Weed Science Commons^™

Effects Of Fertilizer Rates And Pasture Type On Soil Mineral Nitrogen Concentration Under Dairy Pasture, T. A. Cox, D. F. Chapman, Frank R. Mckenzie

IGC Proceedings (1977-2023)

The effects of three rates of nitrogen (N) fertilizer applied to monocultures of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.), and mixed ryegrass / clover swards, grazed by dairy cows on soil mineral nitrogen levels in the top 10cm of soil were studied on a dryland pasture in south-western, Victoria, Australia. Ammonium and nitrate were monitored for 14 months. Clover monocultures had significantly greater NO₃^- levels, however a similar trend was not observed for NH₄⁺ . Increasing fertilizer application rate significantly increased both NO₃^- and NH₄^{+ …}

Nitrogen Fertilization In Paspalum Dilatatum, Poir: Herbage Production, Nutritive Value And Structural Characteristics, G. Acosta, V. A. Deregibus

IGC Proceedings (1977-2023)

It was studied the effect of nitrogen application on structural changes and quantity and quality characteristics of a Paspalum dilatatum Poir sward, under field conditions during two growing seasons. The nitrogen (N) rates were 0 and 440 kg ha^-1 applied during the first year in split applications. The nitrogen fertilization increased leaf, stem and cumulative total dry matter yield, plant height, tiller density, cover ground and leaf crude protein yield.

Growth Responses Of Acacia Angustissima To Vesicular-Arbuscular Mycorrhizal Inoculation, N. Lucena Costa, Valdinei T. Paulino, T. S. Paulino

IGC Proceedings (1977-2023)

The response of Acacia angustissima to VAM species (Acaulospora laevis, A. muricata, Entrophosphora colombiana, Glomus mosseae, G. fasciculatum, G. macrocarpum, G. etunicatum, Gigaspora margarita, G. gigantea and Scutellospora heterogama) was evaluated under greenhouse conditions, in a P-deficient clayey Oxisol of pH 5.5. The soil was sterilized at 110^oC for one hour each day for three days and reinoculated with a soil microbial suspension free of mycorrhizal fungi spores. The several VAM fungi were effective in increasing DM yield, nodulation, and N and P uptake of A. angustissima plants. The most efficient species were E. colombiana, A. …

The Fertilization Of Forage Grasses With Phosphorus In The Cerrado Area Of Uberaba-Mg, Brazil, I. F. Andrade, M. A. Oliveira

IGC Proceedings (1977-2023)

Using an area of Cerrado at the EPAMIG Experimental Station in Uberaba - MG, it was studied the response of four forage grasses to phosphorus application. It was used the grasses: Andropogon gayanus, Brachiaria brizantha, Hyparrhenia rufa, and Panicum maximum. The phosphorus fertilizer used was a yoorin termophosphate and the doses were: 0, 50, 100, 150, and 200 kg/ha of P₂O₅. The experimental design was a randomized complete block with three replications. Each experimental unit measured 6x8m and the measured parameters were: dry matter production, protein production, percentage of dry matter, and protein, and …

Alfalfa Response To Phosphorus Sources Associated With The Application Of Liming And Gypsum-Shoot Numbers, P. Sarmento, M. Corsi, F. P. Campos

IGC Proceedings (1977-2023)

Alfalfa (Medicago sativa L.) was grown in a Typic Mapluolox soil with triple superphosphate (TS), Gafsa phosphate (GP) and GP with gypsum (GP + G). Three rates of phosphorus application were used 50, 100 and 200 mg P dm^-3, before and after liming. Alfalfa was harvested three times. Basal and axillary shoot numbers in alfalfa increased with increasing phosphorus rates. Shoots were produced in higher number with GP in comparison with TS. GP + G resulted in higher basal shoot number than GP. However, there was no gypsum effect on axillary shoot numbers. Liming before or after …

Soil Nitrate Level Variation Under Intensive Nitrogen Fertilized Coastcross Pasture, O. Primavesi, A. C. Primavesi, L. A. Corrêa, H. Cantarella, A. G. Silva

IGC Proceedings (1977-2023)

Nitrate levels in soil profile after the first N application on coastcross pasture, grown on a dark red latosol (Hapludox), in São Carlos, SP, Brazil, under tropical altitude climate, were measured at 7-day intervals, to monitor possible losses in depth. Soil nitrate rates varied with high rates of N-ammonium nitrate (200 kg ha^-1 per cutting) in surface layers. Danger of environmental impact was low in the studied conditions.

Saturated Field Hydraulic Conductivity Variation In Intensively Managed Tropical Pastures, O. Primavesi, A. C. Primavesi, S. R. Vieira

IGC Proceedings (1977-2023)

Saturated field hydraulic conductivity was measured, using a Guelph permeameter, at the depths of 10, 20 and 60 cm, to verify the effect of intensively managed, compared to extensively managed ones, beef cattle production systems on pastures grown on three soils (Hapludox, Eutrudox, Paleudalf), in São Carlos, SP, Brazil, under tropical altitude climate. Significant differences occurred within depths (P < 0.05). However, differences decreased with years and, therefore, differences among soils and between management systems were also reduced. Highest mean conductivity values occurred at 60-cm depth and at the extensively managed sward on the sandy Hapludox. Intensively managed Paleudalf showed high resistance to reduction of conductivity at 10-cm depth. A general year effect appeared claiming for more studies on this matter.

The Effect Of Feed Supplementation And Sward Characteristics On The Ingestive Behaviour Of Grazing Ewes, C. H. E. C. Poli, Marta G. Da Rocha, C. C. Pires, Luis H. E. Farinatti, D. Montagner, G. Bica

IGC Proceedings (1977-2023)

The objective of this study was to assess the effect of protein/energy supplementation and sward physical characteristics on grazing behaviour of lactating ewes grazing Italian ryegrass (Lolium multiflorum Lam.). The experiment was carried out in the spring of 1999 at the Universidade Federal de Santa Maria. The grazing behaviour was assessed in two periods: 2 and 3 September, and 8 and 9 October of 1999, using a group of twelve yearling ewes. Groups of four ewes were either supplemented (with 1% of the animals live weight) with soybean meal (protein source), with corn (energy source) or not supplemented. The …

The Effect Of Sward Surface Height On Sheep Grazing Activities, Paulo C. De F. Carvalho, E. O. Silveira, L. S. Pontes, C. H. E. C. Poli, A. B. Soares, H. M. M. Ribeiro Filho

IGC Proceedings (1977-2023)

The objective of this study was to assess the effect of Italian ryegrass (Lolium multiflorum Lam.) sward height on grazing activities. The experiment was carried out at the Research Station of Universidade Federal do Rio Grande do Sul, Brazil. Yearling no-castrated male lambs behavior was assessed in terms of diurnal grazing, ruminating and idling time in three periods: 27 September 11 and 25 October. Sward surface height was monitored using a sward stick and samples of 0.25 m² were cut to ground level to estimate herbage and leaf lamina mass. The experiment was carried out in a randomised …

Grazing Behavior And Activity Patterns By Free-Grazing Cattle In The Pantanal Region, S. A. Santos, C. Costa, L. V. A. S. Chalita, A. Pott, J. M. Alvarez, A. G. Ortiz

IGC Proceedings (1977-2023)

A study of habitat selection and habitat use by free-grazing cattle was conducted in the Pantanal, from October 1997 to September 1999. Observation periods lasted 13 hours per day during three days in each month. The location and activity duration of each group of animals was recorded by continuous sampling. Rumination, walking and resting times were affected (P < 0,05) by interaction between month and year and grazing time differed (P < 0,05) only between months. On average, cows spent 54.9, 29.6, 10.6 and 4.9% of their diurnal hours grazing, ruminating, walking and resting, respectively. The grazing time spent in each landscape unit was influenced (P < 0,05) by interaction between month and year. The cows exploited more intensively the temporary ponds in 97/98 (26 min ha^-1) and the edge of ponds in 98/99 (23.2 min ha^-1). Therefore, the adequate grazing management practice may not follow fixed rules for the Pantanal.

Impact Of Overseeding Cool-Season Annual Forages On Spring Regrowth Of Tifton 85 Bermudagrass, Ricardo A. Reis, Lynn E. Sollenberger, D. Urbano

IGC Proceedings (1977-2023)

Field observations have shown stand reduction and slow spring regrowth of Tifton 85 bermudagrass (Cynodon spp.) pastures overseeded with temperate forages for grazing during the cool season. This experiment compared the effect of cool-season management programs, including overseeding and use of different grazing treatments, on productivity of Tifton 85 the following warm season. There were seven treatments: four were bermudagrass overseeded with a cool-season annual forage mixture (two grasses and two legumes) and grazed differentially, and three were bermudagrass controls with differences in amount of residual stubble remaining at beginning of autumn. There was only a slight delay in …

Influence Of Grazing Frequency On Biomass Production Using Several Selected Tropical Grasses, P. Mislevy, F. G. Martin, F. M. Pate, N. F. G. Rethman

IGC Proceedings (1977-2023)

To provide commercial growers with forage grasses that produce well throughout the year, there is a constant need for screening and testing new germplasm. Two rhodesgrasses (Chloris gayana cv. Rhods and Callide), four stargrasses (Cynodon nlemfuensis Vanderyst var. nlemfuensis cv. Florona, Zimbabwe, Okeechobee, and Rhodesian No. 2), one bermudagrass (C. dactylon var. dactylon cv. Jiggs), and one creeping signalgrass (Brachiaria humidicola CIAT 6369) were tested under a mob-grazing system. Dry biomass yield increased linearly as grazing frequency (GF) was delayed from 2 to 7 weeks. The cultivars, Florona, Zimbabwe and Okeechobee stargrasses and Jiggs bermudagrass, yielded …

Variation Of Herbage Intake (Hi) From Upland Pasture, As Influenced By The Grazing Initiation Date (Gid), D. Maæešiæ, M. Kneževiæ, Z. Štafa, J. Leto

IGC Proceedings (1977-2023)

Studies were conducted on an experimental pasture belonging to the Arrhenatherethum medioeur. and Lolio-Cynosureth. assoc. with D. glomerata, L. perenne and T. repens as main species, at an altitude of 680 m. Four equally sized paddocks (0.3 ha) were grazed by 10 Charolais heifers. The differences in total herbage dry matter intake (HDMI) between the four paddocks with different grazing initiation dates (GID) were significant (P < 0.05). The results of this experiment show that in order to achieve a higher HDMI and better herbage utilization an earlier initiation of grazing is recommended. That is, grazing should commence when the sward height is about 15 cm.

Nutritive Value Of Double Cropped Corn For Ruminant Production, D. Vaz Martins, A. Fassio

IGC Proceedings (1977-2023)

The viability of double cropping corn (Zea mays L.) in Uruguay, germplasm combination, dry matter yield and nutritive value were evaluated. An early (E) maturing hybrid, an early to medium (E-M) one and an E-M variety were planted as spring crops. One E-M hybrid, one medium to late (M-L) hybrid and a late (L) variety were planted as a second crop. PVC laboratory scale silo of the spring crop and the whole plant of the summer crop were chemically analyzed. The nutritive value of the silages were related to plant maturity stage. No differences were detected in nutritive value among …

Two-Dimensional Monitoring Of Spatial Distribution Of Herbage Mass Under Grazing, S. Ogura, Masahiko Hirata

IGC Proceedings (1977-2023)

Spatial distribution of herbage mass (HM) was monitored two-dimensionally during the grazing season (from May to November) in a bahiagrass pasture rotationally grazed by cattle. An electronic capacitance probe was used to estimate HM in 1464 permanent positions (50 × 50 cm) whose centres formed 1.5 × 1.5 m grids in the central 90 × 34.5 m area of the pasture. The highest mean HM was in September and October, while coefficient of variation in November. The two-dimensional charting of HM showed almost stable spatial patterns throughout the grazing season, with some patches of high HM appearing and disappearing. The …

The Effect Of Herbage Mass Of A Pasture On The Spatially Heterogeneous Grazing By Cattle, S. Ogura, Masahiko Hirata

IGC Proceedings (1977-2023)

To obtain information on spatially heterogeneous grazing by large herbivores at different time scales, spatial distribution of herbage mass and rate of defoliation was investigated on a bahiagrass (Paspalum notatum Flügge) pasture grazed by cattle during 4 to 5-day grazing periods in May, August and October. Pre-grazing herbage mass (M_pre) showed decreasing mean values and increasing spatial heterogeneity with the progress of grazing in all grazing periods, while the rate of defoliation showed inconsistent changes with season. Spatial distribution of the rate of defoliation was always more heterogeneous than that of M_pre. The correlation coefficient …

Relationships Between Spatial Distributions Of Herbage Mass And Utilization In A Pasture Progressively Grazed By Cattle, Masahiko Hirata, S. Ogura

IGC Proceedings (1977-2023)

To obtain some information about the mechanisms behind the spatially heterogeneous grazing of a pasture by large herbivores, the relationships between the spatial distributions of herbage mass, herbage consumption and ingestive behavior were investigated on a bahiagrass (Paspalum notatum Flügge) pasture during a 6-day grazing period with cattle. The animals almost always consumed more herbage from locations with higher pre-grazing herbage masses, which was attributed to greater bite weights. It was suggested that the high spatial heterogeneity in the rate of defoliation was caused mainly by the spatial heterogeneity in both the bite weight and the number of visits …

Adapting Tropical Forages To Low-Fertility Soils, Idupulapati M. Rao

IGC Proceedings (1977-2023)

Tropical forages growing in low-fertility acid soils usually increase the amount of dry matter partitioned to roots at the expense of shoot growth, but substantially different adaptive attributes to such soils have been found, both between and within species. By possessing the C₄ pathway of photosynthesis, grasses are more efficient than legumes in using N, Ca, and P, whereas legume roots are more efficient in extracting nutrients from low-fertility soils. Phosphorus uptake efficiency (mg of P uptake in shoot biomass per unit root length) of the legume Arachis pintoi is several times higher than that of the grass Brachiaria …

Adaptation Of Forage Species To Drought, D. J. Barker, J. R. Caradus

IGC Proceedings (1977-2023)

Variability in rainfall is the single greatest cause of variation in forage production for a given site. Current climate scenarios predict future annual rainfall to decrease at some geographic regions. The intensity of future rainfall is also predicted to increase at other regions, with the expectation of greater variability in soil moisture. The adaptation of forage species to drought is an issue that is likely to remain with us into the future.

Precise definitions are critical to water relations work, and imprecise use of terms has complicated comparisons of some studies on plant response to drought. Drought is a purely …

Spittlebugs: Bioecology, Host Plant Resistance And Advances In Ipm, José R. Valério, C. Cardona, D. C. Peck, G. Sotelo

IGC Proceedings (1977-2023)

Several species and genera of spittlebugs (Homoptera: Cercopidae) are economic pests of grasses in tropical America. These insects compete with grazing animals by reducing forage availability and quality. They may cause serious losses on millions of hectares of improved pastures based on cultivars of several species of Brachiaria (signal grasses). Except for the cultivar Marandu, most of the available commercial cultivars of Brachiaria are susceptible to spittlebugs. In spite of their economic importance, much research need to be done yet. Such insect-plant system encompasses a diverse group of spittlebug species, a diverse group of forage grass species, which are under …