Dry Sheep Equivalents Research Articles

Lime, phosphorus and stocking rate of an extensively managed permanent pasture affect feed-on-offer, sheep growth rate, carrying capacity and wool production

Context Soil acidity constrains pasture productivity, limiting production from grazing animals. Lime application can ameliorate acidity, although the rate is increased when incorporated rather than surface applied. Soils in south-eastern Australia are generally highly erodible, containing valuable native grasses that might be lost if disturbed. Surface application is, therefore, the only option, but the extent to which lime can ameliorate acidity and increase pasture and animal production requires research. Aim This 10-year experiment studied three rates of surface-applied lime, two of superphosphate (P) and two stocking rates (SR) on continuously grazed sheep on acidic soils. Two flocks were studied, one from May 1999 to December 2002, and the second from August 2005 to July 2008. We hypothesised that wool production and animal liveweight would increase as (1) lime rate increased, (2) P rate increased, and (3) peak animal productivity would occur under the combination of the highest rates of lime and P. Key results The experiment coincided with the Millennium Drought reducing forage production, and slowing lime movement into the soil and consequent amelioration. During Flock 1, effective SR (dry sheep equivalents (DSE)/ha) of the low P, low SR and limed treatment became higher by 1 DSE/ha for 10 months during the final flock measurement months, as drought intensified. During Flock 2, effective SR of both high P, high SR and limed treatments were greater by 2 DSE/ha than non-limed counterpart for the first 9 months of 2006. Trends of higher animal production under lime became clearer with time, so were more apparent in Flock 2 than Flock 1, and at higher SR. High lime, high P and high SR had the greatest wool production. High P, low SR and nil lime was initially highly productive, but declined sharply when legumes disappeared, associated with soil aluminium toxicity. Lime maintained superior ground cover under drought, reducing the danger of sward death and soil erosion, demonstrating its sward preservation, sustainability and ecosystem service benefits. Implications With the ever-increasing price of land, farmers must increase their land’s productivity. This trial demonstrated production and environmental benefits associated with acid soil amelioration through lime application.

Optimal sheep stocking rates for broad-acre farm businesses in Western Australia: a review

Sheep stocking rate influences farm profit significantly; however determining the optimal stocking rate is a difficult task. In this paper, we address this challenge through three main steps. First, we review the definition of stocking rate; second, we examine prior research relevant to the review topic and highlight the factors that need to be considered when determining the optimal stocking rate; and third, we make recommendations for improvements in research on establishing the optimal sheep stocking rate. Inconsistency in the definition of stocking rate can lead to miscommunication among researchers, advisers and farmers. If 10 dry sheep equivalents (DSE)/ha is optimal for one flock, it may not be optimal for another flock because the DSE measure does not fully capture the nuances of different patterns of nutritional requirements among sheep classes and feed availabilities and their respective prices and costs. The optimal stocking rate occurs when the marginal economic benefit of an additional animal equals its marginal cost. Determining this point requires an understanding of the quantity and quality of feed available throughout the year, the optimal liveweight profile throughout the year, the impact of seasonal variation, the impact of labour availability, the cost of alternative feeds, prices of livestock and livestock products, the risk preferences of the farmer, and any emission policies relating to greenhouse gases. Farmers tend to use their own judgement to set their stocking rates, with the aim of maximising utility. However, the complexities listed make it a challenging task. Thus, researchers have used various simulation and programming models to aid decision-making over optimal stocking rates, but most farmers continue to rely on their own personal judgement. Moreover, often a focus of this modelling is for sheep systems in eastern Australia. Generalising this research across Australia is difficult due to differences in climatic conditions and markets across Australia. Often farmers are unaware of the profits they are foregoing when choosing either an overly conservative or excessive stocking rate. Our research has shown that foregone income of up to AUD50 per hectare can occur when a stocking rate 30% below or above the optimum is selected. Thus, despite the complexities that underpin the stocking rate decision, we believe that there are potential rewards from further research on the optimisation of stocking rates.

Australian surveys on parasite control in sheep between 2003 and 2019 reveal marked regional variation and increasing utilisation of online resources and on-farm biosecurity practices.

Australian Wool Innovation Limited (AWI) commissioned three cross-sectional surveys of sheep producers' sheep parasite control practices over a 15-year period from 2003 to 2018. The aims were to document current sheep parasite incidence and control practices, to measure change in sheep parasite control practices over time and to inform extension messages for sheep industry advisors and sheep farmers. The surveys were conducted in 2004, 2012 and 2019 measuring sheep parasite control practices in the years 2003, 2011 and 2018. The surveys focused on incidence and control of the three major sheep parasite groups; gastrointestinal nematodes, blowflies and lice. The 2003 and 2011 surveys were paper-based and the 2018 survey was accessed via a link to an online survey. This article is the first in a series of four presenting the results of the three surveys and will cover methods, demographics, production systems and general parasite management. Response rates to the surveys declined each year from the peak response rate in 2003 (n = 1365 in 2003; n = 575 in 2011 and n = 354 in 2018). Mean reported rainfall was significantly lower in 2018 (407 mm) than in 2003 (611 mm) and 2011 (650 mm). The demographics of the respondents and their production systems were largely similar between the three surveys for respondent age, median property size, income from wool and sheep meat, proportion of the property area cropped, median sheep dry sheep equivalent (DSEs), ewes as a proportion of the total flock and median cattle DSEs. Month of weaning was more likely to be in summer months for summer dominant rainfall areas and spring for intermediate and winter dominant rainfall areas. There was a marked increase in the proportion of respondents asking for an animal health history when introducing sheep to their flock from 2011 (9%) to 2018 (65%). Similarly, a greater proportion of respondents isolated introduced sheep for at least 2 weeks in 2018 (82%) compared with 2011 (19%). However, there was a decrease in the use of a quarantine lice treatment for introduced sheep from 2011 (50%) to 2018 (21%). Farmers rated themselves, other farmers or member of their staff as most important sources of information on parasite control in both 2011 and 2018. There was a significant increase in the proportion of respondents visiting the ParaBoss suite of websites from 2011 to 2018 confirming their growing importance for information delivery and decision support.

Performance of sheep systems grazing perennial pastures. 2. Wool quality and lamb growth

This study evaluated wool quality and lamb production from four management systems with Merino ewes grazing a perennial pasture between 2006 and 2010, using different combinations of lambing time, ram breed and percentage of summer-active pasture species. All systems were stocked at a similar midwinter rate (dry-sheep equivalents per hectare of 8, 10.2, 13, 11.2 and 11.2 in the successive seasons 2006–2010). Liveweight, condition score, C fat and eye muscle depth at weaning of both Merino and crossbred lambs were always higher (P < 0.05) for lambs born in July than those born in September. Similarly, the sale weight of lambs born in July was always higher (P < 0.05) than of lambs born in September, partly because these lambs were usually retained for longer before sale. When lambs were born in September, sheep systems that carried higher numbers of ewes per hectare at the same midwinter stocking rate produced sale weights of lambs similar to those with fewer ewes, except where systems with fewer lambs per hectare enabled lambs to be retained for longer in favourable seasons. A higher percentage of lucerne (Medicago sativa, 40% cf. 20%) increased lamb sale weights only in favourable seasons. Clean fleece weights per ewe and staple strength were similar among systems in most years (2008–2010), although mean fibre diameter was lower (P < 0.05) in both late lambing systems (with 40% and 20% lucerne). The results indicate that choice of lambing time, ram breed and the flexibility to alter lamb sale date with seasonal conditions will have a larger impact on the performance of individuals than number of ewes per hectare where systems are grazed at the same midwinter stocking rate.

Performance of sheep systems grazing perennial pastures. 1. Pasture persistence and enterprise productivity

Sheep production can be optimised by matching the pasture supply curve to feed demand. This study evaluated the production from four management systems with Merino ewes during 2006–2010 in southern New South Wales by using different combinations of lambing time (winter, split, spring), ram breed (Merino, terminal), and percentage of summer-active pasture species (40% or 20% lucerne, Medicago sativa). All systems were stocked at a similar midwinter rate (dry-sheep equivalents per hectare of 8, 10.2, 13, 11.2 and 11.2 in the successive seasons 2006–2010), and there were three replicates of each system. Groundcover and pasture persistence were not adversely impacted by sheep system because sheep were removed at predetermined biomass triggers. Wool production per hectare was up to 178% or 12 kg/ha higher (P < 0.001) in systems where a later month of lambing allowed an increase in number of ewes per hectare at the same midwinter stocking rate. The quantity of lamb sold was not consistently higher in any one system, or in systems producing both crossbred and Merino lambs vs only Merino lambs, owing to variation in the weight and age of lambs at sale, but was increased (P < 0.001) by 175 kg/ha with use of 40% compared with 20% lucerne in a high-rainfall year. The risk of requiring high levels of supplementary feeding was higher in systems with later lambing because of below-average rainfall between 2006 and 2009. Large increases in production can be achieved from the same pasture base through choice of management system with different lambing time, stocking rate or ram breed, but flexibility is needed to optimise production in varying seasonal conditions.

Performance of sheep systems grazing perennial pastures. 3. Fertility, fecundity and lamb survival

Management system has the potential to alter the reproductive output of sheep flocks and thereby farm profit. A study was conducted between 2006 and 2010 to evaluate the reproductive performance of four management systems with differing combinations of time of lambing, stocking rate and ram breed, while grazing at a similar midwinter stocking rate (dry-sheep equivalents per hectare of 8, 10.2, 13, 11.2 and 11.2 in the successive seasons 2006–2010). Three systems, winter lambing Merino (WLM), split lambing (SL) and later lambing (LL), grazed replicated farmlets comprising pastures that were 20% lucerne (Medicago sativa), 20% tall fescue (Festuca arundinacea) and 60% phalaris (Phalaris aquatica). A fourth system (high lucerne (HL)) grazed farmlets of 40% lucerne, 15% tall fescue and 45% phalaris. All systems used Merino ewes: in WLM mated to Merino rams, lambing in July; in SL half of the ewes lambing to terminal-breed rams in July, the other half lambing to Merino rams in September; and in LL and HL lambed in September, half to terminal-breed and half to Merino rams. The number of lambs weaned per ewe joined was 10% higher (P < 0.05) in the WLM system (0.99 ± 0.03) than in the September-lambing systems LL and HL, largely a result of a higher number of fetuses per ewe and despite lower (P < 0.05) lamb survival to marking in some years. The SL system weaned a similar (P > 0.05) number of lambs per ewe (0.95 ± 0.03) to all other systems. However, the number of lambs weaned per hectare was least in WLM (4.6 ± 0.2), lower than in the HL and LL systems by 2.7 lambs/ha because of a lower stocking rate. The ranking of systems for fetal number and lamb survival was not consistent among years. Spring-lambing systems produced more lambs per hectare because of a higher stocking rate but fewer lambs per ewe than the WLM system. System differences in pregnancy rate, fecundity and lamb survival were not consistent between years.

Macropods, feral goats, sheep and cattle: 1. Equivalency in how much they eat

The extent to which goats and cattle eat equivalent amounts of forage as sheep has been based on their maintenance energy requirements (MERs) relative to a 50kg wether or dry ewe, known as a dry sheep equivalent (DSE). As such, a 50kg goat was considered 1 DSE and a 450kg steer as 7–8 DSE. In comparison, the DSE of macropods has been based on their basal metabolic rate (BMR) or energy expenditure of grazing (EEg) relative to those of sheep, with a 50kg macropod thought to be 0.7 and 0.45 DSE respectively. Based on published energy requirements of goats, macropods and cattle relative to sheep, their DSE values are estimated to be 1.2, 1.0 and 7.6 respectively. However, relative energy requirements may not be the same as relative dry matter intakes (DMIs), due to differences in forage quality, the structure of digestive tracts and selective foraging capabilities. Allometric equations that predict DMI were developed from published liveweights and intakes of sheep, goats, macropods and cattle. Given DMIs when fed high-quality forage, a 50kg goat was 1 DSE, a 50kg macropod was 0.7 DSE and a 450kg steer was 7.6 DSE. Their DMIs were depressed by 35–50% when fed low-quality forage, but a goat remained as 1 DSE, macropods increased to 1.0 DSE and cattle increased to 8.3 DSE. The capacity of macropods to maintain relatively higher DMIs of low-quality forage than sheep is probably due of their faster digesta passage rates and more expandable stomachs. These DMIs of animals provided ad-libitum quantities of similar forages in small pens are likely to differ from their DMIs when selectively grazing heterogeneous rangeland pastures. Under these conditions, sheep select higher-quality diets than cattle, and kangaroos select higher-quality diets than sheep, which increase the relative DMIs of the smaller herbivores. For this reason, a 50kg macropod is likely to be 1 DSE and consume twice as much forage than previously assumed.

Offsets required to reduce the carbon balance of sheep and beef farms through carbon sequestration in trees and soils

The sustainability of farming is important to ensure that natural resources remain available into the future. Ruminant livestock production generates more greenhouse gas emissions than other types of agricultural production and most livestock mitigation options to date have a modest greenhouse gas reduction potential (<20%). Trees and soils, by comparison, can sequester large amounts of carbon depending on the availability of land. Previous studies on carbon neutral livestock production have shown that farms with a stocking rate of 8 dry sheep equivalents (DSE)/ha can be carbon neutral or carbon positive by sequestering more carbon than is emitted from the farm. However, the carbon offsets required by farms with higher stocking rates (>20 DSE/ha) has yet to be studied in Australia. The challenge is to sequester enough carbon to offset the higher level of emissions that these higher stocked farms produce. This study calculated the carbon balance of wool, prime lamb and beef enterprises using a range of stocking rates (6–22 DSE/ha) and levels of tree cover in two agroecological zones. Emissions from livestock, energy and transport were offset by the carbon sequestered in trees and soils. Additionally, the carbon balance was calculated of a case study, Jigsaw Farms, an intensive sheep and beef farm in south-eastern Australia. The methods used to calculate emissions and carbon stocks were from the Australian National Greenhouse Gas Inventory. The majority of stocking rates were carbon positive over a 25-year period when 20% of the sheep or beef enterprises were covered with trees. This study demonstrated that substantial reductions can be made in greenhouse gas emissions through the use of carbon sequestration, particularly in trees. The results showed that from 2000 to 2014 Jigsaw Farms reduced its emissions by 48% by sequestering carbon in trees and soil. The analysis of different stocking rates and tree cover provides an important reference point for farmers, researchers and policy analysts to estimate the carbon balance of wool, prime lamb and beef enterprises based on stocking rate and the area of tree cover.

Better management of intensive rotational grazing systems maintains pastures and improves animal performance

Grazing management has been identified as a means of increasing livestock production and improving the composition of perennial pastures. The benefits of intensive rotational grazing have been the subject of much debate, but few studies have evaluated contrasting management of intensive rotational systems. A grazing management experiment was established on a pasture with cocksfoot (Dactylis glomerata L., varieties Porto and Kara) as the dominant species, to investigate different stocking rates, paddock numbers and rotation speeds, and a flexible treatment that adjusted grazing time, rest periods and stock numbers for optimal pasture utilisation. Data were collected on pasture composition and diet quality assessed by using faecal analysis, animal weight changes and pasture characteristics. Animal production per hectare was greatest for fast rotations (56 days’ rest) at high stocking rates (HStR, 13.6 dry sheep equivalents (DSE) ha–1), but continuous grazing (CG) was equally productive. Although flexible grazing based on the 3–4-leaf stage was proposed as the best balance between pasture production and quality, this treatment had lower stocking rates (9.2 DSE ha–1) and was not as productive. No treatment negatively affected pasture composition over the 4-year period. Area of bare ground was highest for the HStR CG treatment; however, the 30-paddock rotations were able to limit bare ground at the same stocking rate. The results indicated that intensive rotational grazing could be effectively managed by using green herbage allowance. In spring, green herbage allowance needed to be 1–1.5 kg green dry matter (DM) DSE–1 day–1, which increased to 5 kg green DM DSE–1 day–1 as the quality of green DM decreased, to allow selective grazing to enhance diet quality.

Does establishing lucerne under a cover crop increase farm financial risk?

Rainfed farms in south-eastern Australia often combine annual cropping and perennial pasture phases with grazing sheep enterprises. Such diversity serves in managing diseases, pests and plant nutrition while stabilising income in the face of wide, uncorrelated variations in international commodity prices and local weather over time. We use an actuarial accounting approach to capture the above contexts to render financial risk profiles in the form of distributions of decadal cash balances for a representative 1000-ha farm at Coolamon (34°50ʹS, 147°12ʹE) in New South Wales, Australia. For the soil and weather conditions at this location we pose the question of which approach is better when establishing the perennial pasture lucerne (Medicago sativa L.): sowing with the final crop of the cropping phase, or sowing alone following the final crop? It is less expensive to sow lucerne with the final crop, which can provide useful income from the sale of grain, but this practice can reduce pasture quantity and quality in poorer years. Although many years of field research have confirmed that sowing lucerne alone is the most reliable way to establish a pasture in this area, and years of extension messages to this effect have gone out to farmers, they often persist in sowing lucerne with their final cereal crops. For this region, counting all costs, we show that sowing lucerne alone can reduce farm financial risk (i.e. probability of negative decadal cash balances) at stocking rates >10 dry sheep equivalents (DSE)/ha, compared with the practice of sowing lucerne with a cover crop. Establishing lucerne alone allows the farmer the option to profitably run higher stocking rates for higher median decadal cash margins without additional financial risk. At low stocking rates (i.e. 5 DSE/ha), there appears to be no financial advantage of either establishment approach. We consider the level of equity, background farm debt and overhead costs to demonstrate how these also affect risk-profile positions of the two sowing options. For a farm that is deeply in debt, we cannot suggest either approach to establishing lucerne will lead to substantially better financial outcomes.

Light grazing of crop residues by sheep in a Mediterranean-type environment has little impact on following no-tillage crops

Abstract Crop residue is often grazed by sheep after harvest, over the dry summer period from December to March in Mediterranean environments. However, soil cover provided by crop residues is a key component of conservation agriculture for maintaining favourable soil structure and high yields. A series of 31 site × year experiments was conducted to assess the effect of summer stubble grazing on residue levels and following crop yields. Relatively light grazing, with stocking rates below 10 dry sheep equivalent (DSE) and between 90 and 471 DSE days ha −1 , had no significant effect on the amount of residue, soil properties, soil water, weeds or yield in the following crop. The main effect of grazing was to knock down and scatter the standing crop residues. However, longer term grazing at relatively high intensity (956 DSE days ha −1 ) on heavy soil, over both summer and winter, as in a pasture phase, did significantly reduce residue levels, infiltration and yield (by 59%). The effect of summer grazing on soil mineral N was small and inconsistent, with increased mineral N, by about 3–7 kg N ha −1 , following grazing at two of the 13 sites. By contrast, higher mineral N, by 2–15 kg N ha −1 , was measured in the un-grazed plots at three of the 13 sites. This was due to increased growth of legume pastures in the absence of grazing. More research is needed to confirm the yield effects when cropping after an annual pasture/fallow that is grazed over summer and winter, particularly on different soil types.

Sheep greenhouse gas emission intensities under different management practices, climate zones and enterprise types

Greenhouse gas emissions (GHG) from broadacre sheep farms constitute ~16% of Australia’s total livestock emissions. To study the diversity of Australian sheep farming enterprises a combination of modelling packages was used to calculate GHG emissions from three sheep enterprises (Merino ewe production for wool and meat, Merino-cross ewes with an emphasis on lamb production, and Merino wethers for fine wool production) at 28 sites across eight climate zones in southern Australia. GHG emissions per ha, per dry sheep equivalents and emissions intensity (EI) per tonne of clean wool or liveweight sold under different pasture management or animal breeding options (that had been previously determined in interviews with farmers) were assessed relative to baseline farms in each zone (‘Nil’ option). Increasing soil phosphorus fertility or sowing 40% of the farm area to lucerne resulted in the smallest and largest changes in GHG/dry sheep equivalents, respectively (–66%, 113%), though both of these options had little influence on EI for either clean wool or liveweight sold. Breeding ewes with greater body size or genotypes with higher fleece weight resulted in 11% and 9% reductions, respectively, in EI. Enterprises specialising in lamb production (crossbred ewes) had 89% lower EI than enterprises specialising in fine wool production (Merino wethers). Thus, sheep producers aiming for lower EI could focus more on liveweight turnoff than wool production. Emissions intensities were typically highest in cool temperate regions with high rainfall and lowest in semiarid and arid regions with low aboveground net primary productivity. Overall, animal breeding options reduced EI more than feedbase interventions.

Comparative daily energy expenditure and water turnover by Dorper and Merino sheep measured using doubly labelled water

Details of the energy (food) requirements of domestic herbivores are essential for predicting grazing pressures and subsequent ecological impacts on rangelands. However, these details are lacking for some of the more recently introduced sheep breeds to Australia, such as the Dorper breed sheep, which are principally meat sheep, and it is uncertain how they compare with the traditional Merino, a wool-breed, sheep. We used the doubly labelled water method to compare the field metabolic rate and water turnover rate of Dorpers and Merinos grazing together in a small holding paddock in a typical rangeland environment. We found no significant differences in field metabolic rate (Dorpers 481 ± 125 kJ and Merinos 500 ± 109 kJ kg–0.73 day–1) or water turnover rate (Dorpers 397 ± 57 mL and Merinos 428 ± 50 mL kg–0.8 day–1). As such we conclude that under controlled conditions with limited movement and ready access to feed and water, dry sheep equivalent of 1 is appropriate for Dorpers (that is, one Dorper ewe had a grazing requirement equal to one standard, dry Merino wether). However, we also found that the field metabolic rate for Merinos under these conditions was only around half that measured in published studies for animals ranging freely in a large paddock system. This suggests that more work is needed to fully appreciate the energetic and grazing impacts of Dorpers versus Merinos under more realistic grazing conditions (e.g. large paddock systems) where feed and water are more spread. It also highlights limitations of the current dry sheep equivalent rating system, which has been derived from laboratory measures of sheep metabolic rates.

Corrigendum to: Optimising grain yield and grazing potential of crops across Australia’s high-rainfall zone: a simulation analysis. 1. Wheat

Interest is growing in the potential to expand cropping into Australia's high-rainfall zone (HRZ). Dual-purpose crops are suited to the longer growing seasons in these environments to provide both early grazing for livestock and later regrow to produce grain. Grain yield and grazing potential of wheats of four different maturity types were simulated over 50 years at 13 locations across Australia's HRZ, and sowing date, nitrogen (N) availability and crop density effects were explored. Potential grazing days on wheat were obtained by simulating sheep grazing crops to Zadoks growth stage Z30 at 25 dry sheep equivalents (DSE)/ha. Optimal sowing dates for each maturity type at each location were matched to the flowering window during which risk of frost and heat stress was lowest. Overall, we found significant national potential for dual-purpose use of winter wheat cultivars across Australia's HRZ, with opportunities identified in all regions. Simulated mean wheat yields exceeded 6t/ha at most locations, with highest mean grain yields (8–10t/ha) in southern Victoria, and lower yields (5–7t/ha) in the south-west of Western Australia (WA) and central and northern New South Wales (NSW). Highest grazing days were from winter cultivars sown early (March–mid-April), which could provide 1700–3000 DSE-days/ha of grazing across HRZ locations; this was 2–3 times higher than could be obtained from grazing spring cultivars (200–800 DSE-days/ha). Sowing date was critical to maximise both grazing and grain yield potential from winter cultivars; each 1-week delay in sowing after 8 March reduced grazing by 200–250 DSE-days/ha and grain yield by 0.45t/ha. However, in Mediterranean climates, a lower frequency of early sowing opportunities before mid-April (

Soil carbon and inferred net primary production in high- and low-intensity grazing systems on the New England Tableland, eastern Australia

Management of grazing lands for the accumulation of soil carbon stocks (CS) has been proposed as an effective way to reduce net greenhouse gas emissions from agriculture. However, there are conflicting reports on the effects of grazing management on soil carbon. Most comparisons have involved some combination of no grazing, rotational grazing and set stocking. In the present study we compared two adjacent commercial grazing systems, distinguished on the basis of inputs and livestock productivity, located on New England basaltic landscapes experiencing a cool temperate climate. The high-intensity (H) system sustains an average stocking rate of 18 dry sheep equivalents (dse) ha–1, with a turnoff rate of 9dseha–1year–1, with high levels of investment in assets, management and fertiliser. The low-intensity (L) system, with less intensive management and half the fertiliser of the H system, sustains a stocking rate of 9dseha–1, with a turnoff rate of 3dseha–1year–1, which is slightly higher than the regional average. Pasture biomass production was inferred (back-calculated) from stocking rates and animal feed requirements using published data. From the H and L systems, seven paired landscapes from valley floor to upper hillslopes and plateaux were selected. The seventh included a forest reserve. One hundred and eighty-six undisturbed soil cores (0–0.5m depth) were assessed for bulk density, total C and N, particulate C and a range of plant nutrients. There were few differences in CS, soil pH and nutrient levels between H and L grazing systems. Average CS (0–0.3m) in pasture soils was 103Mgha–1, but was higher in the forest soil at 190Mgha–1. Regression of CS versus soil mass was a satisfactory method of dealing with the bias introduced by the higher soil bulk density in perennial pasture systems compared with the forest. The similarity of CS in H and L pasture soils was despite inferred net primary production being 1.9–3.6MgCha–1year–1 greater in H than L systems, implying higher rates of C turnover in the former. The global warming potential of the inferred annual emissions of CH4 and N2O in the H and L systems was equivalent to approximately 19% and 13% of the cycling atmospheric–plant CO2 carbon respectively.

Optimising grain yield and grazing potential of crops across Australia’s high-rainfall zone: a simulation analysis. 2. Canola

Recent expansion of cropping into Australia’s high-rainfall zone (HRZ) has involved dual-purpose crops suited to long growing seasons that produce both forage and grain. Early adoption of dual-purpose cropping involved cereals; however, dual-purpose canola (Brassica napus) can provide grazing and grain and a break crop for cereals and grass-based pastures. Grain yield and grazing potential of canola (up until bud-visible stage) were simulated, using APSIM, for four canola cultivars at 13 locations across Australia’s HRZ over 50 years. The influence of sowing date (2-weekly sowing dates from early March to late June), nitrogen (N) availability at sowing (50, 150 and 250 kg N/ha), and crop density (20, 40, 60, 80 plants/m2) on forage and grain production was explored in a factorial combination with the four canola cultivars. The cultivars represented winter, winter × spring intermediate, slow spring, and fast spring cultivars, which differed in response to vernalisation and photoperiod. Overall, there was significant potential for dual-purpose use of winter and winter × spring cultivars in all regions across Australia’s HRZ. Mean simulated potential yields exceeded 4.0 t/ha at most locations, with highest mean simulated grain yields (4.5–5.0 t/ha) in southern Victoria and lower yields (3.3–4.0 t/ha) in central and northern New South Wales. Winter cultivars sown early (March–mid-April) provided most forage (>2000 dry sheep equivalent (DSE) grazing days/ha) at most locations because of the extended vegetative stage linked to the high vernalisation requirement. At locations with Mediterranean climates, the low frequency (<30% of years) of early sowing opportunities before mid-April limited the utility of winter cultivars. Winter × spring cultivars (not yet commercially available), which have an intermediate phenology, had a longer, more reliable sowing window, high grazing potential (up to 1800 DSE-days/ha) and high grain-yield potential. Spring cultivars provided less, but had commercially useful grazing opportunities (300–700 DSE-days/ha) and similar yields to early-sown cultivars. Significant unrealised potential for dual-purpose canola crops of winter × spring and slow spring cultivars was suggested in the south-west of Western Australia, on the Northern Tablelands and Slopes of New South Wales and in southern Queensland. The simulations emphasised the importance of early sowing, adequate N supply and sowing density to maximise grazing potential from dual-purpose crops.

Optimising grain yield and grazing potential of crops across Australia’s high-rainfall zone: a simulation analysis. 1. Wheat

Interest is growing in the potential to expand cropping into Australia’s high-rainfall zone (HRZ). Dual-purpose crops are suited to the longer growing seasons in these environments to provide both early grazing for livestock and later regrow to produce grain. Grain yield and grazing potential of wheats of four different maturity types were simulated over 50 years at 13 locations across Australia’s HRZ, and sowing date, nitrogen (N) availability and crop density effects were explored. Potential grazing days on wheat were obtained by simulating sheep grazing crops to Zadoks growth stage Z30 at 25 dry sheep equivalents (DSE)/ha. Optimal sowing dates for each maturity type at each location were matched to the flowering window during which risk of frost and heat stress was lowest. Overall, we found significant national potential for dual-purpose use of winter wheat cultivars across Australia’s HRZ, with opportunities identified in all regions. Simulated mean wheat yields exceeded 6 t/ha at most locations, with highest mean grain yields (8–10 t/ha) in southern Victoria, and lower yields (5–7 t/ha) in the south-west of Western Australia (WA) and central and northern New South Wales (NSW). Highest grazing days were from winter cultivars sown early (March–mid-April), which could provide 1700–3000 DSE-days/ha of grazing across HRZ locations; this was 2–3 times higher than could be obtained from grazing spring cultivars (200–800 DSE-days/ha). Sowing date was critical to maximise both grazing and grain yield potential from winter cultivars; each 1-week delay in sowing after 8 March reduced grazing by 200–250 DSE-days/ha and grain yield by 0.45 t/ha. However, in Mediterranean climates, a lower frequency of early sowing opportunities before mid-April (<30% of years) is likely to limit the potential to use winter cultivars. Prospects to graze shorter season spring cultivars that fit later sowing windows require further examination in south-west WA, the slopes of NSW and southern Queensland.

Effects of fencing on vegetation and soil restoration in a degraded alkaline grassland in northeast China

In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected area, whereas the grazed area was continuously grazed at 8.5 dry sheep equivalent (DSE)/hm2. In the current research, soil and plant samples were taken from grazed and fenced areas to examine changes in vegetation and soil properties in 2005, 2006 and 2008. Results showed that vegetation characteristics and soil properties improved significantly in the fenced area compared with the grazed area. In the protected area the vegetation cover, height and above- and belowground biomass increased significantly. Soil pH, electrical conductivity and bulk density decreased significantly, but soil organic carbon and total nitrogen concentration increased greatly in the protected area. By comparing the vegetation and soil characteristics with pre-degraded grassland, we found that vegetation can recover 6 years after fencing, and soil pH can be restored 8 years after fencing. However, the restoration of soil organic carbon, total nitrogen and total phosphorus concentrations needed 16, 30 and 19 years, respectively. It is recommended that the stocking rate should be reduced to 1/3 of the current carrying capacity, or that a grazing regime of 1-year of grazing followed by a 2-year rest is adopted to sustain the current status of vegetation and soil resources. However, if N fertilizer is applied, the rest period could be shortened, depending on the rate of application.

Crop and livestock production for dual-purpose winter canola (Brassica napus) in the high-rainfall zone of south-eastern Australia

Dual-purpose use of canola (Brassica napus) for forage in winter before seed production is a practice recently developed in southern Australia. The feasibility for dual-purpose spring canola (B. napus annua) in the medium-rainfall zone (450–650mm) has been demonstrated commercially, with significant adoption. Testing of later-maturing, dual-purpose winter canola (B. napus biennis) in long-season, high-rainfall areas (>650mm) has been restricted to mechanical defoliation or crash grazing. We conducted a series of six field experiments to evaluate the crop and livestock productivity of dual-purpose winter canola, involving a variety of stocking rates, grazing regimens and different cultivars at Canberra, ACT, and Young, NSW, in south-eastern Australia in 2007 and 2008. European winter canola cultivars sown between 21 March and 21 April provided 800–1100 dry sheep equivalent (DSE) grazing days/ha in Canberra and 1550–2600 DSE grazing days/ha in Young with little impact on subsequent yield (range 2.6–5.8t/ha), provided the sheep were removed from crops prior to bud elongation. Grazing occurred between 18 June and 1 September in Canberra and between 16 June and 14 August in Young and generally had no effect on harvest index or oil content. High stocking rates for short duration (126DSE/ha for 7 days) reduced sheep live-weight gains and meat production by ∼50% (110g/day; 92kg/ha) compared with stocking rates of low (22DSE/ha for 47 days) or moderate (43DSE/ha for 22 days) stocking rates (mean 220g/day; 182kg/ha) despite similar overall grazing pressure (882–1034 DSE grazing days/ha). The flexibility in sowing date and grazing times afforded by the vernalisation characteristics of winter canola make it an ideal, flexible option in high-rainfall mixed-farming systems. Winter canola could complement or even replace the traditional later-sown spring cultivars (for dual-purpose and/or grain-only production) in areas with high rainfall (>650mm) where early sowing opportunities (March) and cooler spring temperatures can maximise yield. Our results demonstrate significant potential for high livestock production and high grain and oil yield from dual-purpose winter canola in high-rainfall environments.

Livestock weights in response to three whole-farmlet management systems

This paper reports changes in livestock weights recorded in a whole-farmlet experiment, which aimed to examine the profitability and sustainability of three different pasture and grazing management strategies. The assessment of liveweights was considered a key component of measuring the integrated effects of the farmlet-scale treatments. The three farmlets comprised a typical management regime, which employed flexible rotational grazing over eight paddocks with moderate soil fertility (farmlet B), a system based on the same grazing management and paddock number but with higher levels of sown pasture and soil fertility (farmlet A) and a farmlet with moderate soil fertility and intensive rotational grazing over 37 paddocks (farmlet C). Early in the experimental period, there were no significant differences between farmlets in the liveweight of any class of livestock. However, from the second year onwards, as the pasture renovation, soil fertility and grazing management treatments took effect, differences in liveweight between farmlets became more apparent and significant. The stocking rate, which was treated as an emergent property of each farmlet, reached a maximum annual average value after 5 years of 12.6, 8.5 and 7.7 dry sheep equivalents (dse)/ha on farmlets A, B and C representing 84, 113 and 51% of their respective target stocking rates which were 15, 7.5 and 15 dse/ha. The liveweights of ewes, both before joining and during pregnancy, varied with year and farmlet with those on farmlets A and B tending to be significantly heavier than those on farmlet C. From 2003 to 2006, liveweights were significantly (P < 0.001) affected by a wide array of factors and their interactions including: date, ewe age, green digestible herbage, legume herbage mass, proportion of farmlet grazed, stocking rate and level of supplementary feeding. The weights of lambs/weaners/hoggets, both pre- and post-weaning, were at times also higher on farmlets A and B compared with those on farmlet C and were affected by a similar range of factors to those which affected ewe weights. Similar relative differences also applied to the liveweights of the other livestock run on the farmlets, namely wethers and non-reproductive cattle. The results suggest that stocking rate was able to be increased towards the higher target of farmlet A due to the higher level of pasture renovation and soil fertility on that farmlet, which led to high liveweights per head as well as the higher stocking rate. However, as the stocking rate increased on farmlet A, the differences between farmlets in liveweight per head diminished and the need for supplementary feeding increased. In contrast, the intensive rotational grazing practised on farmlet C did not allow the farmlet to increase its stocking rate towards its higher target. It appears that the higher proportion of each of farmlets A and B grazed at any one time allowed all classes of livestock to reach higher liveweights per head than on farmlet C, due presumably to the greater proportion of those two farmlets grazed at any one time.