Percent Ground Cover Research Articles

Effects of mowing and spraying of 2,4,5-T on blackberry (Rubus fruticosus agg.) and pasture species

In a field trial in southern Victoria, boom spraying with 2,4,5-T gave a higher level of control of blackberry than mowing, and mowing in addition to spraying did not improve (P = 0.05) the level of control. In a second trial, spraying was superior to mowing although the difference was smaller than in the first trial, and less marked, and the combination of mowing and spraying resulted in a greater reduction in the percentage ground cover of blackberry. Sprayed thickets were colonized by grasses and weedy species but not by Trifolium repens, which is a basic component of pastures in areas where blackberry is often a weed. It is concluded that repeated mowing, or boom spraying with 2,4,5-T, and topdressing with fertilizer are only moderately successful in attempting to replace blackberry with a productive pasture. This is attributed to the difficulty in killing the extensive root system of blackberry and the effect of 2,4,5-T on T. repens.

Effects of vegetation canopy structure on remotely sensed canopy temperatures

Remote sensing of vegetation temperatures is a promising technique for inferring plant water stress and yield on a large spatial scale. The effects of vegetation canopy structure on thermal infrared sensor response need to be understood before vegetation surface temperatures of canopies with low percentages of ground cover can be accurately inferred. The response of a sensor is a function of vegetation geometric structure, the vertical surface temperature distribution of the canopy components, and sensor view angle. Large deviations between the nadir sensor effective radiant temperature (ERT) and vegetation ERT for a soybean canopy were observed throughout the growing season. The nadir sensor ERT of a soybean canopy with 35% ground cover deviated from the vegetation ERT by as much as 11°C during the mid-day. These deviations were quantitatively explained as a function of canopy structure and soil temperature. Remote sensing techniques which uniquely determine the vegetation canopy temperature(s) from the sensor response need to be studied.

Influence of Fungicide and Insecticide Applications on Persistence of Ladino Clover1

AbstractLadino clover (Trifolium repens L.) is the most important perennial forage legume grown in North Carolina; however, stands often begin to decline within 2‐3 years after seeding. An entomological‐pathological complex has been reported as a major cause for decline of ladino clover. The objectives of this study were to determine the influence of benomyl [methyl l‐(butylcarbamoyl)‐2‐benzimidazolecarbamate] and carbofuran (2, 3‐Dihydro‐2, 2‐dimethyl‐7‐benzofuranyl methylcarbamate) applications on disease and/or insects which influence persistence of ladino clover.The percent ground cover of ladino clover in control, benomyl, carbofuran, and carbofuran plus benomyl treated plots after 3‐1/2 years was 12, 24, 75 and 88%, respectively. Plants treated with carbofuran had less root injury from the clover root curculio (Sitona hispidula Fab.) than fungicide and check plots. Carbofuran and carbofuran plus benomyl applications decreased root and stolon rot and increased yield and persistence of ladino clover. None of the treatments significantly increased tap root longevity. Insect damage and root and stolon rot were highly correlated in plant samples collected throughout the experiment. Results indicate that a pathological‐entomological complex is a major factor involved with lack of persistence of ladino clover.

Effect of Forest Clear-Cut Edge on Breeding Birds in East Texas

Effect of Forest Clear-Cut Edge on Breeding Birds in East Texas

Drought Adaptation of Cowpea. III. Influence of Drought on Plant Growth and Relations with Seed Yield1

AbstractConcurrent studies described drought effects on seed yield, plant water status, and water use of cowpea (Vigna unguiculata L. Walp.). In the present studies, drought effects on the growth of cowpea were determined to analyze possible relationships between seed yield, plant growth, and drought, and to evaluate possible mechanisms for the extreme drought avoidance exhibited by cowpea.Two cowpea cultivars were subjected to different intensities of drought at the vegetative, flowering, and pod filling stages in the field during 2 years having contrasting weather patterns. Plant growth analyses were conducted at the end of the vegetative and flowering stages.Increase in percent ground cover with time during the vegetative and flowering stages was either slowed down or delayed by drought. Increasing levels of drought, as determined by cumulative xylem pressure chamber values, resulted in progressively less leaf area, shoot dry matter, number of leaflets, and average leaflet area with total leaf area having the greatest sensitivity, and leaflet size the least sensitivity to drought. These responses were partially responsible for the extreme drought avoidance by this crop, but they also may have caused yield reductions. Seed yields were correlated with the leaf area index at the end of flowering and with the percent cover duration from the beginning of flowering to pod filling, but they were not correlated with the amount of leaf area present during the vegetative stage. Earliness, determined by the dry weight in pods at the end of flowering, increased with moderate drought and decreased with more severe drought.Specific leaf weight increased with increasing levels of drought and may provide a measure of the long term water status experience of plants due to its correlation with cumulative pressure chamber values. A multiple correlation of seed yield with specific leaf weight and degree days above 35 C at flowering accounted for most of the variation in seed yield due to progressive drought and for three growing seasons with contrasting temperature regimes.

Bidirectional reflectance of crops and the soil contribution

Spectra of cereals, grasses, and corn were measured repeatedly from preflowering to early maturity. The bidirectional and angular aspects were more pronounced for a standing crop such as cereals (oats) than for a clipped sod. The contribution of the soil to the total radiance and the amount of the total radiance were reduced by a greater percentage of ground cover. The effect of angular scattering on radiance decreased with maturity.

Woodcock Movements and Habitat Utilization in Central Alabama

Seventeen American woodcock (Philohela minor) were telemetrically studied during the winters of 1973-75 on a 211-ha farm in Lee County, Alabama. Data from 10 males and 7 females were used to study movements and habitat utilization. Radio-marked woodcock used mixed hardwood-pine and adjacent bottomland hardwood cover types as diurnal habitat. Activity center stem densities averaged 3,818 ?356 (SE) stems/ha for midstory I and 3,997 ? 450 stems/ha in midstory II. Ground cover in the activity centers consisted of 53 ? 4% leaf litter and/or bare soil. Diurnal home range size averaged 9.2 ? 2.3 ha. Half the nocturnal locations were in permanent openings and half were in woodlands. Woodcock were consistently active during daylight hours. Crepuscular flights averaged 183 ? 28 m distance. Nocturnal movement was less than diurnal movement although the difference was not significant. J. WILDL. MANAGE. 43(2):414-420 Managing woodcock for hunting requires analysis of the habitat types utilized by the bird. Quantitative descriptions of woodcock habitat are available for much of the northern portion of the bird's range, but Owen et al. (1977) noted the paucity of information concerning woodcock habitat needs and availability on their southern wintering grounds. Emlen (1956) suggested that differences between preferred and avoided habitats might be associated with vegetational structure rather than specific composition. In statewide surveys in Alabama we had observed numerous woodcock in a variety of forest habitats. The only apparent similarity in variable floristic communities was vegetational structure. Midstory stem density and percent ground cover seemed to be important structural aspects of diurnal woodcock coverts. Telemetric studies of woodcock wintering in east-central Alabama were begun in 1972 and continued through the winter of 1975. Investigators indentified and described diurnal and nocturnal habitat used by woodcock, and measured movements of radio-tagged birds within these habitats. Emphasis was placed on quantitative descriptions of vegetation types utilized most often by instrumented birds. We are especially indebted to P. E. Crow, Jr. for use of his farm as a study area. This study was funded by the Alabama Department of Conservation, Division of Game and Fish, through the Alabama Cooperative Wildlife Research Unit and by the Agricultural Experiment Station of Auburn University.

Transector: An Inexpensive Device to Measure Ground Cover and Botanical Composition of Swards1

AbstractA need for an apparatus capable of simplifying the reading and recording of ground cover and botanical composition on 80 experimental grazing plots prompted the development and testing of the transector.The objective of this manuscript is to describe how to construct and use the device to measure ground cover and/or botanical composition of grazed swards. The transector is a device that uses the line interception method, developed over 25 years ago, to simplify the logistics of pasture sampling and subsequent data analysis. The transector is a lightweight, simple, inexpensive device that is easily constructed and maintained. The only essential materials neded for the transector are two pieces of aluminum patio extrusion. This device makes it possible to take direct readings along a 5‐m long line without moving the transector. Since this device permits a direct reading along the line, it also simplifies the subsequent accumulation of the data for determining ground cover or botanical composition percentages.

Change in percentage ground cover of perennial grasses under different burning regimes

Differences in the ground and perennial grass covers under different burning and grazing regimes are presented for three vegetation types in Kainji Lake National Park. It is shown from the results that perennial grasses established higher basal cover under late burning treatments than under early burning and no burning treatments. Late fires destroy litter which hinders grass growth while no burning treatments cause accumulation of litter. The highest number of grass tillers are produced under late burning treatments, while the lowest occurred under no burning treatments. The early burning plots have intermediate results. Occasional late burning in controlled small blocks of land is recommended for optimum grass production in the study area.

Mulches, microclimate, topsoil and the establishment of vegetative cover on a dispersible soil

Stabilization by vegetation of dispersible subsoil batters which cannot be adequately topsoiled has generally proven unsuccessful. Straw and bitumen mulches were used alone and combined to aid the establishment of pasture grasses and legumes on batters composed of dispersible subsoil, which were covered with either 5 cm or 10 cm of topsoil, or were not topsoiled. The mulches consistently increased plant density, vegetative ground cover, and plant production. However, percentage ground cover at the end of the first season was only 10–26%, unless 10 cm of topsoil was added first. With 10 cm of topsoil, the only treatments to provide sufficient ground cover to control erosion after a year's growth were bitumen–straw and straw. Cover was determined by individual plant growth rather than plant density. Field implications are discussed.

Effect of time of application of herbicides on the long-term control of St. John's wort (Hypericum perforatum var. augustifolium)

The effect of time of application of herbicides on the long-term control of St. John's wort was investigated at Tuena, New South Wales. The herbicides used were: 2,4-D, 2,4,5-T, 2,4-D -i- 2,4,5-T, picloram + 2,4-D, and glyphosate. Each of these was applied in February, May, August and November, 1976, and regrowth of wort monitored until February 1978. The percentage ground cover of unsprayed St. John's wort varied between 75% and 85% over the experimental period. Initially all herbicides reduced the ground cover of St. John's wort from over 75% to less than 15%. Thereafter the regrowth of wort depended on the long-term effect of the herbicides. At the final assessment in February 1978, the most effective herbicide treatments were: from the February and May applications, glyphosate and picloram + 2,4-D; from the August application, picloram + 2,4-D; and from the November application, picloram + 2,4-D, 2,4-D + 2,4,5-T and 2,4-D.

Replacing a nitrophilous weed association with Phalaris aquatica and Medicago sativa on non-arable land

In an experiment (1974 to 1978) carried out on the Central Tablelands of New South Wales, the effects of nine herbicide treatments, two intervals between spraying and sowing, and sowing in late autumn, on the ability of Medicago sativa, Phalaris aquatica and Vicia dasycarpa to establish, develop and replace a nitrophilous weed association (broadleafed plants, annual grasses and native perennial grasses) were measured. Herbicide treatment of the resident species was necessary for the establishment and development of M. sativa and P. aquatica but not for the establishment of V. dasycarpa. Successful treatments were: 2,2-DPA + amitrole, 2,2-DPA + 2,4-D, paraquat + diquat and glyphosate. Intervals of 7 and 28 days between spraying and sowing had no differential effect on establishment. Sowing in late autumn resulted in successful establishment of all species. Over four years the percentage ground cover of sown species on the herbicide treatments increased from 0% in early 1974 to 49% in late 1978; the control treatment rose from 0% to 12%. The percentage ground cover of the nitrophilous weed association on the herbicide treatments decreased from 76% in 1974 to 27% in 1978; the control fell from 76% to 68%. The experiment demonstrated that a nitrophilous weed association can be replaced with perennial pasture species on non-arable land on the Central Tablelands by using aerial techniques. Further research is needed to determine the optimum time of spraying and sowing.

Assessment of Four Techniques for Estimating Yield on Dryland Pastures1

AbstractInformation is limited on the suitability of short‐cut methods of yield assessment in low density pastures in marginal environments. Since this information would be of value to researchers working in such environments, four short‐cut, double sampling techniques were compared with hand clipping to assess their usefulness in estimating yield in large‐scale experiments located on low density, lucerne‐based (Medicago sativa L.) pastures. The methods included the measurement of pasture height (Method 1); percentage ground cover (Method 2); and a combination of Methods 1 and 2 assessed either by calculating the product (HG) of the direct measurement of the parameters (Method 3); and by utilizing a plywood board dropped on the pasture the height measurement of which effectively integrates pasture height and cover into a single expression (Method 4). Percentage ground cover was not correlated with yield and was considered unsuitable for predicting yield in this type of pasture. Significant correlations were apparent between yield and the parameters of height, and a combination of height and cover. Sampling variation is discussed in relation to the use of these techniques. All techniques (excluding percentage ground cover) possessed sufficient sensitivity to distinguish yield differences in grazed lucerne pasture. The board technique, the most sensitive, required 53% less time than the others in data collection than clipping.

URANIUM EXPLORATION WITH COMPUTER‐PROCESSED LANDSAT DATA

A spectral signature has been constructed for an oxidized topsoil found in the vicinity of near‐surface uranium deposits in porous, arkosic sandstones of the Wind River Basin, Wyoming. A new type of contour map, created from Landsat computer compatible tapes, designed to connect regions of equal percentage of ground area covered by a specified target of interest, was applied to a Landsat frame covering the entire basin. The resulting maps showed relatively high percentages of ground cover by this particular topsoil in regions adjacent to open pit uranium mines in the Gas Hills region, as well as on or near known uranium prospects (as yet undisturbed) in the basin interior. A 10,000-pixel test area west of Lander, Wyoming was found to contain only one pixel (a 0.01 percent recognition rate) identified as the topsoil of interest. However, a whole‐frame recognition map produced a much higher (0.58 percent) recognition rate, indicating that the false alarm rate for this signature is still significantly high, although better than what can be expected from photointerpretation of single ratio images or color composite ratio images. This “signature” has been applied to Landsat frames in other geographical areas with known uranium mines in porous sandstone, and oxidized topsoil has been recognized near these mines.

Effect of irrigation termination on yield of soybeans in southern New South Wales

The seasonal water demand and the influence of the time of final irrigation on seed yield of soybeans was determined under furrow irrigation. The three times of final irrigation were ten days after the end of flowering; when the top pods contained full size beans; and when 95 per cent of the pods had turned brown (P95). Measurements of plant height, percent ground cover and leaf relative water content indicated that the irrigation schedule imposed did not limit crop growth. Crop water use was 730 mm or 76 per cent of pan evaporation. Highly significant increases in seed yield due mainly to increased seed weight were obtained by extending the irrigation period. Applying water after the top pods contained full size beans increased yield by 538 kg ha-1 or 16.1 per cent. There was little effect on oil and protein content. The number of days from emergence to P95 was increased from 108 to 11 9 by later irrigations. The irrigation schedule should keep water readily available until physiological maturity of the crop; for cv. Clark 63 this is only three days prior to P95.

Correction - Effect of irrigation termination on yield of soybeans in southern New South Wales

The seasonal water demand and the influence of the time of final irrigation on seed yield of soybeans was determined under furrow irrigation. The three times of final irrigation were ten days after the end of flowering; when the top pods contained full size beans; and when 95 per cent of the pods had turned brown (P95). Measurements of plant height, percent ground cover and leaf relative water content indicated that the irrigation schedule imposed did not limit crop growth. Crop water use was 730 mm or 76 per cent of pan evaporation. Highly significant increases in seed yield due mainly to increased seed weight were obtained by extending the irrigation period. Applying water after the top pods contained full size beans increased yield by 538 kg ha-1 or 16.1 per cent. There was little effect on oil and protein content. The number of days from emergence to P95 was increased from 108 to 11 9 by later irrigations. The irrigation schedule should keep water readily available until physiological maturity of the crop; for cv. Clark 63 this is only three days prior to P95.

Determining Density of Maize Canopy from Digitized Photographic Data1

AbstractPlant and soil scientists have devised many methods with varying degrees of success to determine the density of vegetative cover. Canopy density is important in estimating yield of biomass, characterizing vegetative stress, predicting soil losses from erosion, and planning resource management programs. The objective of this investigation was to examine quantitatively the relationship between the densities of maize (Zea mays L.) canopies and the energy reflected by them.Spectral and spatial data were obtained from color and color infrared (IR) photographs from 10 m above field plots of four growth stages of maize on dark and light‐colored soils.Leaf area index (LAI) measurements were made in the field. Photographs were used for determining percent ground cover 1) by a point grid technique and 2) by microdensity scanning of the three separate emulsion layers of the color photographs and digital analysis of the resulting data.A statistical pattern recognition computer program was used to determine the spectral separability of the digitized photographic data and to classify the data into two categories—green vegetation and soil.Of the emulsion layers of the color IR photographs, classification of the digitized infrared wavelength band best represented the actual percent ground cover. A plot having an LAI of 4.44 had a ground cover of 96.5% as determined by the point grid method and 93.2% by digital analysis of IR data. Classification of data from the visible red (0.59 to 0.71 μm) overestimated percent ground cover and from the green (0.47 to 0.61 μm) underestimated percent ground cover.

Crop-Herbicide Sequences on a Southeastern Coastal Plain Soil

Weeds in corn (Zea maysL.), cotton (Gossypium hirsutumL.), peanuts (Arachis hypogaeaL.), and soybeans (Glycine max(L.) Merr.), grown continuously or in rotation, were controlled with either cultural or herbicidal programs designed for broad-spectrum control. The herbicidal program initially selected for each group was used each year from 1968 to 1971. Herbicides controlled more weeds than cultural practices in all cropping sequences. Weeds were almost eliminated, judging by percent ground cover at harvest time, in five of the eight cropping sequences in each of the last three years of the experiment. Although several rotations drastically reduced the number of weeds, the composition of the weed population was not altered significantly. When cultural weed control practices were used, the cropping sequence and rainfall influenced the level of weeds present at harvest time. More weeds were present at harvest in corn grown continuously and in sequence than in the other crops. In addition to three or four cultivations, we used a yearly average of 86 manhours/ha of hand-hoeing in corn and 195 manhours/ha of hand-hoeing in cotton during the first 6-week period after planting to keep these crops weedfree until the last cultivation. The cropping sequence did not affect the amount of hand-hoeing required in these crops. In general, cropping sequence did not affect crop yield.

Establishment of Centipedegrass and St. Augustine Grass with the Aid of Chemicals1

AbstractThe establishment of Centipedegrass (Eremochloa ophiuroides (Munro) Hack.) and St. Augustine grass (Stenotaphrum secundatum (Walt.) Kuntze) is often slow because weed competition may be severe. An experiment was conducted to determine the effects of single and repeated treatments of atrazine (2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine) and simazine (2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine) on the establishment of these two species. Single treatments of simazine and atrazine at 1.12 kg/ha applied immediately following sprigging satisfactorily controlled grassy weeds and increased percent ground cover. Except for atrazine on St. Augustine grass, herbicide treatments caused early growth retardation without reducing ground cover at the end of the season. The desirability in appearance of the turf was not generally affected by either chemical at the rates used.

Winter Turf Development on Dormant Bermudagrass as Influenced by Summer Cultivation and Winter N Fertilization1

AbstractOverseeded winter turf on dormant bermudagrass is an important practice in providing live turf for a large portion of the year. It has been observed that as vigorous bermudagrass becomes older satisfactory winter turf is more difficult to establish and maintain. Previous research has shown that cultivation of bermudagrass immediately prior to overseeding cool season turfgrasses has improved winter turf. However, no work has been reported showing the effects of bermudagrass summer cultivation on overseeded winter turf quality. This investigation was initiated to study the relationship of thatch removal in the summer on winter turf quality.Thatch was removed from a 5‐year‐old putting green with a vertical mower in early, middle, and late summer and soil top dressing was applied after each aeration. N fertilizer was applied in summer, fall, and winter; P and K were maintained at high levels and the pH at 6.5. Ryegrass and red fescue were overseeded after turf mowing in October. The percent ground cover was measured in December, March, May, and June.The removal of thatch by frequent summer aeration and soil topdressing (cultivation) improved the winter quality of overseeded cool season turf. Excessive nitrogen fertilization in winter, especially on heavily thatched areas, reduced winter turf coverage.The best transition from cool season turf to bermudagrass occurred when the cool season grass persisted into the summer. The increased Poa annua infestation caused by early cultivation was reduced by more frequent cultivation.