The role of plant mass, basal area and density in assessing the herbage mass response to fertility of some native perennial grasses.

1981 ◽  
Vol 3 (1) ◽  
pp. 92 ◽  
Author(s):  
GM Lodge
Keyword(s):  
Field Experiments ◽  
Plant Density ◽  
Basal Area ◽  
Perennial Grasses ◽  
Green Leaf ◽  
Density Data ◽  
Leaf Mass ◽  
Pot Culture

The effects of nitrogen (N) application and differing past fertilizer history on the ,preen leaf mass per plant, plant basal area, green leaf mass per unit of plant basal area and the plant density of some native perennial grasses were investigated in pot culture and field experiments. Data on each of these components of herbage mass were assessed, either individually or in combination with each other, as methods of evaluating the responsiveness of some native perennial grasses to increased fertility. Different mechanisms of increasing plant green leaf mass with applied N (pot culture) and superphosphate (field) were deter- mined in different species and these affected the relationship between green leaf mass anti basal area. Species such as Aristida ramosa and Bothriochloa macra increased their green leaf mass per unit of plant basal area but not their plant basal area. In the glasshouse the application of N significantly (P<0.05) increased the basal area of Chloris truncata, Eragrostis leptostachya, Dichanthium sericeum, Sporoholus elongatus, Danthonia linkii and Stipa variabilis. However, in the field long-term superphosphate application only significantly increased the basal area of C. truncata and D. linkii plants. In the field the mean densities of A. ramosa, D. sericeum and C. truncata plants growing at the unfertilized site were significantly higher than those at the fertilized site and the density of E. leptostachya plants was significantly higher (P<0.01) at the fertilized site. These data indicated that the use of either mass per plant, mass per unit basal area, plant basal area or plant density alone could bias the apparent responsiveness of some species to fertility. To accurately determine the effect of management on the herbage mass of individual native perennial grasses in the field either mass per plant and plant density data, or mass per unit basal area, basal area and plant density data should be combined.

The importance of plant density, plant basal area and plant mass per unit basal area as factors influencing the herbage mass of some native perennial grasses.

1982 ◽  
Vol 4 (2) ◽  
pp. 61 ◽  
Author(s):  
GM Lodge ◽  
AC Gleeson
Keyword(s):  
Plant Density ◽  
Basal Area ◽  
Perennial Grasses ◽  
Green Leaf ◽  
Relative Significance ◽  
Mass Estimate ◽  
Component Field ◽  
The Mean ◽  
The Individual ◽  
Green Stem

Four native perennial grasses, Aristida ramosa R.Br. (wire grass), Bothrioc.llloa macra (Steud) S.T. Blake (red grass), Spovo- bolus elongatus R.Br. (slender rats tail grass) and Stipa variabilis Hughes (corkscrew grass) were collected from 60 randomly allocated quadrats (0.16 m2) in a grazed unfertilized native pasture in November 1979. In each quadrat all plants of each species were counted, harvested individually and their basal areas were estimated. The mass of green leaf, green stem, dead herbage and total herbage of each species was estimated using the mean mass of the individual plants harvested in each of the quadrats. A method for determining the relative importance of the components of this herbage mass viz. plant density, basal area and mass per unit basal area is presented and these values are compared for each species. Plant density contributed significantly fP <0.05) to green leaf, green stem, dead and total herbage mass estimates of A. ramosa and S. elongatus; basal area to all herbage mass estimates of A. ramosa, S. elongatus and S. variabilis; and mass per unit basal area to all herbage mass estimates of A. ramosa and B. macra. The plant basal area of individual plants contributed signifi- cantly more (P <0.05) to the herbage mass estimate of S. vaviabilis and S, elongatus plants than did mass per unit basal area, whereas for B. rnacra mass per unit basal area was the significant (P < 0.05) component. Field procedures for estimating herbage mass and assessing the relative significance of its components are discussed and the extra time taken to collect plant density, plant basal area, and plant mass per unit basal area datais outlined.

Effect of fertility level on the yield of some native perennial grasses on the North-West Slopes, New South Wales.

1979 ◽  
Vol 1 (4) ◽  
pp. 327 ◽  
Author(s):  
GM Lodge
Keyword(s):  
Field Experiments ◽  
Maximum Yield ◽  
Perennial Grasses ◽  
Fertility Level ◽  
Native Grasses ◽  
North West ◽  
The North ◽  
South Wales ◽  
Significant Yield ◽  
Pot Culture

The effect of fertility on the yields of native perennial grasses was investigated in pot culture and field experiments. Yields of six native perennial grasses and Paspalum dilatatum Poir were determined in the glasshouse at five levels of applied phosphorus (P), sulphur (S) and nitrogen (N) and in the field the biomass of individual tussocks of eight native grasses was compared. In pot culture the maximum yields of the native perennial grasses with P, S and N applied were 15 to 75% lower than those of P. dilatatum. Within the native grasses there were significant yield differences: Bothriochloa macra (Steud) S.T. Blake, Chloris truncata R.Br. and Dichanthium sericeum (R. Br.) Camus yielded up to twice as much dry matter as either Aristida ramosa R.Br., Sporobolus elongatus R.Br. or Eragrostis leptostachya Steud. These data indicate that P, S and N are all essential for maximum yield of some native grasses, and large imbalances in the level of these nutrients resulted in seedling mortalities in most native grasses.

Grazing management of natureal pastures at Trangie, NSW

1956 ◽  
Vol 7 (4) ◽  
pp. 233 ◽  
Author(s):  
EF Biddiscombe ◽  
RJ Hutchings ◽  
G Edgar ◽  
EG Cuthbertson
Keyword(s):  
Body Weight ◽  
Plant Density ◽  
Basal Area ◽  
Body Weight Loss ◽  
Perennial Grasses ◽  
Growth Stages ◽  
Natural Pasture ◽  
Continuous Grazing ◽  
Average Rainfall ◽  
Fleece Weight

Results of a 5-year grazing experiment on Stipa-Chlaris natural pasture are presented. Treatments were three rates of stocking each tested with continuous grazing, autumn deferment, and spring deferment. These were studied in relation to: (a) body weight and wool production of Merino wethers; (b) available feed; (c) density and basal area of the perennial grasses. Lighter stocking (one sheep/2 ac) showed little superiority in production per animal under the generally favourable rainfall conditions. There was only one interval of acute feed shortage in which heavier stocking (one sheep/ac) caused extreme body-weight loss and lower fleece weight. The spelling treatments gave no advantage over continuous grazing, either to sheep or to pasture. Effect of stocking rate on perennial grasses mainly depended upon the amount of rainfall received during certain growth stages of the species, e.g. the winter vegetative growth of Stipa, and the March-April maturation of Chloris and Digitaria. Generally, lighter stocking was favourable to plant density and basal area in seasons of average or below average rainfall; heavier stocking was best in wet seasons. Probable reasons for these relationships are discussed.

Top-down and bottom-up forces in mammalian herbivore – vegetation systems: an essay review

Botany ◽  
2009 ◽  
Vol 87 (8) ◽  
pp. 723-739 ◽  
Author(s):  
Roy Turkington
Keyword(s):  
Field Experiments ◽  
Individual Species ◽  
Top Down ◽  
Field Methods ◽  
Bottom Up ◽  
Vegetation Removal ◽  
Mammalian Herbivore ◽  
Resource Levels

For almost 50 years ecologists have debated why herbivores generally don’t increase in numbers to such levels as to deplete or devastate vegetation. One hypothesis is that herbivore populations are regulated at low densities by predators, and a second hypotheses is that plants are fundamentally poor food for herbivores. This has lead to two main hypotheses about the role of herbivores in structuring vegetation: the “bottom-up” and “top-down” hypotheses. Here I survey the literature, with a focus on field experiments designed to investigate the soil resource – vegetation – mammalian herbivore system, specifically asking five questions about how each trophic level responds to (i) resource addition, (ii) vegetation removal, (iii) herbivore removal or reduction, (iv) herbivore addition, and (v) the interaction of resource levels and herbivory? I use these to develop 12 testable predictions. I document the major areas of research as they relate to these 12 predictions, and use these to evaluate weaknesses and limitations in field methods. There are surprisingly few terrestrial studies that conduct factorial manipulations of multiple nutrients or herbivores, even though it is clear that these are essential. Specifically, I argue that a manipulative experimental approach is the most valuable way to advance our theory and understanding, and I advocate the continued use of long-term factorial field experiments that simultaneously manipulate soil resources levels and herbivory (preferably at multiple levels), repeated in a range of environments in which individual species or functional groups are monitored.

scholarly journals Indicators of the Relationship Between the Chemical Composition of Plant and Harvest Potatoes

2021 ◽  
Author(s):  
Serik Abeuov ◽  
Olzhas Shoykin ◽  
Viktor Kamkin ◽  
Yuri Ermokhin
Keyword(s):  
Chemical Composition ◽  
Potato Plant ◽  
Field Experiments ◽  
Correlation Coefficients ◽  
Mineral Fertilizers ◽  
Biochemical Processes ◽  
Phosphorus And Potassium ◽  
The Relationship

The authors carried out long-term research on the effect of mineral fertilizers on the “Gala” potato variety in the Pavlodar region. The relationship was established between the nitrogen, phosphorus and potassium chemical composition of the potato plant in certain phases of growth and development. Various chemical and biochemical processes occur in soil and plants every second. The productivity of plants (y) depends on how the processes take place and proceed, since it is a function of the chemical composition (x) of the leaves: y = f x. The theoretical foundations of plant diagnostics are based on the role of nutrients in the formation of the crop, starting from the early stages of development. According to Yu. I. Ermokhin, the theory of this research provides information on the needs of plants, and in practice these needs must be satisfied. The authors carried out field experiments with fertilizers to obtain the sought-for connections from the low to the optimal content between the ratio of nutrients in the potato plant, which is confirmed by high correlation coefficients (r = 0.79-0.97). If the nitrogen content is higher than the optimal 4.64% in the 7-leaf phase and 4.16% in the flowering phase, then the nature of the ovary takes on a different meaning and the equation is described in a quadratic parabola form. Keywords: potato, harvest, nutrition, fertilizers, plant growth

Techniques for estimating plant basal area and assessing the herbage mass of some native perennial grasses.

1981 ◽  
Vol 3 (1) ◽  
pp. 83 ◽  
Author(s):  
GM Lodge ◽  
JA Taylor ◽  
RDB Whalley
Keyword(s):  
Plant Density ◽  
Unit Area ◽  
Basal Area ◽  
Ground Level ◽  
Field Studies ◽  
Fertilizer Application ◽  
Perennial Grasses ◽  
Individual Species ◽  
Laboratory Studies ◽  
Plant Parts

Techniques for using grid and unmarked transparent perspex overlays to estimate the area of tufted native perennial grasses were investigated in field and laboratory studies. Basal area was overestimated by using an unmarked overlay to trace the periphery of actual or atificial plant bases at ground level; this was caused by the amount of airspace included in the estimate. The compression of hand-held tufts reduced the airspace and improved the estimate of plant basal area. In the laboratory studies, the estimation by eye of filled cells in a transparent grid overlay was accurate over a range of areas from 0.02 to 10.39 cm2, although it required considerable operator training. Changes in herbage mass occur as a result of change in the number of plants per unit area (plant density), the basal area of individual plants or the plant mass per unit of basal area of individual plants. Field studies were undertaken at two sites to collect data on each of these components of herbage mass and to investigate whether or not such information could be used to estimate the herbage mass of individual species in a pasture. The relationship between the mass per unit basal area of certain plant parts would appear to have some potential for use in studies of the seasonal changes in various plant components, such as green leaf and stem. This relationship could be used to examine the response of some species to fertilizer application, grazing and defoliation and hence the process of change in species composition with management. Estimates of the herbage mass per unit area of individual native perennial grasses calculated from plant density, plant basal area and mass per unit of basal area data compared favourably with estimates of total herbage mass of individual species obtained from clipped quadrats. Suggested techniques for collecting data in the field and the time involved in sampling are discussed.

scholarly journals Revisiting the original reasons for excluding inorganic fertilizers in organic farming—Why the ban is not consistent with our current scientific understanding

2021 ◽  
pp. 003072702110200
Author(s):  
Holger Kirchmann
Keyword(s):  
Organic Farming ◽  
Crop Production ◽  
Field Experiments ◽  
Scientific Evidence ◽  
Scientific Understanding ◽  
Rudolf Steiner ◽  
Inorganic Fertilizers ◽  
Carbon And Nitrogen

This paper reviews the original reasons of the organic farming movement for excluding mineral (inorganic) fertilizers. In this paper, their theories and decision criteria for excluding use of inorganic fertilizers in crop production were revisited. Original reasons for banning inorganic fertilizers were subjected to scientific scrutiny, which was not possible when they were formulated 50–100 years ago due to limited knowledge of the soil-crop system. The original reasons were as follows: Rudolf Steiner, the founder of biodynamic farming, played down the physical role of plant nutrients and pointed out “flow of forces” as being most important for soils and crops. Eve Balfour and Albert Howard, founders of the Soil Association in England, claimed that inorganic fertilizer increases the breakdown of humus in soil, leading to a decline in soil fertility. Hans-Peter Rusch, the founder of biological organic farming, considered inorganic fertilizers to be imbalanced products not matching crop composition and not in synchrony with crop demand. When testing these historical statements as scientific hypotheses, older and modern scientific literature was used for validation. Steiner’s belief about the “flow of forces” has not be verified using current methodologies. The claim by Balfour and Howard that inorganic fertilizers accelerate soil organic matter decomposition is not substantiated by data from long-term field experiments on carbon and nitrogen cycling in soil-plant systems. The statement by Rusch that inorganic fertilizers supply crops inappropriately is difficult to uphold, as the composition, time, and rate of application and the placement of fertilizer in soil or on foliage can be fully adapted to crop requirements. In light of accumulated scientific evidence, the original arguments lack validity. The decision to ban inorganic fertilizers in organic farming is inconsistent with our current scientific understanding. Scientific stringency requires principles found to be erroneous to be abandoned.

scholarly journals The role of Debrecen maize hybrids in competitive production

2006 ◽  
pp. 19-21
Author(s):  
Barnabás Forgács
Keyword(s):  
Plant Density ◽  
Higher Plant ◽  
Maize Hybrids ◽  
Term Experiment ◽  
Average Precipitation ◽  
Long Term Experiment ◽  
Plant Densities ◽  
Set Up

I examined the effects of plant density and fertilisation on the yield of the maize hybrid Debreceni 377 SC, developed by the Agrárgazdaság Ltd., using the 3 year data sequence of a long term experiment set up at the Látókép experimental station of DU Center for Agricultural Sciences in years with average precipitation supply.Based on the evaluation of my research results, I found that the application of higher plant densities was more favourable in years with average or higher than average precipitation supply. During the examination of fertilisation effects, it was verified that surplus yield was realised in most cases where smaller fertilisation dosage, 120 kg per hectare active substance was applied.

scholarly journals Reproductive Sink of Sweet Corn in Response to Plant Density and Hybrid

HortScience ◽  
2018 ◽  
Vol 53 (1) ◽  
pp. 28-32
Author(s):  
Martin M. Williams
Keyword(s):  
Essential Role ◽  
Field Experiments ◽  
Plant Density ◽  
Sweet Corn ◽  
Reproductive Traits ◽  
Corn Yield ◽  
Density Data ◽  
Common Response ◽  
Plant Densities ◽  
Corn Plants

Improvements in plant density tolerance have played an essential role in grain corn yield gains for ≈80 years; however, plant density effects on sweet corn biomass allocation to the ear (the reproductive ‘sink’) is poorly quantified. Moreover, optimal plant densities for modern white-kernel shrunken-2 (sh2) hybrids are unknown. The objectives of the study were to 1) quantify the effect of plant density and hybrid on the reproductive sink of sweet corn and 2) determine optimal plant densities for white-kernel sh2 sweet corn. Field experiments were conducted across 2 years on 10 white-kernel sh2 hybrids grown at plant densities ranging from 4.3 to 8.6 plants/m2. Increasing plant density negatively influenced reproductive sink characteristics of individual sweet corn plants, including linear decreases in ear shoots/plant, marketable ears/plant, ear length, filled ear length, ear mass/plant, and kernel mass/plant. Reproductive traits varied widely among hybrids, including ear mass (15.6–20.6 Mt·ha−1) and recovery (32.3% to 42.4%), which is the contribution of fresh kernel mass to total ear mass. Hybrids had a common response to plant density, whereby ear yield was optimized at 5.5 plants/m2 and gross profit margin was optimized at 6.1 plants/m2. Plant density data from 586 growers’ fields suggest current seeding rates have optimized the reproductive sink size for today’s white-kernel sh2 hybrids. However, room exists for improving plant density tolerance, yield, and profitability.

Floristic composition and pasture condition of Aristida/Bothriochloa pastures in central Queensland. II. Soil and pasture condition interactions

2015 ◽  
Vol 37 (2) ◽  
pp. 217
Author(s):  
R. G. Silcock ◽  
T. J. Hall ◽  
P. G. Filet ◽  
A. M. Kelly ◽  
D. Osten ◽  
...  
Keyword(s):  
Soil Type ◽  
Plant Density ◽  
Surface Condition ◽  
Good Condition ◽  
Basal Area ◽  
Ground Cover ◽  
Perennial Grasses ◽  
Tree Cover ◽  
Themeda Triandra ◽  
Heteropogon Contortus

Sustainable management of native pastures requires an understanding of what the bounds of pasture composition, cover and soil surface condition are for healthy pastoral landscapes to persist. A survey of 107 Aristida/Bothriochloa pasture sites in inland central Queensland was conducted. The sites were chosen for their current diversity of tree cover, apparent pasture condition and soil type to assist in setting more objective bounds on condition ‘states’ in such pastures. Assessors’ estimates of pasture condition were strongly correlated with herbage mass (r = 0.57) and projected ground cover (r = 0. 58), and moderately correlated with pasture crown cover (r = 0.35) and tree basal area (r = 0.32). Pasture condition was not correlated with pasture plant density or the frequency of simple guilds of pasture species. The soil type of Aristida/Bothriochloa pasture communities was generally hard-setting, low in cryptogam cover but moderately covered with litter and projected ground cover (30–50%). There was no correlation between projected ground cover of pasture and estimated ground-level cover of plant crowns. Tree basal area was correlated with broad categories of soil type, probably because greater tree clearing has occurred on the more fertile, heavy-textured clay soils. Of the main perennial grasses, some showed strong soil preferences, for example Tripogon loliiformis for hard-setting soils and Dichanthium sericeum for clays. Common species, such as Chrysopogon fallax and Heteropogon contortus, had no strong soil preference. Wiregrasses (Aristida spp.) tended to be uncommon at both ends of the estimated pasture condition scale whereas H. contortus was far more common in pastures in good condition. Sedges (Cyperaceae) were common on all soil types and for all pasture condition ratings. Plants identified as increaser species were Tragus australianus, daisies (Asteraceae) and potentially toxic herbaceous legumes such as Indigofera spp. and Crotalaria spp. Pasture condition could not be reliably predicted based on the abundance of a single species or taxon but there may be scope for using integrated data for four to five ecologically contrasting plants such as Themeda triandra with daisies, T. loliiformis and flannel weeds (Malvaceae).

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