Forage Accumulation Rate Research Articles

Pre-defoliation canopy height for signal grass ‘Basilisk’ in silvopastoral systems

The objective of this study was to compare the response of Urochloa decumbens cv. Basilisk pastures in monoculture and silvopastoral systems (SPS), and to determine the most suitable pre-defoliation canopy height for managing this species in SPS. Four pre-defoliation canopy heights (20, 30, 40, and 50 cm) were tested for signal grass in SPS, alongside a control treatment involving defoliation at 20 cm in full sun. The experiment was conducted using a randomized block design with four replicates. The forage accumulation rate was higher in monoculture (36.5 kg ha-1 day-1 of DM) compared to the silvopastoral system (22.0 kg ha-1 day-1 of DM), and there was no significant effect of pre-defoliation canopy height within the SPS. The density of tillers in monoculture was comparable to that observed in canopies managed at a height of 50 cm within the SPS. Leaf mass and leaf percentage were maximized at heights of 40 cm and 50 cm, respectively. Neither the cultivation system nor the pre-defoliation canopy heights in the SPS influenced the fiber and protein content. Leaf accumulation and mass were higher in monoculture, but the cultivation system did not affect the chemical composition of the forage. Heights between 40 cm and 50 cm in the SPS should be used to maximize tillering, mass, and leaf percentage of signal grass ‘Basilisk’. The chemical composition of the produced forage did not undergo significant changes, neither between systems nor across pre-defoliation heights.

Behavioural compensation of extruded urea level and the effects of supplementation presencefor finished lambs in tropical grass pastures

The objective was to investigate how different levels of soybean meal replacement with extruded urea (EU) in sheep supplementation affected pasture characteristics (Brachiaria spp.), consumption, ingestive behavior and animal performance. Sixty Texel crossbred lambs were randomly divided between treatments: 0, 6, 12, 18 and 24 g of 100 kg−1 body weight (BW) EU supplement under continuous stocking in Brachiaria spp. The animals receiving a supplement in the proportion of 24 g 100 kg−1 BW from the EU had the highest pasture height (39.5 cm) as compared with other treatments. The levels of replacement of soybean meal by the EU had no effect on the supply of forage, forage accumulation rate or structural characteristics. The forage dry matter intake (DMI) as percentage of BW and metabolic BW were adjusted to quadratic equations, and the minimum levels of DMI in relation to BW (1.5 %) and metabolic (55.6 g DM/kg0.75) were estimated at 10 g and 9.4 g 100 kg−1 BW of the EU, respectively. The grazing time of the lambs decreased linearly (P = 0.006) by 4.88 min for each increase in the EU level. In contrast, as EU levels in lamb supplementation increased, the time taken to consume the supplement and the bite rate increased by 4.38 min and 0.28 bites/minutes, respectively. The average daily gain increased linearly up to 18 g 100 kg−1 BW (146 g/day) (P = 0.034). For lambs finishing in Brachiaria spp., the EU can be used in place of soybean meal up to 18 g 100 kg-1 BW without altering animal performance, consumption, or the structural characteristics of the pasture.

Water use efficiency and yield responses of Cenchrus purpureus genotypes under irrigation

AbstractIn tropical regions, water stress is one of the main causes of the reduction in forage productivity, and irrigation strategies can mitigate the problem, especially for highly productive species. The objective of this study was to evaluate the effects of irrigation, genotype and plant size on productive responses and water use efficiency (WUE) of elephant grass (Cenchrus purpureus [Schumach.] Morrone), in the rainy and dry season. The experimental design was randomized in blocks, arranged in split plots, the main plots were established based on the use of irrigation and the subplots were the tall-sized genotypes (IRI 381 and Elephant B) and dwarfs (Taiwan A-146 2.37 and Mott). The genotypes were evaluated for two years and harvested every 60 days. Water use efficiency, total forage accumulation per year and harvest, forage accumulation rate and forage density were evaluated. There was a significant difference between the genotypes in terms of total forage accumulated (P < 0.05). The most productive genotype was IRI 381, which showed the greatest total forage accumulation (42 168 kg of DM/ha in two years) in the irrigated plots. During the rainy seasons, IRI 381 stood out in terms of forage accumulated (24 667 kg of DM/ha). Irrigation favoured increases in forage accumulation around 60%, in both years of evaluation. Irrigation and plant size influenced the productivity and WUE of elephant grass harvested in 60-day intervals. Tall genotypes and Taiwan A-146 2.37 (dwarf size) stood out in most of the productive traits analysed, while Mott was highlighted by its forage density.

Forage Accumulation and Nutritional Characteristics of Brachiaria Cultivars Grown in a Semi-arid Environment

The evaluation of the nutritional value and parameters of ruminal fermentation of tropical forages is important, aiming at its efficient use in ruminant feeding. This study was developed to evaluate the forage accumulation, chemical composition, protodioscin content, digestibility, and in vitro degradation kinetics of different Brachiaria spp. cultivars in different evaluation periods. The research was carried out in the semi-arid region of Brazil, from April 2016 to April 2017. The experiment was laid out as a split-plot arrangement in a randomized block design in which five cultivars ( B. decumbens cv. Basilisk, and B. brizantha cvs. Marandu, Paiaguás, Piatã, and Xaraés) represented the plot and four evaluation periods (establishment, transition, dry, and rainy) the subplot. There was a cultivar × period interaction effect for forage accumulation rate (FAR), for which cv. Xaraés showed the highest mean (54.1 kg/ha.day DM) in the rainy season. The lowest yield was found in cv. Paiaguás in the dry season (24.1 kg/ha.day DM). Cultivars Basilisk, Marandu, and Paiaguás had the highest crude protein content. The highest in vitro dry matter digestibility values were found in cv. Basilisk in the dry, transition, and rainy periods; cv. Marandu in the transition period, and cvs. Paiaguás and Piatã in their establishment. A correlation was found between the parameters of in vitro degradation kinetics and chemical composition. The protodioscin content was highest in cv. Basilisk, during its establishment (5.5 g/kg DM). Cultivars Paiaguás, Piatã, and Xaraés showed low protodioscin values (<1.0 g/kg DM). Cultivars Basilisk, Marandu, Paiaguás, Piatã, and Xaraés can be used as forage options in the semi-arid environment, as their forage accumulation potential and nutritional value are suitable for animal production even in periods of lower water availability.

Diferenças estruturais e produtivas entre os capins braúna, cayana e sabiá diferidos

ABSTRACT The aim of this study was to identify differences in morphogenesis, structure, and forage accumulation rate of Urochloa brizantha cv. MG13 Braúna, from Urochloa cv. Cayana and Urochloa cv. Convert 330 (sabiá grass) during the deferment period. The experimental design was completely randomized, with four replications in experimental plots of 12.25m2. The evaluations took place for two years, 2021 and 2022. The deferment period was 90 days. Phyllochron (PHY) and leaf senescence rate (LSR) were lower at the beginning of deferred, contrary to leaf elongation rate (LER) and population density tillers (PDT). Stem growth rate (SGR) was higher in 2021 and at the beginning of deferment. Leaf growth rate (LGR) and total growth rate (TGR) were higher at the beginning of deferment. The braúna grass presented higher PDT. The SGR and the TGR of cayana grass are superior to those of braúna grass. The braúna grass produces a canopy consisting of lighter and denser byts, compared to other weeds. In Uberlândia, MG, braúna grass with an initial height of 30cm produces less stem, while cayana grass produces more forage during deferral.

Regrowth of brachiariagrasses as related to stubble characteristics under N fertilization and irrigation

Seasonal and annual changes in stubble characteristics can affect the regrowth of warm-season perennial grasses. Understanding these changes and their effects on forage accumulation rate (FAR) can improve defoliation management. Our objective was to describe and relate variations in stubble characteristics with FAR during regrowth of four palisadegrasses [Brachiaria brizantha (Hochst. Ex A. Rich.) Stapf. syn. Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster], genotypes Marandu, Xaraés, Arapoty, and Capiporã, and one signalgrass [Brachiaria decumbens (Stapf.) syn. Urochloa decumbens (Stapf.) R.D. Webster] cultivar Basilisk, in southeastern Brazil. Plots were harvested at 15-cm stubble height every 28 d during the warm season and 42 d during the cool season of years 2005–2006 and 2007–2008. Stubble mass was ∼1,070 kg DM ha−1 greater in the cool than warm season, whereas FAR was less in the cool season. Arapoty and Basilisk showed generally less FAR (∼45 kg d−1) and stubble leaf, stem, dead material, and total mass during the warm season than more productive grasses Capiporã and Xaraés (∼63 kg d−1). Leaf and canopy photosynthesis varied over seasons and years, but they were similar among grasses despite differences in stubble characteristics and FAR. Marandu accumulated more leaf in the stubble than other grasses, resulting in greater residual leaf area index, but it did not increase FAR. Under less favorable growth conditions, grasses increased stubble herbage mass (SHM). More productive grasses generally present greater SHM and leaf mass, indicating that stubble characteristics play an important role in the regrowth of brachiariagrasses.

Production Potential and Quality of Panicum maximum Cultivars Established in a Semi-Arid Environment

This study was conducted to examine the forage production potential and quality of Panicum maximum cultivars in a semi-arid environment, in four different periods. Six cultivars were evaluated: Aruana, Massai, Mombasa, BRS Tamani, Tanzania, and BRS Zuri. The experiment was laid out in a randomized-block design with four replicates, and assessments took place in four different periods (establishment, dry season, transition, and rainy season). Forage accumulation rate (FAR), chemical composition, digestibility, and in vitro rumen degradation kinetics were evaluated. There was an interaction effect between cultivars and evaluation periods for all variables, except dry matter (DM) content. The highest FAR occurred in cvs. BRS Tamani (47.0 kg DM/ha/day) and BRS Zuri (86.9 kg DM/ha/day) in the establishment and rainy periods, respectively, while cv. Aruana showed the lowest FAR (14.5 kg DM/ha/day). The highest crude protein contents were found in cv. BRS Tamani in the transition period; cv. BRS Zuri in the dry season; and cv. Tanzania in the rainy season (128.2, 116.7, and 95.0 g/kg DM, respectively). Cultivar Aruana showed the highest average in vitro dry matter digestibility (810.0 g/kg DM). Cultivars Aruana and Zuri exhibited the highest means of the total in vitro gas production (23.59 and 20.24 mL/100 mg DM, respectively). Cultivars BRS Tamani and BRS Zuri had the best response in terms of forage accumulation and nutritional value. The quality of cv. Massai remained constant throughout the year. All Panicum maximum cultivars evaluated here have the potential for use in animal production systems in a semi-arid environment.

Protodioscin Content, Degradation Kinetics, and In Vitro Digestibility of Marandu Palisadegrass Hay as were Affected by Cutting Interval of the Canopy

Even though marandu palisadegrass is widely used in Brazil, the consumption of this forage may cause photosensitization in ruminants due to the protodioscin. This study aimed to recommend a harvest cutting interval for haymaking that provides a better nutritional value and lower levels of protodioscin. The experimental treatments were four cutting intervals (21 d, 35 d, 49 d, and 63 days of regrowth period up to forage harvest). The experimental design was a completely randomized block design with 4 treatments and 4 replications. We assessed the forage production, chemical composition, in vitro digestibility, in vitro degradation kinetics, and protodioscin content. The forage accumulation rate did not differ with the increased cutting interval. The crude protein contents and in vitro digestibility of dry matter decreased linearly with the increased cutting interval in fresh and hay material. The greatest gas production in hay material was occurred in 21 d cutting interval, which was 26%, 14%, and 5% greater than cutting intervals of 63, 49, and 35 d, respectively. A linear increase was observed in protodioscin concentration in hay according to the cutting interval, which in the hay with 63 d cutting interval was 7%, 29%, and 43% greater than hays with cutting interval of 49, 35, and 21 d, respectively. In addition, protodioscin contents were lower in hay compared to fresh material. The haymaking process reduced protodioscin content in relation to forage before haymaking. Our results showed that the better condition to harvest marandu palisadegrass for hay was at 21 d. The better condition to develop a productive canopy is associated with better nutritive value and lower protodioscin content.

Morphogenetic and structural traits of Ipyporã grass subjected to nitrogen fertilization rates under intermittent grazing

ABSTRACT: This study examined the effects of annual nitrogen (N) rates of 100 and 200 kg ha-1 on the morphogenetic and structural traits of Ipyporã grass (Brachiaria brizantha × Brachiaria ruziziensis) under intermittent grazing during the seasons of the year. The experiment was laid out in a randomized-block design with two treatments and three area replicates. Ipyporã grass pastures were grazed by beef cattle. Morphogenetic and structural traits of the forage canopy were evaluated using the marked-tiller technique. Forage accumulation and tiller density (TD) were also evaluated. Significant interaction effects (P &lt; 0.05) between N rates and seasons were observed for the rest period, leaf lifespan (LLS), phyllochron, stem elongation rate (SER) and final leaf length (FLL). During winter, the rest period was shorter (40 vs. 50 days) in the pastures fertilized with 200 kg ha-1 N. Conversely, in winter, the pastures fertilized with 100 kg ha-1 N showed higher LLS, SER and phyllochron values, but lower FLL values. There was no isolated effect of N rates (P &gt; 0.05) on forage accumulation rate; leaf appearance, elongation or senescence rates; leaf:stem ratio; or TD. However, the effect of seasons was significant for these variables, with the highest values occurring during spring and summer. The use of 200 kg ha-1 N in Ipyporã grass pastures reduces the seasonality of forage production.

Forage yield and structural responses of spineless cactus ‘Orelha de Elefante Mexicana’ at different planting densities

The objective was to evaluate the forage yield and structural responses of spineless cactus ‘Orelha de Elefante Mexicana’ (OEM) (Opuntia stricta (Haw.) Haw) at different planting densities. The experimental design was a randomized block with five treatments and four replicates, during two production cycles of 12 months each. The evaluated densities were 20,000; 25,000; 33,333; 50,000; and 100,000 plants ha-1. The increase in planting density caused a linear reduction in plant height, width, and mass, as well as in number of primary, secondary, tertiary, and overall cladodes. It also caused a linear increase in cladode area index, dry and green yield, water use efficiency, and forage accumulation rate. The increase in planting density promoted a quadratic effect on cladode thickness and dry matter content. Cladode thickness decreased with planting densities up to 47,500 plants ha-1 and increased from this point onwards. As for dry matter content, there was an increase up to the planting density of 61,428 plants ha-1 and a decrease from this point onwards. The increase in planting density of spineless cactus ‘Orelha de Elefante Mexicana’ caused changes in structural responses and in forage yield. The use of greater planting densities increased forage yield.

Ammonia Volatilization, Forage Accumulation, and Nutritive Value of Marandu Palisade Grass Pastures in Different N Sources and Doses

The reduction in ammonia (NH3) losses from volatilization has significant implications in forage production. The objective of this study was to evaluate the impact of N fertilizers (urea, ammonium nitrate, and ammonium sulfate) and four doses (0, 90, 180 and 270 kg N ha−1) on N losses by NH3 volatilization, accumulation, and forage chemical composition of Urochloa brizantha cv Marandu. Two field experiments were conducted to measure NH3 losses using semi-open chambers. The forage accumulation and chemical composition were evaluated in the third experiment; the response variables included forage accumulation, crude protein (CP), and neutral detergent fiber (NDF). Compared to urea, ammonium nitrate and ammonium sulfate reduced NH3 losses by 84% and 87% and increased total forage accumulation by 14% and 23%, respectively. Forage accumulation rate and CP increased linearly with the N levels, while NDF contents decreased linearly with the N levels. In both experiments, NH3 losses and forage characteristics were different according to the rainfall pattern and temperature variations. Our results indicate that the use of nitric and ammoniacal fertilizers and the application of fertilizer in the rainy season constitute an efficient fertilizer management strategy to increase forage yield and decrease losses from volatilization of NH3.

Spring deferment and N-P fertilization in natural grasslands vulnerable to summer water deficit

In Campos grasslands, the production of forage and its variability are driven by the amount of rainfall. In this context, stockpiling forage from spring to summer is a useful tool to maintain the feed supply for livestock, but so far it has not been developed due to the lack of information for farmers decision-making. In this paper we evaluated the response of pasture production to spring grazing deferment in a shallow basaltic grassland in 12 combinations of lime (0 and 1500 kg ha-1 of CaMg(CO3)2), phosphorus (0 and 90 kg ha-1 of P2O5) and nitrogen (0, 75, 150, and 300 kg ha-1 of N, except in the upper two N levels that were evaluated only with lime) addition. Forage accumulation, sward height and nitrogen nutrition index (NNI) were evaluated every 15 days during 75 days. Both sward height and available forage mass increased linearly with the deferment time. The lime application did not affect the forage accumulation rate, while the single nitrogen and phosphorus addition only showed a slight positive effect, however the combined addition of N-P fertilization tripled the forage production. Nitrogen fertilization improved the NNI and was further enhanced by the combined application of N and P. Our results suggest that the capacity of shallow basaltic grasslands to accumulate deferred forage is co-limited by N and P availability.

Effects of timing of nitrogen fertilizer application on responses by tropical grasses

Timing of nitrogen (N) fertilizer application can influence grass regrowth, so it is important to identify how tropical grasses respond to delays in applying fertilizer after defoliation. Our objective was to identify the effects of timing of N fertilizer application after harvest on the productive, morphogenic and structural characteristics of 3 tropical grasses: ‘Xaraés’ (Urochloa brizantha [Hochst. ex A. Rich.] Stapf cv. Xaraés), ‘Marandu’ (Urochloa brizantha [Hochst. ex A. Rich.] Stapf cv. Marandu) and ‘Tanzânia’ (Megathyrsus maximus [Jacq.] cv. Tanzânia). The experiments were performed in a greenhouse, in a completely randomized design, with 5 delays in applying N after harvesting (0, 3, 6, 9 and 12 days). Delaying fertilizer application did not affect the forage mass of Xaraés and Marandu palisade grass (7.4 and 7.8 g/pot, respectively). There was a linear decrease in number of leaves per tiller and leaf appearance rate, but tiller population density and phyllochron increased linearly as fertilizer application was delayed. Grass forage mass (12.2‒10.6 g/pot), number of leaves per tiller (3.1‒2.6 leaves/tiller) and forage accumulation rate (0.47 to 0.41 g DM/d) of Tanzânia guinea decreased linearly as N application was delayed, but tiller population density was unaffected (25 tillers/pot). Based on our results, N fertilizer should be applied to Tanzânia guinea grass pastures as soon as possible after harvest and certainly before 3 days, while there is not the same urgency with Xaraés and Marandu where fertilization could be delayed up to 12 days without significant detriment. These suggestions need to be tested in a field study before being recommended widely.

Effect of grazing management strategies on the yield and nutritional value of Marandu grass in the semiarid of Brazil

The objective of this study was to evaluate the effects of two grazing management strategies on structural, productive and nutritional parameters of Marandu grass (Urochloa brizantha cv. Marandu). A completely randomized block design with two pasture management strategies and eight replications (blocks) was used. The grazing management strategies were: (1) low intensity rotational grazing (LI), with a pre-grazing sward height of 40 cm and a post-grazing sward height of 24 cm, i.e., a defoliation intensity of 50%; (2) High intensity rotational grazing (HI), with a pre-grazing sward height of 40 cm and a post-grazing sward height of 10 cm (±70% defoliation intensity). Pastures were sampled before and after grazing for estimation of forage mass, forage accumulation rate, structural characteristics, nutritional value and dry matter intake.The LI strategy resulted in higher dry matter production than HI before (18.33%) and after grazing (49.06%), increasing pre-grazing forage density by 13.21% (P &lt; 0.05). The production of potentially digestible dry matter was highest (P &lt; 0.05) in LI strategy (21.3% before and 39.6% after grazing, respectively). Higher post-grazing green forage mass (45%) increased the residual crude protein in LI. The LI management strategy increased forage mass production and can be used in Marandu grass pastures.

Forage accumulation and radiation use of alfalfa under deficit irrigation

AbstractThe supply of high‐quality forage is fundamental to the development of ruminant animal production in drought areas where irrigation provides strong support to the forage production. The objective was to explore the response of alfalfa (Medicago sativa L.) growth and radiation use to deficit irrigation in a 2‐yr field study. Two deficit‐irrigation treatments and a full‐irrigation control (CK) were established under flood irrigation. Growth‐related indicators and radiation use were measured regularly. Results showed that deficit irrigation reduced forage accumulation, leaf area index (LAI), plant relative water content (RWC), and radiation use efficiency (RUE) of alfalfa. Compared with CK, slight deficit irrigation (SD) and moderate deficit irrigation (MD) decreased forage accumulation rate by 20 and 30%, respectively. Logistic model as a function of growing degree days (GDD) fitted well LAI change (R2 &gt; .9). Deficit irrigation reduced the average rate of quick growth of LAI from 5 to 36%. Water deficit did not significantly change the GDD corresponding to the rapid growth phase but reduced the growth rate. Under deficit irrigation, decreased LAI did not always lead to significant cumulative intercepted photosynthetically active radiation (CIPAR) decrease, but resulted in significantly lowered RUE. In conclusion, the decrease of forage accumulation of alfalfa under deficit irrigation would be caused mainly by weakened photosynthetic ability (representing RUE).

Defoliation intensity and leaf area index recovery in defoliated swards: implications for forage accumulation

This study evaluated the leaf area index (LAI) recovery mechanisms and forage accumulation rates on the regrowth of different grass species subjected to different defoliation intensities. For that purpose, plots of Pennisetum clandestinum (kikuyugrass), Lolium multiflorum (annual ryegrass), and Avena strigosa (black oats) were defoliated from 20 to 80 % of their initial heights (25, 20, and 25 cm, respectively). At different increments in height, forage samples were collected to ground level and used to estimate tiller population density (TPD), leaf area per tiller (LA), and forage mass. From these data, we calculated the leaf area index (LAI), average leaf area index (aLAI), and average and instantaneous forage accumulation rate (FAR and IFAR, respectively). Data were plotted over time (days) to describe LAI recovery and forage accumulation rates. As the defoliation intensity increased, greater canopy heights were needed for pastures to achieve their maximum forage accumulation rates, which required longer regrowth intervals. The need for high tiller recruitment after defoliation, which delayed canopy LAI recovery, seemed to be one of the main cause. Thus, grazing management strategies that involve costly tiller recruitment could decrease both overall forage production and sward persistence over time. However, the plant ability to recover LAI after successive intense defoliations seems to be species-dependent and related to their phenotypic plasticity.

Principal component analysis of steers performance and structural and nutritional characteristics of Mombasa grass

ABSTRACT: There is little information about whether the increased secondary productivity observed in pastures fertilized with high nitrogen rates is attributable to fluctuations in the nutritional value or pasture structural characteristics, or both. This study aimed to identify a set of factors (structural and nutritional characteristics) that best explain the performance of beef steers grazing Mombasa grass pastures under residual effects of nitrogen fertilizer. The data were collected in Mombasa grass pastures fertilized with increasing rates of nitrogen (N) (100, 200 and 300 kg ha-1) from 2015 to 2017. In 2018, nitrogen fertilization was not used in order to characterize a residual effect of the nutrient. Variables related to pasture structural characteristics such as forage accumulation rate (FAR), canopy height, forage mass (FM) and morphological components were evaluated. The study also evaluated the nutritional value of leaf blades and the performance of beef steers based on average daily gain (ADG) and stocking rate. Principal component analysis was performed using the dataset available. Most of the variance (99.6%) was explained by only two principal components (PCs), of which 90.0% corresponded to PC1. The most influential parameters for PC1, in order of priority, were: FAR, FM, leaf blade and stem masses. These variables were positively associated with stocking rate. Conversely, ADG was not associated with any variable. ADG was the most relevant variable for the second PC; however, this PC explained less variance (9.6%). The structural characteristics of the pasture (FAR, FM and morphological components mass) better explain the fluctuations in the performance of cattle on pastures of Mombasa grass under residual effects of nitrogen fertilizer. The stocking rate is an efficient parameter to support decision-making in managed pastures with variable stocking.

Does the residual effect of n-fertilization applied on corn phase maintain forage production of the following pasture phase in an integrated crop-livestock system?

Nutrient cycling represents an important nutrient source in the Integrated Crop-Livestock Systems (ICLS). In general, only the crop phase of the ICLS is fertilized, however little is known about this residual effect of nitrogen fertilization from summer crop to succeeding winter pasture. This research aimed to evaluate the forage growth dynamic and botanical composition of a mixed pasture of black oat (Avena strigosa Schreb) and ryegrass (Lolium multiflorum Lam.) affected by two canopy height managements (high and low) and nitrogen fertilization applied to either the summer crop (corn) or winter pasture phase of an ICLS. The experiment was established in 2012 in southern Brazil. Black oat and ryegrass were growing during winter season and corn (Zea mays L.) during summer season, being this paper related to the 2014 pasture period. Treatments were composed by two canopy heights (25 and 10 cm) and two N-Fertilization Times (N-Pasture or N-Corn) of 200 kg of N ha-1. Canopy height was regulated by beef steers grazing through continuous stocking with a variable stocking rate. Forage mass was lower in the 10 cm canopy height on average, however this forage mass was composed by greater proportion of ryegrass leaves and lower proportion of dead material in relation to the treatment with 25 cm canopy height. The N-fertilization applied directly on pasture phase (N-Pasture) increased forage mass, tiller population density, participation of ryegrass and ryegrass leaf proportion in the forage mass. Furthermore, when pasture was fertilized with N, the forage accumulation rate increased about 69%, highlighting that the corn N-fertilization did not present significant effect on forage productivity. The residual effect of corn N-fertilization was not enough to maintain high forage accumulation. Thus, the pasture N-fertilization is fundamental to keep high-productive crop-livestock system.

Effects of increasing nitrogen levels in Mombasa grass on pasture characteristics, chemical composition, and beef cattle performance in the humid tropics of the Amazon.

Improving beef cattle production in pasture-based systems without expanding agricultural land has been the focus of several studies over the last decades. Nitrogen fertilization is one of the available strategies with high potential to optimize cattle performance in tropical systems. This study aimed to evaluate the effects of increasing nitrogen levels (150, 300, and 450kgha-1 of Nyear-1) in Megathyrsus maximus cv. Mombasa in the humid tropics of the Amazon. The following parameters were evaluated: pasture agronomic characteristics, herbage chemical composition, and beef cattle performance. A total of 24 nine-month-old Nellore bulls with initial mean weight of 173 ± 1.95kg were used for the performance test. The experimental design was a randomized block with three treatments. Herbage mass and leaf mass contents were increased by the highest nitrogen level (P < 0.05). Nitrogen levels elevated the forage accumulation rate, final leaf blade length, and pre-grazing canopy height(P < 0.05). The crude protein content increased at the highest N level (P < 0.05). The neutral detergent fiber and acid detergent fiber contents decreased with increasing N levels. The stocking rate and total weight gain per hectare were higher in bulls grazing pastures fertilized with 450 compared with 150kgha-1 of Nyear-1(P < 0.05). The average daily gain was influenced by N levels (P < 0.05). Nitrogen levels at 300 and 450kg increased animal weight gain and productivity per area by increasing forage yield and improving the chemical composition of Mombasa grass.

Physiological responses and forage accumulation of Marandu palisadegrass and Mombaça guineagrass to nitrogen fertilizer in the Brazilian forage‐based systems

AbstractIn Brazil, the livestock systems are mainly forage‐based, and nitrogen inputs are an uncommon practice, despite its great benefits. The objective was to evaluate the effect of nitrogen input on the physiological responses of Marandu palisadegrass (Urochloa brizantha [Hochst. ex A. Rich.] R. D. Webster) and Mombaça guineagrass (Megathyrsus maximus [Jacq.] B. K. Simon &amp; S. W. L. Jacobs), and its impacts on the forage accumulation rate (FAR). The experiment was carried out in Sinop, MT, Brazil, in a randomized block design with a 2 × 2 × 5 factorial arrangement (two cultivars: Mombaça and Marandu; unfertilized and fertilized [50 kg N ha−1 cycle−1]; and five seasons: autumn 2015, winter 2015, spring 2015, summer 2015 and autumn 2016) with three replicates. The experimental period was from March 2015 to June 2016, when plots were harvested to mimic intermittent stocking. Fertilized Mombaça presented greater FAR pastures (74.0 kg DM ha−1 day−1) than unfertilized (26.6 kg DM ha−1 day−1) and Marandu fertilized (52.5 kg DM ha−1 day−1), with the greatest values during the summer (147.6 kg DM ha−1 day−1). The greatest leaf (A) and canopy photosynthesis (CP) rates occurred on fertilized pastures during the summer 2015 and autumn 2015. Marandu presented 19% greater A than Mombaça. During the winter, under water stress, Marandu had greater water use efficiency (WUE). However, during the summer 2015 and autumn 16, Mombaça had the greatest WUE (12.76 μmol CO2/mol H2O). In all seasons, Marandu presented the greatest chlorophyll index, which may support the greatest photosynthetic rates. It was concluded that Mombaça was highly responsive to nitrogen input during the rainy season with accumulation over 140 kg DM ha−1 day−1 and is recommended to intensified systems. Marandu had the greatest WUE in the lower precipitation seasons and is an alternative to a year‐round strategy in forage‐based systems.