Increased Pasture Production Research Articles

Soil respiration rate and its sensitivity to temperature in pasture systems of dry-tropics

Tree clearing is a topical issue the world over. In Queensland, the high rates of clearing in the past were mainly to increase pasture production. The present research evaluates the impact of clearing on some soil biological properties, i.e. total soil respiration, root respiration, microbial respiration, and microbial biomass (C and N), and the response of soil respiration to change in temperature. In-field and laboratory (polyhouse) experiments were undertaken. For in-field studies, paired cleared and uncleared pasture plots were selected to represent three major tree communities of the region, i.e. Eucalyptus populnea, E. melanophloia, and Acacia harpophylla. The cleared sites were chosen to represent three different time-since-clearing durations (5, 11–13, and 33 years; n=18 for cleared and uncleared plots) to determine the temporal impact of clearing on soil biological properties. Experiments were conducted in the polyhouse to study in detail the response of soil respiration to changes in soil temperature and soil moisture, and to complement in-field studies for estimating root respiration. The average rate of CO2 emission was 964 g CO2/m2/yr, with no significant difference (P<0.05) among cleared and uncleared sites. Microbial respiration and microbial biomass were greater at uncleared compared with those at cleared sites. The Q 10-value of 1.42 (measured for different seasons in a year) for in-field measurements suggested a small response of soil respiration to soil temperature, possibly due to the limited availability of soil moisture and/or organic matter. However, results from the polyhouse experiment suggested greater sensitivity of root respiration to temperature change than for total soil respiration. Since root biomass (herbaceous roots) was greater at the cleared than at uncleared sites, and root respiration increased with an increase in temperature, we speculate that with rising ambient temperature and consequently soil temperature, total soil respiration in cleared pastures will increase at a faster rate than that in uncleared pastures.

Effects of dose and period of sewage sludge application on soil, tree and pasture components in a Pinus radiata D. Don silvopastoral system

The adequate use of sewage sludge in silvopastoral systems could enhance positive relationships between pasture and trees to increase farm incomes at medium, short and long term. The main aspects related to adequate sewage sludge use as a fertiliser are dose and timing of application, once heavy metal concentrations have been taken into account. This paper aims to evaluate the date and dose of sewage sludge applications on soil (KCl pH, soil organic matter), pasture production and tree growth after the establishment of a silvopastoral system with Pinus radiata D. Don developed on sandy soils with an initial pH of 5. It is concluded that the contribution of sewage sludge does not modify the soil conditions in a consistent manner, but cause detectable edaphic improvements depending on the climatic conditions, the results of which are manifested in enhancement of pasture and trees. The application of high doses of sewage sludge is the best option within those studied, as tree growth and pasture production tend to be increased. There are no clear effects with regard to the date of application, but if the desire is to increase pasture production during the spring season, the sewage sludge will be applied in the first of the application dates, whereas the greatest growth in the diameter of trees is produced in the plots fertilised in February, although the date of application does not appear to have a clear effect on their growth in height.

Optimal management of fertiliser and stocking rate in temperate grazing systems

Phosphorus (P) fertilisers are one of the key tools available for increasing pasture production and the profitability of grazing enterprises. However, recent rapid changes in fertiliser price have increased the importance of developing optimal management strategies for applying P fertiliser and setting stocking rates. We applied a novel combination of process-based grazing systems modelling and randomised cash flow analyses to examine how changes in fertiliser price affect optimal fertiliser application rates and stocking rates for sheep grazing systems in south-eastern Australia, simultaneously taking into account long-term economic viability and environmental sustainability. We used ‘GrassGro’, a grazing systems decision support tool, to simulate three sheep enterprise types (Merino wethers, Merino ewes, crossbred ewes) at two locations (Hamilton, Victoria; Bookham, New South Wales). Gross margins from each year simulated in GrassGro (1966–2007) were randomised 500 times and input to a cash flow analysis that identified the financially optimal stocking rate for a range of fertiliser applications and the financial risk frontiers (combinations of stocking rate and fertiliser input for which the enterprise becomes financially unviable). For all enterprises examined at both locations, the optimal combinations of stocking rate and fertiliser application rate did not vary markedly as fertiliser price changed. Regardless of enterprise type or location, the fertiliser application rate at which the highest gross margins were achieved provided the greatest range of stocking rates that were both financially viable and environmentally sustainable. Increases in fertiliser price reduced the combinations of stocking rate and fertiliser application rate that were viable in the long term, emphasising the importance of well informed grazing management decisions.

Effect of woody vegetation clearing on nutrient and carbon relations of semi-arid dystrophic savanna

Throughout the savanna biome, woody vegetation is cleared to increase productivity of herbaceous pasture. While clearing can result in increased pasture production of semi-arid dystrophic savannas in the short term, it is uncertain whether production is sustained in the long term. There is insufficient knowledge of how clearing affects soil nutrient and organic carbon (SOC) stocks. Using cleared-uncleared site pairs, we evaluated techniques for time-integrated assessment of nutrient and carbon relations in Australian savanna. Short-term in situ resin incubation showed that soil at cleared sites had a higher time-integrated availability of ammonium and nitrate, indicating that nitrogen (N) may turn over faster and/or is taken up slower at cleared sites than uncleared savanna. Nitrate and ammonium availability was approximately 2-fold higher in spring than in summer, likely due to greater uptake and/or loss of nitrate during summer rains. Nitrate was a prominent N source for evergreen trees, especially before summer rain, pointing to a role of trees as permanent N sinks. Stable isotope signatures of soil and vegetation indicate that N input occurs via N2 fixing microbiotic crusts and Acacia species. 30 years after clearing, SOC contained more C4 grass-derived carbon than uncleared savanna, but this shift in C source was not associated with the net C gain often observed in grasslands. Interactions between altered nutrient and C relations and composition of the understorey should be assessed in context of introduced buffelgrass (Cenchrus ciliaris) which had higher macronutrient concentrations than native grasses. Heterogeneity of the studied soils highlights the need for replication at several spatial scales to infer long-term dynamics with space-for-time chronosequences. We conclude that the techniques presented here are useful for gaining knowledge of the biogeochemical processes governing savannas and the systems that result from clearing.

Effects of the different rates of urease and nitrification inhibitors on gaseous emissions of ammonia and nitrous oxide, nitrate leaching and pasture production from urine patches in an intensive grazed pasture system

Minimizing nitrogen (N) losses via ammonia (NH 3) and nitrous oxide (N 2O) emissions into the atmosphere and nitrate (NO 3 −) leaching into surface and ground waters from intensively grazed pastures is essential for environmental protection worldwide. Applying urease inhibitor such as N-(n-butyl) thiophosphoric triamide (nBPT) or (Agrotain) and nitrification inhibitor dicyandiamide (DCD) to grazed pastures has the potential to mitigate such N losses. A lysimeter/mini plot experiment, using Paparua silt loam soil near Lincoln, Canterbury New Zealand, was conducted to quantify these N losses during May 2007 to July 2008. The nine treatments were: cow urine only applied at an equivalent rate of 600 kg N ha −1, urine + DCD at 5 kg ha −1, urine + DCD at 7 kg ha −1, urine + DCD at 10 kg ha −1, urine + double inhibitor (DI), i.e. both Agrotain and DCD applied at 1 L ha −1 and 7 kg ha −1, respectively (or 1:7 of v/w basis), urine + DI (1:10), urine + DI (2:7), urine + DI (2:10) and the control (no urine). These treatments were randomly applied to one set of lysimeters or mini plots in May as autumn and then to another set of lysimeters or mini plots in August as spring applications. Additional nine lysimeters received DCD only at rates equivalent to 5, 7 and 10 kg ha −1 in autumn to see if DCD has any effect on NO 3 − leaching and pasture production and N uptake from non-urine patches in autumn. Gaseous emissions of NH 3 and N 2O, NO 3 − leaching and pasture production and N uptake varied with the types and rates of the applied inhibitors during the two seasons. DCD applied at 7 and 10 kg ha −1 rates with urine was more effective than its lower rate of 5 kg ha −1 and reduced N 2O emissions by 37–53% (autumn) and 47% (spring), NO 3 − leaching losses by 57–55% (autumn) and 26–10% (spring) compared with urine alone. However DCD increased NH 3 emissions by 41% and 18% compared with urine alone treatment after autumn and spring, respectively. DCD applied at higher rates also increased pasture dry matter by 9% and 12% and N uptake by 12% and 6% after autumn and spring applications, respectively. However DCD applied at different rates without urine in autumn had no such effect on either NO 3 − leaching or pasture dry matter yield or N uptake. The DI at 1:7 ratio was more effective than the higher rates of DI and DCD in reducing losses of NH 3 (48% and 51%), N 2O (55% and 63%) and NO 3 − leaching (56% and 42%) as well as increasing pasture production (13% and 17%) and N uptake (7% and 18%) compared with urine alone treatment in autumn and spring, respectively. These results suggest that applying Agrotain + DCD at a ratio of 1:7 (v/w) may provide the best option for both mitigating N losses and improving pasture production in intensively grazed systems.

FACTIBILIDAD TÉCNICA Y ECONÓMICA DE RIEGO POR ASPERSIÓN EN PRADERAS ARTIFICIALES DESTINADAS A LECHE DEL SUR DE CHILE

There are several manners that can be used to increase pasture production, one of which is irrigating during dry periods. It is important to generate information regarding the technical and economic feasibility of investment in equipment for pasture sprinkler irrigation in southern Chile. A total of 60 irrigation projects were carried out, using different combinations of factors involved, such as: different irrigation equipments (quick coupling pipes, hose rewinding drum, central pivot and K-Line); energy sources (gravimetric energy, electricity and oil); water sources (superficial and groundwater); irrigated surface areas (10 and 25 ha) and partial project financing through Law 18.450 (0 and 50% irrigation subsidy). For each project, technical and economic aspects were calculated, analyzing investment and annual costs per hectare. The results showed that the central pivot was the system that required the lowest water flow for the application of the irrigation rate; on the contrary, quick coupling systems used the greatest water flow. In terms of the investment costs, K-Line systems showed the lowest and those of the central pivot were the more expensive. Regarding energy sources, systems with a water fall (gravity) and diesel operation required the lowest investment, whereas electrically powered systems were the most expensive. In general, projects without an irrigation subsidy (Law 18.450) were not economically profitable (for 10 and 25 ha), except for the K-Line projects (10 and 25 ha) and quick coupling projects (10 and 25 ha). On the other hand, some 25 ha subsidized irrigation projects were economically attractive, being outstanding K-Line and central pivot systems, which presented the greatest marginal income of this study, reaching $173.229 ha-1. Systems that used underground water had a negative income, even when they were subsidized.

Effect of rate and form of dicyandiamide application on nitrate leaching and pasture production from a volcanic ash soil in the Waikato

Animal urine has been identified as the main source of nitrate leaching from grazed pastures. The nitrification inhibitor dicyandiamide (DCD) can potentially reduce nitrate leaching losses and increase pasture utilisation of nitrogen (N) from urine. A mowing trial was established on a sandy loam (Typic Orthic Allophanic) soil in the Waikato region to examine the effect of liquid and granular forms of DCD, applied in May at rates of 0, 7, 14 and 28 kg ha‐1, on the fate of urea applied at 600 kg N ha‐1 in artificial urine. The DCD treatments increased pasture production over 211 days by an average of 15% (P < 0.001) and there was no significant effect of rate or form of DCD. Soil sampling 76 days after treatment application showed greater amounts of ammonium remaining in the top 450 mm of soil in the DCD treatments (average ammonium‐N for all DCD treatments of 93 kg N ha‐1 compared with 43 kg N ha‐1 for the urine‐only treatment). Total inorganic N in the top 600 mm of soil at the final (118 day) sampling showed a linear response to DCD application rate (113–190 kg ha‐1 from lowest to highest rate; P < 0.05) and the liquid DCD tended to retain more inorganic‐N than the granular DCD (179 and 131 kg ha‐1, respectively; P < 0.1). Averaged across all DCD treatments, 37% of the applied DCD was measured in the top 450 mm of soil at the day 48 sampling and most of that DCD was found below 150 mm. Leaching of N was measured using ceramic cup samplers at 600 mm depth in the 14 kg DCD ha‐1 treatments and showed that DCD reduced nitrate leaching by 24% from 275 to 208 kg ha‐1 (P < 0.01), with no significant effect of DCD form. Thus, DCD in both liquid and granular forms proved effective in reducing nitrate leaching from urine, indicating its potential for N loss mitigation in grazed pastures.

Climate change effects on pasture systems in south-eastern Australia

Climate change projections for Australia predict increasing temperatures, changes to rainfall patterns, and elevated atmospheric carbon dioxide (CO2) concentrations. The aims of this study were to predict plant production responses to elevated CO2 concentrations using the SGS Pasture Model and DairyMod, and then to quantify the effects of climate change scenarios for 2030 and 2070 on predicted pasture growth, species composition, and soil moisture conditions of 5 existing pasture systems in climates ranging from cool temperate to subtropical, relative to a historical baseline. Three future climate scenarios were created for each site by adjusting historical climate data according to temperature and rainfall change projections for 2030, 2070 mid- and 2070 high-emission scenarios, using output from the CSIRO Mark 3 global climate model. In the absence of other climate changes, mean annual pasture production at an elevated CO2 concentration of 550 ppm was predicted to be 24–29% higher than at 380 ppm CO2 in temperate (C3) species-dominant pastures in southern Australia, with lower mean responses in a mixed C3/C4 pasture at Barraba in northern New South Wales (17%) and in a C4 pasture at Mutdapilly in south-eastern Queensland (9%). In the future climate scenarios at the Barraba and Mutdapilly sites in subtropical and subhumid climates, respectively, where climate projections indicated warming of up to 4.4°C, with little change in annual rainfall, modelling predicted increased pasture production and a shift towards C4 species dominance. In Mediterranean, temperate, and cool temperate climates, climate change projections indicated warming of up to 3.3°C, with annual rainfall reduced by up to 28%. Under future climate scenarios at Wagga Wagga, NSW, and Ellinbank, Victoria, our study predicted increased winter and early spring pasture growth rates, but this was counteracted by a predicted shorter spring growing season, with annual pasture production higher than the baseline under the 2030 climate scenario, but reduced by up to 19% under the 2070 high scenario. In a cool temperate environment at Elliott, Tasmania, annual production was higher than the baseline in all 3 future climate scenarios, but highest in the 2070 mid scenario. At the Wagga Wagga, Ellinbank, and Elliott sites the effect of rainfall declines on pasture production was moderated by a predicted reduction in drainage below the root zone and, at Ellinbank, the use of deeper rooted plant systems was shown to be an effective adaptation to mitigate some of the effect of lower rainfall.

Dung pads increase pasture production, soil nutrients and microbial biomass carbon in grazed dairy systems

In grazing systems dung is an important source of nutrients which can increase soil fertility and contribute to nutrient cycling through increased pasture production. Changes in soil chemical and biological properties and pasture production were measured below and around dung pads created in the field. Almost 65% of the total dung P remained after 45 days and about two-thirds of the pad fresh weight had disappeared in that time, indicating that physical degradation is the mechanism of incorporation of dung P. All the pads bar one were completely degraded by 112 days. At this time, soil pH and EC increased under dung pads as did Olsen extractable inorganic phosphorus (Pi) and total phosphorus (Pt), with these changes observed at 0–5 and 5–10 cm depths. Bicarbonate extractable soil organic phosphorus (Po) was not affected by dung and the observed differences in soil Po:Pi ratios were largely influenced by the substantial addition of inorganic P from dung. Dung increased the P buffering capacity of the 0–5 cm soil samples collected at the end of the experiment, potentially contributing to the increased extractable soil P measured under the pads. Dung also changed soil properties in 0–10 cm samples with increases in soil pH, EC, Colwell P and Colwell K recorded even long after the dung had completely disappeared. Microbial biomass carbon increased under dung pads in the 0–10 cm soil samples in the first 45 days after pads were applied. Total herbage production and ryegrass biomass increased significantly under and around the pads by 112 days after dung was applied. The botanical composition changed significantly with increased ryegrass contents observed, but only under the dung pads. This experiment demonstrated that increases in pasture around dung pads in the field are not solely due to animal rejection.

Trace gas flux and the influence of short-term soil water and temperature dynamics in Australian sheep grazed pastures of differing productivity

Temperate pastures are often managed with P fertilizers and N2-fixing legumes to maintain and increase pasture productivity which may lead to greater nitrous oxide (N2O) emissions and reduced methane (CH4) uptake. However, the diel and inter-daily variation in N2O and CH4 flux in pastures is poorly understood, especially in relation to key environmental drivers. We investigated the effect of pasture productivity, rainfall, and changing soil moisture and temperature upon short-term soil N2O and CH4 flux dynamics during spring in sheep grazed pasture systems in southeastern Australia. N2O and CH4 flux was measured continuously in a High P (23 kg P ha−1 yr−1) and No P pasture treatment and in a sheep camp area in a Low P (4 kg P ha−1 yr−1) pasture for a four week period in spring 2005 using an automated trace gas system. Although pasture productivity was three-fold greater in the High P than No P treatment, mean CH4 uptake was similar (−6.3 ± SE 0.3 to −8.6 ± 0.4 μg C m−2 hr−1) as were mean N2O emissions (6.5 to 7.9 ± 0.8 μg N m−2 hr−1), although N2O flux in the No P pasture did not respond to changing soil water conditions. N2O emissions were greatest in the Low P sheep camp (12.4 μg ± 1.1 N m−2 hr−1) where there were also net CH4 emissions of 5.2 ± 0.5 μg C m−2 hr−1. There were significant, but weak, relationships between soil water and N2O emissions, but not between soil water and CH4 flux. The diel temperature cycle strongly influenced CH4 and N2O emissions, but this was often masked by the confounding covariate effects of changing soil water content. There were no consistently significant differences in soil mineral N or gross N transformation rates, however, measurements of substrate induced respiration (SIR) indicated that soil microbial processes in the highly productive pasture are more N limited than P limited after >20 years of P fertilizer addition. Increased productivity, through P fertilizer and legume management, did not significantly increase N2O emissions, or reduce CH4 uptake, during this 4 week measurement period, but the lack of an N2O response to rainfall in the No P pasture suggests this may be evident over a longer measurement period. This study also suggests that small compacted and nutrient enriched areas of grazed pastures may contribute greatly to the overall N2O and CH4 trace gas balance.

The fate of phosphorus under contrasting border-check irrigation regimes

Flood-irrigation, to the extent that outwash (runoff from border-check bays) occurs, is a major cause of P loss from grazed pastures and has potential to harm surface water quality. We used a combination of rainfall simulation to produce runoff and field sampling of outwash to investigate processes of P loss from treatments receiving no irrigation and irrigation at 10%, 15%, and 20% soil moisture and every 21 days (3w). Intact soil blocks were removed from each treatment, dung removed, soils wetted to about 32% soil moisture, and runoff produced via rainfall simulation. This indicated that P losses were proportional to soil Olsen P concentrations (29.8–51.4 mg Olsen P/kg; 0.096–0.541 mg dissolved reactive P/L). Olsen P concentration was less in those treatments receiving a greater number of irrigations due to increased pasture production and, presumably, loss via outwash. When soil blocks were allowed to dry, concentrations in runoff more than doubled and were paralleled by a decrease in soil microbial biomass P. However, when outwash was sampled in the field, P loss was greater in more frequently irrigated treatments. This was attributed to increased stocking rates and P-release from dung masking any soil effect. However, differences in P loss in outwash from 2 treatments (without recent grazing) were attributed to different soil moisture before irrigation. Assuming 25% of irrigation is lost as outwash, annual loads were estimated to range from 0.7 kg P/ha in the 10% treatment, irrigated 2.6 times a year, to 12.6 kg P/ha in the 3w treatment, irrigated 6.5 times per year. This suggests that the frequency of irrigation and stocking rate dictate the majority of P lost in this system (not soil P concentration). Hence, mitigation practices should be promoted to minimise outwash in intensively sheep-grazed pastures and potential surface water quality impacts.

Lime, sewage sludge and mineral fertilization in a silvopastoral system developed in very acid soils

In recent years, in the European Union, sewage sludge production has been increased as a result of EU policy (European directive 91/271/EEC). Organic matter and nutrient sewage sludge contents, principally nitrogen, indicate it can be used as fertilizer. The objective of the experiment was to compare the effect of no fertilization, three doses of sewage sludge, with or without liming, and the fertilization usually used in the region applied over a period of 3 years on pasture production and tree growth in a silvopastoral system. The experiment was conducted in the northwest of Spain. The soil was very acid (soil pH = 4.5) and had very low nutrient levels, especially P, that is related to site index. It was sown with a grass mixture (25 kg ha−1 of Lolium perenne L. 10 kg ha−1 of Dactylis glomerata L. and 4 kg ha−1 of Trifolium repens L.) in Autumn 1997 under a plantation of 5-year-old Pinus radiata D. Don at a density of 1,667 trees ha−1. Liming and sewage sludge fertilization increased soil pH and reduced saturated aluminium percentage in the interchange complex (Al/IC) in the soil, coming up the effect before with liming. Medium and high sewage sludge doses increased pasture production in the two first years. In a silvopastoral system, positive tree growth response to different fertilization treatments depended on tree age, initial soil fertility, soil pH, the relationship of competition with pasture production and previous liming application.

Establishment, growth and development of plantain and chicory under grazing

Pasture herbs can increase pasture production and feed quality over summer when ryegrass based pasture often constrains livestock production. The growth and development of plantain ('Ceres Tonic'), chicory ('Choice') and red clover ('Redmore') were related to thermal time during establishment. Keywords: Plantago, Cichorium, annual production, thermal time

Pasture production responses to fertiliser on renovated West Coast pakihi soils

Mowing trials were carried out to determine the rates of fertiliser nitrogen (N), phosphorus (P), potassium (K) and sulphur (S) and frequency of application of K for maximum pasture production on extremely infertile humped and hollowed pakihi soils in the Grey Valley (Souters and Sommervilles dairy units), and flipped soils at Cape Foulwind (Bassetts dairy unit) under high annual rainfall (2000 - 3000 mm) on the West Coast. In the first measurement year, there was no significant increase in pasture production above 480 kg N/ha, 56 kg P/ha, 360 kg K/ha and 136 kg S/ha at Souters and Bassetts and a significant increase in pasture production up to 600 kg N/ha, 56 kg P/ha, 360 kg K/ha and 140 kg S/ha at Sommervilles. In the second year, there was no significant pasture production increase above 480 kg N/ ha, 56 kg P/ha, 360 kg K/ha and 136 kg S/ha at all sites. The high N, K and S rates were required because nutrients were not being recycled through returned clippings. This situation would be similar to the early stages of dairy management on these units where only a small proportion of pasture would receive recycled nutrients through return of excreta. Over time, a larger proportion of the pasture would be affected by excreta and fertiliser nutrient requirements would be expected to decrease. There was no increase in pasture production from applying potassium chloride in more than four applications per year at Souters and Bassetts in the first year, but a significant increase in pasture production from eight compared with four applications per year at Sommervilles, where soil QT (quick test) K levels were lower than at the other two sites. Keywords: flipped, hump and hollowed, nitrogen, phosphorus, potassium, sulphur

Benefits or Losses from Clearing Trees to Develop Pastures in Central Queensland, Australia?

Clearing trees to develop land for exotic pastures that enhance pasture production and hence the financial gains, is an important issue in Queensland. Gains from clearing woodlands are questioned. Three tree communities i.e. Acacia harpophylla, Eucalyptus melanophloia and Eucalyptus populnea were selected at three different ages of clearing i.e. 5 yr, 11-13 yr and 33 yr to collect the data on pasture production, soil properties (biological and physicochemical), litter production and nutrient recycling and pasture plant diversity over 2-3 year period of the study. The net economic gains from clearing in terms of pasture production were compared to uncleared pastures and assessed against the tradeoffs of ecological services. The increase in pasture production post-clearing was not consistent with age of clearing. A bioeconomic model, applied to predict pasture production over the 50 years of time of clearing, though suggested economic benefits, however, it is difficult to predict how the loss in ecosystem functions in cleared pastures (> 30 years of clearing), by implication, affect pasture yield over time.

Influence of irrigation method on water use and production of perennial pastures in northern Victoria

The irrigation of pasture for the dairy industry accounts for a large proportion of Australia’s total irrigation water use, particularly in the Murray–Darling Basin. Most pasture is irrigated using the border-check method. The dairy industry is under increasing pressure to use water more efficiently in response to water market reforms and restrictions on future irrigation water availability, creating interest in the potential of alternative irrigation methods. A field experiment was conducted at Tatura, Victoria, Australia between July 2000 and July 2002 to quantify the differences in water use, perennial pasture production and pasture composition under border-check, surge, sprinkler and subsurface drip irrigation. The experiment aimed to assess each irrigation method as it would perform under farm best management practices. Measurements included applied water, tailwater runoff, soil water status, dry matter production and botanical composition. This experiment found that sprinkler and subsurface drip irrigation used on average 2 ML/ha.year (17–23%) less water than border-check irrigation while maintaining or increasing pasture production, consequently having a significantly higher water use efficiency. Surface runoff was significantly reduced under sprinkler and subsurface drip irrigation. Surge irrigation had no advantages over border-check. Although some differences in pasture composition were observed between irrigation treatments, the trends were inconsistent from one season to the next. The high water use by gravity fed irrigation methods is attributed to a combination of higher evaporation and groundwater accessions.

Pasture and sheep responses to lime application in a grazing experiment in a high-rainfall area, south-eastern Australia. II. Liveweight gain and wool production

‘Managing Acid Soils Through Efficient Rotations (MASTER)’ is a long-term pasture–crop rotation experiment commenced in 1992. One of the objectives was to demonstrate the extent of crop, pasture, and animal responses to lime application on a typical acidic soil in the 500–800 mm rainfall zone of south-eastern Australia. Two types of pastures (perennial v. annual pastures) with or without lime application were established in 1992. Fifteen- to eighteen-month-old Merino hoggets were used as test animals and were changed annually. This paper reports the results of sheep responses to liming from the 4 continuous pasture treatments over 6 years from 1992 to 1997. The stocking rate was the same on all plots within a treatment during each rotation period, but was varied between treatments based on the pasture availability and sheep body condition. The most important findings from this study are that the limed treatments carried 29% and 27% more stock (up to 4 DSE/ha) than the unlimed treatments for perennial and annual pastures, respectively. As a result, the limed perennial pastures produced 27% more liveweight gain (62 kg/ha.year) and 28% more greasy wool (13 kg/ha.year) than unlimed perennial pastures, whereas the limed annual pastures produced 34% more liveweight gain (77 kg/ha.year) and 24% more greasy wool (11 kg/ha.year) than unlimed annual pastures. The significant responses to lime in liveweight and wool production were detected from the second growing season after the pastures were established. The increased sheep productivity on the limed treatment was due to a combination of increased pasture production and improved pasture quality. Perennial pastures showed a slight advantage in wool production, but not in liveweight gain. However, the seasonal variation of liveweight was greater on annual pastures than on perennial pastures. The larger variation in liveweight change could lead to more adverse effects on wool quality especially at high grazing pressures. Grazing management can be used to manipulate pasture and animal productivity to increase profits from lime use.

Pasture and sheep responses to lime application in a grazing experiment in a high-rainfall area, south-eastern Australia. I. Pasture production

‘Managing Acid Soils Through Efficient Rotations (MASTER)’ is a long-term pasture–crop rotation experiment commenced in 1992. One of the objectives was to demonstrate the extent of crop, pasture, and animal responses to lime on a typical acidic soil in the 500–800 mm rainfall zone in south-eastern Australia. Two types of pastures (perennial v. annual pastures) with or without lime application were established in 1992. This paper presents the results of the pasture dry matter (DM) responses to lime application over 6 years from 1992 to 1997. Results showed that both perennial and annual pastures responded positively to lime on a highly acidic soil on the south-west slopes of New South Wales. Averaged across pasture types and 5 growing seasons, the limed pastures produced 18% more pasture DM (520 kg/ha, P &lt; 0.05) than the unlimed pastures. Significant responses to lime were detected on perennial pastures (610 kg DM/ha, P &lt; 0.05), but not on annual pastures, although the limed annual pastures produced more DM (420 kg/ha, P = 0.20) than the unlimed annual pastures. There was a large seasonal variation in pasture growth rate with the significant lime responses in winter and spring on both perennial pastures (P &lt; 0.05) and annual pastures (P &lt; 0.10 in winter and P &lt; 0.05 in spring), but no responses in autumn and summer on either perennial or annual pastures. The extra growth in winter is of importance as winter is the period when feed is normally inadequate and limits stocking rates. It is recommended that perennial-based pastures should be promoted for the purposes of productivity, in terms of increasing pasture production and improving feed quality, and for the environmental benefits in terms of alleviating the soil acidity problem and reducing the risk of dryland salinity in the high-rainfall zone in south-eastern Australia.

Influence of long-term irrigation on the distribution and availability of soil phosphorus under permanent pasture

This study examined the influence of irrigation on soil phosphorus (P) distribution and availability under permanent pasture in New Zealand. Soil samples (0–0.075, 0.075–0.15, 0.15–0.25 m) were taken from a long-term field experiment, which included a dryland and 2 irrigation treatments (irrigated at 10% and 20% soil moisture) that had received 25 kg P/ha annually as superphosphate for 52 years. Corresponding data for soil from an adjacent ‘wilderness’ site that had not been used for agriculture for 54 years were included for comparison. Analyses included total P, organic P, and inorganic P; isotopic exchange kinetics (IEK) was used to determine soil inorganic P pools of differing plant availability. Concentrations of total and inorganic P were greater in soil taken from the dryland treatment than the irrigated treatments at all depths. This was attributed to a combination of decreased pasture growth and P transfer in drainage and off-farm produce. Concentrations of organic P were greater in the irrigated treatments (e.g. 0–0.075 m: 672–709 mg P/kg) than in the dryland treatment (e.g. 0–0.075 m: 574 mg P/kg) as a consequence of increased pasture production and soil biological activity. Inorganic P availability (Cp and E1min) was also greater in the dryland treatment than the irrigated treatments. Furthermore, concentrations of inorganic P in the recalcitrant IEK pool (E&gt;3m = E3m–1y + E&gt;1y) in the 0–0.075 m soil from the dryland treatment (479 mg P/kg) were significantly greater than the 10% irrigated (346 mg P/kg) and 20% irrigated (159 mg P/kg) treatments, which was mainly attributed to physico-chemical reactions that decreased the exchangeability of accumulated inorganic P with time. Despite increased P retention capacity at depth (R/r1, 0.15–0.25 m: dryland 6.6, 10% irrigated 10.2, 20% irrigated 12.8), concentrations of total inorganic P in the 0.15–0.25 m soil layer were lower under irrigation (195–266 mg P/kg) than dryland (354 mg P/kg), which indicated that long-term flood irrigation increased P transfer by leaching. The findings of this study revealed that while irrigation improved the utilisation of applied fertiliser P it also resulted in increased P movement to depth in the soil profile.

Botanical Composition and Forage Production in an Emulated Silvopasture

Integrating trees into pasture may increase pasture production and improve nutritive value by altering both species composition and productivity. Our objective was to determine forage yield and botanical composition in response to tree species, tree density, and slope position in an emulated silvopasture (the site had no animals). In 1995, black walnut (Juglans nigra L.) and honey locust (Gleditisia triacanthos L.) trees were planted within plots (r = 3) of predominantly tall fescue (Festuca arundinacea Schreb.) pasture. Trees were planted down slopes in rows to create low, medium, and high tree densities at shoulder‐, mid‐, and toe‐slope positions. Sampling sites (n = 54) under field treatment combinations were harvested May to October at 35‐d intervals in 2002 and 2003. Before spring, summer, and fall harvests, plots were subsampled for botanical composition. Tree species did not affect botanical composition when compared over the two seasons. Plots under honey locust trees tended to have more fescue in a dry year (2002) and more legumes and less dead herbage in a wet year (2003). Greater percentages of warm‐season grasses and fewer weeds were observed at low tree density sites in 2003. Forage mass (5280, 6130, and 4970 kg ha−1 at low, medium, and high tree densities) was 16% greater under medium‐density trees. Plots under black walnut yielded 13% more forage than those under honey locust (5790 vs. 5130 kg ha−1). Appropriately spaced trees have potential to positively alter botanical composition and can support greater forage production in a southern Appalachian silvopasture.