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Remote sensing can serve as a promising solution for monitoring spatio-temporal variability in grasslands, providing timely information about different biophysical parameters. We aimed to develop models for canopy height classification and aboveground biomass estimation in pastures of Megathyrsus maximus cv. Mombaça using machine learning techniques and images obtained from the Sentinel-2 satellite. We used different spectral bands from the Sentinel-2, which were obtained and processed entirely in the cloud computing space. Three canopy height classes were defined according to grazing management recommendations: Class 0 (< 0.45 m), Class 1 (0.45–0.80 m) and Class 2 (> 0.80 m). For modeling, the original database was divided into training data (85%) and test data (15%). To avoid dependency between our training and test datasets and ensure greater generalization capacity, we used a spatial grouping evaluation structure. The random forest algorithm was used to predict canopy height and aboveground biomass by using height and biomass field reference data obtained from 54 paddocks in Brazil between 2016 and 2018. Our results demonstrated precision, recall, and accuracy values of up to 73%, 73%, and 72%, respectively, for canopy height classification. In addition, the models showed reasonable predictive performance for aboveground fresh biomass (AFB) and dry matter concentration (DMC; R2 = 0.61 and 0.69, respectively). We conclude that the combined use of satellite imagery and machine learning techniques has potential to predict canopy height and aboveground biomass of Megathyrsus maximus cv. Mombaça. However, further studies should be conducted to improve the proposed models and develop software to implement the tool under field conditions. [ABSTRACT FROM AUTHOR]

Correct pasture management associated with the adjustment of grazing intensity determines pasture persistence and the level of production per animal and per land area. The objective of this review was to examine the effect of grazing intensity in tropical pastures on the performance and productivity of beef cattle by a meta-analytical approach. The review followed a protocol developed and tested based on the PICOS strategy to formulate the guiding question: population (beef cattle), intervention (high grazing intensities), comparison (low grazing intensities), outcome (animal performance and productivity), and study design (experimental). Data were collected from papers published in the electronic databases of SCOPUS (Elsevier), Web of Science (Main collection), SpringerLink, Wiley Online Library, and Science Direct (Elsevier) by a single cross-reference search. The selected studies were considered relevant when they: (1) were primary research published in the format of a research article; (2) included grazing intensities as a management strategy; and (3) evaluated average daily gain (ADG, kg/animal per day), stocking rates (SR, animal unit (AU)/ha; AU = 450 kg), and weight gain per area (WGH, kg/ha). Thirteen manuscripts were selected due to their methodological strength for data extraction. The means under continuous stocking were 0.67 kg/animal per day for ADG, 518.12 kg/ha for WGH, and 4.19 AU/ha for SR. Under intermittent stocking, the means were 0.62 kg/animal per day for ADG, 980.18 kg/ha for WGH, and 5.10 AU/ha for SR. In tropical forages, the heights of 20 to 40 cm for pastures under continuous stocking and the defoliation intensities of 40 to 50% for those under intermittent stocking result in greater individual performance and animal productivity per land area.

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The experiment was conducted to evaluate the influence of Marandu-grass (Brachiaria brizantha) pasture height (30, 40, 50 and 60 cm) on the canopy structural traits and grazing behavior and forageingestion process by goats. Six goats were used to evaluate behavior during grazing, and four were used to evaluate the ingestion process - all goats were Anglo-Nubian. The adopted experimental design was completely randomized, with two replicates in space and two replicates in time. Increase in the canopy height resulted in an increase in the masses of forage, leaves, stem, and dead material and tiller density, and reduction in leaf/stem ratio. Grazing time increased and idle time reduced as the canopy height was elevated. The correlation between canopy height and bite depth was positive and linear (r = 0.99). The mass of consumed forage, the intake rate, and the bite mass were higher at 60 cm. The correlation between pasture height and bite rate was negative, whereas the correlation between pasture height and the time per bite was positive. On Marandu-grass pastures, the greatest efficiency in forage harvesting by goats occurs at a canopy height of 60 cm.

Knowledge of the aboveground biomass (AGB) of large pasture fields is invaluable as it assists graziers to set stocking rate. In this preliminary evaluation, we investigated the response of Sentinel-1 (S1) Synthetic Aperture Radar (SAR) data to biophysical variables (leaf area index, height and AGB) for native pasture grasses on a hilly, pastoral farm. The S1 polarimetric parameters such as backscattering coefficients, scattering entropy, scattering anisotropy, and mean scattering angle were regressed against the widely used morphological parameters of leaf area index (LAI) and height, as well as AGB of pasture grasses. We found S1 data to be more responsive to the pasture parameters when using a 1 m digital elevation model (DEM) to orthorectify the SAR image than when we employed the often-used Shuttle Radar Topography 30 m and 90 m Missions. With the 1m DEM analysis, a significant quadratic relationship was observed between AGB and VH cross-polarisation (R2 = 0.71), and significant exponential relationships between polarimetric entropy and LAI and AGB (R2 = 0.53 and 0.45, respectively). Similarly, the mean scattering angle showed a significant exponential relationship with LAI and AGB (R2 = 0.58 and R2 = 0.83, respectively). The study also found a significant quadratic relationship between the mean scattering angle and pasture height (R2 = 0.72). Despite a relatively small dataset and single season, the mean scattering angle in conjunction with a generalised additive model (GAM) explained 73% of variance in the AGB estimates. The GAM model estimated AGB with a root mean square error of 392 kg/ha over a range in pasture AGB of 443 kg/ha to 2642 kg/ha with pasture LAI ranging from 0.27 to 1.87 and height 3.25 cm to 13.75 cm. These performance metrics, while indicative at best owing to the limited datasets used, are nonetheless encouraging in terms of the application of S1 data to evaluating pasture parameters under conditions which may preclude use of traditional optical remote sensing systems.

The tools available to farmers to manage grazed pastures and adjust forage demand to grass growth are generally rather static. Unmanned aerial systems (UASs) are interesting versatile tools that can provide relevant 3D information, such as sward height (3D structure), or even describe the physical condition of pastures through the use of spectral information. This study aimed to evaluate the potential of UAS to characterize a pasture’s sward height and above-ground biomass at a very fine spatial scale. The pasture height provided by UAS products showed good agreement (R2 = 0.62) with a reference terrestrial light detection and ranging (LiDAR) dataset. We tested the ability of UAS imagery to model pasture biomass based on three different combinations: UAS sward height, UAS sward multispectral reflectance/vegetation indices, and a combination of both UAS data types. The mixed approach combining the UAS sward height and spectral data performed the best (adj. R2 = 0.49). This approach reached a quality comparable to that of more conventional non-destructive on-field pasture biomass monitoring tools. As all of the UAS variables used in the model fitting process were extracted from spatial information (raster data), a high spatial resolution map of pasture biomass was derived based on the best fitted model. A sward height differences map was also derived from UAS-based sward height maps before and after grazing. Our results demonstrate the potential of UAS imagery as a tool for precision grazing study applications. The UAS approach to height and biomass monitoring was revealed to be a potential alternative to the widely used but time-consuming field approaches. While reaching a similar level of accuracy to the conventional field sampling approach, the UAS approach provides wall-to-wall pasture characterization through very high spatial resolution maps, opening up a new area of research for precision grazing.

Objetivou-se avaliar o efeito da localização das fezes de bovinos sobre as características de perfilhos vegetativos e reprodutivos, a massa dos componentes da planta, a densidade volumétrica da forragem e a altura do pasto de Brachiaria decumbens, cv. Basilisk, manejado sob lotação contínua. O delineamento foi em blocos casualizados, com três repetições, em esquema de parcela subdivida, considerando parcelas os locais próximos e distantes das fezes e subparcelas as categorias de perfilhos vegetativos e reprodutivos. A massa de lâmina foliar viva (LFV) por perfilho em locais próximos às fezes (0,14 g) foi maior que nos locais distantes das fezes (0,08 g), contrariamente ao verificado para a composição de massa de lâmina foliar morta por perfilho. A massa de LFV nos perfilhos vegetativos (0,15 g) foi maior que nos perfilhos reprodutivos (0,06 g). Por outro lado, a massa de colmo (0,38 g) e de lâmina foliar morta (0,20 g) foi maior nos perfilhos reprodutivos. O peso dos perfilhos das plantas próximas às fezes foi maior (0,58 g) que daqueles distantes das fezes (0,17 g). Em locais próximos das fezes, o número de perfilhos vegetativos foi menor, enquanto o de perfilhos reprodutivos foi maior. Maiores massas de colmo verde, forragem verde e forragem total do pasto foram observados nos locais próximos das fezes, quando comparadas aos distantes. Mesmo resultado foi obtido para a altura do pasto. A estrutura do pasto de Brachiaria decumbens é modificada pela localização das fezes dos bovinos em pastejo. A deposição de fezes por bovinos constitui fator de heterogeneidade espacial da vegetação em pastagem.The objective of this study was to evaluate the effect of the cattle feces location on the characteristics of vegetative and reproductive tillers, dry mass content in plant components, forage volumetric density and Brachiaria decumbens cv. Basilisk pasture height managed under continuous stocking. It was used a randomized block design with three repetitions in a split-plot scheme considering the plots the sites next and far from feces and the sub-plots were the vegetative and reproductive tiller categories. Dry mass content of live foliar blade (LFB) per tiller in sites near the feces (0.14 g) was higher than in the sites distant from the feces (0.08 g), opposing to what was verified for composition of dry matter of dead foliar blade per tiller. Content of LFB dry mass in vegetative tillers (0.15 g) was higher than in the reproductive tillers (0.06 g). On the other hand, composition in stem dry matter (0.38 g) and in dead foliar blade (0.20 g) were higher for reproductive tillers. Tiller weight of the plants near the feces was higher (0.58 g) than those far from the feces (0.17 g). On sites near the feces, the number of vegetative tiller was lower, while the number of reproductive tiller was higher. Higher contents of dry matter of the green stem, green forage and total forage of the pasture were observed on sites close to feces when compared to the far ones. The same result was obtained for the pasture height. The Brachiaria decumbens pasture structure is modified by the position of the cattle feces. Cattle feces droppings are a heterogeneous spatial factor of vegetation on grazing areas.

Este trabalho foi conduzido com o objetivo de avaliar as características estruturais da Brachiaria decumbens cv. Basilisk. Foram avaliadas quatro alturas de plantas (10, 20, 30 e 40 cm) dentro de uma mesma pastagem, em um delineamento experimental de blocos casualizados com duas repetições. A variação na altura inicial das plantas no pasto de capim-braquiária apresentou resposta linear e negativa. As massas de lâmina foliar verde, colmo verde, material morto, forragem verde e forragem total aumentaram linearmente com a altura das plantas no pasto. Contrariamente, houve redução linear na relação lâminas foliares verdes/colmos verdes com a altura das plantas no pasto (de 1,16 para 0,58). A altura das plantas no pasto teve efeito mais pronunciado sobre o aumento das massas de colmo verde e material morto que sobre a massa de lâmina foliar verde. A densidade volumétrica de lâminas foliares verdes decresceu (de 97,09 para 39,07 kg/cm.ha de MS) com a altura das plantas no pasto. Mesma resposta ocorreu para as densidades volumétricas de forragem verde (de 181,62 para 107,85 kg/cm.ha de MS) e forragem total (de 283,39 para 195,72 kg/cm.ha de MS). Por outro lado, não houve efeito da altura das plantas no pasto sobre as densidades volumétricas de colmos verdes e material morto, que apresentaram valores médios de 80,95 e 95,61 kg/cm.ha de MS, respectivamente. A altura das plantas no pasto teve efeito quadrático sobre a interceptação de luz pelo dossel. Áreas da pastagem com alturas de 10, 20, 30 e 40 cm apresentaram valores de interceptação luminosa de 56,15; 85,16; 93,39 e 96,57%, respectivamente. Ocorre variação espacial e temporal na estrutura do pasto de B. decumbens manejado sob lotação contínua.This study was carried out aiming to evaluate the structural characteristics of Brachiaria decumbens cv. Basilisk pasture. Four heights of plants (10, 20, 30 and 40 cm) were evaluated within the same grazing area in a randomized block experimental design with two repetitions. Variation in the initial height of the signal grass pasture plant showed a linear and a negative response. The masses of green leaf blade mass, live stem, dead material, live forage and total forage linearly increased with heights of the plants on the pasture. However, it was observed a linear reduction in green leaf blade/live stem ratio and the height of the plants on the pasture (from 1.16 to 0.58). Plant height on the pasture had a stronger effect on the increase of live stem and the dead material masses than it had on the green leaf blade mass. Volumetric density of green leaf blade decreased (from 97.09 to 39.07 kg/cm ha DM) with plant height on the pasture. The same response was found for volumetric densities of live forage (from 181.62 to 107.85 kg/cm.ha dry matter) and total forage (from 283.39 to 195.72 kg/cm.ha dry matter). On the other hand, the plant heights on pasture did not affect volumetric density of live stem and dead material, which showed mean values 80.95 and 95.61 kg/cm.ha DM, respectively. The heights of the plants on pasture had a quadratic effect on light interception by the canopy. Grazing areas with heights of 10, 20, 30 and 40 cm showed light interception values of 56.15, 85.16, 93.39 and 96.57%, respectively. It occurs and temporal variabilities on the B. decumbens pasture structure managed under continuous stocking.

O experimento foi realizado com o objetivo de estudar características estruturais e morfológicas de cinco genótipos de Pennisetum sp. (CE 08 A.D., Venezuela, HV-241, Elefante B e Hexaplóide) sob pastejo no período de seca na Zona da Mata de Pernambuco. Os genótipos foram manejados sob lotação rotacionada (44 dias de descanso e quatro dias de pastejo) ao longo de dois ciclos de pastejo. Os dados foram analisados em delineamento experimental de blocos ao acaso com parcelas subdivididas (os genótipos representaram as parcelas e os ciclos de pastejo, as subparcelas) e quatro repetições. Houve variação nas características estruturais e morfológicas de genótipos de Pennisetum sp. Os genótipos CE 08 A.D. e Elefante B apresentaram maior densidade de lâmina foliar verde, menor porcentagem de material morto e maior densidade de perfilhos basais remanescentes e aéreos novos, com médias de 5,0±0,4 kg de MS/ha/cm, 33,0±0,2%, 22,0±0,2 e 146,0±0,4 perfilhos/m², respectivamente. O HV-241 apresentou alta participação de material morto em sua biomassa aérea (55,6±0,3%), o que pode ser atribuído à alta mortalidade de perfilhos (19,0±0,3 e 114,0±0,4 perfilhos basais e aéreos mortos/m², respectivamente). Os genótipos CE 08 A.D. e Elefante B destacaram-se como promissores para utilização sob pastejo no período de seca. O genótipo HV-241, híbrido de capim-elefante com o milheto, foi mais afetado pelos efeitos do estresse hídrico no período seco do ano.The experiment was carried out to study structural and morphologic characteristics of five Pennisetum sp. genotypes (CE 08 A.D., Venezuela, HV-241, Elephant B and Hexaplóide) under grazing during the dry period in Pernambuco Forest Zone. Genotypes were managed under rotational stocking (44 days of resting and four days of grazing period). The experimental design was randomized blocks in a split plot arrangement, and four replications. The genotypes represented the plots, and grazing cycles, the subplots. There was variation in the structural and morphologic characteristics of the Pennisetum sp. genotypes. The CE 08 A.D. and Elephant B presented high density of green leaf blade, low percentage of dead material and high density of remaining basal tillers and new aerial tillers, with averages of 5.0±0.4 kg DM/ha/cm; 33±0.2%; 22±0.2 and 146±0.4 tillers/m², respectively. The HV-241 presented high participation of dead material in its aerial biomass (55.6±0.3%) due to high tiller mortality (19±0.3 and 114±0.4 basal and aerial dead tillers/m², respectively). The genotypes CE 08 A.D. and Elephant B had been distinguished as promising to be used under grazing in the dry period. The genotype HV-241, elephantgrass hybrid with pearl millet, was more affected by water stress during the dry period of the year.

Foram avaliadas a produção e as características de carcaças de novilhos jovens mantidos em pastagem cultivada de aveia preta (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam) manejada em diferentes alturas. Os tratamentos impostos foram quatro diferentes alturas de manejo da pastagem (10, 20, 30 e 40 cm), obtidas por meio da aplicação de diferentes cargas animais. O delineamento foi o de blocos casualizados, com três repetições. Utilizaram-se animais jovens de aproximadamente dez meses de idade, machos castrados sem padrão racial definido, com peso médio inicial de 210 kg. O aumento no ganho médio diário (GMD) foi condicionado pelo incremento na qualidade e/ou na quantidade de forragem disponível, visto que as ofertas de forragem para os tratamentos de 10, 20, 30 e 40 cm de altura foram de 6, 10, 23 e 51 kg de MS/100 kg de PV/dia, respectivamente. Portanto, o modelo de resposta do GMD em relação às alturas de pastejo resultou em valores de 0,73 e 1,14 kg/animal/dia nos tratamentos de menor e maior GMD, respectivamente, que foram de 10 e 30 cm de altura. Como a variação no GMD foi baixa, o maior ganho por área observado no tratamento 10 cm pode ser atribuído à maior carga animal, ambas com respostas lineares decrescendo com o aumento da altura de pastejo. O peso vivo dos animais antes do abate e o peso de carcaça quente elevaram com o aumento da altura da pastagem, reduzindo apenas no tratamento 40 cm com a redução da qualidade da pastagem. Não houve diferença entre os tratamentos para o rendimento de carcaça, pois todos os valores mantiveram-se em torno de 51%. O escore de condição corporal e o grau de acabamento apresentaram tendência muito similar à evolução do ganho médio diário dos animais.The objective of this trial was to evaluate production and carcass characteristics of young steers grazing a mixture of black oat and Italian ryegrass pasture. Treatments were four different pasture heights (10, 20, 30, and 40 cm) that were obtained with different stocking rates. Fifty-five beef steers averaging 210 kg of body weight and 10 months of age at the beginning of the trial were used in a randomized complete block design with three replicates. The observed increase in the average daily weight gain (ADG) was associated with the quality and/or amount of available forage because herbage allowance increased from 6 to 51 kg DM/100 kg BW when pasture height was enhanced from 10 to 40 cm. Therefore, the ADG was 0.73 and 1.14 kg/animal/day for the treatments with the lowest and highest ADG, which corresponds to 10 and 30 cm pasture height. Considering the low ADG, the greatest gain/area observed on the 10 cm treatment may be explained by a greater stocking rate; both ADG and stocking rate decreased linearly by increasing pasture height. Body weight and hot carcass weight increased until 30 cm of pasture height but decreased at 40 cm because of poorer pasture quality. There was no difference on carcass yield, which averaged 51% among treatments. The body condition score and carcass fat thickness followed the ADG in this trial.

Copyright of Tropical Grasslands / Forrajes Tropicales is the property of International Centre for Tropical Agriculture - CIAT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Through analyzing statistically metrological observation data from 1971 to 2010 and pasture data from 1983 to 2012 at 6 animal husbandry meteorological testing stations of Inner Mongolia grassland, the conclusions were drawn. Those were that annual average temperature rose in a straight line in Inner Mongolia grassland, and the increase rates of annual average temperature in meadow steppe and typical steppe were 0.40 and 0.34 °C/10 a respectively. Annual rainfall had 10-year cyclical characteristics , and precipitation in the 1990s was the most but reduced significantly after 2000. Climate experienced the cold wet - cold dry - warm wet - warm dry periods. Warm and dry climate made the average heights of pasture in meadow steppe and typical steppe of Inner Mongolia cut down 2.4 and 9.3 cm in nearly 12 years than that in the 1990s; the average coverage of herbage decreased by 11 % and 13% ; the average hay yields reduced by 1 019.8 and 671. 4 kg/hm2. [ABSTRACT FROM AUTHOR]

Copyright of Revista Ceres is the property of Revista Ceres and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pasture height measurement and its statistical distribution have been neglected topics in tropical pasture research. Thus, the objective of this study was to fit the single normal (SN), double normal (DN), log normal (LN), gamma (GM) and Weibull (WB) models to relative frequency distributions of pasture height (PHT, cm) of native gramma pastures of the Mexican humid tropics. PHT measurements were done in a study where fixed rotational grazing was used (3-day grazing/27-day rest paddock–1) at three stocking rates of two, three and four F1 (Holstein × Zebu) cows ha−1. Two paddocks per stocking rate were used. Approximately 400 PHT measurements were done on each paddock, before (22 times) and after (23 times) grazing. The models were fit by least squares, using the Marquardt–Lavenberg iteration. The Akaike’s information criterion corrected (AICc) was used to select the model with the best fit. Before grazing, the models with the best fit were the DN and the GM, and after grazing, the best fit was shown by the DN and the LN. With respect to stocking rate, the best models were: LN and GM for two cows ha−1; DN and LN for three cows ha−1; and DN for four cows ha−1. However, the differences between the AICc values of the model with the best fit and the second in rank were small; thus, either could fit the data equally well. In conclusion, PHT of native gramma pastures did not distribute normally, and either the double normal or the log normal models can be used as means to describe the PHT frequency distributions of this type of pastures. [ABSTRACT FROM AUTHOR]

Standing dry matter (SDM, kg ha-1) measurements should be quick and precise, something difficult to achieve using traditional direct cutting methods, but possible to do so when, through double sampling, this traditional method is combined with quick indirect measurements of variables correlated to SDM, such as pasture height (PHT, cm). The objective of the present study was to: 1) estimate the relationship between PHT and SDM; 2) estimate the minimum number of PHT readings (n') necessary to estimate an average; and 3) develop an empirical model, to derive n' from published coefficient of variation values (CV). SDM and PHT were related by simple linear regression through the origin in three studies (S1, 3/III-15/VI, 1995; S2, 18/VII/98-30/I/99; S3, 18/VIII-12/II, 2003). Slopes went from 183 to 303 kg SDM cm-1 PHT; coefficients of determination (R²) ranged from 0.83 to 0.96 and residual standard deviations (RSD) between ±341 and ±1895. In S3, n' values were 61 and 103 before and after grazing, respectively. The third degree polynomial: n'=0.21-0.014(CV)+0.039(CV²)-0.00000209(CV³), n=45, R = 1.00; RSD= ±0.0096, presented the best fit. It was concluded that SDM can be reliably predicted from PHT; before grazing n' values should be lower than after grazing; the use of a third degree polynomial to estimate n' from published CV values is suggested; and also, that it is necessary to study the relationship between SDM and PHT in other pastures under different management conditions. [ABSTRACT FROM AUTHOR]

Correct pasture management associated with the adjustment of grazing intensity determines pasture persistence and the level of production per animal and per land area. The objective of this review was to examine the effect of grazing intensity in tropical pastures on the performance and productivity of beef cattle by a meta-analytical approach. The review followed a protocol developed and tested based on the PICOS strategy to formulate the guiding question: population (beef cattle), intervention (high grazing intensities), comparison (low grazing intensities), outcome (animal performance and productivity), and study design (experimental). Data were collected from papers published in the electronic databases of SCOPUS (Elsevier), Web of Science (Main collection), SpringerLink, Wiley Online Library, and Science Direct (Elsevier) by a single cross-reference search. The selected studies were considered relevant when they: (1) were primary research published in the format of a research article; (2) included grazing intensities as a management strategy; and (3) evaluated average daily gain (ADG, kg/animal per day), stocking rates (SR, animal unit (AU)/ha; AU = 450 kg), and weight gain per area (WGH, kg/ha). Thirteen manuscripts were selected due to their methodological strength for data extraction. The means under continuous stocking were 0.67 kg/animal per day for ADG, 518.12 kg/ha for WGH, and 4.19 AU/ha for SR. Under intermittent stocking, the means were 0.62 kg/animal per day for ADG, 980.18 kg/ha for WGH, and 5.10 AU/ha for SR. In tropical forages, the heights of 20 to 40 cm for pastures under continuous stocking and the defoliation intensities of 40 to 50% for those under intermittent stocking result in greater individual performance and animal productivity per land area. [ABSTRACT FROM AUTHOR]

Knowledge of the aboveground biomass (AGB) of large pasture fields is invaluable as it assists graziers to set stocking rate. In this preliminary evaluation, we investigated the response of Sentinel-1 (S1) Synthetic Aperture Radar (SAR) data to biophysical variables (leaf area index, height and AGB) for native pasture grasses on a hilly, pastoral farm. The S1 polarimetric parameters such as backscattering coefficients, scattering entropy, scattering anisotropy, and mean scattering angle were regressed against the widely used morphological parameters of leaf area index (LAI) and height, as well as AGB of pasture grasses. We found S1 data to be more responsive to the pasture parameters when using a 1 m digital elevation model (DEM) to orthorectify the SAR image than when we employed the often-used Shuttle Radar Topography 30 m and 90 m Missions. With the 1m DEM analysis, a significant quadratic relationship was observed between AGB and VH cross-polarisation (R2 = 0.71), and significant exponential relationships between polarimetric entropy and LAI and AGB (R2 = 0.53 and 0.45, respectively). Similarly, the mean scattering angle showed a significant exponential relationship with LAI and AGB (R2 = 0.58 and R2 = 0.83, respectively). The study also found a significant quadratic relationship between the mean scattering angle and pasture height (R2 = 0.72). Despite a relatively small dataset and single season, the mean scattering angle in conjunction with a generalised additive model (GAM) explained 73% of variance in the AGB estimates. The GAM model estimated AGB with a root mean square error of 392 kg/ha over a range in pasture AGB of 443 kg/ha to 2642 kg/ha with pasture LAI ranging from 0.27 to 1.87 and height 3.25 cm to 13.75 cm. These performance metrics, while indicative at best owing to the limited datasets used, are nonetheless encouraging in terms of the application of S1 data to evaluating pasture parameters under conditions which may preclude use of traditional optical remote sensing systems. [ABSTRACT FROM AUTHOR]