Unfertilized Pastures Research Articles

An assessment of various measures of soil phosphorus and the net accumulation of phosphorus in fertilized soils under pasture

AbstractPhosphorus fertilizer use efficiency of pastures is often low because P accumulates in soils as sparingly‐available forms of inorganic and organic P. The aim of this study was to use sequential chemical fractionation to identify which forms of P have accumulated in soil under permanent pasture from a medium‐term (13 y) field experiment. Treatments included an unfertilized pasture (P0), and treatments designed to maintain soil P fertility at near ‘optimum' (P1) and ‘supra‐optimum' (P2) levels for pasture growth; all levels of soil P fertility were continuously grazed with either a moderate or high stocking rate (SR09 and SR18). Summed concentrations of extractable inorganic and organic P, and residual P (i.e., non‐extractable P) accounted for 20, 31, and 49% of total soil P (as determined by laboratory X‐ray fluorescence), respectively, across all surface (0–10 cm) and subsurface (10–20 cm) soil layers. A large proportion of extractable inorganic and organic P was contained in the NaHCO3 and NaOH soluble fractions across all surface soil layers, and these fractions were also the most important sinks for fertilizer P. The accumulation of organic P appeared to plateau with increasing fertilizer addition, whereas inorganic P continued to increase. The majority of the P that had been applied as fertilizer (70%) was recovered in the surface soil layer (0–10 cm). Approx. 31 and 30% of the added P was recovered in the summed concentrations of extractable inorganic and organic P, respectively, of the surface soil layer at the optimum (P1) agronomic level of soil P fertility.

Soil Organic Matter and Root and Rhizome Responses to Management Strategies in Smooth Bromegrass Pastures

Soil organic matter (SOM) is a key component of pasture production. This study investigated how management strategies that varied amount and form of N input in a long‐term experiment affected concentrations and stocks of total‐soil organic C and N, particulate organic carbon (POC), particulate organic nitrogen (PON), root and rhizome mass, C and N contents in topsoil of smooth bromegrass (Bromus inermis Leyss.) pastures with silty clay loam soils in a wet (2010) and dry (2012) year. Management strategies included: (i) unfertilized pasture grazed with unsupplemented beef cattle (CONT); (ii) unfertilized pasture grazed with dried distillers grains plus solubles (DDGS)‐supplemented beef cattle (SUPP); and (iii) nitrogen‐fertilized pasture grazed with unsupplemented beef cattle (FERT). After 8 yr, management strategies had similar concentrations and stocks of total‐soil organic C and N, POC, and PON, and there were no management strategy × year interactions. From 2010 to 2012, total‐soil organic C and N, POC, and PON stocks increased as soils dried and soil bulk density increased. The CONT and SUPP management strategies had less root and rhizome mass (concentrations and stocks) and greater soil bulk density than FERT. These belowground responses were consistent with earlier research conducted at the site demonstrating greater herbage accumulation and litter deposition in FERT. Management strategies that vary amount and form of N inputs into pasture appear to have low potential to affect total‐soil organic C and N concentrations in the short‐term, but long‐term effects of less root and rhizome contents remain unknown.

Nitrous oxide emissions and herbage accumulation in smooth bromegrass pastures with nitrogen fertilizer and ruminant urine application

Agricultural soils contribute significantly to nitrous oxide (N2O) emissions, but little data is available on N2O emissions from smooth bromegrass (Bromus inermis Leyss.) pastures. This study evaluated soil N2O emissions and herbage accumulation from smooth bromegrass pasture in eastern Nebraska, USA. Nitrous oxide emissions were measured biweekly from March to October in 2011 and 2012 using vented static chambers on smooth bromegrass plots treated with a factorial combination of five urea nitrogen (N) fertilizer rates (0, 45, 90, 135, and 180 kg ha−1) and two ruminant urine treatments (distilled water and urine). Urine input strongly affected daily and cumulative N2O emissions, but responses to N fertilizer rate depended on growing season rainfall. In 2011, when rainfall was normal, cumulative N2O emissions increased exponentially with N fertilizer rate. In 2012, drought reduced daily and cumulative N2O emission responses to N fertilizer rate. Herbage accumulation ranged from 4.46 Mg ha−1 in unfertilized pasture with distilled water to 16.01 Mg ha−1 in pasture with 180 kg N ha−1 and urine in 2011. In 2012, plots treated with urine had 2.2 times more herbage accumulation than plots treated with distilled water but showed no response to N fertilizer rate. Total applied N lost as N2O ranged from 0–0.6 to 0.5–1.7 % across N fertilizer rates in distilled water and urine treatments, respectively, and thus, support the Intergovernmental Panel on Climate Change default direct emission factors of 1.0 % for N fertilizer additions and 2.0 % for urine excreted by cattle on pasture.

Production of Methane Emissions from Ruminant Husbandry: A Review

The aim of this review is to summarize the current knowledge of methane (CH4) production from ruminants. The objectives are to identify the factors affecting CH4 production. Methane is a potent greenhouse gas (GHG). Ruminant livestock constitute worldwide the most important source of anthropogenic emissions of methane. There are two main factors influencing global warming change, an increase in greenhouse gas emissions and depletion of the ozone layer. Methane is associated with both factors. Ruminants (dairy, beef, goats, and sheep) are the main contributors to CH4 production. Their CH4 production is a natural and inevitable outcome of rumen fermentation. Feed is converted into products such as milk and meat. Many factors influence ruminant CH4 production, including level of intake, type and quality of feeds, energy consumption, animal size, growth rate, level of production, and environmental temperature. The methane emissions in dairy cows represent values from 151 to 497 g·day-1. Lactating cows produced more CH4 (354 g·day-1) than dry cows (269 g·day-1) and heifers (223 g·day-1). Dairy ewe generates 8.4 kg·head-1 annually. Holstein produced more CH4 (299 g·day-1) than the Crossbred (264 g·day-1). Methane emission by heifers grazing on fertilized pasture was higher (223 g·day-1) than that of heifers on unfertilized pasture (179 g·day-1). The average CH4 emissions are from 161 g·day-1 to 323 g·day-1 in beef cattle. Mature beef cows emit CH4 approximately from 240 g·day-1 to 396 g·day-1. Suffolk sheep emit 22 - 25 g·day-1. The bison’s annual CH4 emissions per year were 72 kg·head-1. The CH4 emission from manure depends on the physical form of the feces, the amount of digestible material, the climate, and the time they remained intact. The annual emissions from the pens and storage pond at dairy farm were 120 kg·cow-1.

Nitrogen Input Effects on Herbage Accumulation and Presence of Pasture Plant Species

Long‐term responses of pasture plant species to management strategies that vary amount and form of N inputs form a knowledge gap. Our objective was to determine how supplementation of grazing beef cattle (Bos taurus) with corn (Zea mays L.) dried distillers grains plus solubles (DDGS) in unfertilized pasture (SUPP) affects annual herbage accumulation and presence of plant species and functional groups relative to unsupplemented beef cattle on unfertilized (CONT) and N‐fertilized (FERT) smooth bromegrass (Bromus inermis Leyss.) pasture. We addressed this objective in the sixth (2010) and seventh (2011) years of a long‐term experiment in eastern Nebraska, where N input from DDGS supplementation and urea fertilizer averaged 0, 43, and 90 kg ha–1 yr–1 within CONT, SUPP, and FERT, respectively. For these years, annual herbage accumulation averaged 6.87, 6.80, and 10.58 Mg ha–1 (LSD = 1.49) and 66.5, 66.2, and 76.0% of herbage accumulated by 25 June (LSD = 5.3) in CONT, SUPP, and FERT, respectively. Smooth bromegrass occurred in 99.8% of 0.1‐m2 pasture quadrats regardless of treatment. Cessation of N fertilizer input, however, increased presence of annual foxtail (Setaria spp.), annual graminoids, and annuals among quadrats in CONT relative to FERT. Supplementation of DDGS, while shown in previous studies to improve weight gains and N use efficiency in cattle, supplied enough N through excretion to provide an intermediate level of resistance to annual weeds. Nitrogen excreted from cattle supplemented with DDGS, however, did not affect herbage accumulation in subsequent years.

Fertilization and oversowing on natural grassland: effects on pasture characteristics and yearling steers performance

The objective of this study was to evaluate the vegetal and animal production of a natural pasture on a Mollisol soil in the region of Campanha, in RS. The experimental design consisted of complete randomized blocks with three replicates, which enables the comparison between natural unfertilized pastures with fertilized pastures and pastures fertilized and overseeded with Lolium multiflorum, Lotus corniculatus cv. São Gabriel and Trifolium repens cv. Lucero (NPO). Data were submitted to the analyses of variance considering seasons of the year as time repeated measurements. Aberddeen Angus calves of about nine months of age were used in continuous stocking with variable stocking rate in order to maintain forage offer at 13% of live weight. Data were collected between July 7th (2007) and May 3rd (2008), totaling 302 days. Fertilized and oversown pastures showed higher green forage mass mainly in the spring, as result of higher dry matter (DM) accumulation rate. Average daily live-weight gain for fertilized pasture (0.581 kg/day) was higher than for natural pasture (0.473 kg/day). Higher live-weight gains were obtained in the fall (0.869 kg/day). Stocking rate showed interaction with the seasons of the year, with higher stocking rates obtained in oversown pasture (701 kg of LW/ha) and fertilized pasture (667 kg of LW/ha) during the spring. Live-weight gain per hectare from natural pasture (224 kg LW/ha) was lower than on fertilized (310 kg LW/ha) and over-sown pasture (287 kg LW/ha). Forage mass, dry matter content, forage allowance and pasture height explained 61% of the average live weight gain. Despite the good performance of native grasslands in this region in its natural condition, the utilization of different inputs as fertilization and oversowing of winter cultivated species promoted positive differences in forage production and its distribution along the year and in animal yield.

Land-use intensity modifies spatial distribution and function of soil microorganisms in grasslands

Abstract The aim of the present study was to investigate whether land-use intensity (LUI) contributes to spatial variation in microbial abundance and function in grassland ecosystems. At one time point, three sites at low (unfertilized pastures), at intermediate (fertilized mown pastures) and at high (fertilized mown meadows) LUIs were selected in southern Germany. Within each of these nine grassland sites, 54 soil samples (0–10 cm) were taken in a 10 m × 10 m area in spring. Plot-scale spatial dependence and autocorrelation of soil biogeochemical properties, microbial biomass and enzymes involved in C-, N- and P-cycling were analyzed. Applying geostatistics (exponential or spherical model) revealed that most chemical and microbiological properties showed at least a moderate spatial autocorrelation. Chemical soil properties (e.g. C org , N t , pH) were characterized by practical ranges (pRange) of between 1 and 14 m, whereas soil microbiological properties showed a greater variation of pRanges, providing evidence of spatial heterogeneity at multiple scales. The expected decrease in small-scale spatial heterogeneity in high LUI could not be confirmed for microbiological soil properties, because sampling in early spring might have reduced the influence of growing plants and fertilization. However, microbial biomass carbon was significantly greater in high LUIs, indicating that the benefit to soil microbial populations from the long-term increase in substrate and nutrient availability in fertilized grasslands is independent from factors affecting spatial structures in the short-term.

Influence of land-use intensity on the spatial distribution of N-cycling microorganisms in grassland soils

A geostatistical approach using replicated grassland sites (10 m × 10 m) was applied to investigate the influence of grassland management, i.e. unfertilized pastures and fertilized mown meadows representing low and high land-use intensity (LUI), on soil biogeochemical properties and spatial distributions of ammonia-oxidizing and denitrifying microorganisms in soil. Spatial autocorrelations of the different N-cycling communities ranged between 1.4 and 7.6 m for ammonia oxidizers and from 0.3 m for nosZ-type denitrifiers to scales >14 m for nirK-type denitrifiers. The spatial heterogeneity of ammonia oxidizers and nirS-type denitrifiers increased in high LUI, but decreased for biogeochemical properties, suggesting that biotic and/or abiotic factors other than those measured are driving the spatial distribution of these microorganisms at the plot scale. Furthermore, ammonia oxidizers (amoA ammonia-oxidizing archaea and amoA ammonia-oxidizing bacteria) and nitrate reducers (napA and narG) showed spatial coexistence, whereas niche partitioning was found between nirK- and nirS-type denitrifiers. Together, our results indicate that spatial analysis is a useful tool to characterize the distribution of different functional microbial guilds with respect to soil biogeochemical properties and land-use management. In addition, spatial analyses allowed us to identify distinct distribution ranges indicating the coexistence or niche partitioning of N-cycling communities in grassland soil.

Ruminal methane emission by dairy cattle in Southeast Brazil

Ruminal gases, particularly methane, generated during the fermentative process in rumen, represent a partial loss of feed energy and are also pointed to as an important factors in greenhouse effect. This study aimed at quantifying methane (CH4) emission rates from lactating and dry cows and heifers, 24 month-old in average, on pasture under Southeast Brazil tropical conditions, using the tracer gas technique, sulphur hexafluoride (SF6), four animals per category, distributed in four blocks. Measurements were performed in February and June, 2002, with Holstein and Brazilian Dairy Crossbred (Holstein ¾ x Gir (Zebu) ¼), maintained on fertilized Tanzania-grass (Panicum maximum Jacq. cv. Tanzania) and fertilized Brachiaria-grass (Brachiaria decumbens cv. Basilisk) pastures. Heifers of both breeds were maintained on unfertilized Brachiaria-grass to simulate conditions of extensive cattle farming systems. CH4 and SF6 levels were measured with gas chromatography. Differences in CH4 emissions were measured (p < 0.05) for genetical groups. Holstein produced more methane (299.3 g day-1) than the Crossbred (264.2 g day-1). Lactating cows produced more methane (353.8 g day-1) than dry cows (268.8 g day-1) and heifers (222.6 g day-1). Holstein, with greater milk production potential, produced less CH4 (p < 0.05) per unit of dry matter intake (19.1 g kg-1) than the Crossbred (22.0 g kg-1). Methane emission by heifers grazing fertilized pasture (intensive system) was 222.6 g day-1, greater (p < 0.05) than that of heifers on unfertilized pasture (179.2 g day-1). Methane emission varied as function of animal category and management intensity of production system.

Soil phosphorus fractions in sandy soils amended with cattle manure for long periods

Phosphorus fractions were determined in soil samples from areas fertilized or not with farmyard cattle manure (FYM) and in samples of FYM used in the semi-arid region of Paraiba state, Brazil. Soil samples were taken from the 0-20; 20-40 and 40-60 cm layers of 18 cultivated areas, which, according to interviews with farmers, had been treated with 12 to 20 t ha-1 FYM annually, for the past 2 to 40 years. Soil samples were also collected from four unfertilized pasture areas as controls. Phosphorus in the soil samples was sequentially extracted with water (Pw), resin (Pres), NaHCO3 (Pi bic and Po bic), NaOH (Pi hid and Po hid), H2SO4 (Pacid) and, finally, by digestion with H2SO4/H2O2 (Presd). Nine FYM samples were extracted with water, resin, Mehlich-1, H2SO4, NaOH or digestion with H2SO4/H2O2, not sequentially, and the extracts analyzed for P. The sampled areas had homogeneous, sandy and P-deficient soils; increases in total soil P (Pt) above the mean value of the control areas (up to 274 mg kg-1 in the 0-20 cm layer of the most P-enriched samples) were therefore attributed to FYM applications, which was the only external P input in the region. Regression analysis was used to study the relationship between soil P fractions and Pt. The Pacid fraction, related to Ca-P forms, showed the greatest increases (p < 0.01) as a result of FYM applications, rising from 8.4 mg kg-1 in a non-fertilized sample to 43.8 mg kg-1 in the sample with the highest Pt content. The sum of Pw, Pres and Pi bic, considered as labile P, showed comparable increases with Pacid, while Pi hid showed the smallest increase due to FYM applications. Organic P forms also increased, more so the fraction Po hid, considered less labile, than the more labile one, Po bic. The residual P fraction was practically half of Pt, independently of the Pt value. Increases in labile P, Pacid and organic P were justified by the high average concentration of Pw (36 %), Pacid (34 %), and Po hid (30 %) in the FYM. Significant changes in the proportion of P forms among soil layers indicated the downward movement of P in organic forms.

After the hotspots are gone: Land use history and grassland plant species diversity in a strongly transformed agricultural landscape

Abstract.Question:We asked how landscape configuration and present management influence plant species richness and abundance of habitat specialists in grasslands in a ‘modern’(much exploited and transformed) agricultural Swedish landscape.Location:Selaön, south‐eastern Sweden (59°24’ N, 17°10’ E).Methods:Present and past (150 and 50 years ago) landscape pattern was analysed in a 25 km2area. Species richness was investigated in 63 different grassland patches; grazed and abandoned semi‐natural grasslands, and grazed ex‐arable fields. Influence of landscape variables; area, past and present grassland connectivity, present management on total species richness, density and abundance of 25 grassland specialists was analysed.Results:Semi‐natural grasslands (permanent unfertilised pastures or meadows formed by traditional agricultural methods) had declined from 60% 150 years ago to 5% today. There was a significant decline in species richness and density in abandoned semi‐natural grasslands. Total species richness was influenced by present management, size and connectivity to present and past grassland pattern. Landscape variables did not influence species density in grazed semi‐natural grassland suggesting that maintained grazing management makes grassland patches independent of landscape context. The abundance of 16 grassland specialists was mainly influenced by management and to some extent also by landscape variables.Conclusion:Although species richness pattern reflect management and to some extent landscape variables, the response of individual species may be idiosyncratic. The historical signal from past landscapes is weak on present‐day species richness in highly transformed, agricultural landscapes. Generalizations of historical legacies on species diversity in grasslands should consider also highly transformed landscapes and not only landscapes with a high amount of diversity hotspots left.

Effect of surface applied glycine betaine on herbage production and quality of perennial ryegrass - white clover pastures

Osmoprotectants have been reported to reduce the detrimental effects of various environmental stresses in many different plant species. However, there is little research available concerning pasture species. Two experiments were undertaken with the aim of quantifying the effect of surface applications of exogenous glycine betaine (GB) on herbage production and quality of perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.) pastures during periods of moisture stress and cold temperatures over 2 years. Pastures fertilised with GB were compared with unfertilised pastures and pastures fertilised with nitrogen (N). Rates of 0.5, 1.0 and 1.5 kg GB/ha.defoliation were applied in experiment 1 and 5 kg GB/ha.defoliation was applied in experiment 2. Surface applications of GB did not significantly affect herbage production relative to unfertilised pastures; herbage yields averaged 12 248 and 12 693 kg DM/ha over 11 months in experiment 1, and 7253 and 7177 kg DM/ha over 6 months during summer and autumn in experiment 2, for the unfertilised control and GB, respectively. During both experiments, herbage quality parameters were not affected by GB application, although the proportion of white clover in the sward between summer and winter during experiment 1 was greater (P < 0.01) in plots treated with GB than in untreated plots. Application of N fertiliser increased (P < 0.001) herbage production, but did not consistently affect herbage quality. The failure of surface applications of exogenous GB to improve the herbage production or quality of perennial ryegrass–white clover pastures suggests that it is not an appropriate method to enhance plant tolerance to environmental stress at the concentrations applied in these studies.

Effect of surface application of benzylaminopurine before and during water deficit on herbage production and quality

Insufficient water availability is one of the most serious environmental stresses for a plant and can be a major limitation to herbage production in many regions. Plant hormones, such as cytokinins, have been reported to reduce the detrimental effects of low water availability in many different plant species. However, there is little research available concerning the effect on pasture grasses. The aim of the present study was to quantify the effect of surface applications of 6-benzylaminopurine (BAP) before and during water deficit on herbage growth and quality of perennial ryegrass–white clover pastures. Pastures fertilised with BAP were compared with unfertilised pastures and pastures receiving nitrogen. Exogenous BAP application did not significantly affect herbage production or quality relative to unfertilised pastures. Nitrogen fertiliser increased total herbage production, but had little effect on herbage quality compared with BAP. The failure of surface applications of exogenous BAP to improve herbage production or quality suggests that it is not an appropriate method to enhance plant tolerance to water deficit at the concentration applied in this study.

Fertilizer-Derived Uranium and Sulfur in Rangeland Soil and Runoff: A Case Study in Central Florida

Fertilizer applications to rangeland and pastures in central Florida have potential impact on the nutrient–sensitive ecosystems of Lake Okeechobee and the Northern Everglades. To investigate the effects of fertilizer applications, three soil profiles from variably managed and improved rangeland, and four samples of surface runoff from both fertilized and unfertilized pasture were collected. In addition to determining nutrient concentrations, isotopic analyses of uranium (U) and sulfur (S) were performed to provide isotopic evidence for U derived from historically applied phosphate (P)-bearing fertilizer (234U238U activity ratio =1.0 ± 0.05), and Sderived from recently applied ammonium sulfate fertilizer(δ34S=3.5permil).The distribution and mobility of fertilizer−derived U in these samples is considered to be analogous to that of fertilizer−derived phosphate.Variations of U concentrations and234U/238U activity ratios in soils indicate contribution of fertilizer-derived U in the upper portions of the fertilized soil (15–}34 percent of total U). The U isotope data for runoff from the fertilized field also are consistent with some contribution from fertilizer-derived U. Parallel investigations of S showed no consistent chemical or isotopic evidence for significant fertilizer-derived sulfate in rangeland soil or runoff. Relatively abundant and isotopically variable S present in the local environment hinders detection of fertilizer-derived sulfate. The results indicate a continuing slow-release of fertilizer-derived U and, by inference, P, to the P-sensitive ecosystem, and a relatively rapid release of sulfate of possible natural origin.

Sustainable grazing systems for the Central Tablelands of New South Wales. 3. Animal production response to pasture type and management

The main limitations for prime lamb production in the Central Tablelands of New South Wales are low availability of forage early in the growing season (late autumn–early winter) and low nutritive value in the summer. This paper describes the performance of a first-cross lamb breeding enterprise on 4 pasture types and 2 management systems over 4 years for the Central Tablelands region. The pastures studied comprised a traditional unfertilised naturalised pasture, a similar pasture fertilised with superphosphate, a sod-sown fertilised introduced perennial grass pasture and a sod-sown summer growing perennial, chicory (Cichorium intybus L.) pasture. Grazing management involved either continuous grazing or tactical grazing that combined a lower annual stocking rate with an optional summer rest to maintain perennial grass content above 50%. An additional area of chicory pasture was set aside for finishing lambs. Over the experiment stocking rates were increased each year as the pasture became established, with increases ranging from 1.5 ewes/ha for tactically grazed unfertilised natural pasture to 3.6 ewes/ha, for chicory and clover pasture. The feed quality v. quantity problem of summer and autumn was reaffirmed for each pasture type except chicory and the lamb enterprise appeared to be sufficiently adaptable to be promising. Ewes lambed in September and produced satisfactory lamb growth rates (about 280 g/day for twins) on the various pastures until weaning in late December. Thereafter, lamb growth rates declined as the pastures senesced, except chicory, reaffirming the feed quality v. quantity problem in summer and autumn of naturalised and sown grass pastures for producing lamb to heavyweight market specifications. Weaning liveweights (in the range of 32–40 kg) from grass-based pastures were high enough for only about 45% of the lambs to be sold as domestic trade lambs with the remainder as unfinished lambs. In contrast, the chicory and clover finishing pasture produced lamb growth rates of 125 g/day and quality large, lean lambs suitable for the export market. Vegetable matter in the late January shorn wool was insignificant and there was no significant effect of pasture on fleece weight, fibre diameter or staple strength. Position of break in staples of wool from chicory pastures differed from that of the other pasture types and warrants further study on time of shearing. It was concluded that a first cross lamb producing enterprise of suitable genetics was effective in producing trade and store lambs before pasture senescence, but the inclusion of a specialised pasture of summer growing chicory would create greater opportunities. In the unreliable summer rainfall region of the Central Tablelands, the area of chicory pasture needed to maintain lamb growth rates of >125 g/day, estimated from these results, is around 10 lamb/ha of chicory.

Effects of pasture treatments on detached pasture litter mass, quality, litter loss, decomposition rates, and residence time in northern New South Wales

Few data are available on litter quantity and quality and decomposition rates over time and what effects stocking rate, grazing method, legume introduction, and fertiliser application may have. Studies were conducted from spring 1997 to 2001 at 3 pasture sites in northern New South Wales to provide such data by examining the effects of pasture treatments on detached litter mass (kg DM/ha) and quality data (percent carbon (C), nitrogen (N) and C : N ratio) collected at 9 sampling times in 2 replicates of 5 (native pasture) or 4 (sown pasture) treatments and examined for differences over time using cubic spline analyses. For each site, decomposition bags were also used to assess differences among treatments for initial and final detached litter mass, organic matter (OM), N values, the relative rate of decomposition (g/g.day), and residence time (days) for periods March to June 1998, June to September 1998, and September to November 1998. Initial and final data were also collected for detached resident and subterranean clover (Trifolium subterraneum) litter for 6 sampling times from September 1998 to January 1999 for a reduced range of treatments at each site. Similar data were collected at each site for resident litter and grass green leaf material from January to April 1999. Detached litter mass declined (P < 0.05) in unfertilised continuously grazed treatments (Barraba native pasture) and with high continuous stocking rate in the Nundle sown pasture. Litter quality was only significantly affected by grazing treatment at the Barraba native pasture site where the fertilised treatment oversown with subterranean clover tended to have low percent C and a lower C : N ratio and higher percent N and microbial biomass C than other treatments. From autumn to spring 1998, the fertilised, oversown treatment at both native pasture sites generally had high litter DM, OM, and N losses and relative rates of decomposition compared with continuously grazed, unfertilised pasture. For the same period, at the Nundle sown pasture site, OM and N losses and the relative rate of decomposition were consistently higher, and residence time lower, in the continuously grazed, high stocking rate treatment compared with all other treatments. Compared with resident detached litter, both subterranean clover litter and green leaf material at the native pasture sites had higher relative decomposition rates and lower residence times. The implications of these data for the management of both native and sown pastures are discussed.

Sustainable grazing systems for the Central Tablelands of New South Wales. 4. Soil water dynamics and runoff events for differently-managed pasture types

Soil water, runoff amount and quality, pasture production and environmental data were measured for a pastoral prime lamb enterprise in the Central Tablelands of New South Wales from 1998 to 2002. There were 4 pasture treatments: fertilised and sown chicory (CH), fertilised and sown introduced pastures (SP), fertilised naturalised pastures (FN) and unfertilised naturalised pastures (UN). Two grazing management regimes, tactically grazed (TG) and continuously grazed (CG) were imposed on the SP, FN and UN treatments. The CH treatment was rotationally grazed. To compare pasture and grazing system water use, maximum soil water deficit values (SWDMax) were calculated from neutron moisture meter data. SWDMax was influenced by both environmental and management factors. Management factors that influenced SWDMax were herbage mass of perennials, degree of perenniality, and the perennial species present. Environmental factors accounted for >50% of the variation in SWDMax. Inclusion of management factors (perennial herbage mass of C3 and C4 species and percentage perennial herbage mass), accounted for an additional 16% of variation. While the influence of pasture management appears to be relatively small, importantly, management is the only avenue available to land managers for influencing SWDMax. The UNTG and all sown treatments, with greater perennial herbage mass or greater C4 herbage mass consistently produced the highest SWDMax. Runoff amount and quality data are presented for ground cover percentages which generally exceeded 80% for the experimental period. Runoff as a proportion of rain received during the experiment was <3%. Environmental factors explained 47% of variation in runoff, while pasture herbage mass and ground cover percentage explained an additional 2% of variation. Water quality was monitored on 3 treatments (SPTG, FNTG and UNCG) for total nitrogen (N), total phosphorus (P) and total suspended solids (TST) over a 6-month period. The mean values for total N and P were below the acceptable contaminant concentration for agricultural irrigation water. An important outcome of this research is the concept of a practical Targeted Water Management Plan (TWMP) which devises a framework for optimum water usage and productivity at a landscape scale.

Soil, site and management components of variation in species composition of agricultural grasslands in western Norway

AbstractA partitioning of the total variance in species composition of grasslands associated with increasing fertilizer inputs (unfertilized pastures, artificially fertilized hay meadows and intensively cultivated grassland) in western Norway was undertaken. The partitioning was carried out with (partial) constrained ordinations (canonical correspondence analysis) and associated Monte Carlo permutation tests. Explained variation was high (0·651), with soil chemistry, management and site explaining 0·271, 0·228 and 0·052 of the variation, respectively, and the interaction between soil and management explaining 0·100 of the variation. However, much of the measured soil chemistry was considered to be an effect of management. The soil chemistry variable explaining most variation was extractable P content, associated with high soil extractable P contents in the intensively cultivated grassland due to high fertilizer applications. However, soil extractable P content did not explain differences in species composition when grasslands with smaller differences in fertilizer inputs (meadows vs. pastures) were compared. Total soil C and N contents and C:N ratios explained significant variation between all grassland types. Lowest levels of these variables were measured in the grassland with the highest fertilizer inputs, suggesting that total soil N content cannot be used as a predictor of fertility. Significantly higher soil N contents were measured in grasslands of low productivity, probably due to a low decomposition rate of stress‐tolerant plants and the consequent low availability of soil N and accumulation of soil organic matter. Ellenberg N values reflected soil chemical differences in this study with high Ellenberg N values reflecting high Ca, Mg and P contents and pH values and low total C and N contents and C:N ratios.

Untersuchungen zur verdaulichkeit und zum energiegehalt von futterpflanzen auf niedermoorstandweiden in abhängigkeit vom vegetationsverlauf: Investigations about digestibility and energy content of fodder plants on lowland moor large units pasture in dependence from vegetation progress

On lowland moor large units pasture, which are used for holding paddock sheep, several differences in aerosis ability are given, in the apparent digestibility and in the capacity of energy (metabolizable energy and net energy lactation) in connection with stage of vegetation between several care variants (without fertilization, fertilized and combined utilization) of fodder plants. Especially in the second period of vegetation one has to consider a reduction of nutrient concentration in the fodder on unfertilized pasture segments. Under conditions of extensive grassland management with intensive races these relations have a limitative influence on the animal efficiency, because in fodder growth there are imbalances between the energy and protein supply. On the other hand, grass in the fertilized variant shows a higher digestibility and more energy at this time. In relation to the nutrient supply, the combined utilization is the most well-known variant. Lower raw fibre concentrations offer a high feed intake capacity for pasture animals.

Chemical fractionation to characterize changes in sulphur and carbon in soil caused by management

SummaryClassical chemical fractionation of soil sulphur (S) into HI‐reducible S and carbon‐bonded S does not separate S in soil into fractions that have differing mineralization potentials. Other techniques are needed to separate organic S into more labile and less labile fractions of biological significance, irrespective of their bonding relations. We have sequentially fractionated soil S and carbon (C) into their ionic forms released onto ion‐exchange resins and organic S and C extracted in alkali of increasing concentration. We evaluated the technique on pasture and arable soils that had received various fertilizer and cultivation treatments. Total S and C were greater in the soil of the fertilized pasture than in that of the unfertilized pastures. Continuous arable cropping decreased total soil S and C, whereas restoration to pasture caused an accumulation.Resin, 0.1 m NaOH, 1 m NaOH and residual fractions accounted for between 1–13%, 49–69%, 4–16% and 19–38% of total soil S and between 5–6%, 38–48%, 5–7% and 46–53% of total soil C, respectively. Among different S and C fractions, the size of the 0.1 m NaOH and residual fractions changed more with the change in land use and management. The 0.1 m NaOH fraction had a narrower C:S ratio (50–75:1) than did the residual fraction (96–141:1). The significant degree of change in these two fractions, caused by differences in land management, indicates that they may be useful indicators of change in ‘soil quality’.