Agricultural Science Commons^™

Identification And Use Of Key Grass Species In The Assessment Of Range Condition In South Africa, Andrew C. Beckerling, Winston W. Trollope

IGC Proceedings (1977-2023)

This paper explains the concepts and method behind the identification and use of key grass species for the development of user friendly techniques for the assessment of range conditions. A database comprising the frequency of 90 grass species and associated environmental factors from 712 sample sites was used to identify 19 key grass species. Stepwise multiple regression and Detrended Correspondence Analyses (DCA) were used for this purpose. The key species accounted for 90% of the variation in forage production potential and 90% of the variation in the 2 environmental gradients identified in the ordinations. Models were created to predict forage …

Stability Of Arid Western Queensland (Australia) Rangelands And Their Grazing Management, I F. Beale

IGC Proceedings (1977-2023)

Western Queensland rangelands are showing productivity losses which appear to involve grazing management. Changes are required to, arrest this trend. Needs for. information and monitoring of change are indicated. Little information exists for these rangelands, so lntroduction of overseas grazing management systems could create problems. Their application, with monitoring and research, could contribute to sustainabllity.

Grass-Legume Balance Under Grazing In The Humid Tropics Of Costa Rica, M Ibrahim, L'T Mannetje

IGC Proceedings (1977-2023)

A grazing experiment is in progress in Costa Rica with Arachis pintoi, Centrosema macrocarpum and Stylosanthes gulanensis combined with Brachiaria brizantha and B. Humidicola at 2 stocking rates. The proportion of C. macrocarpum declined in all treatments to low levels,· as did S. gulanensls, except at the low stocking rate in association with B. humidicola. A. pintoi maintained a high proportion with B. humidicola, especially at the high stocking rate. The best grass-legume balance was achieved in the combination of A. pintoi with B. brizantha at the high stocking rate. Volunteer species dominated the C. macrocarpum …

Management And Use Of Complex Landscapes: Some Implications Of Spatial Variation For Pasture And Animal Production, J A. Taylor, S J. Cook

IGC Proceedings (1977-2023)

This paper describe.s some of the spatial variation in microclimate,' soils and vegetation across the black speargrass (Heteropogon contorus) grazing lands of south-east Queensland. Differences in the establishment and survival of oversown legumes, and in animal production', associated with this variation were examined in a large­scale grazing trial. The consequences of spatial heterogeneity are discussed in relation to species evaluation, restoration of degraded grazing lands and the development of sustainable grazing systems.

Land Condition And Overgrazing: A Management Paradox For The Savannas Of Northern Australia, Andrew J. Ash, John G. Mcivor, Joel R. Brown

IGC Proceedings (1977-2023)

The tropical savannas of northern Australia have been an important resource for the production of beef for over a century. Excessive stocking rates regimes have led, in some areas, to degradation of the soil and vegetation resource. A state-and-transition model is used to describe the decline in land condition with overgrazing. A grazing study has been established at 2 sites to determine the consequences of a change in land condition for animal production, and pasture production and quality are being related to land condition at additional small sites. Preliminary results indicate that as pasture condition declines, pasture production decreases but …

A Decision-Support System For The Sustainable Use Of Australian Monsoonal Tallgrass Woodlands, J A. Bellamy, D Lowes, N D. Macleod

IGC Proceedings (1977-2023)

Inappropriate grazing management strategies have caused degradation of the extensive rangelands of northern Australia involving changes in pasture composition, invasion of woody weeds, a reduction in total vegetative cover and increased soil erosion. This degradation has reduced productivity, increased variability In production, and threatened the long-term sustainability of the land resource base. To help address the problem, a prototype micro computer-based decision support system, called Landassess DSS, is under development for the monsoonal tallgrass woodlands of northern Australia. Landassess DSS will use object­oriented design and artificial intelligence techniques to integrate a knowledge-based system, a relational database management system and a …

Dynamics Of Stylosanthes Scabra In Tropical Savanna Woodland In Eastern Australia After Treatment With Tebuthiuron, E R. Anderson, P V. Back, M T. Rutherford, M J. Conway, D J. Myles

IGC Proceedings (1977-2023)

This paper records for the first time the effect of the herbicide tebuthiuron aerially applied onto Stylosanthes scabra pastures that had been established in a poplar box (Eucalyptus populnea) woodland in a summer-dominant 616 mm annual rainfall area. Tebuthluron was applied at 1.0 and 1.S kg ai/ha as Graslan pellets. Stylosanthes plant populations and yield were recorded for the 3 years 1988-1991. Results indicate that the tebuthiuron could be used for the control of woody plants in a Stylosanthes pasture without too great a deleterious effect if the rate does not exceed l kg/ha and the pasture has been …

A System For Objective Condition Assessment Of Astrebla Spp. Pastures At The Paddock Level For Better Grazing Management, D G. Phelps, J J. Bushell, O.J H. Bosch, D J. Kent, I F. Beale

IGC Proceedings (1977-2023)

Degradation gradients due to grazing were determined from floristic data collected between January 1990. and November 1991 in the Astrebla correlation between grasslands of Longreach, abundance and Australia. condition A score linear correlation between Astrebla abundance and condition score confirmed strong confirmed linear the presence of gradients. Astrebla Degradation models were further validated by the presence of known grazing gradients. A model constructed from data collected in late to mid summer was then used to illustrate changes in the condition of 4 monitoring sites. A site ;initially in "poorer" condition, and an overgrazed site did not markedly improve in condition. …

Case Studies And Causes Of Weed Invasion Of Sown Pastures On The Wet Tropical Coast Of Eastern Australia, H G. Bishop, T B. Hilder, G A. Lambert, E R. Anderson

IGC Proceedings (1977-2023)

Viability of large and successful sown pasture development on the wet tropical coast of eastern Australia is threatened from invasion of these pastures by unpalatable grass and legume weeds. The main threats discussed are invasion by the unpalatable grass weeds Sporobolus diandrus (tussocky sporobolus) and Sporobolus pyramldalis (giant rat's tall grass) and the unpalatable, annual legume weed Senna obtusifolia (sicklepod). Specific cases of invasion and suggested causes for the problems are discussed. The major causes· suggested for pasture decline and invasion by less productive weedy species are: disease that can suddenly wipe out an otherwise …

Standing Root Biomass And Root Distribution In Brachiaria Decumbens- Arachis Pintoi Pastures Under Grazing, M A. Ayarza, I M. Rao, R J. Thomas, M J. Fisher, C E. Lascano, P Herrera

IGC Proceedings (1977-2023)

A vigorous rooting system is a vital strategy developed by acid•soil• tolerant forage species to cope with soil acidity constraints. The biomass of standing roots and its distribution was characterised under grazing in pastures of Brachiaria decumbens and Arachis pintoi grown alone and in association. Soil cores showed that standing root biomass to the depth of 100 cm was higher than the above ground biomass in the single species pastures. However, the relation was reversed in the grass•legume association. Root mapping showed that while the largest percentage of roots was located in the 0·20 cm depth of soil of the …

Dynamics Of The Vegetation Of A Natural Pasture Under Different Levels Of Forage-On-Offer And Soil Types, Ilsi I. Boldrini, Gerzy E. Maraschin, Joao Riboldi

IGC Proceedings (1977-2023)

To document changes in species composition during 5 years of grazing al different levels of forage,-on-offcr, 60 permanent quadrals of 0.25 m1 were established in 30 ha of annual posture at the Estacno Experimental Agronomica, UPROS, Brazil. Rhizomatous and stoloniferous species dominated In low forage-on-offer treatments while caespitose species dominated in higher forage-on-offer levels. Soil organic matter and water contents increased with increasing levels of forage-on-offer.

First-Year Stand Development Of Subtropical Grass Seedlings And Influence By Initial Plant Density, Bruce Anderson, L E. Moser

IGC Proceedings (1977-2023)

Stands of subtropical grasses develop slowly in mid-continent North America and this may be due partly to initial plant density. Panicum virgatum L. and Andropogon gerardii Vitman seedlings were transplanted from a greenhouse into field plots as pure stands in equidistant spacings at initial plant densities of 2.5, S, 10, 20, 40 and 80 plants/m1. P. virgatum produced higher yields, fewer tillers/plant and leaves/tiller, less basal density and shorter plants than A. gerardii during the first year of growth. Light interception was higher and soil temperatures lower for A. gerardii. Basal density and height increased while tillers/plant decreased …

Use Of Natural 15n Abundance In Estimating Nitrogen Fixation By Centrosema Spp: Influence Of Phosphorus And Strain Of Bradyrhizobium, G Cadisch, S F. Ledgard, J Noseberger, R Sylvester-Bradley

IGC Proceedings (1977-2023)

Isotopic ¹⁵N fractionation during N2 fixation by Centrosema acutifolium, C. brasilianum and C. macrocarpum grown in N·free sand-nutrient solution was investigated as a prerequisite for the use 9f the natural ¹⁵N abundance method to estimate N2 fixation. The natural abundance of ¹⁵N was always lower in shoots than in roots and nodules, and there was little difference between species. In contrast, inoculation strongly influenced isotopic fractionation, leading to average o15N shoot values of -0.64 and -1.37 for Bradyrhizobiumstrains CIAT3101 and 1670 respectively, given adequate phosphorus. P deficiency led to a small legume x P interaction …

Importance Of Legume Nitrogen Fixation In Sustainability Of Pasture In The Cerrados Of Brazil, G Cadisch, E F. Carvalho, A R. Suhet, L Vilela, W Soares, J M. Spain, S Urquiaga, K E. Giller, R M. Boddey

IGC Proceedings (1977-2023)

A pure Andropogon gayanus sward was compared with a Stylosanthes spp.-A. gayanus mixed sward in order to assess the benefit of introducing N2-fixing legumes on the long-term sustainability of grazed pastures. There was no difference between the total dry matter and animal production of the 2 pastures, although the legumes fixed 67-117 kg/ha of N in 1991 with 80% of the legume N obtained from N2 fixation. Litter deposition was 20-35% greater in the mixed sward and the % N in this litter was also higher, leading to twice the amount of N mineralised in the 0-5 cm …

Attainment And Distribution Of Competitive Equilibrium In Tropical Grass-Legume Mixtures, P G. Tow

IGC Proceedings (1977-2023)

An experiment under controlled conditions, using the de Wit competition model, has provided an explanation of competitive relationships in mixtures of Panicum maximum var. trichoglume (green panic) cv. Petrie and Neontonia wightii cv. Tinaroo glycine. Experiments in a tropical upland environment with summer rainfall dominance (to which they ore adapted) have provided further understanding of their relationships. Over a period of 2 years for well-wafered plants in containers and 4 years in a rain-fed field experiment, competitive gains by one species alternated with-gains by the other, and neither species gained significantly overall. Gains by the grass were favoured by …

Managing Woody Weeds In Grazing Ecosystems: Application For Tropical Woodlands Of North-Eastern Australia, Joel R. Brown, John G. Mcivor, Andrew J. Ash

IGC Proceedings (1977-2023)

Shrub invasion of tropical woodlands is reducing the viability of native ecosystems as well as the livestock industry, After shrub invasion, forage supply is reduced and over-grazing and soil erosion are exacerbated. We propose a non-equilibrium model of the system and use that model to develop hypotheses and design experiments to test both competition- and disturbance-based management regimes. This model proposes that disturbance in the form of burning is the primary limiting factor in excluding and limiting shrub seedling establishment and suggests that management decisions focus on maintaining adequate herbaceous biomass for a burning regime that limits woody plant success.

Fire And Grazing Interact To Manipulate Pasture Composition In Heteropogon Contortus (Black Speargrass) Pastures, D M. Orr, C J. Paton

IGC Proceedings (1977-2023)

Aristida spp, (wiregrasses) are invading areas of Heteropogon contortus (black speargrass) pastures in southern Queensland. Interim results from 2 field experiments indicate that increasing the frequency' of annual spring burning over 3 years, with and without grazing, results in a progressive reduction in the yield of Aristida spp. H. contortus yields also increased with increasing frequency of burning under non-grazing but not when grazed, H. contortus yields have increased after burning when grazing has been deferred or where the stocking rate has been halved after the fire. The results suggest that botanical composition in these pastures can be manipulated readily …

Impact Of Grazing Pressure On The Plant Population Dynamics Of Heterpogon Contortus (Black Speargrass) In Subtropical Queensland, D M. Orr, C J. Paton

IGC Proceedings (1977-2023)

Heteropogon contortus is a palatable pasture grass which is being threatened by , increases in grazing pressure, particularly during drought. This paper presents interim results plant population dynamics of H. contortus., as affected by stoc.1s tak. legume augmentation (mainly Stylosanthes sabra cv. Seca) and p1 Jvision of a dry-season supplement for cattle. The study began in 1%8. By 1991, basal ara of H. co11tortus was highest at the light .. Jt stocking rate of 0.187 steers/ha and declined linearly to be longest at the heaviest stocking rate of 0,5 steers/ha. Similarly, survival of the H. contortus tussocks initially present …

Seca Stylo (Stylosanthes Scabra Cv. Seca) Populations Increase Faster Under Light Grazing, D M. Orr, C J. Paton

IGC Proceedings (1977-2023)

Augmentation of native pastures with legumes such as Stylosanthes scabra can increase cattle live-weight gain relative to that from native pasture. In the longer term, however, Stylosanthes spp, density can increase and populations of native grasses may become unstable. This paper reports interim results from a study aimed al monitoring changes in the density of S. scabra cv. Seca in relation to stocking rates, The density of Seca monitored in permanent quadrats increased from 15 plants/m2 in 1988 to 100 and 25 plants/m2 in 1992 at 0.25 and 0.5 beasts/ha respectively. These increases resulted from both the survival of the …

Clover-Based Pasture Systems For Intensive Sheep Production In The Central Highlands Of Papua New Guinea, S Sivasupiramaniam, A K. Benjamin, J Pitala

IGC Proceedings (1977-2023)

This paper describes some of the studies that have been conducted since 1985 to develop clover-based pasture systems for intensive sheep production in the central highlands of Papua New Guinea. The clovers tested were Trifolium repens cv. Haifn (Haifa white clover) and Trifolium semipilosum cv. Safari (Kenya white clover). They were sown together, with setaria (Setaria sphacelata cv. Nandi) and signal grass (Brachiaria decumbens cv. Basilisk) at Menifo (1400 m asl) and with setacia and kikuyu (Pennisetum clandestinum cv. Whittet) at Tambul (2240 m) and Yogos (1950 m) in the central highlands. At Menifo, when rotationally grazed …

An Integrated Approach To Soil-Plat-Animal Interactions On Grazed Legume-Based Pastures On Tropical Acid Soils, M J. Fisher, C E. Lascano, R J. Thomas, M A. Ayarza, I M. Rao, G Rippstein, J.H M. Thornley

IGC Proceedings (1977-2023)

Legume-based pastures developed by the Tropical Pastures Program (TPP) of CIAT give spectacular increases in both stocking rates and animal live-weight gains on the savannas of Latin America, A team within the TPP is addressing the problems of their management for legume persistence and soil-plant-animal interactions, using as Its focus a grazing experiment on 2 oxisols of contrasting texture on the Colombian Llanos. The objective is to model the pastures to forecast the effect of management options on long-term persistence and nutrient cycling in grazed legume•grass associations in the Latin American savannas.

Persistence Of Roundleaf Cassia In Grazed Pastures - A Conceptual Model, R M. Jones, C K. Mcdonald, G A. Bunch

IGC Proceedings (1977-2023)

Roundleaf cassia (Cassia rotudifolla) cv. Wynn is a short-lived perennial that relies on seedling recruitment for long-term persistence. Its persistence is considered in terms of survival of plants from the initial sowing, seed set, seedling recruitment, run-down of reserves of soil seed, and survival of seedlings. The major factor controlling all these stages is soil moisture stress; grazing management 'is less important. A conceptual model of Wynn persistence is presented and progress in mathematical modeiling is reported.·

Variation In Hydrological Characteristics Of The Soils Associated With Grazed Patches In Granitic Landscapes In Northern Australia, M M. Sallaway, D Waters, B Bridge, F P. Wandera

IGC Proceedings (1977-2023)

Under medium to heavy grazing of black speargrass (Heteropogon contortus) landscapes of south-east Queensland, "patchiness" has developed with a change from H. contortus to Aristida spp., Cllrysopogo11 spp. or a,inual grasses. This grazed patch development is associated with changes in soil hydrological characteristics which in turn affect runoff and soil erosion. T!\e soil hydrologic properties were studied using a rainfall simulator and disc permeameter. The remnant H. contortus areas had higher infiltration characteristics mainly due to the maintenance of larger mncropores (1-3 mm). In the Arlstida patches, the contribution of those large macropores has been greatly reduced. Th is effect …

Evaluation Of Pastures For Sustained Beef Production In Subtropical New South Wales, P T. Mears, D L. Garden, R W. Dicker

IGC Proceedings (1977-2023)

Limitations of low-quality grass pastures, soil fertility, mechanisms of legume persistence and the long-term sustainability of pastures for beef production were studied in a humid subtropical environment of New South Wales, Australia. Sustainability of pastures and animal growth responses in 3 experiments (varying from 4 to 10 years' duration) al 2 sites have been analysed and described. Steers or heifers were used lo assess the effects of introducing subtropical or temperate legumes, level of superphosphate and stocking rate on natural grass pastures, Principal factors which improved the level of beef production from pasture were (i) introducing persistent legumes (ii) level …

Bothriochloa Pertusa- A Useful Grazing-Tolerant Grass For The Seasonally Dry Tropics?, R J. Jones, A Kerr

IGC Proceedings (1977-2023)

Data from 2 grazing experiments, small-plot studies, and a vegetation and soil survey showed that Bothriochloa pertusa increased relative to native tufted perennial grasses under heavy grazing pressure and was adapted to a wide range of soils in the 500-1000 mm zone of northern Australia. Ability to grow on low-P soils, lower relative palatability, strong stoloniferous development and good seed production, were features of its success. Annual steer gains on 8. pertusa pastures were similar to those on native pastures, with no species x stocking rate interaction. Steer gains on B. pertusa-Vernno stylo pastures were lower than on Urochloa …

Sustainability Of Sown Pastures In The Tropics And Subtropics, Jose M. Toledo, Daniel Formoso

IGC Proceedings (1977-2023)

Sown pastures in the tropics and subtropics are important components of production systems. Their role in and contribution to land productivity and economic development are well understood; however, their roles in sustainability and environmental protection are rather misunderstood and little known. The main constraints to sustainability of sown pastures fall into two categories: physical, biological and technical constraints include soil and climatic limitations, lack of adaptation of plants to physical and biotic stress and the limitations of farmers or ranchers to apply technology; socioeconomic factors include political instability, poorness of society and the market forces for land, inputs and products. …

Stability In Rangelands: Ecology And Economics, B H. Walker

IGC Proceedings (1977-2023)

Examples of changes in rangelands are presented relating to changes in livestock number, plant species. composition and soil changes (associated with changes in production), The mechanisms Involved are described, using examples, under the headings: event-driven change, threshold effects, non-linear and hysteresis effects, effects of spatial variation, significance of temporal variation, and interactive effects. The implications for management are presented in the form of a proposed optimal control model which maximises a complex function of welfnre based on long-term net economic benefit, in which stocking rate effects on the state of the rangeland feed back on to economic return.

The Role Of Social-Psychological Factors In The Adoption Of Push-Pull Technology By Small-Scale Farmers In East Africa: Application Of The Theory Of Planned Behavior, Denis Waiswa, Beatrice Wambui Muriithi, Alice W. Murage, Dave Mwangi Ireri, Fredah Maina, Frank Chidawanyika, Fahri Yavuz

All Peer-Reviewed Publications

Push-pull technology (PPT) continues to gain relevance among smallholder farmers across the East African region in managing the constraints affecting cereal crop yields including stemborers, fall armyworm, striga weed, and low soil fertility. While previous research has emphasized the significance of socioeconomic factors in explaining farmers' decisions to adopt PPT, the social-psychological factors that influence farmers' adoption intentions have not been extensively studied. Therefore, this study investigated the influence of social-psychological factors on the intention to adopt or increase the land area under PPT based on the theory of planned behavior (TPB). Moreover, this study extends the applicability of the …

Performance Of Eight Lettuce Cultivars In A Water Culture System, Ricky C. Young, Hudson M. Cox, Jacob D. Frodge, Mollie K. Mayabb, Brycen C. Shephard, Alireza Rahemi

Posters-at-the-Capitol

Lettuce (Lactuca sativa L.) is one of the most well-known vegetables in the world. About 27 million tons of lettuce were produced in the world in 2022 and global demand for lettuce is increasing steadily, driven by the importance of fiber consumption. Lettuce can be grown in multiple media, including hydroponic systems in a controlled environment agriculture (CEA) system. Growing lettuce in hydroponic systems is an alternative to lettuce production optimization. Since little information is available about lettuce cultivar trials in hydroponic systems, a research project was developed and executed to study the ability of different types of lettuce …

Wa Insecticide Guide 2025 - Autumn Winter, Rebecca Severtson

PestFacts WA

Registered chemicals for broadacre crops in Western Australia.

The insecticides listed in the tables within this guide can be used on any crop appearing on the chemical label, if the rate used does not exceed the highest rate that is registered for use on that crop.

There are many products with different trade names that contain the same active ingredient. This list is not exhaustive and does not imply any specific recommendations of brand names.