Modelling The Effect Of A Variable Light Extinction Coefficient And Leaf Dispersion On Light Partitioning Between Species In A Grass-Clover Mixture,
2024
Wageningen Agricultural University
Modelling The Effect Of A Variable Light Extinction Coefficient And Leaf Dispersion On Light Partitioning Between Species In A Grass-Clover Mixture, M Nassiri, A Elgersma
IGC Proceedings (1977-2023)
Light partitioning in a grass-clover mixture was studied using a general competition model. The model assumes a fixed extinction coefficient (k) and no leaf dispersion. This was compared with modelling the effect of different k of both species over height as well as the effect of type of leaf dispersion. These new assumptions led to a better estimation of the light partitioning between both species. For grass the effect of variable k and leaf dispersion was similar and in both cases the total absorbed light was lower than under default conditions. For clover the new assumptions led to a higher …
Ecotypic Adaptation Of Medicago Polymorpha Along A Gradient In Central Chile: Growth And Seed Production,
2024
INIA, Chile
Ecotypic Adaptation Of Medicago Polymorpha Along A Gradient In Central Chile: Growth And Seed Production, A Del Pozo, C Ovalle, J Avendano
IGC Proceedings (1977-2023)
Relative growth rate, total dry weight and seed yield on 19 accessions of burr medic (Medicago polymorpha L.) from different bioclimatic conditions, were assessed at Cauquenes (35°58’;72°17’W) in the subhumid mediterranean region. The accessions were sown in microplots over raised beds during two years (1991 and 1992), and swards cut periodically at 2, 6 and 10 cm height. There were significant differences between accessions in both total dry weight and seed yield (P < 0.001, Table 1), but the interaction between accessions and height of cutting was not significant (P > 0.05). Total dry weight was positive correlated with days to flowering (r2 = 0.81; P > 0.01).
Effects Of Nitrogen On The Growth Of Hyparrhenia Diplandra,
2024
Brazzaville, Congo
Effects Of Nitrogen On The Growth Of Hyparrhenia Diplandra, J Nkandza
IGC Proceedings (1977-2023)
The nitrogen effects on Hyparrhenia diplandra were studied. Plants were grown on nutrient solutions of variable concentrations in nitrogen. The supplied nitrogen increased tillering, leaf production, lamina area, total dry matter accumulation and total nitrogen accumulation in lamina. A detailed examination showed that the effect on tillering was the main cause of the differences observed in dry weights between different treatments. The nitrogen supply elongated significantly the lamina and nitrogen deficiency increased its thickness; but this was not enough to compensate the loss of weight in lower nitrogen treatment. The lamina area as well as nitrogen accumulation in the lamina …
Biochemical And Isoenzyme Analysis Of Seven Pennisetum Purpureum (Schum.) Cultivars,
2024
Instituto Biologico
Biochemical And Isoenzyme Analysis Of Seven Pennisetum Purpureum (Schum.) Cultivars, E E. Bach, V B.G. Alacantara, P B. Alcntara, E A. Veasey
IGC Proceedings (1977-2023)
This study characterized seven Pennisetum purpureum cultivars, namely cv. Anão, Bajra, Cameroon, Guaçu, Roxo, Taiwan A-144 and Uruckwami, through biochemical analysis, including protein, glucose and fructose contents, and polyacrylamide gel electrophoresis using the esterase system, by sampling 30, 60, 90, 120 and 150 dayold leaves. Cultivar Taiwan A-144 presented the highest number of nodes per stem and percentage of emerging buds. Protein concentration decreased gradually after 60 days for all cultivars, except for Anão. Cultivar Guaçu presented the highest level of glucose in 90 day old plants, whereas Cameroon presented the highest levels at 120 and 150 days. The esterase …
Effect Of Phosphorous Fertiliser On The Competition Between Two Tropical Grasses And Two Tropical Legumes,
2024
CSIRO, Australia
Effect Of Phosphorous Fertiliser On The Competition Between Two Tropical Grasses And Two Tropical Legumes, F D. Hu, R J. Jones
IGC Proceedings (1977-2023)
The effect of P fertiliser on the competition between grass and legume in four grass-legume mixtures : Urochloa mosambicensis cv. Nixon/ Stylosanthes hamata cv. Verano; Nixon/S.scabra cv. Seca; Bothriochloa pertusa cv. Bowen/Verano and Bowen/Seca were studied. Each mixture was grown in a low P, low N soil, in pots. A standard replacement series design with two P levels (0 and 10 kg/ ha equivalent) and 3 replicates were used. Seventy days after sowing, Nixon mixtures outyielded Bowen mixtures, and Verano mixtures outyielded Seca mixtures. P increased top and root yields of all mixtures but there was no significant (p …
Selection And Agronomic Characterization Of Leucaena Spp. Genotypes For Cold Tolerance. I. Dry Matter Yield.,
2024
INTA, Argentina
Selection And Agronomic Characterization Of Leucaena Spp. Genotypes For Cold Tolerance. I. Dry Matter Yield., M C. Goldfarb, J F. Casco
IGC Proceedings (1977-2023)
Biotypes of Leucaena spp (56) were evaluated in order to identify those with tolerance to low temperature and with desirable characteristics as a forage crop. Selection was done at two phases. Phase I: 92 days old seedlings (n=2800) were subjected at two temperatures treatments during 14 hours: T1= -8 °C and T2= -3 °C. Selection criteria was established as 50% of live leaves remained after treatments were applied. Phase II: Plants that survived phase I were planted at field conditions and agronomic characteristics were measured. Seventeen plants were selected from eleven different biotypes, resulting one from T1 and the rest …
Effect Of Snowtrapping And Fertilization On Production Of Crested Wheatgrass And Native Pastures In Southwest Saskatchewan,
2024
Agriculture and AgriFood Canada
Effect Of Snowtrapping And Fertilization On Production Of Crested Wheatgrass And Native Pastures In Southwest Saskatchewan, M P. Schellenberg, J Waddington
IGC Proceedings (1977-2023)
The benefits of increasing soil water with snow management and fertilizer for annual and perennial crops have been demonstrated for semiarid environments. We examined the combined effect of snow management and fertilizer on forage production. In 1985, vertical wood slat or slotted plastic snow fencing (0.7m high) were erected on crested wheatgrass (Agropyron cristatum) pasture. In 1986, five rates of fertilizer: 400, 200, 100, 50, 0 kg ha-1 nitrogen each with 50 kg ha-1 phosphorous and a sixth treatment with no fertilizer were applied to each side and type of the snowfence. A second site was selected on …
Light Quality Effects On Grass Seedling Growth And Development,
2024
Agriculture and AgriFood Canada
Light Quality Effects On Grass Seedling Growth And Development, P G. Jefferson, R Muri
IGC Proceedings (1977-2023)
The poor establishment success of Russian wildrye (Psathyrostachys juncea Fisch. Nevski) limits its use. Our hypothesis was that Russian wildrye (RWR) was more sensitive to light competition than crested wheatgrass (Agropyron desertorum Fischer ex Link) or Dahurian wildrye (Elymus dahuricus Turcz. Ex Grieseb.). Seedlings were grown under plastic filters that altered both quantity and quality of light. Tiller counts, leaf counts, leaf area, light intensity and red:farred light ratio (above and beside each seedling) were recorded each week for four weeks after planting. Seedling dry weights were determined at four weeks. Low light intensity significantly reduced tiller …
Morphogenesis And Growth Analysis Of Panicum Maximum Cultivars,
2024
Universidade Federal Vicosa
Morphogenesis And Growth Analysis Of Panicum Maximum Cultivars, A Gomide, C A.M Gomide
IGC Proceedings (1977-2023)
Four cultivars of Panicum maximum, grown in pots, were evaluated regarding their leaf appearance and elongation rates, tillering appearance rate, as well as growth indices. Differences among cultivars were found as to leaf appearance and elongation rates and tillering rates. Main tiller leaf appearance was higher relative to primary tiller in the seedling growth, only. Primary tiller showed higher leaf elongation rate in the aftermath growth. No difference among cultivars was found for drymatter yield after 52 d growth period, leaf mortality, net assimilation rate, leaf area ratio and relative growth rate.
Competitive Interactions Between Palatable And Unpalatable Grasses: Effects Of Selective Defoliations Of The Palatable Grasses,
2024
Universidad Nacional del Sur, Bahia Blanca, Argentina
Competitive Interactions Between Palatable And Unpalatable Grasses: Effects Of Selective Defoliations Of The Palatable Grasses, R A. Distel, A S. Moretto
IGC Proceedings (1977-2023)
Selective herbivory of the palatable species appears to be a dominant mechanisms contributing to species competitive replacement in grasslands. Selective herbivory of the palatable species allows unpalatable species to realize a competitive advantage within the community. To test this hypothesis we compare the competitive ability of the unpalatable grasses Stipa trichotoma or S. gyneriodes in the presence of nondefoliated and defoliated plants of the palatable grass S. clarazii. The three species are native to a temperate semiarid grassland of Argentina. The response variables estimated in S.trichotoma and S.gynerioides, at both plant and tiller levels, were higher (P < 0.05) in the presence of defoliated than in the presence of undefoliated plants of S.clarazii. These results support the hypothesis that selective herbivory of the palatable species confers unpalatable species a competitive advantages, contributing to species competitive replacement within the community.
Allelopathic Interactions Among Forage Grasses And Legumes,
2024
EMBRAPA-CPATU
Allelopathic Interactions Among Forage Grasses And Legumes, A P.S Souza Filho, T De J.D. Rodrigues, L.R. De A. Rodrigues, R A. Reis
IGC Proceedings (1977-2023)
Aqueous extracts at 10% were prepared with the shoots of the grasses Brachiaria brizantha cv. Marandú, B. decumbens, B. humidicola, and of the legumes Calopogonium mucunoides, Leucaena leucocephala, Stylosanthes guianensis cv. Mineirão. The effects of the extracts were evaluated on the germination and on the radicleelongation of the forages. The pH, the electric conductivity and the osmotic potential of the extracts were determined. The germination and radicle biossays were conducted in germination chambers, with controlled temperature and photoperiod. The pH and the presence of ions did not contribute to the effects observed. The extracts of the legumes tended …
Early Ontogenetic Responses Of Six Commercial Chloris Gayana Cultivars To Salinity,
2024
IFFIVE
Early Ontogenetic Responses Of Six Commercial Chloris Gayana Cultivars To Salinity, E Taleisnik, H Perez, G Peyrano, C Arias
IGC Proceedings (1977-2023)
Some physiological aspects relevant to pasture establishment under saline conditions were evaluated in six cultivars of Chloris gayana . Two tetraploid cultivars: Boma and Callide, and four diploid ones: Bell, Katambora, Pioneer and a local accession of Pioneer, were analyzed. The effect of salinity on seedling emergence, the number of stolons per plant and frost tolerance were evaluated in the field, while effects on germination, early vegetative growth, regrowth after clipping, ion accumulation and stolon rooting were assessed in the greenhouse. Salinity had a negative effect on seedling emergence. Saline solutions delayed or altogether inhibited germination, but seeds retained viability …
Interpreting Indicators Of A Transfer Of N From Legume To Grass In Competition Studies,
2024
The University of Adelaide
Interpreting Indicators Of A Transfer Of N From Legume To Grass In Competition Studies, P G. Tow
IGC Proceedings (1977-2023)
The transfer of N from legume to grass in mixtures is important for regulating competition. In competition studies which include both monocultures and mixtures, N transfer should be detectable by grass N measurements but may be masked by competitive reductions in grass growth. In the study reported here, whole plant DM and N were measured in Panicum maximum var trichoglume and Neonotonia wightii grown in monocultures and additively in mixtures. While competition reduced whole grass plant DM and N in mixture relative to monoculture, higher grass shoot % N and N yield in the mixture at early harvests appeared reliable …
A Comparison Of Production And Soils In Modified Mixed Prairie Community,
2024
Agriculture and Agri-Food Canada Research Center
A Comparison Of Production And Soils In Modified Mixed Prairie Community, S W. Porter, W D. Willms, J F. Dormaar, B H. Ellert, H H. Janzen
IGC Proceedings (1977-2023)
This study examined the effects of reseeding a Stipa-Agropyron- Bouteloua community to monocultures of crested wheatgrass (Agropyron cristatum (L.) Geartn.), Russian wild rye grass (Elymus junceus Fisch.), and wheat (Triticum aestivum L.) on above and below ground biomass and indicators of soil quality. Summer fallowed wheat produced 10817 kg ha-1 and 4090 kg ha-1 of above ground below ground biomass respectively whereas the native community produced 3191 kg ha-1 above ground and 13013 kg ha-1 of below ground biomass. However wheat, crested wheatgrass and Russian wildrye grass generally showed a lower biological index, phosphatase and dehydrogenase activity.
Nitrogen Use Efficiency Of Timothy Populations,
2024
Agriculture and Agri-food Canada
Nitrogen Use Efficiency Of Timothy Populations, G Belanger, C Murray, R Michaud, F Gastal, J E. Richards
IGC Proceedings (1977-2023)
The objective of this study was to determine the variability in N use efficiency among field-grown timothy (Phelum pratense L.) populations. Shoot biomass and N uptake were measured at the end of the spring growth cycle on six timothy populations fertilized with three N rates at two sites in Eastern Canada. The variability in shoot biomass among populations was similar under limiting and nonlimiting N conditions. The ranking of the populations, however, differed under limiting and non-limiting N conditions, and also between the two sites under limiting N conditions. The differences in shoot biomass among populations under highly N …
Characterization Of The Leaf Anatomy Of Panicum Virgatum Germplasm,
2024
North Carolina State University at Raleigh
Characterization Of The Leaf Anatomy Of Panicum Virgatum Germplasm, D S. Fisher, J C. Burns, J P. Pienaar
IGC Proceedings (1977-2023)
Both the yield and digestibility of C4 grasses have been related to anatomical characteristics. The objectives of the current work were to test switchgrass with varied yield and digestibility for variation in anatomical measurements and to develop a method of graphically representing the anatomy. Six accessions were established in replicated field plots and the lamina were sampled, dehydrated and embedded for anatomical study. Midrib dimensions were excluded from study but perimeters of primary and secondary vascular bundles in the lamina were measured. Lamina thickness was determined at the primary bundle, secondary bundle and at the minimum between the bundles. The …
Relation Of Root And Shoot Morphology Of Grass Seedlings,
2024
University of Nebraska - Lincoln
Relation Of Root And Shoot Morphology Of Grass Seedlings, L E. Moser, A J. Smart
IGC Proceedings (1977-2023)
Grass seedling establishment is dependent on adventitious root development. However, evaluating the establishment status of a seeding by excavating a population of seedlings and determining root morphology is difficult and generally will not be undertaken. Based on both field and greenhouse studies we have found that root and shoot morphological development is closely related within species, for intermediate wheatgrass, [Thinopyrum intermedium (Host) Barkw. and D.R. Dewey], smooth bromegrass (Bromus inermis Leyss.), switchgrass (Panicum virgatum L.), and big bluestem (Andropogon gerardii Vitman) seedling populations. Easily observable developmental stages of seedling shoots were related to adventitious root development. …
Effect Of Lowered Light Quality (R:Fr Ratio) At Targeted Organs On Branching Of Trifolium Repens,
2024
Palmerston North, New Zealand
Effect Of Lowered Light Quality (R:Fr Ratio) At Targeted Organs On Branching Of Trifolium Repens, M J.M Hay, Ch Robin, P C.D Newton, A Cresswell, J Tilbrook
IGC Proceedings (1977-2023)
This report examined results from four similarly conducted experiments using Trifolium repens in which the R:FR ratio but not the photosynthetically active radiation (PAR) of incident light was altered at specific organ(s) of several successive phytomers or just at a single phytomer. Results indicate the local response to lowered R:FR light treatment was similar irrespective of the number of phytomers treated. This response pattern provides the means whereby plants can initiate strong localised responses to a heterogeneous light environment.
Theoretical And Observed Relationships Between Defoliation And Partitioning In Grasses,
2024
Macaulay Land Research Institute, Scotland
Theoretical And Observed Relationships Between Defoliation And Partitioning In Grasses, C P.D. Birch, B Thornton
IGC Proceedings (1977-2023)
A model is presented that analyses the potential effect of vertebrate grazing on the partitioning of grasses. Its conclusions are: 1) When grazing is sufficiently frequent and severe, grasses can increase their net increase in biomass by partitioning growth to reserves. 2) Partitioning growth to reserves greatly reduces leaf growth between defoliations. After repeated clipping, dryland browntop (Agrostis castellana) and red fescue (Festuca rubra) allocated a smaller proportion of growth between defoliations to leaves than ryegrass (Lolium perenne) or rough meadow-grass (Poa trivialis). Browntop and fescue achieved less leaf growth than ryegrass …
Effects Of Light Intensity And Defoliation On The Receptiveness For Primary Induction In Festuca Pratensis Huds,
2024
The Norwegian Crop Research Institute, Norway
Effects Of Light Intensity And Defoliation On The Receptiveness For Primary Induction In Festuca Pratensis Huds, Lars T. Havstad
IGC Proceedings (1977-2023)
Seedlings of Festuca pratensis Huds. (cv. Salten) were raised at three different light intensities (141, 85 or 28 (mol m-2s-1 ) for 7 weeks after emergence and then either left uncut or defoliated 40 or 80% of total leaf area, before transfer to primary induction (6°C, natural short days) for 12, 15 or 18 weeks. Percentage of heading plants was more affected by the duration of primary induction than by light intensity and defoliation prior to induction. The results lend no support to the existence of a juvenile stage in seedlings of Festuca pratensis. Defoliation had less influence on …
