Letteratura scientifica selezionata sul tema "Kikuyu-ryegrass pasture systems"

Improved dryland pastures for sheep and beef cattle production in south-western Victoria are typically based on summer-dormant cultivars of perennial ryegrass (Lolium perenne L.) or phalaris (Phalaris aquatica L.). These are highly productive in spring but exhibit low accumulation rates over summer–autumn. Summer-active perennial pasture species could potentially alleviate this summer–autumn feed gap. Three pasture systems that used different pastures on each of the three landscape classes (crest, slope, and valley floor) were compared over 4 years. The perennial ryegrass system (henceforth Ryegrass) had a different ryegrass cultivar on each landscape class. The Triple system used lucerne (Medicago sativa L.) (crest), perennial ryegrass (slope), and summer-active tall fescue (Lolium arundinaceum (Schreb) Darbysh.) (valley floor). The Novel system used chicory (Cichorium intybus L.) (crest), Italian ryegrass (Lolium multiflorum Lam.) or hybrid ryegrass (L. × boucheanum Kunth.) (slope), and kikuyu (Pennisetum clandestinum Hochst. ex Chiov.) (valley floor). The pastures were grazed by either one (in the case of the Novel system) or three (in the case of the Ryegrass and Triple systems) animal systems that varied over the life of the experiment. Total annual herbage accumulation of the Ryegrass and Triple systems did not differ. The Novel system consistently had lower total annual dry matter accumulation than the other two systems. Lucerne pastures generally had the highest accumulation rates over summer, followed by the chicory pastures. The kikuyu pastures responded well to summer rainfall but otherwise had similar accumulation rates to the perennial ryegrass and tall fescue pastures over summer. Tall fescue pastures grew well in autumn following wet summers. In spring the perennial ryegrass pastures based on Fitzroy or Avalon were highly productive but seldom grew faster than other pastures. The results support the hypothesis that incorporating deep-rooted, summer-active perennial species will increase pasture production over summer–autumn compared with conventional pasture systems but not at the expense of winter–spring production.

Although generally well adapted and productive, the summer-dormant perennial pastures of southern Australia do not provide a year-round, high nutritive value feed base, they fail to respond to summer rainfall, and they are inefficient in using stored soil water, which can contribute to dryland salinity. An experiment was conducted to test the hypothesis that deep-rooted, summer-active perennial pasture species, matched to soil type, can be grown successfully in southern Australia to increase pasture and animal productivity and to provide high quality feed in summer–autumn. Specifically, the experiment compared a traditional perennial ryegrass (Lolium perenne L.) pasture system with two systems based on summer-active species: the triple system with lucerne (Medicago sativa L.) and tall fescue (Lolium arundinaceum (Schreb) Darbysh), and the novel system with chicory (Cichorium intybus L.) and kikuyu (Pennisetum clandestinum Hochst. ex Chiov). The experiment incorporated three livestock systems (two sheep and one cattle) and took into account the three main soil types occurring on the DPI Hamilton research farm. After 4 years the perennial ryegrass, lucerne, and tall fescue components were all persisting well and providing feed with high nutritive value (all with frequency scores >70% in the last year of the experiment). The chicory and kikuyu pastures declined over the life of the experiment and were contributing little at the end (frequency scores <15% in the final year). Lucerne, tall fescue, and perennial ryegrass cv. Banquet were able to respond to summer rainfall events to provide valuable, high-quality feed at a time when the quality of perennial ryegrass pasture is normally at its lowest; April 2007 crude protein per cent dry matter values were Avalon perennial ryegrass 16.6, Fitzroy perennial ryegrass 15.6, kikuyu 24.2, lucerne 25.8, and tall fescue 20.3 following a 98 mm rainfall event in late January 2007. This study has shown that the triple and ryegrass systems were persistent and of high nutritive value, with the sown perennial species contributing the majority of the sward dry matter during the growing season.

Nitrogen (N) fertiliser is applied to pastures in dairy farming systems to ensure productivity, but it is an expensive input that could be damaging to the environment if used excessively. In the southern Cape region of South Africa, N fertilisation guidelines for pastures were developed under conditions different to current management practices, yet dairy producers still base fertiliser programmes on these outdated guidelines. This study aimed to determine the efficiencies of N fertilisation. Various N fertiliser rates (0, 20, 40, 60 and 80 kg ha−1 applied after grazing), as well as a variable rate according to the nitrate concentration in the soil water solution, were assessed on a grazed pasture. Dairy cows returned to a pasture approximately 11 times per year. Pasture production showed a minimal response to fertilisation within each season. The most responsive parameters to fertilisation were the herbage crude protein content, soil mineral N content and urease activity. Reduced microbial activity was observed when more than 40 kg N ha−1 was applied. When considering the soil total mineral N content, N is used inefficiently at rates above 40 kg N ha−1. The results are indicative of an N saturated system that provides a rationale for reducing N fertiliser rates.

The nitrogen-use efficiency (NUE) of a fertiliser has implications for pasture growth and the environment. This study aimed to compare application of urea as a foliar spray or in granular form, to kikuyu (Cenchrus clandestinus (Hochst. ex Chiov.) Morrone) and short-rotation ryegrass (Italian ryegrass, Lolium multiflorum Lam.) pastures in the subtropical dairy region of eastern Australia. The first experiment was a replicated grazing study on a site with a high plant-available soil N (75 mg nitrate-N/kg). The granular rate of urea was 46 kg N/ha.month equivalent, and the foliar spray rate was 40% of the granular rate. Pasture growth rate (51 DM/ha.day with foliar spray vs 45 kg DM/ha.day with granules) and pasture consumed (4942 vs 4382 kg DM/ha) were not significantly different between treatments. However, over the 8 months of the study, soil nitrate-N levels fell from 75 to 22 mg/kg on the foliar plots but only fell to 60 mg/kg on the granular plots. The second experiment was a replicated plot-cut experiment on a site with a low plant-available soil N (8.7 mg nitrate-N/kg). The NUE for kikuyu grass was similar for all treatments with a mean of 14.8 kg DM/kg N for the four foliar treatments (high and low, with and without wetting agent) and 17.4 kg DM/kg N for the granular treatment. The NUE for the ryegrass was also similar for all treatments, with a mean of 13.2 kg DM/kg N for the foliar treatments and 15.8 kg DM/ha for the granular treatment. A third experiment, evaluating absorption of foliar-sprayed urea over time, found that &gt;80% of the urea applied to kikuyu was absorbed by 7 h; for ryegrass, the amount absorbed was only ~45% but increased to ~75% if wetting agent was included. We suggest that the lack of benefit in NUE achieved by applying urea as a foliar spray, which contrasts with results from studies in temperate dairy farm systems, is primarily associated with the substantially lower tiller density and hence the smaller canopy area for absorption of the foliar spray by the new regrowth shoots post-grazing.

Eleven experimental sites in the Sustainable Grazing Systems (SGS) national experiment were established in the high rainfall zone (HRZ, >600 mm/year) of Western Australia, Victoria and New South Wales to measure components of the water balance, and pathways of water movement, for a range of pastures from 1997 to 2001. The effect of widely spaced river red gums (Eucalyptus camaldulensis) in pasture, and of belts of plantation blue gums (E. globulus), was studied at 2 of the sites. The soil types tested ranged from Kurosols, Chromosols and Sodosols, with different subsoil permeabilities, to Hydrosols and Tenosols. The pasture types tested were kikuyu (Pennisetum clandestinum), phalaris (Phalaris aquatica), redgrass (Bothriochloa macra) and annual ryegrass (Lolium rigidum), with subterranean clover (Trifolium subterraneum) included. Management variables were set stocking v. rotational grazing, adjustable stocking rates, and level of fertiliser input. Soil, pasture and animal measurements were used to set parameters for the biophysical SGS pasture model, which simulated the long-term effects of soil, pasture type, grazing method and management on water use and movement, using as inputs daily weather data for 31 years from selected sites representing a range of climates. Measurements of mean maximum soil water deficit Sm were used to estimate the probability of surplus water occurring in winter, and the average amount of this surplus, which was highest (97–201 mm/year) for pastures in the cooler, winter-rainfall dominant regions of north-east and western Victoria and lowest (3–11 mm/year) in the warmer, lower rainfall regions of the eastern Riverina and Esperance, Western Australia. Kikuyu in Western Australia achieved the largest increase in Sm compared with annual pasture (55–71 mm), while increases due to phalaris were 18–45 mm, and those of native perennials were small and variable. Long-term model simulations suggested rooting depth was crucial in decreasing deep drainage, to about 50 mm/year for kikuyu rooting to 2.5 m, compared with 70–200 mm/year for annuals rooting to only 0.8 m. Plantation blue gums dried the soil profile to 5.25 m by an average of 400 mm more than kikuyu pasture, reducing the probability of winter surplus water to zero, and eliminating drainage below the root zone. Widely spaced river red gums had a much smaller effect on water use, and would need to number at least 14 trees per hectare to achieve extra soil drying of about 50 mm over a catchment. Soil type affected water use primarily through controlling the rooting depth of the vegetation, but it also changed the partitioning of surplus water between runoff and deep drainage. Strongly duplex soils such as Sodosols shed 50% or more surplus water as runoff, which is important for flushing streams, provided the water is of good quality. Grazing method and pasture management had only a marginal effect in increasing water use, but could have a positive effect on farm profitability through increased livestock production per hectare and improved persistence of perennial species.

Soil quality of pastures changes through time because of management practices. Excessive soil disturbance usually leads to the decline in soil quality, and this has resulted in concerns about kikuyu (Pennisetum clandestinum)–ryegrass (Lolium spp.) pasture systems in the southern Cape region of South Africa. This study aimed to understand the effects of tillage on soil quality. The soil management assessment framework (SMAF) and the locally developed soil quality index for pastures (SQIP) were used to assess five tillage systems and were evaluated at a scale inclusive of variation in topography, pedogenic characteristics and local anthropogenic influences. Along with assessment of overall soil quality, the quality of the physical, chemical and biological components of soil were considered individually. Soil physical quality was largely a function of inherent pedogenic characteristics but tillage affected physical quality adversely. Elevated levels of certain nutrients may be warning signs to soil chemical degradation; however, tillage practice did not affect soil chemical quality. Soil disturbance and the use of herbicides to establish annual pastures has lowered soil biological quality. The SQIP was a more suitable tool than SMAF for assessing soil quality of high-input, dairy-pasture systems. SQIP could facilitate adaptive management by land managers, environmentalists, extension officers and policy makers to assess soil quality and enhance understanding of processes affecting soil quality.

The aim of this experiment was to test the effects of dietary treatment on sheep meat eating quality as perceived by untrained Australian consumers. Six-month-old Suffolk × Merino lambs (n = 192) were allocated to 1 of 4 nutritional treatments for 60–77 days and were fed: (i) an irrigated perennial ryegrass–clover–kikuyu sward; (ii) irrigated perennial ryegrass–clover–kikuyu pasture for 48–61 days then poor quality straw for the last 12–16 days; (iii) a mixed ration treatment consisting of a high-energy pelleted diet (40% barley grain, 30% wheat grain, 15% hay and 12% lupin grain); or (iv) irrigated pasture for 37–51 days followed by a moderate-energy pelleted diet (36% wheat grain, 35% hay and 24.5% lupin grain) for 23–26 days. The starting liveweight of lambs was 31.5–35.5 kg and the final hot carcass weight was 19–20 kg. The nutritional treatment finishing system employing straw feeding for the last 12–16 days was associated with a loss of liveweight during this period, a decreased tissue depth at the GR site and a decreased content of intramuscular fat and glycogen in muscle. Untrained Australian consumers were asked to rate samples (scale 0–100) of the M. longissimus thoracis et lumborum (LL) from lambs for tenderness, liking of flavour, juiciness and overall liking and then classify the meat as unsatisfactory, good everyday or better than everyday. Straw feeding was also associated with significantly reduced consumer scores for juiciness (P<0.05) and liking of flavour (P<0.10) with no changes in tenderness and overall liking. There was no significant difference in the consumer acceptance of the LL obtained from lambs finished on pasture v. grain-based diets. It is concluded that nutritional finishing systems should be selected to prevent animals from losing weight pre-slaughter and that decisions on pasture v. grain based feeding systems be based on the cost of production.

Fertilized agricultural soils serve as a primary source of anthropogenic N2O emissions. In South Africa, there is a paucity of data on N2O emissions from fertilized, irrigated dairy-pasture systems and emission factors (EF) associated with the amount of N applied. A first study aiming to quantify direct N2O emissions and associated EFs of intensive pasture-based dairy systems in sub-Sahara Africa was conducted in South Africa. Field trials were conducted to evaluate fertilizer rates (0, 220, 440, 660, and 880 kg N ha−1 year−1) on N2O emissions from irrigated kikuyu–perennial ryegrass (Pennisetum clandestinum–Lolium perenne) pastures. The static chamber method was used to collect weekly N2O samples for one year. The highest daily N2O fluxes occurred in spring (0.99 kg ha−1 day−1) and summer (1.52 kg ha−1 day−1). Accumulated N2O emissions ranged between 2.45 and 15.5 kg N2O-N ha−1 year−1 and EFs for mineral fertilizers applied had an average of 0.9%. Nitrogen in yielded herbage varied between 582 and 900 kg N ha−1. There was no positive effect on growth of pasture herbage from adding N at high rates. The relationship between N balance and annual N2O emissions was exponential, which indicated that excessive fertilization of N will add directly to N2O emissions from the pastures. Results from this study could update South Africa’s greenhouse gas inventory more accurately to facilitate Tier 3 estimates.

Modern dairy farming in Australia relies on substantial inputs of fertiliser nitrogen (N) to underpin economic production. However, N lost from dairy systems represents an opportunity cost and can pose several environmental risks. N-cycle inhibitors can be co-applied with N fertilisers to slow the conversion of urea to ammonium to reduce losses via volatilisation, and slow the conversion of ammonium to nitrate to minimise leaching of nitrate and gaseous losses via nitrification and denitrification. In a field campaign in a high input ryegrass–kikuyu pasture system we compared the soil N pools, losses and pasture production between (a) urea coated with the nitrification inhibitor 3,4-dimethyl pyrazole phosphate (b) urea coated with the urease inhibitor N-(n-butyl) thiophosphoric triamide and (c) standard urea. There was no treatment effect (P>0.05) on soil mineral N, pasture yield, nitrous oxide flux or leaching of nitrate compared to standard urea. We hypothesise that at our site, because gaseous losses were highly episodic (rainfall was erratic and displayed no seasonal rainfall nor soil wetting pattern) that there was a lack of coincidence of N application and conditions conducive to gaseous losses, thus the effectiveness of the inhibitor products was minimal and did not result in an increase in pasture yield. There remains a paucity of knowledge on N-cycle inhibitors in relation to their effective use in field system to increase N use efficiency. Further research is required to define under what field conditions inhibitor products are effective in order to be able to provide accurate advice to managers of N in production systems.

Accurate estimation of pasture mass is essential for managing farm systems for top performance. The C-DAX Rapid Pasturemeter has the potential to provide fast, accurate estimates of pasture mass. However, the Pasturemeter has been calibrated for 'typical' temperate dairy pastures and its suitability for use on kikuyu (Pennisetum clandestinium)-based pastures in Northland, is unknown. This study determined the accuracy of the technology for estimation of pasture mass on kikuyu/ryegrass-based dairy pasture on the Northland Agricultural Research Farm at Dargaville, New Zealand. Keywords: pasture mass estimation, kikuyu, Northland, dairy, calibration

Kikuyu is well adapted to the main milk producing areas of the Southern Cape region of South Africa. The strategic incorporation of different types of temperate grasses into kikuyu pastures can increase the seasonal dry matter production, pasture quality, and milk production attainable from these pastures. To determine whether there is production and economical differences between kikuyu based pasture systems, a trial was conducted on the Outeniqua Research Farm near George. The three pasture treatments, namely italian, westerwold, and perennial ryegrass over-sown into kikuyu, were tested. Forty-five Jersey cows were blocked and cows within blocks were randomly allocated to the treatments. The cows received 9 kilograms of pasture (on a dry matter basis) per cow per day, and four kilograms of concentrate per cow per day. Milk production was recorded daily, and milk composition was determined monthly. The cows were weighed and body condition scored monthly. The perennial ryegrass pasture treatment had a higher milk production per hectare (32288 kg/ha) than the westerwold ryegrass pasture treatment (29761 kg/ha) but did not differ from the italian ryegrass pasture treatment (30446 kg/ha). The italian ryegrass pasture treatment had a higher milk protein percentage than the perennial ryegrass pasture treatment (3.84% vs. 3.64%) but did not differ from the westerwold ryegrass pasture treatment (3.75%). When the three pasture treatments were economically compared, the italian ryegrass pasture treatment had the highest margin over specified costs per hectare (R 36,565.03), followed by the perennial (R 33,889.14) and westerwold (R 29,468.09) ryegrass pasture treatments. From the results it seems that the italian ryegrass pasture treatment is the best choice for a kikuyu based pasture system in the Southern Cape region of South Africa. A high level of concentrate supplementation could increase energy intake of grazing dairy cows, but might also reduce fibre digestion within the rumens of high producing dairy cows. To test this hypothesis, two trials were conducted, one during October and November 2007, and the other during March 2008. In both trials twelve rumen cannulated cows were allocated to four groups. Two groups were allocated to each pasture treatment, namely perennial and westerwold ryegrass over-sown into kikuyu. Within each pasture treatment, one group received 4 kg of concentrate per cow per day, and the other 8 kg of concentrate per day. Pasture was allocated at 9 kg per day (DM). Cows were adapted for ten days, after which ruminal pH, and ammonia nitrogen and volatile fatty acid concentration data was collected. An in sacco study was conducted to determine the neutral detergent fibre degradability. After the data was collected, the two groups within each pasture treatment swapped concentrate levels; were adapted, and the same data as described above was collected. During both trials reductions in ruminal pH were observed when a higher amount of concentrate was supplemented. During the first trial there was a significant increase in the time that the ruminal pH remained below pH 5.8 on the westerwold ryegrass pasture treatment (from 80 minutes when the cows received 4 kg of concentrate per day, to 375 minutes when it was increased to 8 kg of concentrate per day). A decrease in neutral detergent fibre degradability was also seen. During the second trial, the percentage of NDF disappearance decreased from 8.45% over a twelve hour period when 4 kg of concentrate was fed, to 4.51% when 8 kg of concentrate was fed on the perennial ryegrass pasture treatment. From the results it appears that feeding a higher level of concentrate supplementation to high producing dairy cows grazing kikuyu pasture systems has a negative effect on neutral detergent fibre digestion within the rumen. It appears that feeding a moderate level of concentrate supplementation when cows are on pasture based systems is more beneficial to the rumen environment and decreases the possibility of sub-clinical ruminal acidosis when cows grazed ryegrass dominant pastures, but had a less pronounced effect when the dominant pasture specie was kikuyu. Future research could examine the relationship between the level of concentrate supplementation and pasture specie more closely, as it would be interesting to find the optimal ratios for each pasture specie. Copyright
Dissertation (MScAgric)--University of Pretoria, 2010.
Animal and Wildlife Sciences
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