Stylosanthes Scabra Cv Research Articles

Responses of selected tropical forage legumes to imposed drought

Drought tolerance is an important attribute for the establishment of forage legumes in the rangelands of the seasonal semi-arid tropics. This experiment examined the seedling rooting depth, plant biomass, and other growth parameters of 5 perennial tropical legumes in response to different watering and drying regimes. Centrosema brasilianum cv. Oolloo and Macroptilium bracteatum (CPI 55770) produced deeper roots, greater root biomass, and more root nodules than Stylosanthes scabra cv. Seca and Desmanthus virgatus (CPI 79653), however only D. virgatus produced deeper roots and increased biomass in response to the drought treatment. Arachis triseminalis (CPI 91423), C. brasilianum and M. bracteatum flowered during the 9-week course of the experiment, with the latter two species producing pods. Seca, A. triseminalis and D. virgatus show adaptations of drought-tolerance, whilst C. brasilianum and M. bracteatum are adapted to drought avoidance.

Evaluation of forage legumes for introduction into natural pastures of semi‐arid rangelands of Kenya

AbstractTo address the potential of legumes to contribute to improved quality and quantity of natural pastures in the semi‐arid rangelands of Kenya, five legume species were introduced and evaluated in a small‐plot field experiment over three growing seasons. The investigated species were glycine (Neonotonia wightii), siratro (Macroptilium atropurpureum), dolichos (Lablab purpureus cv. Rongai), velvet bean (Mucuna pruriens) and shrubby stylo (Stylosanthes scabra cv. seca). Treatments included two cutting heights (ground level and 15 cm) and two cutting intervals (at 2 and 4 months). The mean dry matter (DM) yields of glycine and siratro were highest when the legumes were harvested at ground level at 2‐month intervals (10·31 and 7·81 t ha−1 year−1 respectively). Mean DM yield of stylo was highest when the legume was harvested at 15 cm after 4 months (3·52 t ha−1 year−1). These three legumes also produced high organic matter through litter fall, which contributed to soil fertility. Evidence from a supporting pot experiment showed effective nodulation and potential for N fixation. These legumes also possessed deep tap roots and withstood heavy defoliation. These three legumes were selected for further integration with grasses in natural pastures. The DM yields of dolichos and velvet bean when harvested at 15 cm after 2 or 4 months were low (2·48 and 1·91 t ha−1 year−1), and these species were considered inappropriate for further investigation.

Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 2. Population dynamics of Heteropogon contortus and Stylosanthes scabra cv. Seca

The dynamics of Heteropogon contortus and Stylosanthes scabra cv. Seca populations were studied in a subset of treatments in an extensive grazing study conducted in central Queensland between 1988 and 2001. These treatments were 4 stocking rates in native pasture and 2 of these stocking rates in legume oversown and supplement/spring burning treatments. For the 1999–2000 summer, population data for H. contortus in 5 of these native pasture and supplement/burning treatments were compared with those for an additional burnt treatment. Seasonal rainfall throughout this study was below the long-term mean and mean annual pasture utilisation ranged from 24 to 61%. Increasing stocking rate from 5 to 2 ha/steer in native pasture reduced H. contortus plant density. Increasing stocking rate reduced seedling recruitment as a result of its effect on soil seedbanks. Seedling recruitment was the major determinant of change in plant density, although some individual H. contortus plants did survive throughout the study. Burning in spring 1999, particularly at light stocking rate, promoted seedling recruitment above that in both unburnt native and legume oversown pasture and resulted in increased H. contortus plant density. In the legume oversown treatments, S. scabra cv. Seca density increased rapidly from 15 plants/m2 in 1988 to 140 plants/m2 in 2001 following a lag phase between 1988 and 1993. This increased S. scabra density was associated with an eventual decline in H. contortus plant density through reduced seedling recruitment. It was concluded that H. contortus population density is sustainable at stocking rates of 4 and 5 ha/steer (30% pasture utilisation) and that spring burning at light stocking rate can promote H. contortus populations. Increasing densities of S. scabra need to be managed to prevent its dominance.

Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 1. Pasture yield and composition

An extensive grazing study was conducted between 1988 and 2001 in a Heteropogon contortus (black speargrass) pasture in central Queensland. The study was designed to measure the effects of stocking rate on native pasture, native pasture with legume oversown, and native pasture with animal diet supplement/spring burning on pasture and animal production. Summer rainfall throughout the study was below the long-term mean. Mean annual pasture utilisation ranged from 13% at 8 ha/steer up to 61% at 2 ha/steer. Increasing stocking rate treatments reduced total pasture yields while total yields in legume oversown treatments were similar to those in native pasture at the same stocking rate. When spring burning was possible, total yields were reduced in the subsequent autumn. Increasing stocking rate in native pasture tended to reduce H. contortus and Bothriochloa bladhii, increased the composition of intermediate species, such as B. decipiens and Chloris divaricata, and also changed the frequencies of a range of minor species. Oversowing legumes resulted in Stylosanthes scabra cv. Seca increasing from <1% of pasture composition in 1988 to 50% in 2000 and was associated with a reduction in H. contortus and changes in the frequencies of some minor species. Stocking rates heavier than 4 ha/steer resulted in annual pasture utilisation greater than 30% and were unsustainable because they reduced total yield and resulted in undesirable changes in species composition. It was concluded that pasture production was sustainable when stocking rates were maintained at 4 ha/steer, which equates to 30% annual pasture utilisation, and through the judicious use of spring burning.

Assessment of Stylosanthes seed yield reduction caused by phytoplasma-associated diseases

The effect of Stylosanthes little leaf disease on Stylosanthes scabra cv. Seca seed yield was monitored over 2 consecutive seasons at Southedge Research Station in northern Queensland. The time of initial symptom expression was recorded during weekly assessments to determine what effect time of infection after planting had on seed yield. First flowering date was recorded to establish whether the developmental stage of the plant, as indicated by the onset of reproductive activity, at the time of symptom expression influenced the effect of Stylosanthes little leaf disease on yield. At the end of each season, both diseased and asymptomatic plants were harvested and seed yield determined. Seed yield data from the 1999 season showed that there was no significant difference between the mean yield of symptomatic plants, regardless of when they first showed symptoms, and that of asymptomatic plants. However, during the 2000 season plants that showed symptoms early in the season had a significantly lower seed yield than both asymptomatic plants and plants that became diseased later in the season. This decrease in productivity amounted to a yield loss of 98.8 and 56.5% when the plants showed symptoms at 79�and 110 days, respectively, after planting. If plants became diseased within 30 days of first flowering, they did not produce significant amounts of seed. Yield remained low even when the time between first flowering and initial symptom expression increased up to 60 days, after which yield was extremely variable but within the range of that observed for individual asymptomatic plants. It is concluded that Stylosanthes little leaf disease has little or no effect on seed yield if plants have been flowering for about 8 weeks before symptom expression.

Pasture yield and composition changes in a Central Queensland black speargrass (Heteropogon contortus) pasture in relation to grazing management options

A grazing study commenced in 1988 at Calliope, Central Queensland, measured the effects of stocking rate, legume over-sowing and animal diet supplements/burning on pasture and animal production in a native black speargrass (Heteropogon contortus) pasture. This paper reflects on changes in yield and pasture composition between 1988 and 1996, during which time the seasonal rainfall was below average. At the pasture community scale, the highest stocking rate of 1 steer/2 ha reduced pasture yield but had little impact on pasture composition. The frequency of H. contortus showed no clear differences due to stocking rate although there was a slight overall trend for it to decline with time. The frequency of increaser species such asChloris divaricata was highest at the highest stocking rate. At the individual plant scale, the density of H. contortus plants declined at high stocking rate. The proportion of the sown legume Stylosanthes scabra cv. Seca increased with time reaching a density of 15 plants/m 2 and contributing 33% to the total yield in the legume treatments. Burning has reduced the occurrence of H. contortus compared with that in unburnt native pasture and this may be due to the stocking rates being too high following the fire. These results indicate the stability of pasture composition across a 4-fold range of stocking rates from 1988 to 1996. This study needs to continue, at least through a period of above average rainfall, to determine further effects of stocking rate and pasture type on pasture composition.

Promising tropical grasses and legumes as feed resources in Central Tanzania: VI. Nitrogen balance in growing bulls consuming tropical herbaceous forage legumes

Nitrogen balance was measured in six growing Mpwapwa bulls (mean age 1.5 years, weight 131 kg) fed Cenchrus ciliaris hay and cassava as basal diet (negative control) supplemented with dried leaves from four herbaceous legumes: Macrotyloma axillare cv. Archer (MAA), Stylosanthes scabra cv. Seca (SSS) and Neonotonia wightii cv. Mpwapwa (NWM); or with Fish meal (FM) as positive control in a 6×6 Latin square design. All treatments with protein were formulated to provide the same energy and protein levels of intake. The digestible organic matter intakes were 13.9, 13.6, 14.2, 13.8 and 13.6 g per kg body weight (BW) per day in treatments supplemented with MAA, SSS, FM and NWM respectively and these were similar ( P>0.05) but significantly higher ( P<0.05) compared to the negative control. The crude protein contents of the DM consumed ranged from 8.6 to 9.5% among the supplemented diets and these were higher than the unsupplemented treatment of only 3.9%. Nitrogen intake, faecal nitrogen output, urinary nitrogen output and nitrogen balance were significantly higher ( P<0.001) in the supplemented diets compared with the negative control. For the negative control treatment, nitrogen balance was 0.09 g per kg W 0.75 whereas N balance ranged from 0.19–0.32 g per kg W 0.75 in the other treatments. The ranking was: FM>SSS>MAS>MAA>NWM but they were not significantly different from each other. Only when calculated as percent N retained, was FM superior to NWM ( P<0.05). It is concluded that using leaves from these legumes as protein supplements will have an effect on N balance in growing Mpwapwa bulls comparable to fish meal.

Promising tropical grasses and legumes as feed resources in Central Tanzania IV. Effect of feeding level on digestibility and voluntary intake of four herbaceous legumes by sheep

An experiment involving comparison of 4 legumes fed at 5 levels was conducted to study the effect of the level of feeding on digestibility and voluntary intake by Blackhead persian rams. The legumes were Neonotonia wightii cv. Mpwapwa (NWM), Stylosanthes scabra cv. Seca (SSS), Macrotyloma axillare cv. Archer (MAA) and Macroptilium atropurpureum cv. Siratro (MAS). The forages were cut at 8 weeks and dried in the sun. Sixteen sheep were used and fed 600, 900, 1200, 1500 and 1800 g/day in a split plot design. Among the species compared, SSS and NWM had higher ( P < 0.05) organic matter (OM) digestibility than MAA and MAS. Differences in intakes among species were observed, with MAS having lower OM intakes ( P < 0.05) than the other species. Increasing feeding level allowed the selection of more leafy diet with significant improvement ( P < 0.05) in OMD in SSS, and MAA, but not of MAS and NWM. Significant improvement ( P < 0.05) in intakes of OM and digestible OM were observed in all species, as feeding level was raised from 600–1800 g per day, to allow for the selection. The level of feeding allowing maximum intakes of OM with the least refusal was, on the average, 1200 g with 19.6% refusals, ranging from 900 g per day with refusals of 10.3% for MAS, to 1500 g per day with refusals of 29.4% for SSS. The maximum OM intakes were 20.5 g kgW −1 d −1 and 25.5 g/kg BW/day for MAS and SSS, respectively. Estimated maximum intake at infinite feeding level was, on the average, 26 g/kg BW/day. A realistic value for SSS could not be obtained, but was, probably, considerably higher than that for the others. To obtain a maximum value for animal production, refusals of approximately 40% would be required. Among the legumes studied, SSS seems to be the most promising species for the semiarid areas of Central Tanzania.

Transpiration effciency and its relationship with carbon isotope discrimination under well-watered and water-stressed conditions in Stylosanthes scabra

Stylosanthes scabra cv. Seca is a widely sown tropical pasture legume in northern Australia and has a high degree of drought resistance. Identification of traits contributing to the drought resistance of Seca may be valuable for use in breeding programs. Transpiration efficiency (TE) has been suggested as one such trait contributing to drought resistance. Carbon isotope discrimination (Δ) has been proposed for estimating TE indirectly in C3 plants. A glasshouse experiment was conducted using 8 accessions of S. scabra to identify whether Seca differs in TE from other accessions of S. scabra and to determine the relationship between TE and Δ under both well-watered and water-stressed treatments. Seca maintained the highest TE (lowest Δ) under both control and stress treatments, and leaf Δ was significantly and negatively correlated with TE under both control and stress conditions. A significant and negative relationship was found between Δ and dry matter production under stress treatment. The interaction between accession and watering treatment was not significant for either TE or Δ. We also found a signirficant agreement between the performance in the field and in the laboratory for these 8 accessions. These results indicate that TE could be one of the significant factors contributing to drought resistance of Seca. Furthermore, Δ and/or specific leaf area may be useful as selection criteria in breeding programs to identify the lines with high TE.

Promising tropical grasses and legumes as feed resources in Central Tanzania V. Effect of supplementing Cenchrus ciliaris hay with leaves from four legumes on intake and digestibility by growing Mpwapwa bulls

In Trial 1, six growing Mpwapwa bulls (mean age 1.5 years, mean body weight 158 kg) were used in a 6 × 6 Latin square design to study the effect on intake and digestion of supplementing Cenchrus ciliaris cv. Kongwa hay with four different legume leaf proteins. Hay alone and fish meal (FM) treatments were included as negative and positive control treatments, respectively. The grass hay was fed allowing above 40% refusal to maximize selectivity and contained 5.1% crude protein (CP), 76.1% neutral detergent fibre (NDF), 9.9% lignin and 3.1% silica. The protein sources were dried leaves of Macroptilium atropurpureum cv. Siratro (MAS), Macrotyloma axillare (MAA), Neonotonia wightii cv. Mpwapwa (NWM), Stylosanthes scabra cv. Seca (SSS) and FM. The protein sources were fed aiming at supplying approximately 150 g CP/day. The legume CP contents varied from 18.6–20.6% and the FM contained 54.7%. In Trial 2 in a completely randomised block design, 8 bulls were used to measure the digestibility of the legumes alone. Selective feeding resulted in consumption of hay containing 6.2% CP. The apparent digestibility of organic matter (OM) and NDF were 58.3 and 62.5%, respectively. Supplementing the hay resulted in intake of a diet with CP ranging from 8.0–8.5%. Despite the increased CP intake, neither the digestibility of OM nor NDF increased significantly, implying that the protein was not a first limiting factor for fibre digestion. The grass hay OM intakes varied between 21.0 and 22.2 g/kg body weight (BW) per day (77.3–86.0 g/kg BW 0.75/d) and were not improved by protein supplementation. Significant improvements ( P < 0.001) in daily intakes of total OM and CP were observed by supplementation, although total NDF was not improved. All protein supplements except MAS improved ( P < 0.05) digestible OM intakes compared to the unsupplemented hay. Calculated digestible and metabolizable energy values for the diets were not improved by supplementation. However, an improvement in total energy and protein intake may be obtained as a result of supplementation. It is concluded that it is beneficial to use MAA, NWM, SSS and also FM in C. ciliaris-based diets to improve total intake of CP by growing bulls. Total intake of OM and digestible OM may also be improved, but the levels are only on the order of 10%. The use of legume supplements and allowing ample feed refusals may result in an estimated daily BW gain of 200–400 g.

The Relationship between Anthracnose Severity and Populations of Bacteria on the Phylloplane of the Tropical Pasture Legume Stylosanthes Scabra

Populations of gram-negative bacteria, spore-forming bacilli, pseudomonads, and total bacteria were monitored on leaves of the tropical pasture legume Stylosanthes scabra cv. Fitzroy showing different severity levels of anthracnose caused by Colletotrichum gloeosporioides . Leaves were either disease-free or were grouped on the basis of percentage of leaf area visibly diseased into low-, moderate-, and high-severity classes. Data on bacterial populations, collected on nine different occasions during a growing season, were analyzed with the population estimates as dependent variables and anthracnose severity class as the treatment. Meteorological variables were summarized using the maximum likelihood factor analysis and used as covariates. Of the three bacterial groups, only the spore-forming bacilli showed a statistically significant negative relationship between their population density and anthracnose severity. Total bacterial populations were assessed independently and also tended to rise with increasing disease severity. This suggested a possible antagonism of spore forming bacilli toward the anthracnose pathogen. A simple in vitro method for differentiating modes of antagonism was developed. Twenty-four bacterial isolates collected from the leaf surface were tested using this method; of these, 19 showed a degree of antagonism. The method proved incapable of differentiating between modes of antagonism. Further work is necessary to establish the nature and effectiveness of this putative antagonism.

Survival of Colletotrichum gloeosporioides on Stylosanthes scabra cv. Fitzroy during the dry season

Infected stems of the tropical pasture legume Stylosanthes scabra cv. Fitzroy were assessed over two consecutive dry seasons to determine if Colletotrichum gloeosporioides survived as conidia on lesions formed during the previous wet season or as hyphae within infected tissue. In the second season, infected stem pieces placed on the soil surface (debris) and in a 15�C incubator at the beginning of the dry season were assessed in addition to the material from living plants. Infective conidia were present in sufficient numbers to be detected in all but the initial sample in each season, and C. gloeosporioides could be isolated from lesions on plant tissue throughout both dry seasons. Conidium density on live stems was variable in the first season, where no rain fell until the onset of the wet season in mid-November. Conidia were present in similar densities on stems throughout the second dry season, when intermittent light rain fell during the assessment period. The mean density of conidia was significantly higher on live stems than on debris or stems stored at 15�C. Large numbers of conidia were produced on stem pieces from living plants and debris after incubation under conditions conducive to sporulation. Conidia were, therefore, present or could be rapidly produced to initiate an epidemic once favourable conditions for dispersal and infection occurred.

Seasonal nutrient intake and phosphorus kinetics of grazing steers in northern Australia

The growth of Bos indicus cross-steers grazing native grass and native grass-legume (Stylosanthes scabra cv. Seca) pastures was monitored for 392 days in five unreplicated experimental paddocks, each grazed by three steers. Two phosphorus (P) fertilizer rates: F1, 4-5 kgP/ha every 2 years and F2, 9.0 kgP/ha annually, together with an unfertilized control, FO, were studied. P supplement was supplied to cattle in two additional paddocks (FOS and F1S) at the rate of 5 gP/ha/day-l. In the dry, wet and late wet seasons, pasture yield and pasture component yield were measured. At the same time, the nutrient intake and P kinetics of resident steers were measured using chromic oxide capsules and intravenous injections of 32P . Additional non-resident steers, fistulated at the oesophagus, grazed the pastures intermittently to provide estimates of dry matter digestibility, fibre, nitrogen (N) and P content of the selected diet. Phosphorus fertilizer increased legume and native grass growth which resulted in more dry matter containing higher concentrations of P and N than unfertilized pastures. Both P fertilizer and supplement increased dry matter intake and liveweight gain of cattle. During the experimental period of 13 months, steers which grazed pastures that received the (F2) fertilizer treatment gained on average 0.43 kg/day compared with 0.19 kg/day for those which grazed unfertilized FO pastures. Supplementation increased wet season liveweight gain from 0.45 to 0.59 kg/day and 0.46 to 0.73 kg/day for FO and F1 treatments respectively. Only cattle which grazed pastures that received the F1S and F2 treatments gained weight in the dry season. Nitrogen was the primary nutrient limiting cattle growth from unfertilized pastures in the dry season, but when pastures were fertilized (4.5 kgP/ha every 2 years) and legumes established, P was the primary limiting nutrient. Intakes of P ranged from 7 to 35 mg/kg LW and were lower than those recommended by recognized authorities for the steer growth rates we recorded. Both the absorption and faecal excretion of dietary P were closely related to P intake. Endogenous faecal P values varied with P intake in the range 9-22 mg/kg liveweight. Endogenous faecal P was also related to dry matter intake and plasma inorganic P. The coefficient of P absorption was lowest (0.65) for steers grazing unfertilized native pasture (FO), but increased with P intake to 0.85 for steers grazing the F1S treatment. We conclude that the P requirements of growing cattle grazing native grass and native grass-legume pastures in northern Australia are about half those recommended by most authorities.

Residual effects of phosphorus fertiliser in a stylo-native grass pasture on a duplex red earth soil in the semi-arid tropics of North Queensland

A field experiment was established to define the phosphorus (P) requirement for establishment and maintenance of a mixed legume pasture (Stylosanthes scabra cv. Seca, S. hamata cv. Verano, S. guianensis cv. Graham, Macroptilium atropurpureum cv. Siratro) introduced into a native grass pasture on an infertile duplex red earth. Rates of 0, 5, 10, 20, and 40 kg P/ha were applied to separate plots in year 1 (1982), 2, and 3. In year 5 (1986 growing season), half of each plot that had received 20 and 40 kg P/ha in year 3 was refertilised at the original rate to ensure that maximum yields were defined. Bicarbonate- or acid-extractable soil P concentrations of 8 mg/kg were sufficient for 80% maximum legume yield. The residual value of applied P in the surface soil, as measured by soil analysis, decreased exponentially, but an initial application of 40 kg P/ha was still sufficient to produce near-maximum legume yield after 5 years. Phosphorus application increased the dry matter yield of legume. During the establishment phase (years 1 and 2 after planting) yields reached maximum at 10 and 20 kg P/ha, respectively, but increased linearly in subsequent years. When the original rates were reapplied in year 5, peak yield occurred at 20 + 20 kg P/ha, and there was no difference between this yield and that from plots receiving 40 kg P/ha in year 1. Native grass yields increased with P application only in years 4 and 5 of the experiment. Stylos demonstrated good tolerance to low P supply. In year 1, 80% of the total legume yield consisted of Graham stylo and Siratro, whereas in subsequent years, Seca and Verano made up 70 and 20%, respectively, of the total, irrespective of treatment. Yield of legume at nil P, relative to maximum, increased from 5% in year 1 to 42% in year 5.

Effect of superphosphate application on macro-nutrient and micro-nutrient concentrations in grazed stylo-native grass pasture in tropical Australia

Soils of northern Australia are generally old, strongly weathered, and of low fertility status. Some knowledge of the status of nitrogen, phosphorus and sulfur and its effects on pasture productivity is available from small plot trials, but few detailed studies of macro-nutrient and micro-nutrient levels in grazed pastures have been reported. Such a study from a site near Mareeba in north Queensland has recently been completed. The major components of the pasture were kangaroo grass ( Themeda triandra), giant speargrass (Heteropogon triticeus) and the legumes, Stylosanthes scabra cv. Seca and S. hamata cv. Verano, which were oversown into the native grass pasture 6 years previously. Generally, the effects of superphosphate on nutrient concentration were minor compared with the effects of season, plant part and species. Superphosphate application increased concentrations of P and S, but decreased concentrations of Zn and Mo and the N/S ratio in both sets of legume and grass. There was no effect on the concentrations of N, K, Na, Ca, Cu and Co. Fertilizer effects did not often interact significantly (P &lt; 0.05) with season, species and plant part (green leaf and stem). Seasonal changes in nutrient concentration were not consistent for all nutrients. As the growing season progressed from December to June, concentrations of the mobile nutrients, N, P, K, Na, Cl, S, Se and I decreased, the immobile nutrients Ca and Mo increased, but Mg, Cu and Co and the N/S ratio remained relatively constant. Both Zn and Mn concentrations remained constant with season in the legumes, but increased in the grasses. Season * species interactions were often significant for the grasses possibly due to the differing maturity patterns of kangaroo grass and giant spear grass. Cattle grazing the native pasture during the wet season are likely to be deficient in N, P, Na, S and Cu based on the nutrient concentrations in plucked pasture samples and published dietary requirements. However, cattle grazing productive stylo - native grass pasture which has received adequate single superphosphate are likely to suffer only from Na deficiency. At suboptimal levels of superphosphate, a deficiency of P in the diet is also indicated.