Morphogenetic And Structural Determinants Of Plant Regrowth After Defoliation,
2024
AgResearch, NZ
Morphogenetic And Structural Determinants Of Plant Regrowth After Defoliation, D F. Chapman, G Lemaire
IGC Proceedings (1977-2023)
Responses of forage plants to defoliation can be delineated at two levels: physiological responses and morphological responses. Physiological responses are generally defined as occurring over short time-scales, whereas morphological responses are generally considered as being long-t<;rm. The extent to which physiological and morphological responses influence pasture characteristics and production depends on the defoliation regime, and the balance obtained between the supply and demand of growth resources by plants. Where defoliation is relatively infrequent and lax, plants may maintain balanced growth of root and shoot purely through shortterm physiological responses. However, as defoliation severity increases, morphological adjustments are needed to ensure homeostatic, whole-plant growth. The adaptability of forage species to various points on the continuum of defoliation pressure from lenient to severe depends on their inherent morphological and physiological characteristics. We concentrate on morphogenetic and structural determinants of plant regrowth following defoliation, drawing out the important linkages with the physiological responses. We examine the relationships between plant morphogenesis and sward structure, placing particular emphasis on phcnotypic plasticity as a process whereby plant and population structure can alter to maintain homeostatic growth in response to variation in defoliation management. The imporlnnce of meristem positioning within the sward and of meristem activity, interacting with defoliation management, as determinants of plant production and persistence is discussed. Relationships between plant morphogenesis, herbage growth dynamics and barvestable herbage production are examined and we identify the collection of fundamental physiological and morphological information for a wider array of forage species as an important research goal for improving the productivity and sustainability of the world's grasslands.
Physiology Of Plants Recovering From Defoliation,
2024
University of California, Davis
Physiology Of Plants Recovering From Defoliation, J H. Richards
IGC Proceedings (1977-2023)
Short-term, whole-plant physiological responses of forage plants to defoliation and the characteristics that allow them to rapidly replace lost tissues are the focus of this review. The physiology of defoliationtolerant plants after moderate to severe defoliation has two distinct phases; the first is a transient period of one to a few days and the second is a readjustment of physiological activity and plant morphogenetic Integration that occurs over several weeks. When whole-plant photosynthetic capacity is reduced by substantial defoliation the effects of reduced carbon supply rapidly propagate through a growing plant, affecting shoot growth, root respiration, nutrient uptake and root …
Nitrogen And Phosphorus Nutrition Of Digitaria Eriantha: Is It Limited By Absorption Capacity Or Rate Of Supply?,
2024
University of Witwatersrand
Nitrogen And Phosphorus Nutrition Of Digitaria Eriantha: Is It Limited By Absorption Capacity Or Rate Of Supply?, M C. Scholes, R J. Scholes, J Retief
IGC Proceedings (1977-2023)
Digitaria eriantha was grown from seed collected from low and high nutrient habitats. The plants were grown with either a high or low nutrient supply for 12 weeks. Rates of nitrogen and phosphorus absorption were measured on excised roots using colorimetric assays. The grasses from the low nutrient areas achieved the same maximum uptake rates regardless of the level of N supplied, This was not so for the grasses from the high nutrient site which increased their uptake rates with increased N supply. Plants from the low nutrient site showed markedly increased P absorption when supplied with high levels of …
Effect Of Nitrogen In Fertilizer In Combintation With Potassium And Phosphorus On Rangeland Yield In Cameroon,
2024
Universite de Dschang
Effect Of Nitrogen In Fertilizer In Combintation With Potassium And Phosphorus On Rangeland Yield In Cameroon, E T. Pamo, S Yonkeu
IGC Proceedings (1977-2023)
A study was carried out at Wakwa Animal Research Station on the response of natural pasture to nitrogen fertilization in the presence of P 11osphorus and potassium, and a cutting frequency of 4 weeks. A Cmpletely randomized design with 6 replicates was used. Six fertiliser: 0, SO, 100, 150, 200, 2SO units of N/ha in association with 100 units of P and 100 units K after zero timing was applied after every cutting 0, 10, 20, 30, 40, SO units of Nlba were respectively added to plots which received 0, SO, 100, ISO, 200 and 250 units of Uha. Three …
Vegetation Analysis Of Semi-Arid Regions In North-Eastern Iran,
2024
University of Agricultural Science, Gorgan, Iran
Vegetation Analysis Of Semi-Arid Regions In North-Eastern Iran, M Mesdaghi
IGC Proceedings (1977-2023)
Production of semi-arid rangelands under the 3 conditions of complete protection, moderate and severe grazing were evaluated using double sampling techniques, For production, 1 m2 and for canopy coverage, 25x60 cm quadrats were used, In Gholestan National Park, which was protected for 30 years, the grasses Festuca ovi11a, Agropyro11 tricliopliorum, A. imermedium associated with Medlcago saliva and Onobrycl1is spp. dominated. The dry matter yield in this grassland was about 1500 kg/ha. Under moderate grazing on key areas, the yield declined to 700 kg/ha. The percentage of grasses decreased, liut there were still some grasses even in poor conditions. On the …
Termites Have A Minor Role In The Decomposition Of Senescent Grass Tussocks In A Semi-Arid Woodland In Eastern Australia, J C. Noble
IGC Proceedings (1977-2023)
Decomposition of dead tussocks of 2 grass species (Eragrostis eriopoda and Thyridolepis mitchellima) was studied with and without termites present, both in the absence of large ve.rtebrate herbivores, After 3 years, little tussock residues of either species remained icrespective of treatment, but E. er/opoda decayed much more rapidly than T. mitchellia11a during the first 8 months post mortem (c. 275 cf, 13 kg/ha/month respectively). Thereafter, rate of decay differed little between species. Overall, removal of termites had no significant effect, The data presented in this paper therefore suggest that abiotic processes are dominant influences mediating litter decomposition of …
A Bioeconomic Stocking Rate Model For The Semi-Arid Savanna Of Natal, South Africa,
2024
University of Natal, Pietermaritzburg
A Bioeconomic Stocking Rate Model For The Semi-Arid Savanna Of Natal, South Africa, G P. Hatch, N M. Tainton
IGC Proceedings (1977-2023)
Grazing trials were conducted on 2 sites located In semi-arid savanna of Natal. Three stocking strategies were applied at each site to provide light, intermediate and heavy stocking. Data collected over 5 seasons were used to.develop a bioeconomic stocking rate model. While individual animal performance and nett return per livestock unit (R/LSU) decreased with increased stocking, net return per ha (Riha) increased, Net return was significantly related (P 0, 01) to rainfall and stocking rate, while no significant effect of range condition was detected. Although Increased stocking may be justified In the short• term, this may be associated with both. …
Use Of Water Balance Models To Examine The Role Of Climate In Annual Legume Decline In Southern Australia,
2024
NSW Agriculture
Use Of Water Balance Models To Examine The Role Of Climate In Annual Legume Decline In Southern Australia, M Blumenthal, R Ison
IGC Proceedings (1977-2023)
fhe content of annual medic and subclover (Trifo/ium subterraneum) in rasture Leys has been declining in southern Australia over the last decade. The models GROWEST and ASW were used to simulate available soil water, dry matter yield and seed production of a temperate annual pasture legume using actual climatic data for Forbes in 1987-89. GROWEST was also used to predict DM and seed production and the site and composition of the seed bank for the period 1957-89 for the subclover cultivars Dalkeith and Woogenellup. The period 1979-82 consisted of below average seasons with DM yields restricted to below 3000 kg/ha/year. …
Effects Of Fertilizers And Rest On The Overgrazed Semi-Arid Ranges Of Central Anatolia,
2024
Cumhuriyet (Republik) University
Effects Of Fertilizers And Rest On The Overgrazed Semi-Arid Ranges Of Central Anatolia, U Buyukburc
IGC Proceedings (1977-2023)
To improve the degenerated natural village pastures of Turkey in semi arid regions, different fertilisers and resting treatments were tested. The experiment was established on two rangelands, which showed different plant communities (Thymus squarrosus L. and Artemisia fragrans L.). Each species was dominant in vegetation and had 38-70% weight of total herbage production. At the beginning of the experiment, the dry yield varied from 200 to 565 kg/ha and the average plant cover was 20- 28.5%. Fertilisers, especially 75 or 100 kg/ha of ammonium sulphate, plus superphosphate, or using equal amount of diammonium phosphate DAP (20+20), significantly increased dry yield …
Pasture Composition Influences Soil Erosion In Eucalyptus Woodlands Of Northern Queensland,
2024
QDPI
Pasture Composition Influences Soil Erosion In Eucalyptus Woodlands Of Northern Queensland, J C. Scanlan, J G. Mcivor
IGC Proceedings (1977-2023)
Runoff and soil loss in grazed Eucalyptus woodlands of north Queensland were monitored over a 5-year period. As ground cover increased, runoff and soil loss decreased. When cover exceeded 50%, runoff and erosion were small. Ground cover was a function of standing dry mailer which decreased as tree cover and stocking rate increased and differed between pasture types. Simulated soil losses from these woodlands was <10-2800 kg/ha/year, and runoff was 5- 16 mm/year. Annual soil losses (simulated) were proportional to the square of the annual simulated runoff.
Physiological Response Of White Clover Genotypes To Water Deficit,
2024
AgResearch, NZ
Physiological Response Of White Clover Genotypes To Water Deficit, D J. Barker, J R. Caradus, M T. Mcmanus
IGC Proceedings (1977-2023)
Three plants from each of 2 white clover (Trifolium repens L.) cultivars, Grasslands Kopu and a breeding line selected from germplasm of Syrian origin, were grown in large pots of soil and physiological characteristics measured during a continuous drying phase of 18-37 days. By the end of the experiment, leaf water potential was -2.5 MPa, gravimetric soil water content was 13% (considerably lower than -1.5 MPa), and leaf relative water content was 60%. A 91- fold increase in leaf praline concentration indicated that water stress had altered plant metabolism. Differences in the rate of soil drying occurred between eultivars, but …
Forecasting Annual Drought Conditions For Arid And Semi-Arid Rangelands,
2024
USDA, Agricultural Research Service
Forecasting Annual Drought Conditions For Arid And Semi-Arid Rangelands, C L. Hanson, J R. Wight
IGC Proceedings (1977-2023)
Long-term weather forecasts (>14 days) have improved, but still lack accurate enough information to be valuable; thus, drought forecasts must be based on historical records and calculated probabilities of occurrence. The use of regression techniques to investigate linear dependence between current and preceding years' precipitation or forage yield is illustrated. A 3-state Markov process is used to determine relationships between below-average, average and aboveaverage consecutive annual herbage yields, and winter and spring precipitation amounts. Methods for using natl/ml resource simulation models to forecast ecosystem components such as herbage production, runoff, and erosion with their associated probabilities of occurrence are …
Effects Of An Existing Lucerne Sward On Establishment And Productivity Of Three Over Drilled Grass Species,
2024
Lincoln University
Effects Of An Existing Lucerne Sward On Establishment And Productivity Of Three Over Drilled Grass Species, A Z. Ayalsew, B A. Mckenzie, M L. Smetham
IGC Proceedings (1977-2023)
Effects of contrasting lucerne (Medicago saliva L.) cover (open versus closed canopy) on establishment of overdrilled Bromus wifldeowii Kunth cv. Grasslands Matua prairie grass, Pllalari:r aq11a1ica L. cv. Grasslands Matu phalaris and Loli11m pere111Ie L cv. Grasslands Nui perennial ryegrass were investigated. Prairie grass seedling survival was unaffected by lucerne cover at 84%. However, survival of ryegrass and phalaris was reduced to 35 and 46% of their respective values 'under open canopy. Productivity of all 3 species was affected by canopy state. Leaf area per plant, tiller number per plant and dry matter production were all lower under …
Seasonal Water Use And Productivity Of Lucerne-Grass Pastures,
2024
Lincoln University
Seasonal Water Use And Productivity Of Lucerne-Grass Pastures, B A. Mckensize, R J. Lucas, P Gyamtsho
IGC Proceedings (1977-2023)
A. long-term grazing experiment at Lincoln University examined the yield and water use efficiency (WUE) of pure lucerne (Medicago saliva L.), luceme plus Grasslands Matua prairie grass (Bromus wildenowii Kunth.) and lucerne plus Grasslands Maru phalaris (Phalaris aqualica L.). Pure lucerne, lucerne-phalaris and lucerneprairie yielded 12.7, 11.6 and 10.4 t DM/ha/year. Production from deep soils was 16% greater than from shallow soils. Over a 6 month growth cycle from 29 Sept 88 until 16 May 89 total evapotranspiration did not vary between pasture types and mean water use was 378 mm. Water use was 10% higher on …
The Piosphere Effect Of A Goat Corral On The Productivity Of Arid Mediterranean-Type Rangelands In Northern Chile,
2024
Universidad de Chile
The Piosphere Effect Of A Goat Corral On The Productivity Of Arid Mediterranean-Type Rangelands In Northern Chile, S Lailhacar, A Mansilla, L Faundez, P Tonini
IGC Proceedings (1977-2023)
Arid rangelands of northern Chile consist of open shrub formations associated with a seasonal herbaceous stratum. Small pastoralists (comuneros) use the available fodder fer goat raising, by managing individual flocks under continuous grazing. Since each flock spends nights in a corral, a piosphere effect has evolved around it. Through radial transects and quadrals starling from the corral, cover, density, diversity and yield were determined for herbaceous and woody species. Except for shrub diversity and herbage yield, all other total variables showed significant increments with distance. When individual species were considered, different response trends were observed. Some species decreased, others increased, …
Tactical Grazing Can Help Maintain Stability Of Semi-Arid Wooded Grasslands,
2024
CSIRO
Tactical Grazing Can Help Maintain Stability Of Semi-Arid Wooded Grasslands, K C. Hodgkinson
IGC Proceedings (1977-2023)
Arid and semi-arid wooded grasslands in Australia and elsewhere are prone to soil and plant productivity decline when used for pastoral production. Typically, degradation is characterised by woody plant increase, palatable perennial grass decline, unpalatable grass increase and lowered productive capacity of the soil, New grazing management that maintains productivity of plant and soil resources and sustains rehabilitation is required. In a grazing experiment on a mulga (Acacia aneura) woodland, grazing-induced death and impaired seed productivity were observed in palatable perennial grasses. A tactical grazing management to prevent an adverse change in pasture composition and productivity was designed involving progressively …
Temporal Patterns Of Soil Loss In Tropical Grazing Lands,
2024
Queensland Department of Primary Industries
Temporal Patterns Of Soil Loss In Tropical Grazing Lands, D J. Myles, A J. Pressland, J C. Scanlan, P D. Fleming
IGC Proceedings (1977-2023)
Rates of soil erosion in grazing lands of north Queensland were measured at 3 sites over 3 years. Within years, soil loss was highest during summer, even though rainfall was often higher in autumn than in summer. This pattern is explained by lower cover and higher rainfall intensities during summer than autumn. Grazing management should aim at having sufficient cover at the end of the dry season (September-October) to prevent soil loss from high intensity storm rains common at this time of year.
Management Strategies To Improve Indigenous Meat Goat Productivity In Semi-Arid Areas Of Southern Africa,
2024
University of Zimbabwe
Management Strategies To Improve Indigenous Meat Goat Productivity In Semi-Arid Areas Of Southern Africa, L R. Ndlovu
IGC Proceedings (1977-2023)
The semi-arid areas of southern Africa are characterised by low and erratic rainfall coupled with sandy soils which result in severe fluctuations in feed quality and quantity. Goats are an important component of farming systems in these areas but their meat production is constrained by shortage of feed in the dry season. Young goats are particularly vulnerable and management systems that prevent weight loss during the dry season are needed. Positive growth rates in kids· aged 8-60 weeks were obtained in response to feeding 200-400 g of Dolichos lablab (a drought-tolerant fodder) or Acacia lorti/is pods (a naturally occurring feed …
Infiltration Measurements In The Semi-Arid Woodlands Of Eastern Australia- A Comparison Of Methods,
2024
CSIRO
Infiltration Measurements In The Semi-Arid Woodlands Of Eastern Australia- A Comparison Of Methods, R S.B Greene
IGC Proceedings (1977-2023)
The infillracion race of bare, scony, runoff zones of a massive red earth soil in a semi-arid woodland was measured using a disc permeameter (waler supply potential +10 mm), rainfall simulalor and a i arge, bounded, runoff plol, The steady slate infiltration race measured with the disc permeameter was higher than Chai measured wilh the rainfall simulator, Raindrop impact and overland flow effecls wilh the rainfall simulator rearranged parlicles at Che soil surface and resulced in Che formalion or a rain-induced crust. This cruse had a lower infillralion rate than Che surface formed wilh the disc permeameler. The infillrationratcmeasured with …
Plant Demography And Grassland Community Balance: The Contribution Of Population Regulation Mechanisms,
2024
Texas A&M University
Plant Demography And Grassland Community Balance: The Contribution Of Population Regulation Mechanisms, David D. Briske, Jonathan W. Silvertown
IGC Proceedings (1977-2023)
It is widely recognised that many grassland communities are stable,though the mechanisms that maintain this stability are only poorly understood. We identify and discuss processes that contribute to stability at three levels of grassland organisation: 1) the individual plant, 2) the population, and 3) the community. At the level of the individual plant, the classical theory of apical dominance does not consistently explain the response of tiller recruitment to defoliation. At the level of the population, conclusions regarding tiller recruitment in response to radiation quality in the competitive neighbourhood and the contribution of dormant axillary buds to annual tiller recruitment …
