Ryegrass Pasture Research Articles

Deriving seasonally optimal nitrogen fertilization rates for a ryegrass pasture based on agricultural production systems simulator modelling with a refined AgPasture model

AbstractProductive pasture systems require a regular supply of mineral nitrogen (N) to replace the N removed through the export of animal products and other loss pathways such as leaching and emissions. High spatial and temporal variability of both N supply by the soil and demand by the plant means that synchronizing these is challenging, and early indicators are lacking. Optimum fertilization rates for an irrigated ryegrass pasture in Canterbury, New Zealand, were determined in a simulation study with twenty fertilization rates using the Agricultural Production Systems Simulator with a refined version of APSIM's pasture module (AgPasture). Improvements in AgPasture included ideal N concentrations for tissues of different ages (growing, mature, senescent and dead) and allowing N remobilization to occur from all tissue stages. The critical N concentration curve (the minimum N concentration required to achieve maximum aerial biomass) was tested as an early indicator for guiding N fertilization, which maximizes plant growth while avoiding unnecessary environmental impacts. Highest pasture yields were achieved with application rates of 20, 30, 140 and 160 kg N ha−1 for winter, autumn, summer and spring. These rates also minimized simulated N losses. Pasture N contents corresponding to the standing dry matter of the pastures were similar to the critical N curve in summer and spring, but lower critical N concentrations were obtained for autumn and winter. Before the critical N reference curve can be used to guide fertilization for pastures, further experimental studies, model testing and parameterization are required. It is also possible that season‐specific critical N curves need to be established for pastures.

Management opportunities for boosting productivity of cool-temperate dairy farms under climate change

Improved knowledge of the effects of climate change on farming systems can help increase long-term production, economic performance, and mitigate risk. Here we assessed the effects of stocking rate and seasonal calving times on pasture and milk production under short and long term climate changes on dairy farms in Tasmania, Australia. Annual and monthly perennial ryegrass pasture production was simulated from 1971 to 2065 to examine trends in pasture productivity, forage requirements, and impacts on milk production in 2015 and 2050. The projected future climate for the study region indicates a mean warming of up to 1.4°C, with moderate declines in rainfall of up to 5%. Despite lower rainfall, climate change will likely have a positive impact on pasture yields, with annual production increasing by 13–16%, even though summer growth is reduced and inter-annual variability is increased. We found that greater pasture production is conducive to greater forage conservation, and together these factors allow intensification of stocking rates. These effects increase milk yields by 3–16% per annum and reduce reliance on purchased feeds, which together implies greater profitability of cool-temperate Australian dairy systems under future climates. We also found that total milk production in a spring calving system allows greater stocking rates and pasture utilisation compared with an autumn calving system, and whilst milk produced per animal declines under higher stocking rates, milk yield per hectare increases. Overall, our results suggest that global warming and climate change will positively affect pasture growth rates in Tasmania, and that greater production and conservation of home-grown feeds will be conducive to increased farm milk yields, provided that stocking rates are intensified sustainably.

Fertiliser and seasonal urine effects on N2O emissions from the urine-fertiliser interface of a grazed pasture

Significant areas of ruminant-grazed pastures are simultaneously covered by excreted urine and fertiliser nitrogen (N). However, the effect of overlapping N inputs on nitrous oxide (N2O) emission factors has not been studied. Three rates of 15N-labelled urea fertiliser were applied with either no urine, an autumn-urine or a spring-urine application. These treatments were applied to perennial ryegrass pasture (Lolium perenne L.) and N2O fluxes were determined over 373 days using standard static closed chamber techniques. Cumulative N2O-N fluxes ranged from 766 to 4332 g N2O-N ha–1 (0.36%–0.74% of total N applied) and were lowest in the absence of urine; however, no fertiliser rate effect occurred regardless of urine presence or season of application. Urine-elevated N2O-N fluxes followed urine applications for up to 40 days, resulting in lower fertiliser contributions to the N2O-N fluxes at these times. Total 15N recoveries as N2O-N were ≤0.04% and did not differ with fertiliser rate.

Molecular genetics-nutrition interactions in the expression of AANAT, ADRB3, BTG2 and FASN genes in the heart, kidney and liver of Australian lambs supplemented with Spirulina (Arthrospira platensis)

Quantitative reverse transcriptase polymerase chain reaction was used to assess the messenger RNA (mRNA) transcription levels and expressions of Aralkylamine N-acetyltransferase, Adrenergic beta-3 receptor, B cell translocation gene 2, and Fatty acid synthase genes. In total, 432 heart, kidney and liver samples from 48 purebred and crossbred Australian prime lambs supplemented with Spirulina (Arthrospira platensis) blue-green cyanobacterial microalgae over a 9-week feeding trial were utilized for fatty acid composition and mRNA extraction. The aim was to assess the effect of dietary Spirulina supplementation on the mRNA expression profiles of genes controlling fatty acid metabolism in the heart, kidney and liver. Fourty-eight weaned lambs belonging to four breeds under the same management conditions were maintained on ryegrass pasture and randomly allocated to three treatment groups that comprised the control and two levels of Spirulina supplementation: Low (100 mL/head/day of 1 g Spirulina powder dissolved in 10 mL of water (10 % wt:vol)) and High (200 mL/head/day of 2 g of Spirulina dissolved in 10 mL of water (20 % wt:vol)). Both the low and high levels of Spirulina supplementation regimes strongly up-regulated the transcription of all the selected genes and increased ω-3 and ω-6 polyunsaturated fatty acid compositions in the tested organs. Breed and sex did not influence gene expression patterns; however, significant variations in response to Spirulina supplementation underpin the genetics-nutrition interactions that could be of practical importance for manipulating meat quality in the Australian dual-purpose prime lamb industry for a healthy polyunsaturated fatty acid profile.

Relationships between heat stress and metabolic and milk parameters in dairy cows in Southern Brazil.

This study approached the relationships between heat stress and metabolic and milk parameters in a commercial herd of Holstein cows located in southern Brazil. A total of 50 multiparous cows at different lactations and lactation stages were selected in order to obtain 450 samples during two consecutive years (2011 and 2012). The animals were fed a partial mixed ration along with ryegrass pasture in a semi-confinement system. Blood, milk, and urine samples were taken during the summer and winter for a total of eight samples. Three intervals of temperature-humidity index (THI) were established during the summer months (January and February) as follows: low group (LOW), THI between 75 and 81 (N = 100); moderate group (MOD), THI between 81 and 82 (N = 150); and severe group (SEV), THI between 83 and 90 (N = 150). The group of cows sampled during winter (July) constituted the control group (CON; THI = 59, N = 50). Increased total protein, albumin, glucose, and cholesterol occurred in heat-stressed cows. Increased AST activity was also observed in heat-stressed cows, but triglycerides and beta-OH-butyrate did not show any difference among groups. Lower lactate and higher pO2 were seen in cows with heat stress than CON. Cows in SEV had a 21% milk yield decrease, while lactose and protein decreased with fat not being affected. Heat stress had strong effects on metabolic, clinical, and performance parameters in Holstein cows.

A critical view on the soil fertility status of minimum-till kikuyu–ryegrass pastures in South Africa

Cultivated pastures provide increased productivity and contribute inter alia to food security. Rangelands in the southern Cape region of South Africa have had a low animal production potential and were therefore improved through time as cultivated pastures. Initially, annual pastures were established by conventional tillage methods, but from the 1990s permanent pastures were established on a minimum-tillage regime. Lime and fertiliser guidelines, which were developed for annual pastures established by conventional tillage methods, were followed on minimumtillage systems, despite changes in the soil physical properties and stratification of biological parameters. The study aim was to survey the soil fertility of irrigated minimum-till kikuyu–ryegrass pastures in the southern Cape region. This study highlights changes in soil fertility and identified potential detrimental effects of elevated levels of extractable phosphorus and zinc, which were drastically increased in the topsoil layer. The necessity for remedial and preventative strategies to mitigate nutrient loading in cultivated pasture soil are stressed. Fertiliser guidelines should be applied strictly and should fit the farming system. In doing so, the dual goals of economic and ecological sustainability should be achieved.

Seasonal dry matter production, botanical composition and forage quality of kikuyu over-sown with annual or perennial ryegrass

The seasonal growth and low forage quality of kikuyu restrict milk production. The aim of this study was to determine the yield and nutritional value of irrigated kikuyu over-sown with perennial, Italian or Westerwolds ryegrass grazed by dairy cows. The three pasture systems reached optimum growth during different months and seasons. Lowest growth rates occurred during winter. Peak growth rates occurred during spring for the Italian ryegrass–kikuyu, summer for the Westerwolds ryegrass–kikuyu, and late spring and early summer for perennial ryegrass–kikuyu pasture. All three pasture systems had similar total annual dry matter yields (kilograms dry matter [DM] per hectare) during year 1, but the perennial ryegrass–kikuyu pasture achieved a higher annual DM yield during year 2. As kikuyu density increased in kikuyu–ryegrass pastures from winter to summer, the DM and neutral detergent fibre content increased, whereas the metabolisable energy content decreased. All three treatments were deficient in calcium during all seasons and in phosphorus during summer and autumn as a pasture for high-producing dairy cows.

Effect of dietary supplementation with Spirulina on the expressions of AANAT, ADRB3, BTG2 and FASN genes in the subcutaneous adipose and Longissimus dorsi muscle tissues of purebred and crossbred Australian sheep.

BackgroundThe demand for healthy, lean and consistent meat products containing low saturated fatty acid content and high quality polyunsaturated fatty acids (PUFA), especially long-chain (≥C20) omega-3 PUFA, has increased in recent times. Fat deposition is altered by both the genetic background and dietary supplements, and this study aimed to assess the effect of dietary Spirulina supplementation levels on the mRNA expression patterns of genes controlling lipid metabolism in the subcutaneous adipose tissue (SAT) and Longissimus dorsi (ld) muscle of Australian crossbred sheep.MethodsTwenty-four weaned lambs belonging to four breeds under the same management conditions were maintained on ryegrass pasture and fed three levels of Spirulina supplement (control, low and high). In terms of nutrient composition, Spirulina is a nutrient-rich supplement that contains all essential amino acids, vitamins and minerals. It also is a rich source of carotenoids and fatty acids, especially gamma-linolenic acid (GLA) that infer health benefits. After slaughter, subcutaneous adipose tissue (SAT) and ld samples were subjected to mRNA extraction and reverse transcription using quantitative polymerase chain reaction (RT-qPCR) to assess the mRNA expression levels of the Aralkylamine N-acetyltransferase (AANAT), Adrenergic beta-3 receptor (ADRB3), B-cell translocation gene 2 (BTG2) and Fatty acid synthase (FASN) genes, which are associated with lipid metabolism.ResultsBoth low and high Spirulina supplementation levels strongly up-regulated the transcription of all the selected genes in both SAT and ld tissues (mostly in the subcutaneous adipose), but sheep breed and sex did not influence the gene expression patterns in these tissues.ConclusionsThe evidence indicates that high Spirulina supplementation level resulted in a decrease in intramuscular fat content in Australian purebred and crossbred sheep due to the enhanced production of melatonin in sheep muscle tissues and strong up-regulation of mRNA expression of BTG2 in SAT which negatively affected fat deposition. In contrast, low Spirulina supplementation level strongly up-regulated the ADRB3 and FASN genes responsible for fat production. These findings are consistent with the observed phenotypic data suggesting that low Spirulina supplementation level can increase lamb production, with higher long-chain PUFA content.

Effects of concentrate supplementation on enteric methane emissions and milk production of grazing dairy cows

Although concentrate supplements in ruminant diets have been recognised as an effective enteric methane mitigation strategy, very few studies have examined the effects of concentrate supplementation on enteric methane emissions under grazing conditions. Twenty four multiparous Holstein Friesian cows were used in a crossover design study to investigate the effects of two concentrate feeding levels across two periods on enteric methane emissions and milk production of grazing dairy cows. Each period had a duration of four weeks (three weeks for diet adaptation and one week for measurements) and no interval in between them. Dietary treatments consisted of two concentrate feeding levels per cow (1 vs. 5kg; as-fed basis) offered daily in equal meals during milking. Enteric methane emissions from cows grazing perennial ryegrass pasture were measured during the final week of each period using the sulphur hexafluoride tracer technique. Milk yield and liveweight were determined daily during each methane measurement period, whereas milk composition and body condition score (BCS) were determined weekly. Daily herbage intake by individual cows during methane measurement weeks was estimated using an energy requirement model and animal records and diet composition. In period 1, cows receiving 5kg concentrate supplement were estimated to reduce herbage intake by 1.8kg DM/d compared to cows receiving 1kg of concentrate, whereas in period 2 cows receiving the 5kg concentrate supplementation were estimated to reduce herbage intake by 4.4kg DM/d, compared to cows receiving 1kg of concentrate. In both periods, milk yield increased with increasing concentrate level, with an average milk response to concentrate supplementation of 0.68kg milk DM/kg concentrate DM over the two periods. Concentrate feeding level had no effect on milk fat, protein or total solids contents. In period 2, lactose content increased in cows offered 5kg/d concentrate. Increasing concentrate feeding level increased liveweight and BCS in period 1, but not in period 2. Feeding 5kg of concentrate supplement increased enteric methane emission by 34g/d in period 1 (323 vs. 357g/d) and 41g/d in period 2 (349 vs. 390g/d) compared to 1kg of concentrate supplement. However, enteric methane emission per unit of estimated feed intake (dry matter or gross energy) or milk output (gross or energy corrected) was not affected by level of concentrate supplementation. It was concluded that under generous grazing conditions (high allowance of good quality herbage) a moderate increase in concentrate supplementation resulted in a simultaneous increase in milk yield and enteric methane emission, so that enteric methane emission per unit of milk yield was unaffected. Thus, a moderate level of concentrate supplementation of dairy cows grazing pastures of high digestibility would not be an effective enteric methane mitigation strategy.

Deploying four optical UAV-based sensors over grassland: challenges and limitations

Abstract. Unmanned aerial vehicles (UAVs) equipped with lightweight spectral sensors facilitate non-destructive, near-real-time vegetation analysis. In order to guarantee robust scientific analysis, data acquisition protocols and processing methodologies need to be developed and new sensors must be compared with state-of-the-art instruments. Four different types of optical UAV-based sensors (RGB camera, converted near-infrared camera, six-band multispectral camera and high spectral resolution spectrometer) were deployed and compared in order to evaluate their applicability for vegetation monitoring with a focus on precision agricultural applications. Data were collected in New Zealand over ryegrass pastures of various conditions and compared to ground spectral measurements. The UAV STS spectrometer and the multispectral camera MCA6 (Multiple Camera Array) were found to deliver spectral data that can match the spectral measurements of an ASD at ground level when compared over all waypoints (UAV STS: R2=0.98; MCA6: R2=0.92). Variability was highest in the near-infrared bands for both sensors while the band multispectral camera also overestimated the green peak reflectance. Reflectance factors derived from the RGB (R2=0.63) and converted near-infrared (R2=0.65) cameras resulted in lower accordance with reference measurements. The UAV spectrometer system is capable of providing narrow-band information for crop and pasture management. The six-band multispectral camera has the potential to be deployed to target specific broad wavebands if shortcomings in radiometric limitations can be addressed. Large-scale imaging of pasture variability can be achieved by either using a true colour or a modified near-infrared camera. Data quality from UAV-based sensors can only be assured, if field protocols are followed and environmental conditions allow for stable platform behaviour and illumination.

Sustainable perennial pastures in Northland

In the northern half of Northland, perennial ryegrassbased pastures have exhibited poor persistence. Nineteen tall fescue and ryegrass pastures in the region infected with either MaxP or AR37 fungal endophytes, respectively, had high levels of endophyte-infected tillers and low levels of contamination from wild endophytes. On surveyed farms, MaxP-infected tall fescue pastures had good contents of sown grass, which were higher than sown grass contents in AR37-infected ryegrass pastures, but on two far-north monitor farms these temperate grasses failed to compete with summer active C4 grasses such as kikuyu and carpet grass. For tall fescue and perennial ryegrass to form productive pastures in this region, sown seed should have high levels of viable endophyte, soil fertility should be adequate for good grass and legume growth, and pastures should be well managed. Summer droughts may still be too severe in some years for these temperate grasses to persist in the face of C4 grass competition. Keywords: Endophyte, Epichloë, Neotyphodium, Lolium perenne, Festuca arundinacea, soil fertility

Assessment of tillage effects on soil quality of pastures in South Africa with indexing methods

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.

Comparison of cattle and goat grazing behaviour in an Italian ryegrass pasture invaded by Rumex obtusifolius L.

Comparison of cattle and goat grazing behaviour in an Italian ryegrass pasture invaded by Rumex obtusifolius L.

Efeito da adubação nitrogenada na produção de forragem, teor de proteína bruta e taxa de lotação em pastagens de azevém

O objetivo desta pesquisa foi avaliar a produção e o teor de proteína bruta da forragem de três pastagens de azevém (Lolium multiflorum Lam) cv. Comum, adubadas com 50, 100 e 150 kg de N/ha, na forma de ureia, de maio a outubro de 2012, onde foram conduzidos cinco ciclos de pastejo. Na avaliação da pastagem de azevém foram usadas vacas da raça Holandesa (530 kg PC) que receberam diariamente suplementação alimentar de 4,5 kg de concentrado. Avaliou-se a massa de forragem no pré e no pós-pastejo, a composição botânica e estrutural do azevém, e a taxa de lotação. Foram coletadas amostras de forragem pelo método de simulação de pastejo para análise de proteína bruta. O delineamento experimental foi o inteiramente casualizado com três tratamentos (níveis de N) e três repetições (piquetes). Os valores médios para produção de forragem, teor de proteína bruta e taxa de lotação foram: 4827; 6344 e 6123 kg/ha; 20,17; 21,51 e 22,82%; 2,3; 2,95 e 3,32 UA/ha para os tratamentos de 50, 100 e 150 kg de N/ha, respectivamente. O nível máximo de nitrogênio recomendado é de 100 kg de N/ha.

Perfil de ácidos graxos na carne de novilhos superjovens da raça Devon, terminados sob diferentes sistemas de alimentação

The objective of this study was to evaluate the fatty acid profile of meat of Devon steers finished in feedlot, or winter pasture (pasture of ryegrass - Lolium multiflorum Lam), or tropical pasture (association of millet pasture - Pennisetum americanum (L.) Leeke - and alexander grass – Brachiaria plantaginea). At the beginning of finishing the average weight of steers was 320 kg and the age was 15 months. A completely randomized design with three treatments and variable number of repetitions. The roughage:concentrate ratio from feedlot was 60:40. The lipid content of Longissimus dorsi muscle was influenced by the feeding system, the winter pasture showed higher lipid content in comparison to tropical pasture, while the lipid content of feedlot was intermediary. The tropical pasture showed intramuscular fat more saturated in relation to winter pasture, mainly due to the higher participation of C15:0, C17:0 and C20:0 acids. The feedlot and winter pasture animals showed meat with higher content of monounsaturated fatty acids in relation to tropical pasture, but there was no effect of the diet on the total polyunsaturated fatty acids. The winter pasture provided meat with higher conjugated linoleic acid (CLA) and of omega-3 acids in relation to feedlot, while the tropical pasture did not differ from the other two treatments. Pasture finishing provided omega6/omega3 ratio more benefic in relation to feedlot finishing. The winter pasture finishing provided meat with intramuscular fat more benefic in comparison to feedlot finishing, mainly due to higher CLA content, higher omega-3 acids and lower omega-6/omega3 ratio. Tropical pasture finishing resulted in meat with intermediate nutritional value between winter pasture and feedlot.

The influence of season on lambs' feeding preference for plantain, chicory and red clover

The objective of the three studies reported here was to examine the grazing preference and diet selection of lambs for plantain (Plantago laceolata), chicory (Cichorium intybus L.) and red clover (Trifolium pratense) compared with New Zealand’s conventional ryegrass (Lolium perenne) pasture. Study One investigated the diet selection of lambs for 7 days at the beginning of March, using transects with tagged plants on a mixed plantain, chicory and red clover sward. Study Two was an outdoor preference experiment conducted in both March and May by observation of lambs on adjacent monocultures of plantain, chicory and red clover. Study Three was an indoor feeding trial that aimed to determine the intake rate and relative preference of weaned lambs for two herbages (chicory and plantain), two legumes (lucerne and red clover) and ryegrass pasture, in both spring (November) and summer (March). Study One determined that when grazing the mixed sward for a period of 7 days, the mean day that lambs commenced grazing red clover, chicory and plantain was Day 1.6 ± 0.1, 4.8 ± 0.2 and 6.2 ± 0.2, respectively, with significant (P < 0.05) differences between all species. In relation to preference as observed in Study Two, more lambs (P < 0.05) were seen to be grazing red clover at any time, and more lambs were grazing chicory (P < 0.05) than plantain. There was, also an interaction of season with preference, with plantain becoming more acceptable (P < 0.05) to the lambs in May (late autumn) versus March (early autumn). In Study Three, the term ‘preference’ refers to the natural logarithm of the ratio of amounts eaten between the forage being tested and the alternative forage offered simultaneously. This was established in triplicate by offering pairs of all the plant species side by side to individually penned lambs. The results indicated that plantain was consumed at a similar rate (P > 0.05) to that of ryegrass, whereas red clover and chicory had higher voluntary feed intakes, likely due to lower fibre content. The intake rate of chicory was greater in summer than spring and may be related to increased palatability due to the increased water-soluble carbohydrate content of chicory in summer. Regardless of season, average preference for red clover was always higher (P < 0.05) than that of chicory, plantain and ryegrass. Plantain was considerably less preferred in summer than spring. Differences in diet selection and preference may offer a unique opportunity to manipulate utilisation of pastures using a diverse range of plant species.

Qualidade da carne de cordeiros lactentes suplementados com teores de glicerina bruta em comedouro privativo

The objective of this research was to evaluate the effect of crude glycerin in the supplement provided in creep feeding on the physico-chemical and sensory characteristics of meat from suckling lambs kept in pasture ryegrass. Thirty two suckling lambs, sixteen male and sixteen female, were distributed into 4 diets with different concentrations of crude glycerin: 0, 10, 20 and 30% crude glycerin, in the replacement of corn, in the isoproteic supplement (18% CP) provided daily in amounts equivalent to 2% of body weight. The experimental design was randomized blocks, with each variable data submitted to analysis of variance at 5% significance and the significant results subjected to regression analysis. There was no effect (P>0,05) of contents of crude glycerin on the chemical composition and cholesterol content of lamb meat. On the other hand, there was increased linearly (P>0,05) pH and cooking losses by the use of crude glycerin. No influence (P>0,05) of crude glycerin concentration on the texture profile analysis (TPA), sensorial analysis by triangular test and even when was evaluated attributes color, tenderness and juiciness of lamb meat. Up to 30% of crude glycerin in the supplement provided in creep feeding for suckling lambs grazing ryegrass do not compromise the physical-chemical and sensorial quality of the lamb meat.

Effect of climate variability on pasture-based dairy feeding systems in south-east Australia

The Australian dairy industry relies primarily on pasture for its feed supply. However, the variability in climate affects plant growth, leading to uncertainty in dryland pasture supply. This paper models the impact of climate variability on pasture production and examines the potential of two pasture-based dairy feeding systems: (1) to experience winter deficits; (2) to carry forward the conserved pasture surpluses as silage for future use; and (3) to conserve pasture surpluses as hay. The two dairy feeding systems examined were a traditional perennial ryegrass-based feeding system (ryegrass max. – RM) and a system that incorporated double cropping into the perennial ryegrass pasture base (complementary forage – CF). The conditional probability of the RM and CF systems to generate pasture deficits in winter were 94% and 96%, respectively. Both systems could carry forward the surplus silage into the following lactation almost once in every 4–5 years with the RM system performing slightly better than the CF system. The proportions of the grain-based concentrates fed in the two systems were 25% and 27% for the RM and CF systems, respectively. This study suggests that double-cropping systems have the potential to provide high-quality feed to support the feed gaps when pasture is not available due to increased variability in climatic conditions.

Chemical and physical amelioration of subsoils has limited production benefits for perennial pastures in two contrasting soils

While broad acre grazing is the major agricultural land use in Southern Australia, there has been comparatively little research on the effect of alleviating subsoil limitations on pasture production under field conditions. The effect of modifying the physical and chemical properties of soil on perennial pasture production and root distribution was studied on 2 major soil types in two regions of Southern Victoria, Australia. Soil treatments included the deep placement of fertilisers, lime and organic matter, and soil disturbance to a range of depths. The Ellinbank field site on a Ferrasol was monitored for 2 years, while the Curdievale site on a Sodosol was monitored for 1 year. There were substantial changes in soil physical and chemical characteristics as a result of the soil treatment. Soils were softer, less acidic and had increased nutrient availability within the profile. However, these changes did not result in consistent gains in pasture productivity, over-and-above the normal practice of surface applied nutrients and lime. The deep placement of organic matter at the Ellinbank site resulted in an initial increase in pasture production, but this effect declined with time. The perennial ryegrass (Lolium perenne L.) based pasture was shallow-rooted and substantial modifications to the soil profile did not result in significant changes to root distribution. It appears that the productivity of perennial ryegrass pasture in high rainfall regions can be maintained at a productive level, with a localised nutrient and water supply.

Soil quality characteristics of kikuyu–ryegrass pastures in South Africa

Development of a soil quality index for kikuyu (Pennisetum clandestinum)–ryegrasss (Lolium spp.) pasture systems in the southern Cape of South Africa is important since there are certain warning signs that their sustainability is being threatened. A total of 142 pastures throughout the region were sampled and several soil physical, chemical and biological indicators were quantified. A minimum data set of the most sensitive indicators was chosen using principal component analyses. Linear scoring functions for these indicators were used to develop a soil quality index. The most sensitive indicators were: extractable P>gravel content>water holding capacity (WHC)>exchangeable acidity (EA)>soil organic matter (SOM)=penetration resistance (PR)>exchangeable Mn. The soil quality index (SQI) was equated as: SQI=0.13 (PR)+0.16 (Gravel)+0.15 (WHC)+0.14 (EA)+0.17 (P)+0.12 (Mn)+0.13 (SOM). This soil quality index is appropriate for pasture systems in the southern Cape of South Africa, and may be useful for similar pasture systems in other areas.