Pasture Height Research Articles

Ultrasonic Arrays for Remote Sensing of Pasture Biomass

The profitability of agricultural industries that utilise pasture can be strongly affected by the ability to accurately measure pasture biomass. Pasture height measurement is one technique that has been used to estimate pasture biomass. However, pasture height measurement errors can occur if the sensor is mounted to a farm vehicle that experiences tilting or bouncing. This work describes the development of novel low ultrasonic frequency arrays for pasture biomass estimation. Rather than just measuring the distance to the top of the pasture, as previous ultrasonic studies have done, this hardware is designed to also allow ultrasonic measurements to be made vertically through the pasture to the ground. The hardware was mounted to a farm bike driving over pasture at speeds of up to 20 km/h. The analysed results show the ability of the hardware to measure the ground location through the grass. This allowed pasture height measurement to be independent of tilting and bouncing of the farm vehicle, leading to 20 to 25% improvement in the R 2 value obtained for biomass estimation compared with the traditional technique. This corresponded to a reduction in root mean squared error of predicted biomass from about 350 to 270 kg/ha, where the average biomass of the pasture was 1915 kg/ha.

PSXI-32 Potential improvements in milk production of mid lactating Holstein cows through changes in the defoliation intensity on a mixed pasture

Abstract An experiment was performed to study the effect of two contrasting defoliation intensities of a fescue based pasture on milk production of 24 mid lactating multiparous cows. The animals were blocked according to parity, body weight (587 ± 42 kg), body condition score (2.77 ± 0.16) and calving date, and were randomly allocated to one of these two treatments: lax treatment (TL) 12 cm and control treatment (TC) 6 cm, with four replications. It was used a second-year pasture of Festuca arundinacea and Lotus corniculatus (2530 ± 180 kgDM/ha), divided into eight plots of 0.3 ha. Each plot was grazed by three cows during as many days as necessary until the defoliation height of each treatment was achieved. This would be determined by daily measures of the pasture height. Animals had one grazing session from 8:00 to 16:00 h. Both treatments received 7.5 kgDM of supplementation (17% Crude Protein; 2.81 Mcal/kgDM) in individual troughs. The cows were milked twice a day (05:00 and 17:00 h). Milk production was registered daily while milk composition was measured at the beginning and at the end of the experiment (samples from two consecutive milking). For milk yield results, a mixed model was used (Glimmix procedure, SAS 9.2, 2010) to analyse with treatment, day and their interaction as fixed effects and block as a random effect. While milk composition was analysed with only treatment as fixed effect. Milk yield was greater for TL than TC, while there was no difference in milk composition between treatments (Table 1). There is a significant effect of the day and an interaction between treatment and day (Figure 1), as difference was greater for TL to the end of the grazing period. This leads to the conclusion that it is possible to improve the milk production through less defoliation intensity.

Morphogenetic and structural characteristics, yield and chemical composition of signal grass under deferred grazing

ABSTRACT The effects of four deferred grazing strategies (30, 60, 90 and 120 days) on morphogenic and structural characteristics, herbage accumulation, and chemical composition of signal grass (Brachiaria brizantha cv. Xaraés) were evaluated. The experiment was conducted in Rondonópolis, Mato Grosso, Brazil, during the transition period between the rainy and the dry season, from April to August 2013. The number of live leaves and leaf lifespan were quadratically affected (p < 0.05) by the period of deferment. Pasture height linearly increased (p < 0.05) with increasing deferment periods, reaching a maximum of 54.33 cm at 120 d of deferment. The leaf: stem ratio linearly increased (p < 0.05) with increasing deferment periods and remained higher than 1 during all evaluation periods. Total dry matter accumulation increased linearly (p < 0.05), with an average of 7817 kg/ha at day 120 of the deferment. Concentrations of crude protein and neutral detergent fiber were not affected by the length of the deferment period (p < 0.05). A deferment period of up to 120 days resulted in increased dry matter accumulation, a higher leaf: stem ration, and only slight changes in the structural characteristics and chemical composition of Xaraés pasture grass.

An innovation systems approach to understanding the impacts of grass grub damage in irrigated Canterbury dairy pastures

An innovation systems approach involving agribusiness representatives, researchers and farmers identified that damage caused by grass grub (Costelytra giveni) was a key factor contributing to areas of reduced yield within high-producing pastures. Using a recognised yield mapping technique, areas of ‘Low’ and ‘High’ pasture height were identified in different paddocks over 3 years; ‘Low’ areas had significantly higher numbers of grass grub larvae than ‘High’ areas. Pasture production was measured for the ‘Low’ and ‘High’ pasture height areas, and the difference was calculated to be 6800 kg DM/ha for 2018/19. This difference persisted after grass grub larvae were no longer active. Farm systems modelling analysis estimated this ‘yield gap’ led to a $650/ha/year difference in profit. A survey of farmer perceptions of grass grub damage on 23 central Canterbury dairy farms estimated 19% of pastures were affected by grass grub, with 11% of the area in those paddocks being damaged. Econometric modelling showed differences in farmer perceptions of grass grub damage. Data from the survey and the pasture measurements were combined with the farm systems modelling results to estimate a $1,870,000/year regional-scale impact of the ‘yield gap’. An integrated pest management approach is suggested to control grass grub damage.

Assessing the ability of a stationary pasture height sensing device to estimate pasture growth and biomass

Good pasture management requires an accurate knowledge of whole-farm feedbase, yet most systems for measuring pasture growth are manually operated and time consuming. A newly developed pasture-measuring device enables remote measurement of pasture height on a regular basis. This study investigated the accuracy of such a device compared with a rising plate meter, then assessed the device on a pure perennial ryegrass paddock at a research farm, followed by field testing in a perennial ryegrass/white clover paddock on a commercial dairy farm. A strong correlation (R2 = 0.93) was obtained between collected DM yield and device-derived pasture height within the pure perennial ryegrass paddock but the correlation was weaker (R2 =0.68) with data from the dairy farm perennial ryegrass/white clover paddock. There is considerable potential to improve upon these initial data through the use of adjusted calibrations. Findings demonstrate the device has the potential to accurately estimate pasture growth.

Photogrammetry for assessment of pasture biomass

New tools are required to provide estimates of pasture biomass as current methods are time consuming and labour intensive. This proof-of-concept study tested the suitability of photogrammetry to estimate pasture height in a grazed dairy pasture. Images were obtained using a digital camera from one site on two separate occasions (May and June 2017). Photogrammetry-derived pasture height was estimated from digital surface models created using the photos. Pasture indices were also measured using two currently available methods: a Rising Plate Meter (RPM), and Normalised Difference Vegetation Index (NDVI). Empirical pasture biomass measurements were taken using destructive sampling after all other measurements were made, and were used to evaluate the accuracy of the estimates from each method. There was a strong linear relationship between photogrammetry-derived plant height and actual biomass (R2=0.92May and 0.78June) and between RPM and actual biomass (R2=0.91May and 0.78June). The relationship between NDVI and actual biomass was relatively weaker (R2=0.65May and 0.66June). Photogrammetry could be an efficient way to measure pasture biomass with an accuracy comparable to that of the RPM but further work is required to confirm these preliminary findings.

Association among pasture-level variables and dairy cow responses to supplements

In grazing systems, the marginal milk-production response to additional feed (i.e. supplement) is dependent on the relative feed deficit of the cow. We hypothesised that the relative feed deficit could be defined by post-grazing residual (PGR), with a greater PGR indicating a smaller relative feed deficit. The objective of our study, therefore, was to determine the relationship between post-grazing residual and the marginal milk-production response to supplements. We undertook a computerised literature search utilising keywords associated with grazing systems and supplementary feed. We collated data from 26 experiments and 90 treatments, wherein pasture-level, supplementary-feed, and milk-production variables were reported. A meta-analysis was undertaken using random coefficient regression fitted as a mixed model to determine the marginal milk-production response to supplements. On average, pasture DM intake declined (P &amp;lt; 0.001; –0.28 kg/kg supplement DM) and milk, fat and protein yields increased (P &amp;lt; 0.001; 0.64 kg, 20 g and 30 g/kg supplement DM respectively) with an increased supplement use. For every kilogram of DM supplement consumed, PGR pasture height and mass increased by 1.4 mm and 42 kg DM/ha. Associated with every 10-mm increase in post-grazing pasture height in the control treatment, marginal milk response declined (P &amp;lt; 0.05) by 9%. These results will enable farmers to use the change in PGR when feeding supplements, to estimate likely marginal milk-production response to supplementary feeds.

Beef cattle performance on signal grass pastures deferred and fertilized with nitrogen

ABSTRACT The effect of four nitrogen levels (0, 40, 80 and 120kg N ha-1), applied before deferment on the beef cattle production and structural variables on Urochloa decumbens (signal grass) were assessed from January to October 2012 and from January to September 2013. A randomized block design with three replicates was adopted, in an arrangement of repeated measures in time (grazing period). An interaction effect between nitrogen level and grazing period was observed on extended-plant height and herbage mass. As the nitrogen levels were increased, extended-plant height, herbage mass, total herbage allowance, and efficiency of conversion of fertilizer into herbage were increased. Throughout the grazing period, pasture height, extended-plant height, percentage of leaves, herbage and morphological components allowance, and percentages of leaves and stems in the herbage apparently selected by the animal decreased. Nitrogen levels had no effect on average daily gain or gain per area in the first year. A fixed deferment period with increasing levels of nitrogen fertilization on signal grass pastures does not influence the average daily gain per animal, reduces the efficiency of the nitrogen fertilizer and negatively changes the structural characteristics of the pasture.

Defoliation dynamics, pasture intake and milk production of dairy cows grazing lucerne pastures in a partial mixed-ration system

The effect of lucerne pasture allocation on defoliation dynamics, pasture intake and animal production was investigated in a subtropical partial mixed-ration dairy system. The study took place at the Gatton Research Dairy, south-eastern Queensland, with a 28-day adaptation period followed by an 8-day treatment period during November and December 2016. Twenty-four multiparous Holstein Friesian dairy cows were offered 11 kg of dry matter (DM)/cow.day as partial mixed-ration dairy system, and four levels of daily pasture allocation measured to 5-cm residual pasture height (averaging 30.6, 20.5, 15.1 and 10.9 kg DM/cow.day). Cows with lower allocations were forced to graze further down the vertical plane and pasture intake and milk yield significantly (P &amp;lt; 0.001) declined. Cows grazed the top grazing stratum (TGS) across 80% of the pasture area before re-grazing another area of the paddock, regardless of the allocation level. Pasture intake (kg DM/ha) of the TGS was at least 2.9 times higher than that of the lower strata, regardless of allocation level. Therefore, the decline in pasture intake is explained by the transition from grazing the TGS to grazing lower strata. When the horizontal utilisation of the TGS approached 100%, the proportion of ungrazed, uncontaminated pasture approached 0% of the area, and intake and milk production declined. Grazing management strategies for lucerne should allocate pasture to lactating dairy cows to achieve horizontal utilisations approaching 0% for proportion of ungrazed, uncontaminated pasture to maximise intake and production. Secondary grazing herds or mechanical methods should be used to remove residual pasture to the ideal height for pasture regrowth.

A Preliminary Investigation of the Potential of Sentinel-1 Radar to Estimate Pasture Biomass in a Grazed Pasture Landscape

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.

Assessing and Modeling Pasture Growth under Different Nitrogen Fertilizer and Defoliation Rates in Argentina and the United States

Core Ideas Model‐based approach identified sets of adaptive practices for pasture management across seasons. Suitable combinations of N rate and residual heights can improve the use of N fertilizer and water. The increment in residual pasture mass and N fertilizer may be crucial for more efficient use of water. Pasture growth responses to residual leaf area increased with N fertilization. The objectives of this research were to (i) evaluate the effects of N fertilizer, irrigation, and residual pasture heights on pasture growth, (ii) validate the ability of the SALUS model to predict dynamics of pasture growth, and (iii) evaluate during long‐term period the effects of using different N fertilizer levels and defoliation strategies on pasture growth, N fertilizer use, and water use efficiency (WUE). Eight single‐season experiments were performed at plot scale (8 m2) in Buenos Aires (Argentina, ARG) and Michigan. In ARG different N fertilizer rates (from 0–500 kg N ha−1) were imposed on both rainfed and irrigated tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] pasture during autumn, spring, and summer. In the United States, three residual pasture height treatments (30, 60, and 120 mm) were imposed on both tall fescue and ryegrass (Lolium perenne L.) pasture in the spring and summer. The SALUS was parameterized to simulate tall fescue and ryegrass growth using soil, weather, and different pasture treatments previously tested in ARG and the United States. Results showed that the SALUS accurately represented the response of herbage mass to irrigation and added N in the ARG site (RMSE &lt; 650 kg DM ha−1) and to differences in residual pasture heights in the U.S. experiment (RMSE &lt; 509 kg DM ha−1). Ten‐year simulations (2000–2010) demonstrated that suitable combinations of N fertilizer and residual pasture heights can significantly improve the use of N fertilizer by ∼300% and water by ∼230% through increases in herbage production.

Modeling the Nutritive Value of Defoliated Tall Fescue Pastures Based on Leaf Morphogenesis

Core Ideas The leaf morphogenetic‐based model predicted the pasture nutritive value variance generated by in an ad hoc experiment. Variation in fiber digestibility with the age and length of leaves is the main driver for declines in pasture digestibility of vegetative regrowth. The morphogenetic approach was designed to enable its potential integration with some of the available pasture growth models. The model provided mechanistic understanding and predictions that allow for the exploration of new management strategies. The leaf morphogenesis of plants is the most important determinant of the nutritive value dynamics in vegetative pasture regrowth. The aim of this study was to develop a simulation model of the pasture nutritive value dynamics based on a morphogenetic approach that takes into account the effects of leaf age and leaf length on forage digestibility in relation to defoliation management. The model was developed and evaluated with detailed data from two independent experiments (Exp. 1 and Exp. 2, respectively) on tall fescue [Lolium arundinaceum (Schreb.) Darbysh.], including descriptions of morphogenesis, neutral detergent fiber (NDF) and digestibility of NDF (NDFD) and dry matter (DMD) of leaf blades. The model precisely and accurately simulated the forage digestibility dynamics of pasture regrowth observed under different residual pasture heights in Exp. 2. The main calculated statistics for NDF, NDFD, and DMD were root mean square deviation &lt; 4% points, R2 ≥ 0.92, concordance correlation coefficient ≥ 0.86 and bias correlation factor ≥ 0.89. The evaluated model was used to investigate the responses of forage nutritive value to several combinations of residual pasture heights (2–15 cm) and defoliation intervals (one to five leaves per tiller). This study highlights the inclusion of the NDFD trait associated to leaf morphogenesis as a mechanistic way to improve predictions of DMD dynamics in vegetative regrowth under different defoliation managements.

Mapping and Monitoring of Biomass and Grazing in Pasture with an Unmanned Aerial System

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.

Forage quality and performance of sheep in Massai grass pastures managed at pre-grazing canopy heights

The objective of this study was to evaluate the effects of pasture height at pre-grazing of Massai grass on the quality of available forage, forage intake and the performance of lambs raised for meat production. The treatments consisted of four pre-grazing canopy heights (35, 40, 45 and 50 cm). Pastures were managed by the intermittent stocking method and 32 sheep were used. Dry matter intake (DMI) was estimated by Lipe® indicator. Green forage allowance was not affected by pre-grazing heights. There was no effect of heights on the chemical composition of the stem or the leaf blades, except for crude protein content of leaf blades, which showed an inverse linear effect. Grazing time had a quadratic response in function of canopy height. The minimum point was at 42.6 cm, with 502.9 min/day. DMI increased linearly with increasing pasture height. Average daily weight gain (ADG) and stocking rate (SR) responded linearly to pre-grazing heights. Weight gain per hectare was not affected by height as a result of the compensation between SR and ADG. The increase from 35 to 50 cm in Massai grass canopy height reduces its nutritional value and individual performance and increases DMI of sheep intended for meat production. Keywords : Panicum maximum, tropical pasture, voluntary intake

Mitigation of enteric methane emissions through pasture management in integrated crop-livestock systems: Trade-offs between animal performance and environmental impacts

We evaluated the effect of different grazing intensities by steers on animal performance, herbage intake and CH4 emissions in the stocking period of a soybean-beef cattle integrated system in southern Brazil. Treatments consisted of different grazing intensities, defined by target sward heights (10, 20, 30 and 40 cm) of mixed black-oat (Avena strigosa Schreb.) and Italian ryegrass (Lolium multiflorum Lam.) pastures under continuous stocking. Grazing management affected herbage utilization and, consequently, animal performance and CH4 emission. At the individual level, CH4 emission and animal performance had optimal values when pasture height was managed within a range of 23–30 cm. At the farm level, we found a positive linear effect of grazing intensity on animal live weight gain per hectare and the associated environmental costs of land use. Liveweight gain increased by 90 g ha−1 day−1 and CH4 emissions increased by 500 g CO2eq ha−1 day−1 for each cm of target sward height reduction. Given that most producers graze pastures to very short heights, large-scale adoption of target heights within 23–30 cm in southern Brazil has the potential to achieve 13–14% of the mitigation target for GHG emissions from the whole agricultural sector and 22–25% of the target for enteric fermentation from the livestock sector pledged by the Brazilian Government in the Paris Agreement. We conclude that adequate grazing management is the key strategy to improve animal production and reduce the environmental impact from livestock in ICLS.

SOYBEAN CULTIVATION IN A CROP-LIVESTOCK SYSTEM WITH Azospirillum brasilense INOCULATION

ABSTRACT The objective of this study was to evaluate the phytomorphological parameters of soybean in a crop-livestock system inoculated with Azospirillum brasilense. The experiment was conducted in Santa Maria, Brazil, for two agricultural years (2 Paper extracted from the doctoral thesis of the first author. 012/2013 and 2013/2014) in a randomized complete block design with three replications. In the winter, the black oat and ryegrass pasture was managed with sheep under different grazing systems: (I) - a conventional grazing (CG) system, where the animals remained in the pasture throughout the experimental period without any pasture height control; (II, III, and IV) - systems with post-grazing pasture heights of 10, 20, and 30 cm, respectively; and (NG) - one control without grazing. All treatments received two nitrogen doses (50 and 100 kg ha-1) and inoculation or no inoculation (A. brasilense). The soybean cultivar BMX Potência RR was sown using no-tillage on 16 November 2012 and 1 December 2013. In each plot, seven rows of plants with spacing of 0.45 m were used, and in four rows, the seeds were inoculated with the bacterium A. brasilense. The phytomorphological variables and grain productivity were evaluated. In a croplivestock system, soybean has better productivity when established on black oat and ryegrass pasture managed with post-grazing pasture heights of between 20 and 30 cm. Areas under conventional grazing in the winter led to smaller soybean plants with lower first and last pod heights. Inoculation with A. brasilense should not be used alone in soybean cultivation.

Impact of Rotational Grazing Systems on the Pasture Crop Coefficient for Irrigation Scheduling

AbstractCrop coefficient (Kc) estimations of ryegrass pasture (Lolium perenne) that matches the actual plant canopy represented by height (h) in rotational grazing systems have been assessed. This study investigated the impacts of grazing rotations on Kc, using non‐weighing percolation lysimeters. The FAO Penman–Monteith equation was used to estimate the reference evapotranspiration (ETr) from daily weather data. A water balance approach was applied to drainage data from 20 lysimeters to calculate actual evapotranspiration (ETa). Based on ETa and ETr, Kc was estimated for the different pasture growth stages of a grazing rotation.Results showed that Kc and h can be modelled by a linear relationship. Pre‐ and post‐grazing pasture heights were typically 30 and 10 cm, respectively, for which estimated Kc values were 1.0 and 0.6, respectively. Thus, due to variations in pasture height at different grazing stages, the conventional irrigation scheduling using a single Kc of 1.0 does not take into account the dynamic water demand for rotationally grazed pasture. Irrigation scheduling that incorporates variations in Kc with pasture growth stage will lead to more efficient water use and importantly less drainage and overland flow, perhaps the biggest environmental challenge for pastoral irrigators in New Zealand, without impacting on productivity. Copyright © 2018 John Wiley &amp; Sons, Ltd.

Morphological, environmental and management factors affecting nutritive value of tall fescue (Lolium arundinaceum)

The aim of this study was to quantify the relative importance of leaf age and leaf length on the dynamics of neutral detergent fibre (NDF), and 24-h in vitro digestibility of NDF (NDFD) and dry matter (DMD) of tall fescue (Lolium arundinaceum (Schreb) Darbysh.). Mini-swards were conditioned and used to conduct two experiments, the first with 4-cm plant stubble height in spring–summer 2009 and autumn–winter 2011, and the second with 4-cm or 10-cm plant stubble height in spring–summer 2011. Plants were harvested at consecutive leaf-appearance intervals to measure nutritive value up to the four-leaf stage. In parallel, leaf morphogenetic traits (appearance, elongation and lifespan) and sheath length of the successive leaves produced on marked tillers were measured. Leaf NDF contents remained stable with increasing leaf age and length but showed a marked variation across seasons. Leaf NDFD and DMD showed a consistent decrease with increasing leaf age and length, and irrespective of growing season or residual pasture height. The negative effect of leaf age and length on digestibility was related to variations in sheath tube length and associated differences in leaf appearance and elongation rates. These findings highlight the relevance of monitoring the sheath tube length as a complementary measure to leaf stage for further management of the NDFD and DMD of grass forages. Although the focus of this study was tall fescue swards, the same morphogenetic implications on forage nutritive value could apply to other temperate and tropical grass species; however, the testing of this hypothesis warrants carefully controlled investigations.

Animal performance, production, and quality of Tanzania grass fertilized with nitrogen

This study aimed to assess forage production, animal performance, and the chemical composition of Tanzania grass pasture fertilized with 50, 100, 200, and 400 kg ha-1 of nitrogen. The variables analyzed were: leaf mass, daily accumulation rate, leaf/stem ratio, average daily gain, stocking rate, live weight gain per unit of area crude protein, neutral detergent fiber, and in vitro dry matter digestibility of leaves. The pasture management maintained the pasture height at 50 cm by using a continuous grazing method with the adjustment of stocking rate. The experimental design was a randomized block with three replicates. The leaf mass increased linearly in response to nitrogen, with an increase of 1003 kg (34%) observed between a nitrogen content of 50 and 400 kg ha-1. Nitrogen did not affect the average daily gain, but increased the stocking rate and live weight gain ha-1. The value of crude protein and neutral detergent fiber were higher with increased nitrogen levels, whereas the leaf digestibility did not affect nitrogen use. The comparison of 50 and 400 kg ha-1 levels indicated that there was an average increase of 19.2% in the leaf crude protein. The increased application of nitrogen fertilizer in Tanzania grass improved the chemical composition and animal performance; with regard to studied variables, the dose of 200 kg ha-1 resulted in the greatest improvement.

Forage productivity and nutritive value during pasture renovation in integrated systems

Integrated crop-livestock-forestry systems are strategies to diversify production in the same area, aiming at higher sustainability. Corn is one of the most used crops in integrated systems due to its multiple uses on the farm. The objective of this study was to evaluate the effect of light restriction on morphological and productive characteristics of the forage components (corn for silage and pastures) in integrated livestock production systems. The experiment was carried out on Embrapa’s integrated systems in Sao Carlos, SP, Brazil, during two growing seasons. In the integrated crop-livestock (iCL) system corn was sown simultaneously with Piata-grass. In the integrated crop-livestock- forestry (iCLF) system, besides corn and Piata-grass, Eucalyptus urograndis trees were planted in single 15 × 2 m rows. Corn productivity and pasture yield and nutritive value were evaluated in iCL and iCLF systems. In iCLF, evaluations were made in four positions relative to the tree lines: 1.5, 3.75, 7.5, and 11.25 m. Photosynthetically active radiation (PAR) transmission by trees was also measured in the same positions. Results of the corn crop indicated that the position relative to the tree lines affected (P < 0.001) all morphological characteristics and production parameters. Production was not affected by position relative to the tree lines in the first year but was lower in the position closer to the trees in the second year. As an average of all positions evaluated in iCLF, corn DM production in the first agricultural year was 43.3% inferior compared to the second year (5266.1 vs. 9816.7 kg DM ha−1). In iCL, the average corn DM production for the two years was 10082 kg DM ha−1. For the corn, the relationship between PAR transmission and the relative yield (production in each position in iCLF divided by the production in iCL) was influenced by drought in the 2013/2014 growing season. Considering the results for the renovated pastures, position relative to the tree lines affected pasture height (P < 0.0001), specific leaf area (P < 0.0012), digestibility (P < 0.0085) and crude protein (P < 0.0001).