intortum (Mill.) U rb. and Paspalum gttenoarum Arech. pasture mixture to 14, 28, 42, 56, and 70daysofrestcombinedwith 2.0%, 3.5%, 5.0%, 6.5%, and 8.0% BW(i.e., kg dry matter (DM) on offer/day/100 kg body weight) as grazing …

Effects Of Treading And The Return Of Excreta On A Perennial Ryegrass - White Clover Sward Defoliated By Continuously Grazing Sheep, M L. Currl, R J. Wilkins

IGC Proceedings (1977-2023)

Grazing sheep may affect the association between grass and clover in a mixed sward by defoliation, treading, and the circula­tion of nitrogen (N) via excreta. Our objective was to examine the effect of treading and excreta on a perennial ryegrass (Lolium perenne)-white clover (Trifolium repens)sward defoliated by sheep at high and low stocking rates. Established swards of perennial ryegrass and white clover were continuously stocked from May to October with yearling wether sheep at 25 and';5() head/ha. Sward production and species composition were measured inside graze-through cages that allowed defoliation without treading and excreta return, and …

Legume Establishment In Grass-Dominant Swards: Concept And History In Kentucky, T H. Taylor, W C. Templeton Jr

IGC Proceedings (1977-2023)

Grassland farming has been practiced for 2 centuries in central Kentucky and for shorter periods in other parts of the state. Savannas and tallgrass prairies were severely grazed by domestic animals and row-cropped by early settlers, destroying most of the indigenous plant species. By the early part of the 19th century, beef cattle were being produced on bluegrass (Poa pratensis L.) pastures and driven on foot to east-coast markets. During the first century of settlement, farmers learned to top-seed legumes into grass sods, and in the course of the last hundred years development of grassland technology for establishing legumes …

Establishment Of Grasses On Cracking Clay Soils: Seedling Morphology Characteristics, L A. Watt

IGC Proceedings (1977-2023)

Although native grasses establish readily on the cracking black clay soils of northwestern New South Wales, it has proven dif­ficult to establish introduced summer grasses. Young grass seedlings were examined to see if morphological differences exist that may explain their differing capacities for establishment. It has been shown that relative differences in the primary and secondary root growth of vario1-,s species can have important ef­fects on the agronomic characteristics of those species. Low soil moisture conditions near the soil surface will restrict greatly or possibly even prevent the growth of secondary roots of young aeedlings. It is well known that …

Seed And Seedling Dynamics Of Annual Medic Pastures In South Australia, E D. Carter

IGC Proceedings (1977-2023)

Annual species of Medicago (i.e., medics) are the key to successful cereal-pasture rotations in the integrated crop-livestock farming systems on the neutral to alkaline soils of southern Australia. However, many medic stands have deteriorated in recent years. This deterioration has prompted research on the effects of grazing sheep on the seed-seedling dynamics of annual medic­based pastures in the Mediterranean environment of South Australia, aiming to quantify the impact of medic seed reserves in or on the soil upon pasture establishment and productivty.

Animal-house experiments involving the feeding of purepod and pod-chaff diets to sheep and a field experiment have been …

Mortality Of Sorghum Plants After Cutting, Y Takasaki, Y Takasaki, H Nojima

IGC Proceedings (1977-2023)

Sorghum (Sorghum spp.) is usually harvested twice a year in most of Japan but three times a year in southern Japan. Some sorghum plants die after cutting, which leads to low aftermath yield. The purpose of this study was to clarify what cultural fac­tors cause death and what plants die in the sorghum stands. Three field experiments were carried out from 1977 to 1979 to investigate the effect of sowing date, planting density, nitrogen (N) level, and cultivar on mortality rate after cutting. In 1979 the effect of high temperature on mortality was investigated. In­formation about what plants die was …