Limitations imposed by nitrogen deficiency on the productivity of subterranean clover-based annual pasture in southern Australia

1980 ◽  
Vol 31 (1) ◽  
pp. 95 ◽  
Author(s):  
PS Cocks
Keyword(s):  
Nitrate Nitrogen ◽  
Nitrogen Deficiency ◽  
Subterranean Clover ◽  
Growing Season ◽  
Mineral Nitrogen ◽  
Botanical Composition ◽  
Mediterranean Environment ◽  
Potential Productivity ◽  
Grazed Pasture ◽  
Rates Of Growth

Potential productivity of pasture in the Mediterranean environment of southern Australia and limitations imposed on productivity by nitrogen deficiency were studied on grazed subterranean clover-based annual pasture at Kybybolite, S.A. Estimates of monthly growth, botanical composition and nitrogen uptake were made on the basis of growth in open and closed quadrats. Ammonium and nitrate nitrogen in the top 10cm of soil were measured frequently, and six estimates of the response of pasture to nitrogen were made during the growing season. Potential herbage productivity was assumed to be 5 % of photosynthetically active radiation. Grazed pasture yielded 12.6 t of dried herbage per hectare compared with a calculated potential of 28.7 t ha-1. It was calculated that nitrogen deficiency probably accounted for about 59 % of the shortfall. Maximum rates of growth in mid spring (October) reached 160 kg ha-1 day-1 in the presence of added nitrogen compared with a calculated potential of 180 kg ha-1 day-1, and measured growth of only 98 kg ha-1 day-1 in the absence of nitrogen. Pasture responded least to added nitrogen in autumn even though, in that season, grasses and herbs dominated subterranean clover. Low responsiveness was associated with high levels of mineral nitrogen in the soil before and for 2 weeks after the first autumn rains. Thereafter mineral nitrogen remained very low, and pasture increasingly responded to nitrogen until it matured in late spring. During this time the proportion of legume steadily increased until, by the end of spring, it reached 50 %. In all, it was calculated that soil released 184 kg nitrogen, and clover fixed 146 kg nitrogen, per hectare over the growing season. In order to reach its potential productivity the pasture needed a further 406 kg nitrogen per hectare. In the absence of fertilizer nitrogen, economically unacceptable on the annual pastures of southern Australia, subterranean clover will need lo fix this extra nitrogen if annual pastures are to reach their potential productivity.

The effects of grazing on the phosphorus requirement of an annual pasture

1971 ◽  
Vol 22 (1) ◽  
pp. 81 ◽  
Author(s):  
PG Ozanne ◽  
KMW Howes
Keyword(s):  
Subterranean Clover ◽  
Growing Season ◽  
Maximum Growth ◽  
Grazing Pressure ◽  
Light Interception ◽  
Botanical Composition ◽  
Stocking Rate ◽  
Phosphorus Requirement ◽  
Root Size

The applied phosphorus requirement of a pasture sown to subterranean clover was measured with and without grazing. Under moderate grazing pressure, in the year of establishment, the pasture required about 50 % more phosphorus than when ungrazed. In the following season, at a higher stocking rate, the grazed areas needed twice as much phosphorus as the ungrazed to make 90% of their maximum growth. In both years this difference in requirement between stocked and unstocked treatments was present throughout the growing season. Increased phosphorus requirement under grazing is associated with the need for greater uptake of phosphorus under conditions where redistribution of absorbed phosphorus within the plant is prevented by defoliation. It does not appear to be due to effects of defoliation on root size. Nor does it depend on differential light interception or on changes in botanical composition.

Effects of Liming and Cultivation on the Establishment and Persistence of Rainfed Mediterranean Pastures

1994 ◽  
Vol 30 (4) ◽  
pp. 453-459
Author(s):  
N. Moreira ◽  
H. Trindade ◽  
J. Coutinho ◽  
J. F. Almeida
Keyword(s):  
Native Species ◽  
Dry Matter ◽  
Subterranean Clover ◽  
Fold Increase ◽  
Dry Matter Yield ◽  
Botanical Composition ◽  
Mediterranean Environment ◽  
Seedling Density ◽  
Bare Ground ◽  
Seed Mixture

SUMMARYThe influence of liming and method of cultivation on the dry matter yield, botanical composition and seedling density of a rainfed pasture grown in a Mediterranean environment from a commercial seed mixture based on subterranean clover was investigated. Liming resulted in a 2.5-fold increase in pasture dry matter yield. Yields were greater when the soil was scarified before sowing than when it was ploughed, and when the lime was spread after cultivation rather than before. Liming and scarifying increased the proportion of sown species (subterranean clover, white clover and tall fescue) and reduced the proportion of native species and bare ground. Subterranean clover seedling density was higher after scarifying than after ploughing.Uso de cal en pastos mediterráneos regados por precipitaciones

Effect of environmental factors on the growth of grazed pasture in south-western Victoria

2006 ◽  
Vol 46 (4) ◽  
pp. 545 ◽  
Author(s):  
H. A. Birrell ◽  
R. L. Thompson
Keyword(s):  
Climatic Factors ◽  
Subterranean Clover ◽  
Botanical Composition ◽  
Stocking Rate ◽  
Daily Growth ◽  
Pasture Production ◽  
Grazed Pasture ◽  
Herbage Yield ◽  
Western Victoria ◽  
Stocking Rates

This paper presents work from several studies on pasture production that were conducted in south-west Victoria at the Pastoral Research Institute, Hamilton. The frequency with which pasture growth commenced for each week of autumn in the years from 1965 to 1991 was assessed. The median period for the commencement of growth was in the third week of March (although the average date was March 27). Autumn data from several trials conducted over 3 decades were collated and analysed. A relationship between the grazed pasture yield (average of stocking rates plots) at the end of autumn and the rainfall showed that 200 mm of rainfall in the 3 months to the end of May was optimal while higher rainfall depressed the growth. The average daily growth rates of introduced pasture (perennial rye grass, Lolium perenne L. cv. Victorian, phalaris, Phalaris aquatica L. cv. Australian, subterranean clover Trifolium subterranneum L. and volunteer species) were measured in 2- and 4-week growth periods (G 2 and G 4, kg DM/ha.day) for the seasonal growth cycles over 4 years (1980–84 except 1983) when grazed by Merino wether sheep at stocking rates of 10, 13 or 18 sheep/ha. The rainfall throughout the study was lower than normal. Although differences in the animal performance between the stocking rates were only small, at the low stocking rate capeweed (Arctotheca calendula L.) in patches became the major component of the sward. Greater variation in G 2 than in G 4 indicated that growth responded quickly to current environmental conditions. A nonlinear regression accounted for 74% of the variance in G 2 when related to the 3 climatic factors of daylength, soil temperature at 10 cm depth and the soil moisture to a depth of 10 cm, and a plant factor of green herbage yield. The 26 % of unaccounted variance appears to be associated with an effect of stocking rate, possibly botanical composition. The botanical composition was not continuously monitored hence the only sward character included in the investigation was herbage yield. Comparison of the patterns of pasture growth from different latitudes indicated that while the growth pattern in south-western Victoria is erratic, it is intermediary between Mediterranean and temperate pasture types. Understanding this aspect has implications for improving the efficiency of animal production in this environment.

The control of slender thistle, Carduus pycnocephalus L. and C. tenuiflorus Curt. (Compositae), in pasture by grazing management

1973 ◽  
Vol 24 (6) ◽  
pp. 831 ◽  
Author(s):  
GM Bendall
Keyword(s):  
Perennial Ryegrass ◽  
Subterranean Clover ◽  
Field Trials ◽  
Grazing Management ◽  
Botanical Composition ◽  
Economical Method ◽  
Farm Programme ◽  
Improved Pasture

The effect of grazing management on slender thistle populations and botanical composition of improved pasture was studied in two field trials in southern Tasmania. Deferring grazing until winter or spring reduced slender thistle populations in both trials. The reasons underlying these observations are discussed. Spring grazing favourably altered pasture botanical composition by increasing the frequency of perennial ryegrass and subterranean clover and reducing the frequency of weed grasses. These changes arc discussed in relation to thistle control. It is suggested that deferred autumn grazing may be incorporated into the farm programme as an economical method for the control of slender thistle in pasture.

POTENTIAL VEGETATIVE PRODUCTIVITY IN CANADA

1983 ◽  
Vol 63 (1) ◽  
pp. 1-10 ◽  
Author(s):  
M. TOLLENAAR
Keyword(s):  
Photosynthetic Efficiency ◽  
Theoretical Estimate ◽  
Growing Season ◽  
Crop Growth ◽  
Light Interception ◽  
Crop Species ◽  
Potential Productivity ◽  
Crop Growth Rate ◽  
Water Nutrients ◽  
Productivity Estimate

Duration of the growing season appears to be the single most important factor limiting vegetative productivity in Canada. A theoretical estimate of annual vegetative productivity in the absence of limitations due to water, nutrients or soil structure, shows that potential productivity in the 5-mo growing season of Southern Canada is in the range of 25–55 tonne/ha. Maximum productivity, however, lies considerably below the potential productivity estimate due to lower-than-expected photosynthetic efficiency during periods of high solar irradiance. Crop growth rates appear to be rather independent of variation in radiant flux density during the growing season. Consequently, a realistic estimate of maximum vegetative productivity can be obtained by multiplying number of days of full light interception by a crop canopy, by a crop growth rate of 230 kg∙h−1∙day−1 and adding the weight of the crop at the onset of full light interception by the canopy. Maximum vegetative productivity could likely be improved by extending the period of full light interception by crop canopies through the cultivation of perennial species or double-crop sequences. Alternatively, vegetative productivity could likely be improved through increased photosynthetic efficiency. Very high photosynthetic efficiencies of crops grown under field conditions have been reported occasionally in the literature, but factors underlying this high photosynthetic efficiency have not yet been identified.Key words: Vegetative production, photosynthetic efficiency, potential productivity, duration of growing season, crop species

Physiological and ecological studies on the oestrogenic isoflavones in subterranean clover (T. subterraneum L.) VII. Effects of nitrogen supply

1969 ◽  
Vol 20 (6) ◽  
pp. 1043 ◽  
Author(s):  
RC Rossiter
Keyword(s):  
Protein Synthesis ◽  
Nitrogen Deficiency ◽  
Subterranean Clover ◽  
Nitrogen Supply ◽  
The Other ◽  
Biochanin A ◽  
Ecological Studies ◽  
Carbon Substrates ◽  
Low Nitrogen ◽  
Practical Implications

In experiments with young plants of the Dwalganup strain of subterranean clover, nitrogen deficiency was associated with increased concentrations of isoflavones in the expanded leaves and cotyledons. In the first trifoliate leaves the concentration of total isoflavones (formononetin+genistein+ biochanin A) was approximately doubled at low nitrogen supply. Biochanin A was much less affected than the other two isoflavones. The increase in isoflavone contents of nitrogen-deficient leaves was associated with decreased protein synthesis, but not always with increased sugar contents. The supply of carbon substrates for isoflavone synthesis may depend on starch as well as sugar contents. Practical implications of the results are considered briefly.

The effects of length of growing season, with and without defoliation, on seed yield and hard-seededness in swards of subterranean clover

1981 ◽  
Vol 32 (5) ◽  
pp. 783 ◽  
Author(s):  
WJ Collins
Keyword(s):  
Seed Yield ◽  
Subterranean Clover ◽  
Growing Season ◽  
Absolute Scale ◽  
Growing Seasons ◽  
Short T2 ◽  
Relative Scale ◽  
Seed Yields

The effects of length of growing season and defoliation on seed yield and hard-seededness were examined in two strains of subterranean clover (Seaton Park, Midland B) grown in swards in the field. All plots were sown at the same time and the length of growing season was varied by altering the time of finish of the season (by withholding water). There were three length of growing season treatments: T1 (short), T2 (intermediate) and T3 (control). The defoliation treatments were D0, uncut (control), and D1, defoliated at weekly intervals until the commencement of flowering. Reducing the length of growing season drastically reduced seed yield. Thus when the growing season was only 3 weeks shorter than the control (i.e. T2 compared with T3), seed yields averaged over strains and defoliations were reduced by at least one half. With a further reduction of 2 weeks in the length of the season (T1) seed yields were only about one-third of those obtained in the control (T3). The reductions in seed yield were due to reductions in both the number of mature burrs produced and to a lesser extent in mean weight per seed. Although defoliation increased seed yield in all growing seasons, the effect when measured on a relative scale was greater in T2 than in either T1 or T3. But on an absolute scale the size of the response was greater in T2 and T3 than in T1. The rate of breakdown of hard-seededness was faster in Seaton Park than in Midland B, but it decreased in both strains with increasing length of growing season.

Copper nutrition of subterranean clover (Trifolium subterraneum L. cv. Seaton Park). I. Effects of copper supply on growth and development

1981 ◽  
Vol 32 (2) ◽  
pp. 257 ◽  
Author(s):  
DJ Reuter ◽  
AD Robson ◽  
JF Loneragan ◽  
DJ Tranthim-Fryer
Keyword(s):  
Root Growth ◽  
Growth And Development ◽  
Copper Deficiency ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Growing Season ◽  
Internode Elongation ◽  
Plant Parts ◽  
Lateral Branches

Effects of severe and moderate copper deficiency on the development of leaves and lateral branches, on the distribution of dry weight within the plant, and on seed yield of Seaton Park subterranean clover were assessed as part of three glasshouse experiments. Copper deficiency markedly depressed top and root growth without producing any distinctive symptoms. It retarded phasic development by delaying development of leaves and lateral branches, senescence of plant parts, and flowering: it also depressed the proportion of stem plus petiole in plant tops and decreased internode elongation, pollen fertility and the number of burrs and seeds formed. As a result of its effect in delaying flowering, copper deficiency would depress seed production particularly strongly when low soil water supply shortens the growing season. The need for suitable procedures for diagnosing copper deficiency is emphasized by the lack of specific plant symptoms in this species.

Severity of root rot in mature subterranean clover and associated fungal pathogens in the wheatbelt of Western Australia

2009 ◽  
Vol 60 (1) ◽  
pp. 43 ◽  
Author(s):  
Tiernan A. O'Rourke ◽  
Tim T. Scanlon ◽  
Megan H. Ryan ◽  
Len J. Wade ◽  
Alan C. McKay ◽  
...  
Keyword(s):  
Western Australia ◽  
Root Rot ◽  
Fungal Pathogens ◽  
Lateral Roots ◽  
Subterranean Clover ◽  
Growing Season ◽  
Root Diameter ◽  
Root Disease ◽  
Soil Dna ◽  
Tap Root

Pasture decline is considered to be a serious challenge to agricultural productivity of subterranean clover across southern Australia. Root disease is a significant contributing factor to pasture decline. However, root disease assessments are generally carried out in the early part of the growing season and in areas predominantly sown to permanent pastures. For this reason, in spring 2004, a survey was undertaken to determine the severity of root disease in mature subterranean clover plants in pastures located in the wheatbelt of Western Australia. DNA-based soil assays were used to estimate population density in the soil of a variety of soil-borne pathogens known to commonly occur in the Mediterranean-type environments of southern Australia. The relationships between severity of disease on tap and lateral roots and root diameter, root length, nodulation, and total rainfall were determined. The survey showed, for the first time, that severe root disease is widespread in spring across the wheatbelt of Western Australia. There was a positive correlation between rainfall and tap root disease, and between tap root disease and average root diameter of the entire root system. Despite the high levels of root disease present across the sites, the DNA of most root disease pathogens assayed was detected in trace concentrations. Only Pythium Clade F showed high DNA concentrations in the soil. DNA concentrations in the soil, in particular for Phytophthora clandestina and Rhizoctonia solani AG 2.1 and AG 2.2, were higher in the smaller autumn sampling in 2006. This study suggests that the productivity of subterranean clover-based pastures is severely compromised by root rot diseases throughout the growing season in the wheatbelt of Western Australia.

Effects of time and rate of paraquat application on yield and botanical composition of annual pastures containing subterranean clover in a Mediterranean climate

1973 ◽  
Vol 13 (64) ◽  
pp. 556
Author(s):  
DW Barrett ◽  
GW Arnold ◽  
NA Campbell
Keyword(s):  
Dry Matter ◽  
Mediterranean Climate ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Botanical Composition ◽  
Minimum Loss ◽  
Major Species ◽  
Nitrogen Phosphorus ◽  
Clover Content ◽  
Made In

Pastures containing subterranean clover (Trifolium subterraneum) and either Vulpia spp. or Bromus rigidus as the other major species were sprayed at 0, 0.07, 0.14 and 0.21 kg a.i. ha-1 of paraquat ion between June and early October in Western Australia. Spraying removed the grasses and produced pastures containing up to 95 per cent clover. Mid-winter applications were more effective in increasing clover content than those made in spring. These changes in botanical composition were evident in the year following spraying, but were less marked. Yields of dry matter were reduced by paraquat, especially 'in the period immediately following spraying. These losses tended to decline as the growing season progressed, but at the close they were still evident on the Bromus rigidus pasture sprayed in July. Yields at the end of the subsequent season were similar on all treatments. Paraquat applied in mid-August at 0.14 kg a.i. ha-1 to both pastures produced the greatest change in botanical composition with the minimum loss of yield. The concentrations of nitrogen, phosphorus, calcium and magnesium were higher in mature herbage on paraquat treatments. Total yields of nutrients were similar between treatments because of reduced dry matter yield.

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