Effects of defoliation management on the productivity of an irrigated Persian clover sward

1994 ◽  
Vol 34 (2) ◽  
pp. 205 ◽  
Author(s):  
CR Stockdale
Keyword(s):  
Leaf Area ◽  
Growth Rates ◽  
Ground Level ◽  
Maximum Growth ◽  
Fungal Disease ◽  
Area Index ◽  
Herbage Yield ◽  
Defoliation Treatment ◽  
Negative Effect ◽  
Persian Clover

A field experiment investigated the effects of frequency and height of defoliation on the productivity of an irrigated Persian clover (Trifolium resupinatum) sward. Combinations of 4 intervals of harvest (3, 6, 9, 12 weeks) and 2 heights of defoliation (to ground level or 5 cm above ground level) were used in a randomised block experiment, with 2 additional treatments of 4 and 18 weeks between harvests defoliated to ground level. Total herbage accumulation ranged from 8.46 to 13.90 t DM/ha and varied according to defoliation management. Except for the very short defoliation intervals, harvesting to 5 cm was less productive than harvesting to ground level. The effects of leaf area index, herbage yield, and infection with leaf fungal disease on growth rates were assessed. Leaf area had a positive effect, and fungal disease a negative effect, on herbage growth rates, while maximum growth rates in autumn-winter were achieved when herbage yield reached about 2.0 t DM/ha. Dead matter accumulation increased with the interval between harvests, and weeds invaded the plots at both the shortest and longest defoliation intervals. The quality of seed produced (seed weight) was not influenced by defoliation treatment (0.1112 g/100 seeds, on average). Defoliation interval was positively related to number of inflorescences and quantity of seed set, but height of defoliation did not significantly affect these variables. It was concluded that the optimum interval of harvest was 6-9 weeks. Height of defoliation had only minor effects, due to the small difference in residual dry matter between the treatments.

Effect of previous cutting interval and of leaf area remaining after cutting on regrowth of Macroptilium atropurpureum cv. Siratro

1974 ◽  
Vol 14 (68) ◽  
pp. 343 ◽  
Author(s):  
RJ Jones
Keyword(s):  
Leaf Area ◽  
Practical Implication ◽  
Soluble Sugars ◽  
Ground Level ◽  
Fold Increase ◽  
Water Soluble ◽  
Hot Water ◽  
Lag Phase ◽  
Area Index ◽  
Plant Yield

Experiments with Siratro were conducted at Samford, south east Queensland to study the effects of previous cutting and defoliation treatments on regrowth. In the first experiment, swards of Siratro were cut at 7.5 cm above ground level every 4 weeks, every 8 weeks or cut once at 16 weeks during spring and summer. Regrowth of all treatments over ten weeks was measured after varying (by leaf removal) the stubble leaf area index (LAI) of the plots cut every four weeks. Pattern of regrowth yield was similar for all treatments with a pronounced lag phase after cutting. Regrowth yield after 10 weeks differed between treatments and was linearly related (P < 0.01 ) to residual LAI in the stubble at the start of regrowth. In the absence of stubble leaves, plots previously cut at 16 weeks or at 8 weeks yielded marginally more than those cut every 4 weeks. There were no marked treatment differences in gross root morphology other than a two fold increase in stolon rooting for the 16-week treatment. Nitrogen content of the roots (mean 1.38 per cent) was unaffected by treatment, but the per cent hot water soluble sugars were lower for the 16 week defoliation treatment than for the 8-week and the 4-week treatments. In the second experiment individual plants were cut to a uniform stubble every 4 weeks and either 0, 5, or 10 leaves were left. Dry weight of regrowth and stolon development were greatest when most leaves were left. Two thirds of the plants died after six cuttings with complete defoliation but none died when either 5 or 10 leaves were retained. Plant survival was not related to plant yield or degree of stoloniferous development. However, there was a strong correlation between stolon number and plant yield under this intensive cutting regime. The practical implication of the results in the management of Siratro is discussed.

scholarly journals Comparisons of Herbicide Treated and Cultivated Herbicide-Resistant Corn

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
H. Arnold Bruns ◽  
Hamed K. Abbas
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Growth Rates ◽  
Negative Impact ◽  
Growth Yield ◽  
Yield Component ◽  
Dry Matter Accumulation ◽  
Negative Effects ◽  
Area Index ◽  
Relative Growth Rates

Four glyphosate resistant corn (Zea maysL.) hybrids, a glufosinate-ammonium resistant hybrid, and a conventional atrazine resistant hybrid gown at Stoneville, MS in 2005, 2006, and 2007 with furrow irrigation were treated with their respective herbicides and their growth, yield, and mycotoxin incidence were compared with untreated cultivated plots. Leaf area index (LAI) and dry matter accumulation (DMA) were collected on a weekly basis beginning at growth stage V3 and terminating at anthesis. Crop growth rates (CRGs) and relative growth rates (RGRs) were calculated. Plots were later harvested, yield and yield component data collected, and kernel samples analyzed for aflatoxin and fumonisin. Leaf area index, DMA, CRG, and RGR were not different among the herbicide treated plots and from those that were cultivated. Curves for LAI and DMA were similar to those previously reported. Aflatoxin and fumonisin were relatively low in all plots. Herbicide application or the lack thereof had no negative impact on the incidence of kernel contamination by these two mycotoxins. Herbicides, especially glyphosate on resistant hybrids, have no negative effects on corn yields or kernel quality in corn produced in a humid subtropical environment.

Productivity of Vegetable Crops in a Region of High Solar Input. IV. Field Chamber Measurements on French Beans (Phaseolus vulgaris L.) And Cabbages (Brassica oleracea L.)

1975 ◽  
Vol 2 (4) ◽  
pp. 461 ◽  
Author(s):  
PJM Sale
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Growth Rates ◽  
Dark Respiration ◽  
Gas Analysis ◽  
Large Field ◽  
Co2 Uptake ◽  
Vegetable Crops ◽  
Area Index ◽  
French Beans

Net CO2 uptakes have been measured for crop canopies of French beans and cabbages, sown at two plant densities, using a large field assimilation chamber and a semi-closed gas-analysis system. For both species, the maximum rates of uptake were a little less than 40 mg CO2 dm-2 (ground area) h-1, and light saturation of the canopy occurred at 600-650 W m-2 (French beans) or about 800 W m-2 (cabbages). Net CO2 uptake decreased with leaf area index at values below about 5, but was relatively insensitive to temperature over the range used. Once this leaf area index was reached, the relationship between net uptake and solar radiation remained fairly constant throughout the growth period. For both species, dark respiration rates were markedly dependent on temperature, and also were lower at night than during the day when measured at the same temperature. For both French beans and cabbages, growth analyses showed the maximum growth rates to be 18-19 g dry weight m-2 (ground area) day-1. The mean growth rate from emergence to harvest for an overwintered cabbage crop was 5.5 g m-2 day-1. It is suggested that the main advantage of the region in terms of plant productivity lies in the long frost-free growing season and the ability of frost-tolerant crops to maintain fairly high growth rates throughout a mild and comparatively sunny winter.

Predicting the effects of hardwood competition on red pine seedling growth

1992 ◽  
Vol 22 (10) ◽  
pp. 1510-1515 ◽  
Author(s):  
Alan S. White ◽  
Katherine J. Elliott
Keyword(s):  
Leaf Area ◽  
Seedling Growth ◽  
Negative Impact ◽  
Ground Level ◽  
Red Pine ◽  
Area Index ◽  
Clear Cut ◽  
Site Characteristics ◽  
Early Effects ◽  
Highly Correlated

Pin cherry (Prunuspensylvanica L.f.) and striped maple (Acerpensylvanicum L.) are potentially important competitors of red pine (Pinusresinosa Ait.) planted on recently clear-cut hardwood sites. By experimentally manipulating initial competitor densities on 2.0-m2 plots, we were able to quantify and compare the effects of competitor species on red pine seedlings 2 years after planting on two sites in western Maine. Various measures of competitor biomass and leaf area index (LAI) were highly correlated; thus, we used LAI to quantify competitor abundance. On the site with poorer growth for both competitors and red pine, the only red pine variable significantly correlated with competitor LAI was specific leaf area (SLA) of current needles. On the site with better growth for all species, various measures of red pine biomass as well as diameter at ground level and SLA were significantly correlated with competitor LAI. Seedling height was not significantly correlated with competitor LAI at either site. Although there were no significant differences between competitor species in terms of their effect per unit of LAI, pin cherry tended to achieve much higher LAI (and biomass) than did striped maple and thus had a greater negative impact on red pine seedling growth. We conclude that general predictions of the early effects of competition under field conditions are possible, but that the strength of the relationships may be influenced by the extent to which microsite factors and site characteristics are incorporated.

The influence of leaf area and radiation on the growth of clover in swards

1962 ◽  
Vol 13 (4) ◽  
pp. 615 ◽  
Author(s):  
WR Stern ◽  
CM Donald
Keyword(s):  
Growth Rate ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Crop Growth ◽  
Light Regime ◽  
Agricultural Practice ◽  
Area Index ◽  
Crop Growth Rate

A study was made of the light regime and the growth of clover: (a) in mixed swards with varying proportions of grass; (b) in specially designed cultures in which grass and clover competed for light alone. The growth of the clover showed direct dependence on the level of radiation at the surface of the clover leaf canopy; it was positive when radiation values were above about 60–80 cal/cm²/day but fell to zero or negative rates at lower radiation levels. A relationship is presented between the level of radiation, the leaf area index, and the crop growth rate. It is shown that the optimum leaf area index increases with increasing levels of radiation; and further that as the leaf area index increases, the level of radiation required for maximum growth rate also rises. The implications in agricultural practice are discussed briefly.

Studies of grain production in Sorghum bicolor (L. Moench). V.* Effect of planting density on growth and yield

1975 ◽  
Vol 26 (1) ◽  
pp. 31 ◽  
Author(s):  
KS Fischer ◽  
GL Wilson
Keyword(s):  
Growth Rate ◽  
Grain Yield ◽  
Leaf Area ◽  
Growth Rates ◽  
Dry Matter ◽  
Leaf Growth ◽  
Crop Growth ◽  
Area Index ◽  
Crop Growth Rate ◽  
Net Assimilation

Growth analysis was applied to grain sorghum (cv. RS610) grown at low, medium and high population densities, i.e. 14,352, 143,520 and 645,836 plants ha-1 respectively. The medium densities had two arrangements of plants, square (S) and rectangular (R). Crop growth rates, inflorescence growth rates, leaf area indices, net assimilation rates and leaf growth rates were calculated from growth functions of plant dry matter and leaf area over time. Differences in crop growth rate between populations in the early stages were attributed to leaf area development—specifically to the initial leaf area (dependent on seedling number) and not to differences in leaf growth rates. Peak crop growth rates were 15.0, 27.5, 26.0 and 45.8 g m-2 day-1 for the low, medium (S), medium (R) and high populations respectively.The large difference between the growth rates of the medium (S) and the high populations was not explained by differences in the amount of radiation intercepted. Although leaf area indices were 4.6 and 10.2 respectively for the two populations, both canopies intercepted almost all of the noon radiation. Light extinction coefficients were 0.45 and 0.29 respectively. The relationship between net assimilation rate and leaf area index was such that for comparable leaf area indices above 2, plants at higher densities showed greater improvement in yield per unit increment in leaf area index. A maximum grain yield of 14,250 kg ha-1 was obtained at the high population density as a result of higher dry matter production, but a similar harvest index to that of the crops grown at the other densities. Inflorescence growth rate (g m-2 day-l) slightly exceeded crop growth rate in the latter part of grain filling, which indicated that there was some retranslocation to the grain of previously assimilated material. The maximum grain yield represents an efficiency of utilization of short-wave solar radiation during crop life of 2.5 x 10-6g cal-1. *Part IV, Aust. J. Agric. Res., 26: 25 (1975).

The seasonal growth characteristics of irrigated cotton in a dry monsoonal environment

1965 ◽  
Vol 16 (3) ◽  
pp. 347 ◽  
Author(s):  
WR Stern
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Growth Rates ◽  
Dry Matter ◽  
Seasonal Effect ◽  
Cotton Yield ◽  
Seasonal Growth ◽  
Seed Cotton ◽  
Area Index ◽  
Seed Cotton Yield

Cotton plantings were made at the Kimberley Research Station (128° 36´ E., 15° 42´ S.) from September to July to give overlapping growth curves extending from September 1961 to December 1962. Crop growth was examined in relation to radiation and temperature. Beginning at the third week from sowing, each planting was sampled 12 times at intervals of 15 days. At each sampling, dry matter, leaf area index, number and dry weight of bolls, and seed cotton yield were determined. The development of total dry matter and leaf area index showed a strong seasonal trend. The number of bolls produced was less in the late plantings, and the seed cotton yield was correspondingly lower. The highest seed cotton yields and the highest ratios of seed cotton to total dry matter (30%) were obtained with January–February plantings. The growth rates between 50 and 100 days were used to analyse seasonality; the highest seasonal growth rate was 164 mg dm-2 day-1 in December–January and the lowest value was zero in early September. By using fitted harmonics, a multiple correlation was established between maximum and minimum temperatures and growth rates 30 days later. Potential rates of net photosynthesis of tops were calculated from observed radiation data with the use of the de Wit model and with allowance for light wastage, root growth, and respiration. There was good agreement between observed and potential growth rates from December to April. Midday stomatal apertures declined from November to May, and this appeared to be a seasonal effect. An annual pattern for the diffusive resistance of carbon dioxide through the leaf surface into the substomatal cavities is calculated. Radiation did not appear to be the primary limiting factor, and the seasonal growth pattern was interpreted in terms of the composite effect of maximum and minimum temperatures on extension growth, stomatal opening, and the presence or absence of suitable sinks for carbohydrates. Growth rates are evaluated against rates observed elsewhere, and means of exploiting the Kimberley environment are discussed.

scholarly journals Urban Forest Growth and Gap Dynamics Detected by Yearly Repeated Airborne Light Detection and Ranging (LiDAR): A Case Study of Cheonan, South Korea

2019 ◽  
Vol 11 (13) ◽  
pp. 1551 ◽  
Author(s):  
Heejoon Choi ◽  
Youngkeun Song ◽  
Youngwoon Jang
Keyword(s):  
Change Detection ◽  
Leaf Area ◽  
Growth Rates ◽  
Urban Forest ◽  
Urban Forests ◽  
Forest Growth ◽  
Airborne Lidar ◽  
Light Detection And Ranging ◽  
Light Detection ◽  
Area Index

Understanding forest dynamics is important for assessing the health of urban forests, which experience various disturbances, both natural (e.g., treefall events) and artificial (e.g., making space for agricultural fields). Therefore, quantifying three-dimensional changes in canopies is a helpful way to manage and understand urban forests better. Multitemporal airborne light detection and ranging (LiDAR) datasets enable us to quantify the vertical and lateral growth of trees across a landscape scale. The goal of this study is to assess the annual changes in the 3-D structures of canopies and forest gaps in an urban forest using annual airborne LiDAR datasets for 2012–2015. The canopies were classified as high canopies and low canopies by a 5 m height threshold. Then, we generated pixel- and plot-level canopy height models and conducted change detection annually. The vertical growth rates and leaf area index showed consistent values year by year in both canopies, while the spatial distributions of the canopy and leaf area profile (e.g., leaf area density) showed inconsistent changes each year in both canopies. In total, high canopies expanded their foliage from 12 m height, while forest gap edge canopies (including low canopies) expanded their canopies from 5 m height. Annual change detection with LiDAR datasets might inform about both steady growth rates and different characteristics in the changes of vertical canopy structures for both high and low canopies in urban forests.

Net Carbon Exchange Rates of Field-Grown Crops in Relation to Irradiance and Dry Weight Accumulation

1977 ◽  
Vol 4 (4) ◽  
pp. 555 ◽  
Author(s):  
PJM Sale
Keyword(s):  
Exchange Rates ◽  
Leaf Area ◽  
Growth Rates ◽  
Co2 Flux ◽  
Large Field ◽  
Co2 Uptake ◽  
Carbon Exchange ◽  
Area Index ◽  
Stages Of Growth ◽  
Net Carbon Exchange

A range of summer and winter vegetable crops has been grown under favourable conditions, and the relation between net carbon exchange and irradiance determined at several stages of growth, using large field assimilation chambers and semi-closed gas analysis systems. For all crops, leaf area index was an important determinant of net carbon exchange rate during early stages of growth, and rates increased markedly from day to day during the period of rapid vegetative development. Except for cauliflower and cucumber, for which leaf area ceased to be so important as the crops developed, maximum rates of CO2 uptake were achieved at maximum leaf areas, and were in excess of 90 mg CO2 dm-2 (ground area) h-1 for sweet corn, about 64 for rockmelon, 50 for broad bean, cauliflower and cabbage, and 45 mg dm-2 h-1 for cucumber. For both rockmelon and cucumber, net carbon exchange rates in the morning were often greater than those at the same irradiances in the afternoon, which suggests partial stomatal closure at about midday. In all crops, variations in temperature of up to 10°C either side of the ambient temperature, imposed at any time during the day, generally had little effect on negative CO2 flux (uptake), but positive CO2 flux at night was strongly influenced by temperature. In cucurbits uptake was reduced at temperatures above 35°C, but rapidly recovered when the temperature was again lowered. High growth rates were achieved by all crops for most months of the year, and the efficiency of utilization of incident energy was also high compared with other reported values. However, growth rates were not related to the maximum rates of CO2 uptake in the day, for net carbon exchange over each 24 h depended also on factors such as the ratio between day- and nightlength and night temperatures.

The productivity of irrigated legumes in northern Victoria. 2. Effect of grazing management

2005 ◽  
Vol 45 (12) ◽  
pp. 1577 ◽  
Author(s):  
K. B. Kelly ◽  
C .R. Stockdale ◽  
W. K. Mason
Keyword(s):  
Leaf Area ◽  
White Clover ◽  
Growth Rates ◽  
Carbon Balance ◽  
Red Clover ◽  
Subterranean Clover ◽  
Net Photosynthesis ◽  
First Year ◽  
Second Year ◽  
Persian Clover

The productivity of irrigated white (Trifolium repens L.) and red (Trifolium pratense L.) clover swards was compared in an experiment of more than 3 years duration. It was hypothesised that white clover would be more productive than red clover when defoliation was frequent and intense, and less productive when defoliation was infrequent and lax. The experiment was a factorial design involving 2 species of clover [white clover (cv. Haifa) and red clover (cv. Redquin)], 2 grazing frequencies and 2 grazing intensities (with the criteria for both being based on quantities of herbage present before/after grazing). There were 4 extra treatments sown: perennial ryegrass (Lolium perenne L. cv. Grasslands Nui) and white clover (cv. Haifa), lucerne (Medicago sativa L. cv. Validor), Persian clover (Trifolium resupinatum L. cv. Maral) or subterranean clover (Trifolium subterraneum L. cv. Trikkala), but only 1 defoliation treatment was used for each of these treatemnts. There were 4 replicated blocks of all treatments. Apparent growth rates [calculated from measurements of dry matter (DM) removed by grazing] of white clover ranged from a low of 10 kg DM/ha.day in winter to a high of 70 kg DM/ha.day in summer. The growth rates of white clover swards were superior to those of ryegrass and white clover swards over summer, but were generally lower from May to October. In 2 of the 4 years, frequent grazing of white clover resulted in greater (P<0.05) production than infrequent grazing (average of 12.8 v. 10.7 t DM/ha) whereas intensity of grazing only affected DM net accumulation in the first year (P<0.05). The data show no evidence of a decline in productivity over time. Sward structure of white clover was influenced by grazing treatment with the numerically highest yielding treatment (frequent and hard) having the highest density of stolon tips (vegetative buds). In relation to days of regrowth, the frequently grazed treatment had higher levels of net photosynthesis in spring and summer compared with the infrequently grazed treatment. The frequently grazed treatment achieved positive carbon balance immediately after grazing and reached maximum levels of photosynthesis at 8–10 days, whereas the infrequent treatment showed negative carbon balance for the first 2–3 days after grazing with maximum photosynthesis being achieved later than in the frequently grazed treatment. When net photosynthesis was related to leaf area, there were fewer differences between the 2 treatments. The exception was in spring when photosynthesis was lowest where the initial leaf area was highest in the infrequent and hard treatment. Maximum photosynthesis was achieved at diminishing leaf area index from spring through to winter. Red clover was the most productive legume in the first year after establishment, but it did not persist beyond the second year and its DM net accumulation was reduced by more frequent grazing (12.4 v. 15.3 t DM/ha in the first year and 6.1 v. 9.1 t DM/ha in the second year; P<0.05). The DM net accumulation of lucerne was greater than that in any other treatment (an average of 16.7 t DM/ha in the 2 completed years), whereas the annual legumes, subterranean clover and Persian clover, averaged 6.6 and 10.7 t DM/ha.year, respectively. The seasonal growth rate data showed that lucerne had very good summer production whereas the annuals tended to be at least as good as the perennials from May to October.

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