Katambora Rhodes Grass Research Articles

Replacement series studies of competition between tropical perennial and annual grasses and perennial grass mixtures in northern New South Wales

Seedlings of three perennial tropical grasses, Chloris gayana cv. Katambora (Rhodes grass), Panicum coloratum var. makarikariense cv. Bambatsi (panic grass), and Digitaria eriantha ssp. eriantha cv. Premier (digit grass), were each grown in replacement series mixtures with seedlings of the annual summer-growing grass weeds Urochloa panicoides (liverseed grass) and Echinochloa colona (awnless barnyard grass). A separate experiment examined the competitiveness of seedlings of the three perennial tropical grasses when two species were sown together. Plants were sown 50 mm apart in boxes at a density of 307 plants/m2. Maximum likelihood estimates were used to derive parameters of a non-linear competition model using the dry weights of perennial and annual grasses. Seedlings of the summer-growing annual liverseed grass competed aggressively with those of the tropical perennial Katambora Rhodes grass. However, Bambatsi panic seedlings were equally competitive with those of awnless barnyard grass, while those in a Premier digit-barnyard grass mixture were inhibited by the presence of each other. In the perennial grass mixtures study, the performance of both Premier digit and Bambatsi panic was adversely affected by the presence of Katambora Rhodes grass.

Establishment and persistence of perennial grass and herb cultivars and lines in a recharge area, North-West Slopes, New South Wales

Two adjacent sites, one previously cropped and the other a native pasture, were sown with perennial temperate and tropical grasses and herbs (Expt 1), Phalaris aquatica (phalaris) and Festuca arundinacea (tall fescue) cultivars or lines (Expt 2), and perennial tropical grasses (Expt 3) near Manilla, NSW. Establishment, herbage mass and plant frequency were assessed in 2003–06 to (i) identify cultivars/lines with superior persistence, (ii) detect possible mechanisms required for successful production and persistence in a summer-dominant rainfall environment, and (iii) examine the comparative performance of the species groups when sown into previously cropped and native pasture areas. Plots were fertilised annually and grazed or mown at least seasonally. Most cultivars/lines persisted at the previously cropped site, while those on the native pasture site had to be resown and generally failed to persist beyond the first year. At the previously cropped site, summer-dormant tall fescue cv. Resolute MaxP® was the most persistent of the grasses evaluated in Expt 1. Grasses such as Lolium perenne cv. Avalon and Bromus stamineus cv. Gala did not perenneate, but regenerated annually from seed. Native grasses generally had poor establishment; however, Austrodanthonia richardsonii and A. fulva tended to increase in plant frequency over time. Chloris gayana (Rhodes grass) cv. Katambora and Panicum maximum (panic) cv. Gatton were the only tropical grasses that established in Expt 1, and both had plant frequencies similar (P > 0.05) to the temperate grasses at the final assessment. In Expt 2, Resolute MaxP again was the most persistent cultivar/line. Several experimental lines of phalaris (e.g. T39 and M225) had high herbage mass and good persistence compared with commercial cultivars. In Expt 3, Katambora Rhodes grass and Digitaria eriantha ssp. eriantha (digit grass) cv. Premier were the most persistent cultivars and had the highest herbage mass. These data highlighted summer dormancy in temperate grasses and frost tolerance in tropical grasses as two possible mechanisms important for persistence of grasses on the North-West Slopes of NSW and the risks associated with sowing perennial grasses into established native pastures.

In vitro digestibility using caecal liquor of diets containing poor quality roughages and green forages fed to domesticated ostriches ( Struthio camelus var. domesticus)

The objective of this study was to compare in vitro organic matter digestibility (IVOMD) of ostrich diets using the normal (NTT) and reverse (RTT) modified Tilley and Terry methods of in vitro digestion. The IVOMD values of green forages were determined using the RTT method only. Four ostrich diets and four green forages were digested in vitro using caecal liquor collected from ostriches slaughtered at the Norton Commercial ostrich producers (Copro) abattoir. The diets included a control diet of a concentrate and legume hay, silverleaf desmodium uncinatum (CN), and the three others consisting of a concentrate with either veld hay (VH), Katambora Rhodes grass hay (RG) or maize stover (MS). Lucerne (LU), Midmar Rye grass (MRG), Russian Comfrey (RC) and Kenyan White clover (KWC) were the green forages used. The forages were grown under the recommended management levels and were cut before flowering. There was no interaction ( P>0.05) between diet and method of digestion. The RTT gave higher ( P<0.01) IVOMD than the NTT method. However, both methods showed a similar trend in the digestion of the diets. The MS and RG diets had similar and greater ( P<0.05) IVOMD than the control and veld hay diets. The amounts of organic matter (OM) digested differed ( P<0.01) with either diet or forage type. Kenyan White clover and MRG had similar and greater ( P<0.05) IVOMD than LU and RC, which were not different ( P>0.05). The values of IVOMD in dry matter for the forages were: MRG > KWC > LU > RC, and all the differences were significant ( P<0.05). The study showed that the NTT method needs to be modified to suit hind gut fermenters and IVOMD can, therefore, be used to rank the nutritive value of ostrich feeds.

Effects of Acacia nilotica and Acacia karoo diets on Haemonchus contortus infection in goats

This study was carried out to determine the effects of Acacia karoo and Acacia nilotica diets on Haemonchus contortus infections in goats. Twenty-four Boer goats of mixed sex (live weight 17–22 kg) were randomly assigned to four treatment groups, namely: A. nilotica (AN) group, A. karoo (AK) group, control infected with H. contortus (HC) group and the non-infected control (NHC) group. Animals in the AN, AK and HC groups were orally infected with a single dose of 3000 HC third stage larvae. The AN and AK groups had dried leaves of AN and AK, respectively, included in their basal diet at a rate of 40% dry matter (DM) while the HC and NHC groups had the basal diet throughout the experiment. All animals received a total feed allowance of 500 g DM per day and Katambora Rhodes grass hay ad libitum for roughage. Parameters measured included faecal egg counts and live weight. At the end of the experiment, three animals from each group were slaughtered and abomasal worm burdens were determined. A significant decrease in the faecal egg counts was recorded in animals in the AK group ( P<0.05) relative to those in the AN and HC groups. The worm burdens were reduced by 34% in the AK group ( P<0.05) and by 10% in the AN group (non-significant) relative to the infected control group. The study indicates that the difference in the effects of the two forages on HC infections may be related to type and concentration of tannins.

Degradability and flow rate studies in sheep fed a basal diet of Katambora Rhodes grass hay (Chloris gayana), supplemented with Silverleaf desmodium (Desmodium uncinatum)

Degradability and flow rate studies in sheep fed a basal diet of Katambora Rhodes grass hay (Chloris gayana), supplemented with Silverleaf desmodium (Desmodium uncinatum)

Degradability and flow rate studies in sheep fed a basal diet of Katambora Rhodes grass hay (Chloris gayana), supplemented with Silverleaf desmodium (Desmodium uncinatum)

Degradability and flow rate studies in sheep fed a basal diet of Katambora Rhodes grass hay (Chloris gayana), supplemented with Silverleaf desmodium (Desmodium uncinatum)

Digestibility and nitrogen balance in goats given different levels of crushed whole soybeans

Sixteen growing male castrate indigenous goats (20 months old, average liveweight 17±4.5 kg) were divided into four groups of four goats each and fed diets based on Katambora Rhodes Grass ( Chloris gayana) hay and maize containing either 0, 11, 22 or 33% crushed whole soybean (diets I, II, III and IV, respectively) for 30 d of which 23 were adjustment days and 7 d collection period. Apparent nutrient digestibility and nitrogen balance were determined from d 24 to 30. Digestibility of crude fibre was less ( P < 0.05) for goats fed diets III and IV than for those fed diets I and II. This effect appeared to be related to the percentage of soybean (crude fat) in the diets. Digestibility of crude fat rose as percentage soybean increased, with diet IV having a greater ( P<0.05) crude fat digestion coefficient than the other three diets. Apparent digestibility of crude protein was greater ( P<0.05) with diets III and IV, than with diets I and II. Nitrogen balance was positive in all four groups and increased as the percentage of soybean in the diet increased.

Tiller dynamics and growth of Rhodes grass after defoliation: A model named TILDYN

The dynamics in tiller population and dry-matter accumulation of a grass sward, cut at different time intervals, was compared with a descriptive simulation model. The model was validated against experimental data of tiller number, and dry-matter accumulation for irrigated cv. Katambora Rhodes grass ( Chloris gayana Kunth), cut at intervals of 1, 2, 3 or 4 weeks. The model predicted that the initial rate of regrowth following long cutting intervals was much slower than the regrowth following short cutting intervals. The simulations also showed that relatively high dry-matter yields alternated with relatively low dry-matter yields when the interval between cuttings was long. These results were in reasonable agreement with the measured values. The fluctuation in the number of tillers and dry-matter yield was attributed mainly to the formation of culmed-vegetative tillers, common to Rhodes grass at an early stage of development, which renders them incapable of regrowth after defoliation.