Chloris Gayana Cv Research Articles

Performance of Perennial Grass Species under Supplemental Irrigation

The study was conducted at Agricultural Research Centre with the objective of identifying the best-performing perennial grass species under supplemental irrigation and advising the promising cultivated fodder grass for smallholder livestock producers. Randomized Complete Block Design of six perennial grass species with three replications was employed. The six perennial grass species used were T1 (Brachiaria mutica_18659), T2 (Cynodon aethiopicus), T3 (Pennisetum sphacelatum), T4 (Brachiaria decumbense), T5 (Chloris gayana cv. Masaba), and T6 (Brachiaria mutica_6964). The result revealed that agronomic performance of cover, vigor, and height was varied (P<0.001) among perennial grass species. Furthermore, effects of cover (P<0.05), vigor (P<0.05) and height (P<0.001), and dry matter contents (P<0.05) of perennial species over years were found. The dry matter yields and contents of P. sphacelatum (22.85 ton ha-1 and 41.7%) followed by C. aethiopicus (12.53 ton ha-1 and 40.6%) of perennial grass species performed better (P<0.001) than others. The highest (P<0.001) dry matter yield (20.3 ton ha-1) was obtained during the second year of harvest than the first (12.65 ton ha-1) and third (11.36 ton ha-1) year harvests. Similarly, the highest (P<0.001) dry matter percent of the perennial grass species was also found during the second year harvest (50.1%) than the first (25.8%) and third (40.0%) year harvests. The lowest dry matter yield was recorded by C. gayana at the first year (8.5 ton ha-1) and third year (8 ton ha-1) harvests. Likewise, B. mutica_18659 provided the lowest dry matter yield (12.9 tons ha-1) during the second harvest period. Hence, smallholder farmers can preferably be advised to use P. sphacelatum and C. aethiopicus perennial grass fodder crops resources under supplemental irrigation.

Yield, Yield Components, and Nutritive Value of Perennial Forage Grass Grown under Supplementary Irrigation

There is a distinct seasonality in the availability of feeds in the highlands of Ethiopia, reaching a peak and low levels towards the end of the rainy and dry season, respectively. Consequently, this trial was conducted to assess the yield performance and nutritive value of nine perennial grasses accessions from seven grass species under supplementary irrigation to produce feed year-round. The evaluated grasses species were two Urochloa (U. decumbens cv. ILRI-10871 and ILRI-13205), two Setaria (S. sphacelata cv. ILRI-143 and ILRI-6543), one Phalaris (Phalaris aquatica cv. Sirrosa), coloured Guinea (Panicum coloratum cv. Coloratum), Desho (Pennisetum glaucifolium cv. Kindu kosha), Napier (Pennisetum purpureum cv, ILRI-16791), and Rhodes (Chloris gayana cv. Massaba) variety. The experiment was carried out in a randomized complete block design. The chemical compositions of the grasses were scanned by, the near infrared spectroscopy (NIRS). Results indicated that the plant height, dry matter, and crude protein yield were significantly affected by year, species ( P < 0.001 ), and their interaction ( P < 0.05 ). Moreover, species were significantly influenced in vitro dry matter digestible yield, relative feed value, and nutrient content (DM, CP, NDF, ADF, ADL, and IVDMD). Napier grass had superior in dry matter, crude protein, and in vitro dry matter digestible yield than the other perennial grasses species tested together. Thus, among the tested grasses species, Napier grass showed outstanding potential as a forage plant followed by Phalaris and Desho grass under supplementary irrigation in the central highland of Ethiopia.

Morphoecological characteristics of grasses used to restore degraded semi‐arid African rangelands

AbstractProgressive loss of productivity and plant diversity is a concern in global rangelands. In African rangelands, this process is partly attributed to heavy and uncontrolled grazing by livestock and wildlife, leading to land degradation. Therefore, restoring such degraded rangelands is critical for enhancing ecosystem health and securing the livelihoods of millions of people.Active restoration strategies, for example, reseeding using indigenous perennial grasses, have been identified as a viable ecological solution for restoring degraded African rangelands. Grass species indigenous to African rangelandsCenchrus ciliarisL. (African foxtail grass),Eragrostis superbaPeyr. (Maasai love grass),Enteropogon macrostachyus(Hochst. Ex A. Rich.) Monro ex Benth. (Bush rye grass),Chloris roxburghianaSchult. (Horsetail grass) andChloris gayanaKunth. cv Boma (Rhodes grass) were established in a semi‐arid rangeland in Africa under natural conditions to compare their morphoecological characteristics and suitability for use in ecological restoration. Biomass dry matter yields, plant densities, basal cover, seed production, tiller densities and plant height were measured.Chloris gayanacv Boma andE. superbaproduced significantly higher dry matter biomass yields and attained higher seed production than other species. High biomass and seed production indicate their suitability to support livestock production and replenish depleted soil seed banks, respectively.Enteropogon macrostachyusandC. ciliarisdisplayed significantly higher values for components of establishment and ecological restoration success, that is, plant densities, tiller densities and basal cover. Overall,C. roxburghianaranked lowest in the measured morphoecological characteristics.Successful restoration of degraded African semi‐arid rangelands using indigenous grass reseeding can best be achieved through careful selection of grasses to take advantage of their specific morphoecological characteristics. This selection should primarily be informed by the intended use of the rangeland and the specific challenges of restoring each site.

Germination of leucaena and Rhodes grass seeds in saline and alkaline conditions

Saline and alkaline groundwater can be used for irrigation of pastures. Using leucaena (Leucaena leucocephala cv. Tarramba) and Rhodes grass (Chloris gayana cv. Topcut), the effects of saline (electrical conductivity [EC], 0-20 dS m), sodic (sodium absorption ratio [SAR], SAR 5-30), and alkaline (0-855 mg L CaCOj equivalent) water on seed germination was investigated, with seedling root growth also measured in leucaena. For leucaena, germination decreased at EC > 15 dS m1, but SAR at values of up to 30 had no effect on germination. Alkalinity was found not to influence germination of leucaena (up to 855 mg L CaCO equivalent). Germination of 'Topcut' Rhodes grass was not reduced significantly with any EC, SAR or alkalinity treatment used in this study. Root growth in leucaena was inhibited by salinity > 5 dS m, SAR > 5 and alkalinity (as CaCO) > 24 mg L. It was found that the inhibition of root elongation of leucaena at high SAR values could be attributed to Ca deficiency, i.e. activity of Ca at the root cell plasma membrane. Germination of leucaena and Topcut Rhodes grass was highly tolerant of the salinity and alkalinity found in alkaline and saline groundwater (including water extracted from coal seams) when used for irrigation.

EFFECTS OF BRACHIARIA GRASSES ON SOIL MICROBIAL BIOMASS CARBON, NITROGEN AND PHOSPHORUS IN SOILS OF THE SEMI ARID TROPICS OF KENYA

<p>A study was conducted to investigate the changes in microbial biomass carbon (C), nitrogen (N) and phosphorus (P) following cultivation of Brachiaria grasses in semi-arid region of Kenya. The Brachiaria grass cultivars included<em> Brachiaria decumbens </em>cv. Basilisk, <em>B. brizantha</em> cvs Marandu, MG4, Piatã and Xaraes, <em>B. humidicola</em> cv. Llanero and <em>B. </em>hybrid cv. Mulato II which were compared with two locally cultivated forage grasses (<em>Chloris gayana cv. </em>KAT R3 and <em>Pennisetum purpureum cv. </em>Kakamega 1) and a bare plot (negative check). The grass treatments were evaluated with fertilizers application (40 kg P applied at sowing and 50 kg N ha<sup>-1</sup> in each wet season) and with no fertilizer applications. Microbial biomass C, N and P were determined on field moist rhizosphere soil (18-23% by weight) from a depth of 10 cm. Microbial biomass was influenced (p < 0.01) by grass cultivars and N and P fertilizers. Generally, microbial biomass N was higher in plots with grasses than in the bare plots. A significant enrichment of organic matter was noted in the microbial biomass when Brachiaria grasses are grown with N and P fertilizers. Among Brachiaria cultivars, the highest microbial biomass C was recorded in plots with cv. Mulato II and the lowest from the plots with cv. MG4. Brachiaria grasses with fertilizers application accumulated the highest microbial C and N compared to grasses without fertilizers, but no interaction was observed between fertilizer and grass cultivars. The cv. Marandu had the highest microbial biomass N (21.2 mg N kg<sup>-1</sup>) in fertilizer treatments whereas cv. Mulato II hybrid had the highest microbial N (14.6 mg N kg<sup>-1</sup>) in no fertilizer treatments. </p>

Growth rate and nutritive value of sown tropical perennial grasses in a variable summer‐dominant rainfall environment, Australia

AbstractGrowth rate, proportion of leaf and stem and nutritive value of sown tropical perennial grasses have not previously been documented for the dryland, frost‐prone summer‐dominant rainfall region of eastern Australia. An experiment was conducted in northern inland New South Wales with Chloris gayana (Rhodes grass) cv. Katambora and Digitaria eriantha (digit grass) cv. Premier, and compared to Sorghum bicolor ssp. bicolor x S. bicolor ssp. drummondii (forage sorghum). The grasses were harvested every 2 or 6 weeks and fertilized at five rates of nitrogen (N; 0–300 kg N ha−1) over two growing seasons (September–May), 2006–2007 and 2007–2008. Growing season rainfall was below median for both years of the experiment and growth rate was highly variable, reflecting variable rainfall. Sorghum generally had the highest growth rate. Digit grass generally had higher growth rates than Rhodes grass, was more responsive to growing season rainfall, commenced growth earlier and had a longer growing season. Nitrogen application extended the growing season of both perennial grasses. Growth response to N application was minimal when rainfall was low and response following significant rainfall was higher for fertilized than unfertilized grasses. In general, the proportion of green leaf was greater than green stem, although the proportion of stem increased when defoliation interval increased. Nutritive value of the perennial grasses was higher in leaf than stem and declined during the growing season. Differences between the grasses were slight, but indicated that fertilized digit grass defoliated at 2‐week intervals had higher growth rate and nutritive value than Rhodes grass.

Overhead-irrigation with saline and alkaline water: Deleterious effects on foliage of Rhodes grass and leucaena

Saline and alkaline water represents a potentially valuable resource provided its irrigation does not decrease plant growth. Although the adverse effects of salts within the rooting environment are well-studied, comparatively little is known regarding the direct effects of overhead-irrigation of saline and alkaline water on plant foliage. The present study examined the potential deleterious effects of saline (electrical conductivity, EC, ≤15dSm−1) and alkaline (≤2000mgL−1, CaCO3 equivalent) water on foliage of Rhodes grass (Chloris gayana cv. Reclaimer) and leucaena (Leucaena leucocephala ssp. glabrata cv. Tarramba) under a range of growing-conditions. Foliage of leucaena was sensitive, with necrosis and chlorosis evident for saline water at an EC ≥3dSm−1 and alkaline water containing ≥500mgL−1 (CaCO3 equivalent). For leucaena, this damage to the foliage reduced relative shoot fresh mass and chlorophyll fluorescence for saline-treatments, but alkalinity did not reduce relative shoot fresh mass or chlorophyll fluorescence in any treatment. In contrast to leucaena, relative shoot fresh mass of Rhodes grass was not reduced by foliar-applied salinity in any treatment (nor did alkalinity reduce growth of Rhodes grass). It was noted that growing conditions influenced the magnitude of the deleterious effects, with salinization of the soil slightly increasing tolerance to foliar-applied saline water for leucaena. This study has demonstrated that whilst saline and alkaline water can potentially be used for overhead irrigation, differences in observed tolerance exist between plant species, and are influenced by growing conditions.

THE CHEMICAL COMPOSITION AND NUTRITIVE VALUE OF Brachiaria GRASS CULTIVARS AT KATUMANI DRYLAND RESEARCH STATION IN SOUTH EASTERN KENYA

The study was conducted at Kenya Agricultural and Livestock Research Organisation, Katumani, Machakos to evaluate the herbage quality of Brachiaria grass cultivars in semi arid regions of Eastern Kenya. Brachiaria cultivars namely B. decumbens cv. Basilisk, Brachiaria hybrid Mulato II, four Brachiaria brizantha cultivars Marandu, Xaraes, Piata, MG4 and Brachiaria humidicola cv Llanero were assessed with reference to their chemical and nutritive composition at 22, 24 and 28 weeks post seedling emergence. Rhodes grass (Chloris gayana cv KATR3) and Napier grass (P. pupureum cv. Kakamega I) were included as controls. There were significant differences (p<0.05) among the cultivars for crude protein, crude fibre (NDF, ADF and ADL) Ash, Calcium, Phosphorus, Dry Matter Digestibilty and Metabolisable energy during the the week 22 and 24 post seedling emergence harvest. At week 28 harvest interval, however, ADL values for all the cultivars were similar and only Marandu was significantly different (p<0.05) in terms of metabolizable energy from the rest. The mean CP content of the grasses decreased from 11.1% at week 22 to 6.3% at harvest week 28 harvest intervals. MG4, Mulato II and Xaraes were the only grasses able to meet minimum CP (7.0%) requirement for rumen microbial function throughout the harvest period. Ash and phosphorus values decreased whereas Calcium content increased for all the cultivars during the harvest intervals, with Mulato II recording the highest ash (15%) content during this period. Chloris gayana KATR3 recorded highest average NDF (72.9%), ADF (48.1%) and ADL (6.1%) content during this period. Xaraes, Marandu and Mulato II were the only cultivars able to achieve the highest metabolizable energy of 7.0 MJ/kg DM recorded for the grass cultivars throughout the harvest intervals. These results indicate that Brachiaria grasses can be a good source of forage for livestock and a boost to the forage resource base in the semi arid regions of Kenya. Further research is needed to quantify their productivity in both dry and wet periods and to assess the effect of feeding on animal production performance.

Management of the Root Knot Nematode (Meloidogyne Javanica. Treub) and Sore Shin (Rhizoctonia Solani. Kuhn) Using A Nematicide and Poor Host Crops in Rotations

In a long term study the effects of a nematicide and six rotations: root-knot-susceptible tobacco, Nicotiana tabacum L. cv.‘KM10’ grown continuously (ContKM10), root-knot-resistant tobacco cv. ‘RK8’ grown continuously (ContRK8), grass-grass-grass-KM10 (G-G-G-KM10), grass-grass-grass-RK8 (G-G-G-RK8), KM10-Crotalaria juncea (KM10-Cr) and RK8-Crotalaria juncea (RK8-Cr), on root knot nematode, Meloidogyne javanica and sore shin, Rhizoctonia solani infection were studied. The nematicide used was ethylene dibromide (EDB) and was applied to each tobacco crop, as is standard practice. Chloris gayana cv. ‘Rhodes Katambora’, presumably a poor host of nematodes, was the grass used in all the grass-grass-grass-Tobacco rotations. The treatments were arranged in a randomized complete block design. ContKM10, KM10-Cr, G-G-G-RK8, ContiRK8 and RK8-Cr reduced root knot galling while G-G-G-KM10 increased galling. Sore shin increased with every year of rotation regardless of rotation, except in the case of G-G-G-KM10 and G-G-G-RK8 which reduced infection relative to other rotations. With the exception of G-G-G-RK8, all rotations that included RK8 suppressed root knot infection but did not suppress sore shin infection. The rotations including KM10 suppressed nematodes only with EDB treatment yearly and did not suppress sore shin except the rotation G-G-G-KM10. The role of Crotolaria juncea was masked by either RK8 or EDB. Host plant resistance in the form of RK8 was effective in controlling nematodes but did not reduce sore shin except mildly when rotated with the grass. This work recommends the use of resistant cultivars with broad-spectrum resistances.

Field studies of the effects of pre-sowing weed control and time of sowing on tropical perennial grass establishment, North-West Slopes, New South Wales

Two separate experiments on the North-West Slopes of New South Wales investigated: (1) the effects of differing lengths of pre-sowing weed control (2 years, 1 year, and 3–4 months in the spring immediately before sowing) on the soil seed density of liverseed grass (Urochloa panicoides) from November 2005 to November 2007 and its seedling density at establishment (December 2007), as well as on subsequent herbage mass and plant frequency of this species and Panicum coloratum var. makarikariense cv. Bambatsi (Expt 1); and (2) the effects of cultivar, time of sowing (November 2006, January 2007, and March 2007), and defoliation in the autumn after sowing, on the over-wintering ability of 5 tropical perennial grasses (Expt 2). The cultivars sown in Expt 2 were Bambatsi, Dichanthium aristatum cv. Floren, Chloris gayana cv. Katambora, Digitaria eriantha var. eriantha cv. Premier, and Bothriochloa bladhii var. glabra cv. Swann. At sowing (November 2007), liverseed grass seed and seedling densities in Expt 1 were lowest (P < 0.05) in the 2-year pre-sowing weed control treatment (15 and 13/m2, respectively), and the subsequent herbage mass of Bambatsi (January and October 2008) was highest (P < 0.05) in this treatment. In Expt 2, 59 frosts occurred in 2007, and Floren, Bambatsi, and Swann sown in March of that year over-wintered poorly and had lower (P < 0.05) herbage mass and plant frequency in the following spring compared with the other sowing times. These differences were also evident in autumn and spring 2008, up to 23 months after sowing.

Seedling competition of lucerne in mixtures with temperate and tropical pasture species

Two replacement series studies were conducted to quantify the competitive ability of seedlings of Medicago sativa (lucerne) sown in mixtures with temperate and tropical species. A temperate mixtures study (Expt 1) consisted of lucerne cv. Genesis sown with each of Phalaris aquatica (phalaris) cv. Atlas PG, Lolium arundinaceum (tall fescue) cv. Resolute MaxP, Cichorium intybus (chicory) cv. Puna, Trifolium subterraneum (subterranean clover) cv. Clare, Austrodanthonia richardsonii (wallaby grass) cv. Taranna and Avena sativa (forage oats) cv. Eurrabie. There was also an additional mixture of chicory and subterranean clover. A tropical grass mixtures study (Expt 2) included Genesis lucerne sown with each of Panicum coloratum var. makarikariense cv. Bambatsi, Dicanthium aristatum cv. Floren, Chloris gayana (Rhodes grass) cv. Katambora, Digitaria eriantha subsp. eriantha cv. Premier and Bothriochloa bladii subsp. glabra cv. Swann. In Expt 1, lucerne-phalaris mixtures were equally competitive, whereas lucerne-tall fescue mixtures over-yielded. Chicory was aggressive in mixtures with lucerne and subterranean clover; similarly forage oats was more competitive than lucerne. Subterranean clover was competitive against lucerne at harvest 1, but by harvest 2 the low cutting height had reduced its competitiveness. Lucerne was more aggressive than wallaby grass. In Expt 2, all tropical grass-lucerne mixtures over-yielded; however, lucerne was generally more competitive than the grasses, except for Rhodes grass at harvest 1. While our study indicated that mixtures of lucerne seedlings with phalaris or tall fescue may be compatible, mixtures with tropical grasses were more likely to result in lucerne seedling dominance. This competitiveness may be overcome by either spatial or temporal separation and we discuss the concept of using mixtures to exploit environmental niches.

Effects of depth and time of sowing and over-wintering on tropical perennial grass seedling emergence in northern New South Wales

Two studies were conducted in northern NSW to examine some of the factors affecting the successful emergence of seedlings of five species of tropical perennial grasses [Panicum coloratum var. makarikariense cv. Bambatsi (panic), Digitaria eriantha ssp. eriantha cv. Premier (digit), Chloris gayana cv. Katambora (Rhodes grass), Dichanthium aristatum cv. Floren (bluegrass), and Bothriochloa bladhii ssp. glabra cv. Swann (forest bluegrass)]. The first experiment investigated the effects of depth and time (month) of sowing on tropical perennial grass seedling emergence, while a second series of studies examined the effects of contact of dispersal/sowing units with the soil, particularly over winter, on subsequent seed germination and seedling emergence. No seedling emergence of any species occurred in September 2006 and June–August 2007. From October 2006 to May 2007 there were significant effects (P < 0.001) of species, sowing time, depth, and their interaction on predicted emergence. From December to March, predicted emergence was always lower for surface-sown caryopses compared with those sown at 10 and 25 mm depth, and Bambatsi was the only species that had >50% emergence from a depth of 50 mm. Recovery of intact caryopses from 300 μm nylon mesh bags stored in the soil for 6 and 12 months was low for all species. Similarly, predicted germination of caryopses from field soil surface and buried locations (2007 and 2008) and those from florets and coated seeds (2008) was low, indicating that these species had a poor ability to over-winter in moist soil.

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.

Herbage mass and persistence of pasture legumes and grasses at two potentially different saline and waterlogging sites in northern New South Wales

Two adjacent sites (a naturalised pasture and a previously cropped area) with differing potentials for salinity/sodicity and waterlogging near Tamworth, New South Wales were sown with temperate perennial grasses and legumes, temperate annual legumes and tropical perennial grasses to assess their herbage mass and persistence from 2003 to 2006. Plots were either grazed or mown seasonally. Days to flower in the establishment year and seedling regeneration were assessed each year for the annual legumes. In May 2003, salinity levels at soil depths >0.6 m were as high as 8 and 12 dS/m at the naturalised pasture and previously cropped sites, respectively, but generally were >5 and >3 dS/m at a soil depth of 0–0.10 m for these sites in 2004–05. With below average rainfall, no waterlogging was observed at the previously cropped site and only short-term waterlogging of a few days duration occurred at the naturalised pasture site. Under these conditions Puccinellia ciliata cv. Menemen did not establish or perform well, but Thinopyrum ponticum (cvv. Dundas and Tyrrell) was productive and persistent compared with Phalaris aquatica. At both sites, Digitaria eriantha cv. Premier and Chloris gayana cv. Katambora were the best tropical grasses, while the performance of Bothriochloa bladhii subsp. glabra cv. Swann was good at the previously cropped site and Panicum coloratum subsp. makarikariense cv. Bambatsi was best at the naturalised pasture site. At both sites, Medicago sativa had the highest herbage mass and persistence, with cv. Aquarius being superior to cv. Salado after 3 years. Compared with M. sativa, the herbage mass and persistence of Trifolium fragiferum was low. Of the annual legumes, M. polymorpha cv. Scimitar and Melilotus sulcatus had the highest herbage mass.

Growth Response of Various Perennial Grasses to Increasing Salinity

ABSTRACT Although the effect of salinity on plant growth has been the focus of a substantive research effort, much of this research has failed adequately to separate the various growth-limiting aspects of salinity; thus, the results are confounded by multiple factors. Eight perennial grass species were grown in a sand-culture system dominated by sodium chloride (NaCl) [electrical conductivities (ECs) between 1.4 and 38 dS m−1], with sufficient calcium (Ca) added to each treatment to ensure that Na-induced Ca deficiency did not reduce growth. Of the eight perennial grass species examined, Chloris gayana cv. ‘Pioneer’ (Rhodes grass) was the most salt-tolerant species, while Chrysopogon zizanioides cv. ‘Monto’ (vetiver) was of only moderate tolerance. However, observed salinity tolerances tended to be lower than those expected from published values based on the threshold-salinity (bent-stick) model. This discrepancy may be due in part to differences in the evapotranspirational demand between studies; i.e., an increase in demand accelerates the accumulation of sodium (Na) in the shoots and hence decreases apparent salinity tolerance. It was also observed that the use of a non-saline growth period (to allow seed germination and establishment) results in the overestimation of vegetative salinity tolerance if not taken into consideration. This situation is particularly true for species of low salt tolerance, due to their comparatively rapid growth in the non-saline medium compared with growth at full salinity.

Monensin supplementation of lactating cows fed tropical grasses and cane molasses or grain

Effects of monensin (Mon) on performance of Holstein–Friesian cows fed tropical grasses and cane molasses (M) or cereal grain were examined in three experiments. In experiment 1 (incomplete 4 × 4 Latin square), three rumen-fistulated cows [188 ± 11 days in milk (DIM)] were fed mixed diets based on rhodes grass ( Chloris gayana cv. Callide) hay where M was substituted for wheat grain (W) at rates of 0 (M0), 125 (M125) or 250 (M250) g/kg dry matter (DM). A fourth diet contained M250 plus 0.02 g Mon/kg DM (M250 + Mon). Substituting M for W tended ( P < 0.10) to decrease the ratio of rumen molar proportions of acetate + butyrate (Bu):propionate (Pr) (4.3 versus 3.8 and 4.0 for M0, M125 and M250, respectively). There were no treatment effects ( P > 0.10) on intake, organic matter digestibility, milk production or liveweight (LW) change. In experiment 2, 48 cows (173 ± 28.3 DIM) grazing kikuyu ( Pennisetum clandestinum cv. common) pastures and supplemented with maize silage and a grain-based concentrate were offered either M (2.6 kg DM/(cow day)) or barley grain (B) (2.7 kg DM/(cow day)). Within each supplement type, half were fed 0 or 320 mg of Mon/(cow day). There were Mon × supplement interactions (Mon × S; P < 0.05) on the rumen molar proportion of Pr and Bu at 15:00 h, with B + Mon having the highest value for Pr (0.259 mmol/mmol) and lowest value for Bu (0.121 mmol/mmol). A Mon × S effect ( P < 0.05) on milk fat content was noted with Mon causing a lower value regardless of energy source (31 and 36 g/l versus 40 and 38 g/l for B + Mon, M + Mon, B − Mon and M − Mon, respectively). As a main effect, M as opposed to B, reduced yields of milk ( P < 0.05; 16.2 l/(cow day) versus 18.0 l/(cow day)) and protein ( P < 0.05; 479 g/(cow day) versus 538 g/(cow day)). Monensin reduced milk fat yield ( P < 0.05; 669 g/(cow day) versus 562 g/(cow day)), raised milk protein concentration ( P < 0.05; 31 g/l versus 29 g/l) and caused LW gain rather than loss ( P < 0.05; +0.06 kg/(cow day) versus −0.30 kg/(cow day)). No treatment effects on pasture intake were noted. In experiment 3, 48 cows (91 ± 16.1 DIM) grazing kikuyu pasture and supplemented with grain-based concentrate, sugar cane silage and 2.7 kg DM/(cow day) of M were supplemented with either 0 or 320 mg Mon/(cow day). Monensin reduced ( P < 0.05) milk fat content (33 g/l versus 30 g/l) and tended ( P < 0.10) to reduce milk protein content (29 g/l versus 28 g/l). No effects of Mon on other milk production parameters, LW change or pasture intake were noted. Feeding monensin to mid-lactation Holstein–Friesian cows offered diets based on tropical grasses, and cane molasses or grain, improves rumen fermentation efficiency, thereby improving energy efficiency resulting in higher LW gain. Monensin had no effect on milk yield, but reduced milk fat concentration.

Effect of pH on Na induced Ca deficiency

Although it is well known that high Na concentrations induce Ca deficiency in acidic conditions, the effect of high pH on this competitive mechanism is not so well understood. The effect of Ca activity ratio (CAR) and pH on the Ca uptake of mungbeans (Vigna radiata (L.) Wilczek cv. Emerald) and Rhodes grass (Chloris gayana cv. Pioneer) in Na dominated solution cultures and in soil was investigated. Changes in pH in the alkaline range were shown not to affect the critical CAR of 0.024 (corresponding to 90% relative root length) for mungbeans grown in solution culture. Results from soil grown mungbeans confirmed those from solution culture, with a critical CAR of 0.025. A critical CAR of 0.034 was also established for soil grown Rhodes grass. The similarity of critical values established for mungbeans and Rhodes grass in solution culture and soil justifies the use of both solution culture and soil solution measurement as techniques for studying plant growth and limitations across plant species.

Effect of Mn deficiency and legume inoculation on rhizosphere pH in highly alkaline soils

Although plant growth is often limited at high pH, little is known about root-induced changes in the rhizospheres of plants growing in alkaline soils. The effect of Mn deficiency in Rhodes grass (Chloris gayana cv. Pioneer) and of legume inoculation in lucerne (Medicago sativa L. cv. Hunter River), on the rhizosphere pH of plants grown in highly alkaline bauxite residue was investigated. Rhizosphere pH was measured quantitatively, with a micro pH electrode, and qualitatively, with an agar/pH indicator solution. Manganese deficiency in Rhodes grass increased root-induced acidification of the rhizosphere in a soil profile in which N was supplied entirely as NO3-. Rhizosphere pH in the Mn deficient plants was up to 1.22 pH units lower than that of the bulk soil, while only 0.90 to 0.62 pH units lower in plants supplied with adequate Mn. When soil N was supplied entirely as NO3-, rhizosphere acidification was more efficient in inoculated lucerne (1.75 pH unit decrease) than in non-inoculated lucerne (1.16 pH unit decrease). This difference in capacity to lower rhizosphere pH is attributable to the ability of the inoculated lucerne to fix atmospheric N2 rather than relying on the soil N (NO3 ) reserves as the non-inoculated plants. Rhizosphere acidification in both Rhodes grass and lucerne was greatest in the meristematic root zone and least in the maturation root zone.

Phyto-extraction of Copper, Iron, Manganese, and Zinc from Environmentally Contaminated Sites in Ethiopia, with Three Grass Species

Rhodegrass (Chloris gayana cv. Kallide) and forage setaria (Setaria sphacelata cv. Kazungula), two indigenous grass species, and oat (Avena sativa L.), a recently introduced forage crop, were grown on contaminated sites in Ethiopia, to determine their potential in removing copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) from the soils. Soil pH influenced the availability and plant uptake of micronutrients; therefore, the grasses grown at the industrial waste site with a high pH, had the lowest micronutrient concentrations. Setaria and rhodesgrass had higher concentrations of all the micronutrient metals than oat. Rhodesgrass and setaria accumulated concentrations of Fe and Mn, normally considered toxic to many crops, without developing chlorotic symptoms and yield suppressions. Iron in setaria and Zn in rhodesgrass declined significantly with advancing maturity. Considering biomass yield and tissue concentration, it was found that setaria removed the greatest quantity of micronutrients per unit area of soil.

Effects of alkalis, oxidants and urea on the nutritive value of rhodes grass ( Chloris gayana cv. Callide)

Two in sacco experiments were conducted to evaluate the impact on the nutritive value of rhodes grass hay ( Chloris gayana cv. Callide) of treatment with alkalis or oxidants. In Experiment 1, three alkalis (Ca(OH) 2, NaOH, CaO) and two oxidants (NaOCl and H 2O 2) were applied at levels of 0, 20, 40, 60 or 80 g/kg of dry matter (DM). NaOH, Ca(OH) 2 and CaO had negative linear effects ( P<0.05) on the neutral detergent fibre (NDF) content and positive linear effects ( P<0.05) on the 48 h in sacco disappearances of DM, organic matter (OM), NDF and acid detergent fibre (ADF). NaOCl reduced ( P<0.05) NDF content but had no effect ( P>0.05) on the in sacco disappearances. H 2O 2 had no effect ( P>0.05) on the composition or digestibility of rhodes grass hay. In Experiment 2, effects of urea (0, 20, 40, 60 and 80 g urea/kg DM) and water (250, 500 and 750 g/kg DM) treatment of rhodes grass hay were examined in a 5×3 factorial experiment. Significant interactions between water and urea ( P<0.05) occurred for concentrations of crude protein (CP) and NDF, and 48 h in sacco disappearances of DM, OM (OMD) and NDF. The combinations of water (g/kg DM) and urea (g/kg DM) that resulted in the highest concentrations of CP (281 g/kg DM) and OMD (747 g/kg DM) were 250+80 and 500+80, respectively. NaOH, Ca(OH) 2, CaO and urea significantly alter the NDF content and digestibility of rhodes grass hay, and urea also increases its CP content. Overall, NaOH was the most efficacious, followed by Ca(OH) 2, CaO, urea, NaOCl and H 2O 2.