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Globally, declining soil quality due to soil degradation is of great concern, and directly affects crop production, soil health and sustainability of natural resources. In conventional farming practices, the loss of fertile topsoil via runoff and erosion from arable land is a big concern. In addition, changes in land use and management practices result in loss of soil organic carbon (SOC) stock by -10-59%. The change from conventional till (CT) with residue burning/removal to no-till (NT) farming with residue retention/conservation agriculture (CA) practices have been recognised as important soil management practices for sustaining soil health and reversing land degradation. Worldwide, NT/CA practices are now being adopted on about 180 million ha (i.e. ~14% of arable land). CA practices promote soil health by increasing organic carbon, and soil aggregation, thus improving infiltration and minimising erosion losses. In addition, CA has the potential to increase SOC sequestration, reduce greenhouse gas (GHG) emissions and help to mitigate global climate change. Among sustainable food production systems, CA is often advocated with a view to increase food production while conserving natural resources and SOC. This special issue 'No-till farming: prospects, challenges--productivity, soil health, and ecosystem services' addresses and critically reviews these important issues and aims to foster awareness of NT farming. The collection of 15 papers lucidly covers various facets of NT farming. A summary and salient findings of these papers are provided in this Editorial. NT farming is a promising practice, which not only improves soil physical, chemical and biological health but also enhances carbon sequestration, crop productivity and mitigates GHG emissions through appropriate crop residue and nutrient management strategies. The adage says 'one size won't fit all' or 'a single recipe will not solve all problem/challenges', so we need to adopt site-specific NT systems for higher benefits and productivity and sustaining soil health. Keywords: carbon sequestration, climate smart agriculture, conservation agriculture, food security, greenhouse gases, GHG, no-till farming, simulation model, soil health, soil properties., In 2050 the world population is estimated to reach ~10 billion, an increase of 25% despite the Covid-19 mortalities, therefore, there is a continuous need for increasing food production. Soils [...]

Once upon a time there was enough naturally occurring nitrogen (N) to provide food for the world's peoples. Then there was not in the western regions. Now there is due to industrially produced NH3. But this transition from plenty, to scarcity, to plenty has come with a tremendous environmental cost. This paper provides an historical overview of the growth of knowledge about N and about its impacts, both positive and negative. The paper also explores three scenarios of what might have been, if in 1700 the world had the N-knowledge that we have now. The paper then projects N use to feed the world's people in 2050 under three scenarios of per-capita protein consumption: increasing, constant and decreasing relative to nutritional guidelines. The three projected results for 2050 annual N use from producing and consuming food are 320, 230 and 170 Tg N respectively. The latter is equivalent to 1970 levels. Given that the first scenario (increasing protein) is most likely without utilising our N-knowledge, the paper ends with suggestions for improvements in N use and management. Additional keywords: diet, historical perspective, impacts, projections., Introduction The history of nitrogen (N) use by people is a field well fertilised with materials detailing the evolution of knowledge about N (e.g. Erisman et al. 2008; Galloway et [...]

Degradable materials have been suggested to overcome accumulation in the field of persistent plastic residues associated with the increasing use of polyethylene mulches. New degradable materials have been proven successful for increasing crop productivity; however, their degradation in the field has been hardly addressed. A qualitative scale was used in the present study to assess the above-soil and in-soil degradation of degradable mulches during the cropping season. Degradation was determined in three biodegradable plastic mulches (Biofilm, BF; Mater-Bi, MB; Bioflex, BFx), two paper sheet mulches (Saikraft, PSA; MimGreen, PMG) and one oxo-degradable plastic mulch (Enviroplast, EvP). Polyethylene (PE) mulch was used as control. Mulches were tested in five Spanish locations (Castilla-La Mancha, La Rioja, Navarra, Aragon and Catalunya), with three crop seasons of processing tomato. Biodegradable plastic mulches BF and MB degraded more and faster above-soil than paper mulches; among biodegradable mulches BF degraded more than MB, and MB more than BFx. The above-soil degradation of the oxo-degradable mulch EvP was highly dependent on location and crop season, and it degraded more than PE. Main environmental factors triggering above-soil degradation were radiation, rainfall and crop cover. In-soil, paper mulches and BF degraded more and faster than MB, whereas BFx and EvP barely degraded. Environmental factors triggering in-soil degradation during the crop season were rainfall and irrigation water. The effect of soil parameters (organic matter, nutrient availability) on degradation during the cropping season was not evidenced. The qualitative scale used proved convenient for determining mulch field degradation. A visual scale for supporting the qualitative evaluation is provided. In order to standardise parameters and criteria for future studies on field mulching degradation evaluation, a unified degradation qualitative scale is suggested. Additional keywords: biodegradation, Lycopersicon esculentum, oxo-degradation, paper, plastic, qualitative scale., Introduction Plastic mulches were first used in commercial agriculture in the early 1960s. Their use has expanded worldwide and they have increasingly replaced other types of mulches (e.g. paper, straw). [...]

Mulch materials of different origin and colour are available in the agricultural sector as sustainable alternatives to the use of polyethylene (PE). Mulching modifies soil temperature and consequently affects crop yields. This work assessed the thermal and productive responses of different mulch materials in two different geo-climatic conditions during a 3-year integrated field study on processing tomato (Lycopersicon esculentum Mill.). Two biodegradable plastic mulches (BD1, BD2), one oxo-degradable material (OB), two types of paper (PP1, PP2) and one barley-straw cover (BS) were compared with two control treatments: black PE and manual weeding (MW). Soil temperature variables (maximum, minimum and mean temperature, soil growing degree-days and soil temperature amplitude) and production variables (marketable and total yield, mean fruit weight) were considered. Thermally, PE could be considered an atypical mulch causing higher temperatures in the soil, but it is not associated with a higher yield. Responses of PE, PP2 and MW were independent of the geo-environmental conditions, whereas OB, BDI and BD2 had similar thermal and productive responses to each other in different environments. Tomato yield was correlated positively only with the minimum soil temperature, especially when excluding PE. Additional keywords: mulching, soil temperature, yield, polyethylene, degradable plastics, papers., Introduction Mulching is a technique used in cultivation worldwide, especially for vegetable crops, offering many advantages. Mulches reduce weed growth, minimise or eliminate soil erosion, and often enhance total yields [...]

The Peel-Harvey estuarine system in Western Australia's south-west is affected by poor water quality, algal blooms, and fish kills. Phosphorus (P) discharge from agricultural activities is the main source of poor water quality. The catchment's soils are naturally infertile, but P application has increased P fertility. This paper draws on and undertakes a meta-analysis of 20200 surface (0-10 cm) and profile (to 100 cm depth) soil samples collected in the period 1983-2018. Soil P content was high, with 70% of samples with Colwell P content in excess of agronomic requirements; Production is more likely limited by low soil pH(CaC|2) and low K (92% and 67% of paddocks respectively). Strong P stratification in the soil is evident, particularly topsoil; sandy soils are saturated to depth; and clay soils show signs of P saturation in the topsoil. Management of P in sandy soil near the estuary is a high priority as is P stratification in highly P retentive soil. Soil P stocks increased since clearing compared with uncleared soils (1221 kg [ha.sup.-1] [m.sup.-1] and 285-694 kg [ha.sup.-1] [m.sup.-1], respectively). Thirteen percent of samples had P content in excess of agronomic requirements in 1983, rising slowly to 69% in 2018. Landholder practices need to be analysed in detail to confirm if this accumulation occurs everywhere or is only confined to actively farmed land. Keywords: eutrophication, P saturation, P management, P loss, P efficiency, water quality, Peel-Harvey, estuary health., Introduction Soils in south-west Western Australia (SWWA) were deficient in phosphonis (P) when land clearing for agriculture commenced in the 1800s. To overcome P deficiency, superphosphate application, particularly in the [...]

Following cultivation, substantial loss of soil organic matter occurs in surface soil layers. No-till is an agronomic practice to reverse or slow the loss of soil organic matter. We reviewed 95 research papers that used [sup.13]C natural abundance of soils to quantify the impact of tillage on the C dynamics of cropping systems. New C (from current cropping systems) accumulated in the surface soil under no-till, whereas the most extreme cultivation (mouldboard ploughing) mixed new C throughout the soil. There was a decline in soil C with years of cultivation. Compared with land that had been tilled, no-till generally had little impact on the accumulation on soil organic C. Tillage and residue retention caused stratification in C stocks that depended on tillage depth, with the highest C concentrations and stocks found in the surface under no-till. Shifts in the [delta][sup.13]C signature indicated significant exchange of 'new' C for the original (old) C. Tillage methods had no impact on the size and [delta][sup.13]C signature of the microbial biomass pool. Change in [delta][sup.13]C indicates that microbial biomass rapidly incorporates new carbon. The largest change in the [delta][sup.13] values ([DELTA][sup.13]C) was observed in the coarse sand fraction, whereas the smallest change occurred in the clay fraction. Comparison of conventional vs no-till showed inconsistent results on the effect of tillage on C in the different particle size fractions. Natural [sup.13]C abundance data show that no-till cropping systems do not result in increases in soil organic C in the top 0.30 m of soil. Keywords: tillage, no-till, zero till, [C.sub.3], [C.sub.4], soil microbial biomass, [delta][sup.13]C, C sequestration., Introduction The preferential fixation of [sup.12]C over [sup.13]C during photosynthesis results in the [delta][sup.13]C signature of [C.sub.3] plants (Calvin cycle) being lower (more negative) than that of [C.sub.4] plants (Hatch-Slack [...]

This paper presents a parameterisation and test of an algorithm to calculate distributions of the major nutrient cations between the solution and exchangeable phases of soil when cation exchange capacity (c) may vary. Two contrasting soils were considered: a volcanic subsoil where c is dominated by variable-charge surfaces, and an alluvial silt loam topsoil with stable c. Experimental treatments consisted of applying either water or solutions of Ca[Cl.sub.2], KC1, Mg[Cl.sub.2], or NaCl. Solution concentrations of [Ca.sup.2+], [K.sup.+], [Mg.sup.2+], and [Na.sup.+] varied by up to two orders of magnitude, and were simulated well, particularly when using logi0-transformed data. The ratios of the solution concentrations of [K.sup.+], [Mg.sup.2+], and [Na.sup.+] to [Ca.sup.2+] also were generally simulated well. However, the algorithm's description of soil acidity needs further checking. For the variable-charge soil, cation concentrations were strongly influenced by fitted parameters associated with anion exchange. For the alluvial soil, fitted parameters had little influence, and the cation calculations were dominated by information gathered front the initial (equilibrium) distributions between phases. The algorithm has strong potential for forecasting changes in solution concentrations of the major nutrient cations, using relatively small amounts of fitting data. Keywords: anion exchange, cation exchange, model, soil solution, variable-charge soil., Introduction Although plant uptake of the major nutrient cations is strongly affected by their concentrations in the solution around the roots, soil fertility testing rarely involves analysis of the soil [...]

Difficulties forecasting cation exchange processes may limit the use of soil solution analyses in routine soil testing for agriculture. An important part of those difficulties is the need for much data and expertise to parameterise existing models that can be used for variable charge soils. This paper proposes an algorithm to simulate concentrations of the major nutrient cations in the soil solution. It is designed to have only modest data requirements, be applicable for variable charge soils, and be simple to implement in crop and environment simulation packages. It is based on a Gaines-Thomas type approach to cation exchange, adapted to allow for variations in cation exchange capacity. It includes interactions with anions and anion exchange, which may affect cation behaviour in variable charge soils. Assumptions and limitations of the approach are described, and some issues associated with parameterisation, implementation, and future extension are discussed. Keywords: algorithm, cation exchange, soil acidity, soil solution, variable charge soils., Introduction Plant uptake of the major nutrient cations is strongly affected by their concentrations in the soil solution (Tinker and Nye 2000; White and Greenwood 2013). These in turn may [...]

Difficulties forecasting cation exchange processes may limit the use of soil solution analyses in routine soil testing for agriculture. An important part of those difficulties is the need for much data and expertise to parameterise existing models that can be used for variable charge soils. This paper proposes an algorithm to simulate concentrations of the major nutrient cations in the soil solution. It is designed to have only modest data requirements, be applicable for variable charge soils, and be simple to implement in crop and environment simulation packages. It is based on a Gaines-Thomas type approach to cation exchange, adapted to allow for variations in cation exchange capacity. It includes interactions with anions and anion exchange, which may affect cation behaviour in variable charge soils. Assumptions and limitations of the approach are described, and some issues associated with parameterisation, implementation, and future extension are discussed. Keywords: algorithm, cation exchange, soil acidity, soil solution, variable charge soils. Received 13 August 2020, accepted 23 September 2020, published online 28 October 2020, Introduction Plant uptake of the major nutrient cations is strongly affected by their concentrations in the soil solution (Tinker and Nye 2000; White and Greenwood 2013). These in turn may [...]

This paper presents a parameterisation and test of an algorithm to calculate distributions of the major nutrient cations between the solution and exchangeable phases of soil when cation exchange capacity (c) may vary. Two contrasting soils were considered: a volcanic subsoil where c is dominated by variable-charge surfaces, and an alluvial silt loam topsoil with stable c. Experimental treatments consisted of applying either water or solutions of Ca[Cl.sub.2], KCl, Mg[Cl.sub.2], or NaCl. Solution concentrations of [Ca.sup.2+], [K.sup.+], [Mg.sup.2+], and [Na.sup.+] varied by up to two orders of magnitude, and were simulated well, particularly when using [log.sub.10]-transformed data. The ratios of the solution concentrations of [K.sup.+], [Mg.sup.2+], and [Na.sup.+] to [Ca.sup.2+] also were generally simulated well. However, the algorithm's description of soil acidity needs further checking. For the variable-charge soil, cation concentrations were strongly influenced by fitted parameters associated with anion exchange. For the alluvial soil, fitted parameters had little influence, and the cation calculations were dominated by information gathered from the initial (equilibrium) distributions between phases. The algorithm has strong potential for forecasting changes in solution concentrations of the major nutrient cations, using relatively small amounts of fitting data. Keywords: anion exchange, cation exchange, model, soil solution, variable-charge soil., Introduction Although plant uptake of the major nutrient cations is strongly affected by their concentrations in the solution around the roots, soil fertility testing rarely involves analysis of the soil [...]

Sulfate sorption by the soil affects the rate of sulfate leaching, which impacts on the availability of soil sulfate for plant uptake. In Australia, plant-available sulfur is measured using 0.25 M KC1 heated for 3 h at 40[degrees]C to extract soil sulfur ([S.sub.KC140]). This paper describes a technique referred to as a sulfate buffering index (SBI), which provides a measurement of sulfate sorption. SBI when combined with the estimates of the q and ft parameters of the Freundlich equation, can be used to define a sorption curve. The equation is S = [ac.sup.b] - q; where S is the amount of sulfate adsorbed (mg S [kg.sup.-1]), c is the equilibrium concentration of sulfate measured in solution (mg S [L.sup.-1]) and a, b and q are coefficients that describe the soil sulfate sorption curve. Coefficients S and c were measured using six sulfate solution concentrations ranging from 0 to 250 mg S [kg.sup.-1]. The adsorption curve was fitted using the modified Freundlich equation including setting of b = 0.41 and q = [S.sub.Kc140] using recently collected soil samples. The modified Freundlich a coefficient or SBI was calculated as SBI = (S + [S.sub.Kc140])/[c.sup.0.41]; where S and c were determined using 50 mg S [kg.sup.1] of added sulfate. The SBI ranged within 1-40. The [S.sub.KC140] was related to SBI below a depth of 10 cm ([r.sup.2] = 0.71) but not for the 0-10 cm soil layer where S sorption was minimal. Additional keywords: crop management, leaching. Received 6 January 2020, accepted 1 July 2020, published online 30 July 2020, Introduction Sulfur deficiency in wheat (Triticum aestivum L.) and canola (Bmssica napus L.) occurs when sulfate fertilisers are not applied to soils low in natural sulfur reserves (Anderson et al. [...]

Local soil knowledge (LSK) has been recognised for its importance in sustainable soil management and agroecosystems. This paper examines peer-reviewed articles and grey literature documents on LSK during 2003-2018. Research continues to be geographically focused on developing countries, but often in collaboration with researchers from developed countries. There were five key research themes: soil classification and agreement between local and scientific soil knowledge (Theme 1), value of LSK for soil management and decision-making (Theme 2), scientific approach to the incorporation of LSK (Theme 3), application of LSK for identification of and solutions to soil problems (Theme 4) and factors influencing soil knowledge development (Theme 5). Although Theme 1 continued to be a prevalent research area, confirming the importance of visible and topsoil characteristics identified by farmers, examining subsurface soil properties has garnered less research. For LSK to be thoroughly documented requires support by a pluralistic scientific assessment and greater incorporation of social science methodologies. An overarching finding from Themes 2-4 was the importance of designing national programs that incorporate LSK derived from local people and other stakeholders (e.g. scientists and policymakers) to conserve soils. Local soil maps, using LSK terminology, could broaden the appeal and use of maps by local stakeholders to support sustainable land-use planning from the field to national policy-making processes. Finally, cultural and political aspects, known to influence LSK, should be given greater consideration in further research to sustain and develop this knowledge (Theme 5). Additional keywords: ethnopedology, farmers, rural development, soil classification, soil health. Received 21 August 2019, accepted 1 December 2019, published online 14 January 2020, Introduction In order to ensure our food production and land management systems are sustainable, there is a need for farmers to maintain healthy soil (Pauli et al. 2016). Flowever, increasing [...]

In addition to promoting plant growth, the incorporation of flyash material into soil also has the potential to affect the solubility and plant availability of some elements. This paper reports on the effect of 2 flyash products (FAP) on the extractability and plant uptake as a function of pH of selected elements of concern in the environment: As, B, Cd, Co, Cu, Cr, Mn, Pb, Ni, and Zn. The results for the growth response of maize plants (Zea mats L.) in the FAP-amended soils have been reported in a companion paper. The addition of the FAP to the soils used in this study at rates up to 5% w/w resulted in increased levels of Cu, Mn, Ni, As, and Co in an acetic acid extract. The levels of Cr, Mn, Ni, Pb, Zn, As, and Co in these extracts all showed a dependency on pH for some soils. Maize plants grown in the amended soils exhibited an increase in the plant uptake of Cu, Mn, and Ni in some soils. However, none of the elements studied increased the plant uptake to levels which would generally be considered toxic to plants or cause problems in the food chain. The presence of the FAP decreased the plant availability of Ni at low pH and levels of Mn and CA in the acetic acid extract were decreased, most likely due to sorption of these elements by the FAP. There is no evidence that either the flyash alone, or the 2 FAP used in tiffs study would pose a threat to plants or the environment when used at levels of up to 5% w/w. Possible beneficial effects for the environment were observed as the incorporation of FAP into soils has the capacity to reduce the uptake and potential toxicity of CA, Ni, or Mn in some soils. Additional keywords: flyash, soft acidity, soil amendments, acetic acid extract, plant uptake, contaminants., Introduction The application of flyash wastes to soils has been shown to improve the soil water-holding capacity and enhance plant growth by amending soil pH, and by supplying micronutrients (Aitken [...]

This paper describes the development of a diffuse reflectance spectral library from a legacy soil sample. When developing a soil spectral library, it is important to consider the number of samples that are needed to adequately describe the soil variability in the region in which the library is to be used; the manner in which the soil is sampled, handled, prepared, stored, and scanned; and the reference analytical procedures used. As with any type of modelling, the dictum is 'garbage in = garbage out' and hopefully the converse 'quality in = quality out'. The aims of this paper are to: (i) develop a soil mid infrared (mid-IR) diffuse reflectance spectral library for cotton-growing regions of eastern Australia from a legacy soil sample, (ii) derive soil spectral calibrations for the prediction of soil properties with uncertainty, and (iii) assess the accuracy of the predictions and populate the legacy soil database with good quality information. A scheme for the construction and use of this spectral library is presented. A total of 1878 soil samples from different layers were scanned. They originated from the Upper Namoi, Namoi, and Gwydir Valley catchments of north-western New South Wales (NSW) and the McIntyre region of southern Queensland (Qld). A conditioned Latin hypercube sampling (cLHS) scheme was used to sample the spectral data space and select 213 representative samples for laboratory soil analyses. Using these data, partial least-squares regression (PLSR) was used to construct the calibration models, which were validated internally using cross validation and externally using an independent test dataset. Models for organic C (OC), cation exchange capacity (CEC), clay content, exchangeable Ca, total N (TN), total C (TC), gravimetric moisture content [θ.sub.g], total sand and exchangeable Mg were robust and produced accurate results ([R.sup.2.sub.adj]. > 0.75 for both cross and test set validations). The root mean squared error (RMSE) of mid-IR-PLSR predictions was compared to those from (blind) duplicate laboratory measurements. Mid-IR-PLSR produced lower RMSE values for soil OC, clay content, and [θ.sub.g]. Finally, bootstrap aggregation-PLSR (bagging-PLSR) was used to predict soil properties with uncertainty for the entire library, thus repopulating the legacy soil database with good quality soil information. Additional keywords: mid-IR diffuse reflectance spectroscopy, spectral library, partial least squares regression, baggingPLSR, legacy soil data., Introduction Diffuse reflectance spectroscopy (DRS) has been used in soil science research since the 1950s and '60s (e.g. Brooks 1952; Bowers and Hanks 1965). However, it is only in approximately [...]

This paper describes a long-term, paired-catchment study, its broad findings, and considerations for future resource management of brigalow lands in north-eastern Australia. The Brigalow Catchment Study (BCS) commenced in 1965 with a pre-clearing calibration phase of 17 years to define the hydrology of 3 adjoining catchments (12-17 ha). After 2 catchments were cleared in 1982, 3 land uses (brigalow forest Acacia harpophylla, cropping, and grazed pasture) were monitored for water balance, resource condition and productivity, providing information for scientific understanding and resource management of the major land uses of the brigalow bioregion. In addition, this paper draws upon several project reviews to highlight the value of the BCS as an 'outdoor laboratory', its data resource, and to reflect on the study's scientific rigor to support present and future value. An assessment of the BCS against national and international attributes of best practice for long-term studies showed the study to rate highly in aspects of design, implementation, monitoring, and data management, and moderately in formal publication, strategic management, and networking. The literature shows that Brigalow Catchment Study is the longest paired-catchment study in Australia, and continues to sample the interactions between climate, soils, water, land use, and management. Finally, this paper provides the context for component-specific papers on changes in hydrology, productivity, and salt balance. Results from the study to date include: a doubling of runoff after clearing, a reduction in wheat yield by more than 60% over 20 years, a halving of pasture availability 3 years after clearing, a decline in cattle liveweight gain of 4 kg/ha.year over an 8-year period with a constant stocking rate, and the leaching of 60% of the root-zone (0-1.5 m) chloride after clearing for cropping. Unanticipated applications of the data from the study include: (i) a crucial set of soil samples for calibration of the RothC soil carbon model used to estimate Australia's soil carbon emissions; and (ii) estimates of deep drainage as a basis for salinity risk assessment in the region. Additional keywords: hydrology, erosion, long-term, runoff, land use, Acacia harpophylla., Introduction In the 1960s, world scientific curiosity as to anthropogenic impacts on the hydrological cycle was high. The coordinating council of UNESCO's International Hydrological Decade initiated studies of worldwide hydrological [...]

This paper aims to establish the means and ranges of clay, silt, and sand contents from field texture classes, and to investigate the differences in the field texture classes and texture determined from particle-size analysis. The results of this paper have 2 practical applications: (1) to estimate the particle size distribution and its uncertainty from field texture as input to pedotransfer functions, and (2) to examine the criteria of texture contrast soils in the Australian Soil Classification system. Estimates of clay, silt, and sand content for each field texture class are given and this allows the field texture classes to be plotted in the texture triangle. There are considerable differences between field texture classes and particle-size classes. Based on the uncertainties in determining the clay content from field texture, we establish the probability of the occurrence of a texture contrast soil according to the Australian Soil Classification system, given the texture of the B2 horizon and its overlying A horizon., I enjoy doing the soil-texture feel test with my fingers or kneading a clay soil, which is a short step from ceramics or sculpture. Hans Jenny (1984) Introduction Particle-size distributions [...]

Absorption of water by relatively dry soil and by chromatography paper, and desorption of water by clay, were measured at constant temperatures close to 278 K, 293 K, and 306 K. Within experimental error, temperature affected absorption of water by soil and chromatography paper simply according to the temperature dependence of the kinematic viscosity and of the air-liquid surface tension of pure water. Desorption of water by saturated bentonite slurry, where there were no air-water interfaces, scaled simply according to the temperature effects on the kinematic viscosity of pure water. Additional keywords: unsteady flow, temperature dependence, viscosity, surface tension., Introduction Effects of temperature on liquid water flow in porous materials are attributed to the temperature dependences of the kinematic viscosity and of the surface tension of water as tabulated [...]

The combined slope length and slope steepness factor (LS) is crucial in soil erosion models such as the revised universal soil loss equation (RUSLE), and is often calculated from digital elevation models (DEMs). With highresolution DEMs becoming increasingly available in recent years, we face considerable challenges in selecting the optimal DEM for erosion modelling. In this paper, we present a case study on LS factor computation using various DEMs at resolutions ranging from 1 to 90 m over a burnt national park in New South Wales, Australia, aiming to assess the effects of DEM resolution on LS and hillslope erosion estimation. The LS was calculated based on RUSLE specifications and incorporated a variable cutoff slope angle that improves the detection of the beginning and the end of each slope length. Results show the trend of an increase in the estimated LS value as the DEM resolution became coarser. We consider 5-10-m DEMs to have optimal resolution because the LS values calculated at this range were closer to the LS values measured at the 12 soil plots over the study area. We also assessed different sampling methods for LS value extraction and statistical analysis. The sampling method based on contributing area was more representative compared with point-based and buffer sampling methods. Findings from this study will be useful for choosing the optimal DEM resolution and sampling method in hillslope erosion modelling. Additional keywords: sampling scale, slope, slope length, soil erosion, RUSLE. Received 21 February 2019, accepted 13 May 2019, published online 3 July 2019, Introduction Terrain factors are important in predicting soil losses using erosion models such as the revised universal soil loss equation (RUSLE) (Renard et al. 1997). The slope length and steepness [...]

Using Australian sugarcane regions as a case study, we present an approach for prediction of in-field nitrogen (N) mineralisation over a crop season. The approach builds on the statistical modelling applied in Allen et al. 2019, which demonstrated good predictive ability on data from a laboratory incubation study (an external [R.sup.2] of 0.84 in a cross-validation exercise), and adjusts those mineralisation rates according to soil moisture and temperature factors. The required field soil temperature and moisture conditions were simulated using a mechanistic model for the response of soil conditions to input climate data. We investigate drivers of variability in the predicted in-season mineralised N, and compare predictions with currently implemented N fertiliser discounts, which are based on a relationship with soil organic carbon content. The main purpose of this paper is to illustrate the potential use of the results in Allen et al. (2019) for calculating predictions of in-season mineralised N that could be applicable under field conditions in the Australian sugarcane regions. A thorough test to properly validate predictions has not yet been conducted, but collecting data to do so should be the focus of further work. Additional keywords: Soil N supply, statistical models, simulation models, soil indices, climate data, climate forecasts. Received 13 February 2019, accepted 1 July 2019, published online 23 September 2019, Introduction There is increasing global focus, including within the Australian sugar industry, towards efficient agricultural nitrogen (N) management by: matching N supply with crop demand; utilising the continuous supply of [...]

The UPNESS index derived from the Fuzzy Landscape Analysis Geographic information system (FLAG) model was calculated for the Wagga Wagga and Kyeamba Creek Catchments in NSW, Australia. The model uses only digital elevation data to derive UPNESS and several other indices of relative height in the landscape. UPNESS is an index of surface and subsurface water accumulation calculated as the set of cells above any given point in a raster grid that is connected by a continuous monotonic uphill path. Accumulation of groundwater causes increased secondary weathering, solubilisation of rock and soil minerals, and soil pedogenic development. In this paper the UPNESS index is compared with depth to a shallow water table and groundwater electrical conductivity (EC). Reasonable relationships with [r.sup.2] = 0.71 and 0.74 were found between the UPNESS index and depth to watertable and groundwater EC, respectively, in the Wagga Wagga study area. UPNESS was then used to predict spatial extents of waterlogged to seasonally waterlogged, saline, and sodic soil landscapes within the Kyeamba Catchment, a larger catchment, with soil landscape mapping at a scale of 1 : 100 000. Most differences between UPNESS and soil landscape mapping occurred in broad valleys where deeply incised channels have caused UPNESS calculations to be more restricted to the stream lines than mapped boundaries. In valley-filled areas with little incision, the UPNESS index derived similar areas but with substantially more detail than the soil landscape mapping. The UPNESS index provides an efficient method to help differentiate seasonally and fully waterlogged, saline, or sodic soils from the drier soils in a catchment. This may aid in objectively establishing initial soil landscape boundaries with detail that would otherwise be too costly to obtain. Additional keywords: groundwater modelling, landscape modelling, subsurface water, soil wetness, Fuzzy Landscape Analysis GIS., Introduction In this paper the UPNESS index derived in the FLAG model was tested against depth to watertable and groundwater EC to assess how well it represents the subsurface accumulation [...]

This paper presents results using the Burgers equation in spherical coordinates for the investigation of soil water dynamics around porous cup samplers under field conditions. The analysis reveals that the yield (V) of the porous suction-cup sampler is a power function of inflow duration (7) and source moisture strength (A). It also shows that the shock front velocity and moving boundary of the front are both power functions of A and time. The analysis further demonstrates that the asymptotic shock front velocity derived from a similarity solution is the samefor different versions of Burgers equation, indicating the validity of different versions of Burgers equation for the same flow patterns. The observation using time domain reflectometry shows that a moisture shock was induced around the sampler following application of a vacuum, which justifies the application of Burgers equation. The values of A were derived using field data to determine the location and the front velocity of the shock. Additional keywords: soil-water flow, TDR., Introduction In this paper, we aim to investigate the transient movement of water towards a porous cup sampler, which can be regarded theoretically as a spherical sink. In this case, [...]

Rare earth elements (REEs) are applied widely to increase crop production in China but less attention has been paid to the principle adverse effects of the accumulation of REEs in soils. In this paper we studied the effects of lanthanum (La) on two indicators of microbial activity: dehydrogenase activity and C[O.sub.2] evolution. The soil was collected from crop land of the Chinese Academy of Sciences' Red Soil Ecological Experimental Station. Application of La decreased soil pH and there were significant negative correlations between soil pH and added La. Significant positive correlations were also observed between 0.05 M HCl extractable La and added La, indicating that exogenous La was highly available in soil. Additions of La decreased soil dehydrogenase activity and the recorded maximum decrease was 64% after 1 day of incubation with an application of 1000 mg La/kg dry soil. The inhibition of soil dehydrogenase activity by La was gradually alleviated on prolonged incubation time. Addition of La at low concentrations slightly increased soil C[O.sub.2] evolution but decreased it if at greater concentrations. The recorded maximum decrease in soil C[O.sub.2] evolution was 33% after 56 days of incubation with an application of 1000 mg La/kg dry soil. The results in this paper indicated that agricultural use of REEs such as La at excessive levels would produce harmful effects to soil microbial activity and microbially mediated soil function. It is likely that change in soil dehydrogenase activity can be used as a sensitive indicator in assessing the level of REEs pollution in soil. Additional keywords: rare earth elements, soil, pH, extractability., Introduction Rare earth elements (REEs) are a group of 17 trivalent metallic elements which have similar chemical properties, and their relative atomic mass varies from 139 (lanthanum) to 175 (lutetium). [...]

Large quantities of wastewater are generated from municipal and industrial sources in New Zealand. More stringent discharge standards and recent improvements in wastewater treatment technology have contributed to the production of large quantities of solid residuals. Increasing public, cultural, and regulatory pressures to protect water quality have resulted in significant interest in applying residuals to plantation forests. In a well-managed land application site, the forest ecosystem can efficiently handle organic contaminants and recycle nutrients provided through the residuals, resulting in significant increase in plant growth. Due to large variations in characteristics of different residuals, land application system design must be tailored to match a particular residual with the assimilation capacities of a particular soil-plant system. In New Zealand, many wastewater irrigation systems are employed in forested land as an alternative treatment of liquid residuals. In recent years, large-scale forested land application of municipal and pulp and paper industrial solid residuals have also increased as a preferred alternative to landfilling. It has been suggested that natural abundance of [sup.15]N can be used to trace the fate of residual-derived N in the ecosystems. This technique can resolve one of the main environmental concerns associated with application of residuals in forested land, namely nitrate leaching. Intensive research indicates that significant economic and social benefits can be achieved with minimal adverse impact on the receiving environment. This paper provides an overview of the research issues associated with application of residuals on forested soils in New Zealand, such as sustainability, beneficial effects, and potential adverse impacts on soil and environmental quality. Performances of 4 case studies, representing application of 2 liquid residuals and 2 solid residuals to forested soils in New Zealand, are discussed. Additional keywords: biosolids, effluent, environment, groundwater, land application, [sup.15]N natural abundance, waste., Introduction Large quantities of municipal and industrial wastewater are generated every year worldwide. Most of this wastewater is treated to remove solids, pathogens, and other contaminants, and the resulting effluent [...]

This paper is the first of two describing how soil macromorphological and chemical data can be combined with a minimum of hydrological data to distinguish between, and to quantify, past and present hydrological processes. These processes are relevant to both waterlogging and dryland salinity. The purpose of this first paper is to establish a methodological framework. It also describes the initial interpretation of the macromorphological features of the toposequence studied at Gatum on the Dundas Tablelands in western Victoria. A modified version of the soil feature-system-domain grouping method was used. Macromorphological data combined with only limited piezometric data showed that: (1) The soil feature-system-domain grouping method makes it possible to distinguish between the effects of past and present hydrological processes on soil macromorphology at Gatum. (2) Waterlogging of the surface horizons at Gatum is often caused by perching of soil water within the B-horizon (as opposed to on top of the B-horizon). Changes in soil structure and in colour of cutans and mottles can be an indicator of this first restricting layer. (3) It is likely that interpedal cracks and old tree root holes act as preferred paths for water to flow through this first restricting layer. (4) A second fresh perched water table can occur on top of the pallid zone. Where the pallid zone reaches close to the surface the two perched water tables may merge and cause a local increase in waterlogging, as indicated by local soil morphology. When this occurs, hillside seeps can occur quite high up on the slopes, even when there is no apparent irregularity in surface topography. (5) The permanent saline water table occurs on top of the bedrock and causes salting problems where it comes too close to the soil surface. Salting problems at the bottom of a slope are more severe where fresh perched water tables increase waterlogging On the basis of these findings the suitability of various management options to reduce waterlogging and salinisation is discussed. Further findings regarding restricting layers, flow paths through the soils, and relations between duration of saturation and soil morphological features, are discussed in a companion paper (by J. Brouwer and R. W. Fitzpatrick, pp. 927-946 in this issue). Additional keywords: soil colour, soil-water-landscape models, duplex soils, Dermosols, Chromosols, Hydrosols., Introduction Waterlogging or saturation of topsoils is a major constraint to agricultural production in southern Australia. So is dryland salinity. To understand the occurrence and driving mechanisms of seasonal waterlogging [...]

This paper is the second of two describing how soil macromorphological and chemical data can be combined with soil hydrological data to distinguish between, and to quantify, past and present hydrological processes relevant to waterlogging and dryland salinity. The first paper provides a methodological framework for the study, and describes the initial interpretation of the macromorphological features of the toposequence studied, using the soil feature-system--domain grouping method. This second paper deals with the added value of extensive piezometric and other hydrological observations relative to soil macromorphological studies, and with quantitative relationships between soil colour and duration of waterlogging. As with the first paper, this paper focuses on a soil toposequence at Gatum on the eastern Dundas Tableland in western Victoria. For the the broad crest with yellow gradational soils or Dermosols (Plinthoxeralfs), the hydrological data confirmed the conclusion from macromorphological observations that: (1) There are three levels at which downward flow of water is restricted: at the top of the largely unaltered mottled zone, that is at 0.8-1.0 m depth, well below the top of the yellow Bt1-horizon (fresh water); at the top of the pallid zone, at about 3-3.5 m depth (fresh water); and on top of the unweathered ignimbrite (saline water). (2) Below about 30 mm depth, down at least as far as 2.0 m and sometimes even more, the major pathways for downward movement of water are indeed root channels, with or without live roots, and not interpedal cracks. The 3-dimensional spacing of the rootholes above and through the less-permeable mottled zone, and the (horizontal) conductivity, storage capacity, and thickness of overlying horizons determine the extent of ponding, runoff, and deep infiltration taking place. In addition, the hydrological observations showed that: (3) If rainfall is regular, well-spaced, and not excessive, ponding is unlikely to take place even where there is a rainfall surplus and there are layers restricting downward flow of water. Furthermore, along the toposequence with yellow duplex soils or Dermosols, Chromosols, and Hydrosols, (4) There were generally good correlations between duration of saturation at the bottom of the E-horizon and colour aspects of the E-horizon (value and chroma of the matrix) and of the B2-horizon (hue, value, and chroma of the matrix). Based on these findings additional suggestions are made for improving identification and management of water logging and salinisation processes. Additional keywords: soil colour, redoximorphic features, waterlogging, perched aquifers, Plinthoxeralf-Natrixeralf-Plinthoxeralf-Natraqualf hydro-toposequence., Introduction Waterlogging or saturation of topsoils is a major constraint to agricultural production in southern Australia (e.g. McFarlane and Cox 1992; Cox et al. 1996; Fitzpatrick et al. 1996). Soil [...]

Quirk and Schofield (1955) in their paper on the effect of electrolyte concentration on soil permeability in relation to sodicity designated 2 concentrations: the threshold concentration, which related to the first discernible effect on soil structure; and the turbidity concentration, at which the dismantling of the soil microstructure is indicated by the appearance of dispersed particles in the percolate--this occurs when the electrolyte concentration is about one-quarter of the threshold concentration. This behaviour is explained in terms of clay domains, which are assemblages of many clay particles in parallel alignment. Within a clay domain, slit-shaped pores with surface separations about equal to the thickness of clay crystals exist. When calcium is the dominant exchangeable ion the clay domains are stable because where contiguous crystals overlap the surfaces reside in a potential well as a result of strong attractive forces. These attractive forces are similar to those responsible for the stability of Ca-montmorillonite and Ca-vermiculite crystals. A model of 3 clay crystals is used to illustrate how crystal interaction within a clay domain, in terms of classical repulsive diffuse double-layer forces and modern attractive forces, affect domain stability. Attention is drawn to a misconception, now prevalent in the literature, which does not recognise the basic significance of the turbidity concentration with respect to microstructure and wrongly contends that the concentration of electrolyte required to effect the dispersion to flocculation transition in soil suspensions can be used for predicting the level of electrolyte required to sustain soil permeability or infiltration rate in irrigation practice. It is shown that the flocculation concentration is almost 8 times the turbidity concentration. The application of the threshold concentration concept in irrigation practice is discussed. It is demonstrated that the threshold and turbidity concentration comfortably explain the behaviour of a heavy clay soil subjected to border-check irrigation and Cajon sandy loam in Arizona. Additional keywords: interparticle forces, permeability, electrolyte concentration, swelling, dispersion., Introduction The paper `The effect of electrolyte concentration on soil permeability' (Quirk and Schofield 1955) was republished as a Benchmark Paper in 1984 (Levey). This paper has also been referred [...]

The author advises that there were errors in various cells in Table 1 of the above paper. The corrected table is provided below. https://doi.org/10.1071/SR20094_CO Table 1. Environmental variables according to [...]

Nitrogen (N) is invaluable for maintaining agricultural production, but its use, and particularly inefficient use, can lead to environmental losses. This paper reviews N use efficiency (NUE) and N surplus indicators for dairy production systems to assess their utility for optimising N use outcomes and minimising environmental N losses. Using case-study examples, we also assess realistic goals for these indicators and discuss key issues associated with their use. Published whole-farm NUE and whole-farm N surplus values ranged within 10-65% and 40-700 kg N [ha.sup.-1] [year.sup.-1] respectively. In a study of five catchments across New Zealand, whole-farm NUE was more strongly affected by catchment differences in soil and climatic conditions than by differences in management. In contrast, whole-farm N surplus differed both between and within-catchments and was a good indicator of N losses to water. Realistic goals for both NUE and N surplus thus depend on the agro-climatic context of the dairy system and on its economic and environmental goals. Crop and animal NUE values can be valuable indicators for optimising fertiliser and feed use and minimising N losses. However, global or national whole-farm NUE values appear of limited value if the ultimate goal for setting targets is to reduce the environmental impact of N use; whole-farm level targets based on N surplus would be a more useful indicator for this purpose. Our review also reinforces the importance of standardising the variables that should be used to estimate NUE and N surplus values, to ensure equitable comparisons between different systems. Finally, NUE and N surplus targets should also be set in the context of other agro-environmental considerations. Additional keywords: animal NUE, crop NUE, dairy systems, nitrogen use efficiency (NUE), whole-farm NUE., Introduction The availability of reactive nitrogen (N) in the form of fertiliser has increased agricultural production and led to intensification of all agricultural systems, including dairy production systems. Although the [...]

Animal production systems provide nutritious food for humans, income and survivability for numerous smallholder farms and transform residues to valuable products. However, animal production is implicated in human health issues (diet-related diseases, zoonosis, antimicrobial resistance) and environmental burdens (ammonia and greenhouse gas emissions, eutrophication of surface waters, biodiversity loss). This paper reviews changes in global animal production and associated nitrogen (N) and phosphorus (P) flows over the past 50 years, during which time total animal production roughly tripled. Cattle still dominate the world in terms of animal biomass, but the number and total production of pigs and poultry have increased faster. Animal production systems are highly diverse and respond to changes in markets. Specialised systems have become more dominant, especially in developed and rapidly developing countries. The annual production of N and P in manure is similar to the amounts of N and P in synthetic fertiliser produced annually, but manure nutrients are often not recycled effectively and used efficiently by plants. Nutrient losses greatly depend on the system, management and regulations. Nitrogen and P use efficiency (NUE and PUE respectively) at the animal level is in the range 5-45%, depending on animal category, feeding and management. NUE of mixed crop-animal systems may range from 5% to 65% depending on NUE at the animal level, and the utilisation of manure nitrogen and new nitrogen inputs. Potentially, values for PUE are higher than those for NUE. Solutions for improving NUE and PUE in animal production are based on a coherent set of activities in the whole chain of 'feed production-animal production-manure management'. A high efficiency at the system level is achieved through combination of high NUE and PUE at the animal level and effective recycling and utilisation of manure N and P in crop production. Specific regional regulations (low-emission manure storage and application, proper application limits and timing) greatly contribute to high efficiency at a system level. Additional keywords: feed, livestock density, manure management, nitrogen balance, nitrogen use efficiency, phosphorus balance, phosphorus use efficiency, system., Introduction For growth, maintenance of body functions and (re)production, animals (including humans) require some 22 nutrient elements (N, P, K, Mg, Ca, S, Fe, Mn, Zn, Cu, Mo, Cl, Co, [...]

The development and implementation of a national data schema for soil data in Australia over the last two decades, coupled with advances in information technology, has led to the realisation of more comprehensive state and national soil databases. This has facilitated increased access to soil data for many purposes, including the creation of many digital soil-mapping products, such as the Soil and Landscape Grid of Australia. Consequently, users of soil data have a growing need for clarity concerning the quality of the data; many new users have little understanding of the varying quality of the data. To date, statements about the quality of primary soil data have typically been qualitative and/or judgemental rather than explicit. The consequences of poor-quality primary data and of the lack of a coding system for data quality are growing with increased usage and with demand for soil data at the regional to national scale. Pillar 4 of the Global Soil Partnership and the National Soil Research, Development and Extension Strategy both identify the need to improve the quality of soil data. Various international standards do exist with respect to the quality of soil data but these tend to focus on general principles and quality-assurance frameworks rather than the detail of describing data quality. The aim of this paper is to stimulate a discussion in the Australian soil science community on how to quantify and describe the quality of primary soil data. We provide examples of the data quality issues and propose a framework for structured data-quality checking procedures and quality coding of soil morphological and analytical data in Australia. Additional keywords: DSM, soil databases, soil morphology. Received 23 May 2016, accepted 24 November 2016, published online 14 December 2016, Introduction The demand for high-quality, complete, soil-attribute data at the local to continental scale continues to increase and most recently has been driven by the needs of developing the GlobalSoilMap [...]

This paper explores the importance of the N loss pathways relative to the immobilisation and soil mineral N supply during a cotton season. Despite using an agronomic practice of splitting urea application to reduce losses and an optimal rate (232 kg urea-N [ha.sup.-1]) for the experiment, the average fertiliser recovery was 32%, which indicates that soil N mineralisation is a key source of N for irrigated cotton production systems. A large amount of the fertiliser (62 kgN[ha.sup.-1]) was immobilised in the soil at the end of the season and during the season the soil supplied 159 kg N [ha.sup.-1] to the plant via mineralisation. During the season, large N losses occurred from the field via the atmospheric, deep drainage and surface run-off pathways (143 kgN[ha.sup.-1]). The losses occurred directly after fertilisation, predominantly at the start of the season when the majority of the urea fertiliser was applied (180 kg urea-N [ha.sup.-1]). This indicates that the fonn, placement and timing of the fertiliser did not synchronise with soil and crop N dynamics and irrigation practice. Over the course of the measurement season, based on the N inputs, losses and storage budget, a 42kgN[ha.sup.-1] soil deficit was observed. Further longer term work is required to quantify the magnitude and significance of the soil N stock across different systems., Introduction Synthetic nitrogen fertiliser is a critical component in modern agriculture and underpins the green revolution. As a result, the production and consumption of synthetic nitrogen fertiliser has grown exponentially [...]

With the introduction of the cation ratio of soil stability (CROSS) to replace the sodium adsorption ratio (SAR) on the basis of differential effects of K and Mg to Na and Ca, respectively, there is a requirement for a similar index involving these cations to replace the exchangeable sodium percentage (ESP). The exchangeable dispersive percentage (EDP) is derived and proposed to replace ESP. This paper uses two datasets, one where exchangeable K. concentration is relatively high and exchangeable Na low, and a further dataset where Mg dominates the cation exchange capacity. EDP is validated against these datasets and further mathematical investigation of the contribution of Mg to dispersion is undertaken. Mineralogy appears to affect turbidity results at a given dispersive index, and an improved criterion for assessment of Mg effect on dispersivity is presented. Additional keywords: aggregate stability, cation ratio of soil stability, ESP, exchangeable cation ratio, sodium adsorption ratio, turbidity. Received 2 October 2015, accepted 8 February 2016, published online 5 September 2016, Introduction Sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) are traditionally used as indices for assessing soil structural stability upon interaction with water. Whilst these indices are used to [...]

The author advises that the funding information was incorrectly specified in the above paper. The correct information is provided below. Declaration of funding. This work was supported by a Gyeongsang [...]

Correct estimation of the soil-water retention curve (WRC) is of paramount importance to characterise the hydraulic behaviour of soils. This paper studies the influence of two different soil-wetting processes (waterlogging soil, WP; capillary rise to saturation, CRJP) on the estimate of the WRC. The two procedures were applied on undisturbed loam soil samples with three degrees of soil structure: (i) consolidated soils under conventional tillage (CT), reduced tillage (RT) and no tillage (NT); (ii) freshly tilled soil under CT and RT; and (iii) CT and RT after secondary tillage plus some intense rainfalls events. WRCs were estimated with time-domain reflectometry (TDR) pressure cells and volumetric water content was measured at saturation conditions (for the WP method) and at pressure heads of 0.5, 1.5, 3, 5, 10, 50, 100, 500 and 1500 kPa. The same cores were used to determine the soil bulk density ([ρ.sub.b]), which was subsequently used to estimate the saturated water content under CRP. The [ρ.sub.b] value of the consolidated soil under NT was significantly higher (P < 0.001) than under CT and RT. No effect of the wetting process on the WRC of consolidated soils was observed. Only the freshly tilled soil samples under RT were significantly affected by the wetting process. In these cases, the water draining after WP collapsed the more unstable soil macropores and increased the volume of the smaller ones. However, this effect was minimised by the CRP method, which prevented the collapse of the more unstable soil pores. This work demonstrates that the soil-wetting process may have an important effect on the characterisation of the water-holding capacity on freshly tilled soils. Additional keywords: hydraulic properties, undisturbed soil samples, water holding capacity., Introduction The soil-water retention curve (WRC), which is defined as the relationship between the matric potential (ψ) and soil volumetric water content (θ), is essential to characterise the hydraulic and [...]

Dryland cereal production systems of south-eastern Australia require viable options for reducing nitrous oxide ([N.sub.2]O) emissions without compromising productivity and profitability. A 4-year rotational experiment with wheat (Triticum aestivum L.)--canola (Brassica napus L.)--grain legumes wheat in sequence was established at Wagga Wagga, NSW, Australia, in a semiarid Mediterranean-type environment where long-term average annual rainfall is 541 mm and the incidence of summer rainfall is episodic and unreliable. The objectives of the experiment were to investigate whether (i) tillage increases [N.sub.2]O emissions and (ii) nitrogen (N) application can improve productivity without increasing [N.sub.2]O emissions. The base experimental design for each crop phase was a split-plot design with tillage treatment (tilled versus no-till) as the whole plot, and N fertiliser rate (0, 25, 50 and 100 kg N/ha) as the subplot, replicated three times. This paper reports high resolution [N.sub.2]O emission data under a canola crop. The daily [N.sub.2]O emission rate averaged 0.55 g [N.sub.2]O-N/ha. day, ranging between -0.81 and 6.71 g [N.sub.2]O-N/ha.day. The annual cumulative [N.sub.2]O-N emitted was 175.6 and 224.3 g [N.sub.2]O-N/ha under 0 and 100 kg N/ha treatments respectively. There was no evidence to support the first hypothesis that tillage increases [N.sub.2]O emissions, a result which may give farmers more confidence to use tillage strategically to manage weeds and diseases where necessary. However, increasing N fertiliser rate tended to increase [N.sub.2]O emissions, but did not increase crop production at this site. Additional keywords: conservation tillage, greenhouse gases, nitrogen fertiliser, trace gas emission., Introduction In Australia, the agriculture sector is the dominant source of anthropogenic nitrous oxide ([N.sub.2]O), accounting for 78.6% of the net national [N.sub.2]O emissions (Commonwealth of Australia 2014). Globally, 70% [...]

Transient salinity associated with increased dispersion of clays is arguably one of the most economically important soil constraints in Australia because it occurs on land that is regularly cropped. However, this issue is rarely studied. This paper examines the occurrence of transient salinity on agricultural land in the south-west of Western Australia and the factors causing it. We analysed four soil datasets from the region, collected at scales varying from the entire southwest to a single paddock. A variety of soil parameters were correlated with increased electrical conductivity ([EC.sub.1:5]). The most significant relationships were invariably with measures of exchangeable sodium ([Na.sup.+]; 53-85% of variance accounted for), and this factor appears to be most responsible for transient salinity. Another parameter correlated with increased [EC.sub.1:5] was alkalinity. This has been associated with the increased dispersion of kaolinite and consequent decreases in soil hydraulic conductivity; kaolinite is the most common clay mineral in the south-west of Western Australia. Other factors correlated with increased [EC.sub.1:5] were increasing clay, increasing depth in the soil profile and decreasing rainfall. These factors are environmental indicators of transient salinity. Affected soils might be ameliorated by application of agents to increase soil hydraulic conductivity, such as gypsum and/or elemental sulfur. Additional keywords: alkaline soils, clay mineralogy, dispersion, sodic soils. Received 18 February 2015, accepted 26 August 2015, published online 6 June 2016, Introduction Two kinds of soil salinity occur in agricultural areas of Australia (Rengasamy 2002). 'Dryland salinity' generally refers to soil salinity associated with a shallow water table. Typically in this [...]

Decision support systems (DSS) that provide advice on best N fertiliser management practice ideally need to assess the effect that fertiliser type, rate and management have on N loss. Currently only nitrate leaching and denitrification losses can be assessed in Australian DSS that use output from the Agriculture Production Simulator (APS1M). This paper describes a simple spreadsheet-based model for estimating N[H.sub.3] loss from urea, urea ammonium nitrate and ammonium sulfate that can be used in conjunction or independent of current DSS. The use of scaling factors that reduce N[H.sub.3] emission on the basis of factors known to be key determinants of N[H.sub.3] loss, including type of fertiliser used, rate of fertiliser applied, management of fertiliser, rainfall and crop development was found to account for 85% of the variance between predicted and observed values when tested against 40 case studies. The model also had good predictive power with a root mean square error (RMSE) equivalent to 4.8% of N applied. Additional keywords: ammonium sulfate, ammonia volatilisation, model, N use efficiency, urea, urea ammonium nitrate., Introduction Adoption of fertiliser management practices that minimise loss of applied N and concomitantly increase N use efficiency is required to offset the rising cost of fertiliser N. Australian-based-decision support [...]

Information on the geographic variation in soil has traditionally been presented in polygon (choropleth) maps at coarse scales. Now scientists, planners, managers and politicians want quantitative information on the variation and functioning of soil at finer resolutions; they want it to plan better land use for agriculture, water supply and the mitigation of climate change land degradation and desertification. The GlobalSoilMap project aims to produce a grid of soil attributes at a fine spatial resolution (approximately 100 m), and at six depths, for the purpose. This paper describes the three- dimensional spatial modelling used to produce the Australian soil grid, which consists of Australia-wide soil attribute maps. The modelling combines historical soil data plus estimates derived from visible and infrared soil spectra. Together they provide a good coverage of data across Australia. The soil attributes so far include sand, silt and clay contents, bulk density, available water capacity, organic carbon, pH, effective cation exchange capacity, total phosphorus and total nitrogen. The data on these attributes were harmonised to six depth layers, namely 0-0.05 m, 0.05-0.15 m, 0.15-0.30 m, 0.30-0.60 m, 0.60-1.00 m and 1.00-2.00 m, and the resulting values were incorporated simultaneously in the models. The modelling itself combined the bootstrap, a decision tree with piecewise regression on environmental variables and geostatistical modelling of residuals. At each layer, values of the soil attributes were predicted at the nodes of a 3 arcsecond (approximately 90 m) grid and mapped together with their uncertainties. The assessment statistics for each attribute mapped show that the models explained between 30% and 70% of their total variation. The outcomes are illustrated with maps of sand, silt and clay contents and their uncertainties. The Australian three-dimensional soil maps fill a significant gap in the availability of quantitative soil information in Australia. Additional keywords: GlobalSoilMap, digital soil mapping, spatial modelling, Cubist, kriging, spatial uncertainty, three-dimensional mapping, Australia. Received 14 December 2014, accepted 4 June 2015, published online 25 September 2015, Introduction Soil is essential for life on land. We need it for our food, for the capture and storage of water and energy, and for other ecosystem services. We need [...]

Given the wide variety of ways one can measure and record soil properties, it is not uncommon to have multiple overlapping predictive maps for a particular soil property. One is then faced with the challenge of choosing the best prediction at a particular point, either by selecting one of the maps, or by combining them together in some optimal manner. This question was recently examined in detail when Malone et al. (2014) compared four different methods for combining a digital soil mapping product with a disaggregation product based on legacy data. These authors also examined the issue of how to compute confidence intervals for the resulting map based on confidence intervals associated with the original input products. In this paper, we propose a new method to combine models called adaptive gating, which is inspired by the use of gating functions in mixture of experts, a machine learning approach to forming hierarchical classifiers. We compare it here with two standard approaches--inverse-variance weights and a regression based approach. One of the benefits of the adaptive gating approach is that it allows weights to vary based on covariate information or across geographic space. As such, this presents a method that explicitly takes full advantage of the spatial nature of the maps we are trying to blend. We also suggest a conservative method for combining confidence intervals. We show that the root mean-squared error of predictions from the adaptive gating approach is similar to that of other standard approaches under cross-validation. However under independent validation the adaptive gating approach works better than the alternatives and as such it warrants further study in other areas of application and further development to reduce its computational complexity. Received 1 October 2014, accepted 6 May 2015, published online 18 September 2015, Introduction Inference based on data from a single measurement technique is often easier than inference based on two very different measurement techniques but the benefit of using more than one [...]

Digital soil mapping is founded on the availability of covariates that are used as surrogates for the spatial patterns in soil properties. One important subset of covariates represents the patterns due to terrain, and these are typically derived from a digital elevation model at a suitable resolution. When each digital soil mapping exercise requires the calculation of terrain covariatcs, there is a clear potential for inconsistent methods and for choosing the covariates that are easiest to derive rather than those that are most relevant. The creation of open repositories of relevant terrain covariates that are correctly derived avoids these problems and fosters the application of digital soil mapping and other modelling activities that benefit from landscape properties. This paper describes the creation of a suite of commonly used terrain covariates from the 1-arcsecond (~30 m) resolution digital elevation models for Australia that were released through CSIRO's Data Access Portal and the TERN Data Discovery Portal. The methods used to derive the terrain covariates are described and their characteristics are identified. Received 30 September 2014, accepted 9 September 2015, published online 2 November 2015, Introduction Digital soil mapping relies on readily available covariates for prediction, including various terrain parameters derived from digital elevation models (DEMs). The terrain parameters represent properties of the land surface [...]

A 'Report Card', which summarises the current knowledge of the status and trend in land condition in the agricultural areas of the south-west of Western Australia, was published in 2013 by the Department of Agriculture and Food, Western Australia. The Report Card draws on best available evidence from government and industry on the current condition and trend of 10 soil- and water-related natural resource themes relevant to agriculture, and discusses the implications of these results for the agricultural industries. The report also discusses the three main factors driving the performance of the land, namely climate, land characteristics and land management. The first two factors are largely out of the control of land managers, but in a drying and warming climate of the agricultural areas of Western Australia, land- management practices need to be able to respond to these changing conditions. The paper briefly explains the methodologies used to assess the seven soil-related themes in the Report Card and summarises the major findings. The results indicate that, for soils, the situation and outlook for our natural resources is mixed. Although there has been progress in some areas, such as managing wind and water erosion, the status and trend in many indicators of resource condition, such as soil acidity, soil compaction and water repellence, are adverse. The predicted growth in global demand for food and fibre brings many opportunities to the Western Australian agri-food sector but also challenges, especially in light of the Report Card findings. One of these challenges is our need to achieve agricultural productivity growth while ensuring our natural resources are healthy and resilient. Additional keywords: land management, resource condition monitoring, soil condition, soil hazard, soil trend, sustainability indices. Received 25 September 2014, accepted 7 May 2015, published online 11 September 2015, Introduction State of Environment reports published in 2007 (Environmental Protection Authority 2007) and 2011 (State of Environment Committee 2011) indicate that soil condition in the south-west of Western Australia is [...]

In this paper, we present a framework for a space-time observation system for soil organic carbon (STOSSOC). We propose that the RothC model be embedded within the STOS-SOC, which is driven by satellite-derived inputs and readily available geospatial inputs, such as digital soil maps. In particular, advances in remote sensing have enabled the development of satellite products that represent key inputs into soil carbon models, examples being evapotranspiration and biomass inputs to soil, which characterise space-time variations in management and land use. Starting from an initial calibrated base for prediction, as new observations are acquired, data assimilation techniques could be used to optimise calibration algorithms and predicted model outputs. We present initial results obtained from the implementation of the proposed STOS-SOC approach to the 1445-[km.sup.2] Cox's Creek catchment in northern New South Wales, Australia. Our results showed that use of satellite-derived biomass inputs with a MODIS satellite product (MOD 17 A3) improved the accuracy of simulations by 16% compared with carbon inputs derived through other methods normally adopted in the spatialisation of the RothC model. We further discuss the possibility of improving the capabilities of the STOS-SOC for future applications. Additional keywords: digital soil mapping, MODIS products, space-time modelling, soil organic carbon, RothC model. Received 14 July 2014, accepted 21 April 2015, published online 11 September 2015, Introduction The modelling of changes in soil organic carbon stocks (SOC) has received more attention recently, due to the fact that small changes in SOC can have a large impact [...]

Soil chronosequence data may easily be interpreted in a too straightforward and simple a way if some relevant theoretical background is not kept in mind. This paper discusses pedological concepts that are considered relevant for soil chronosequence studies and may provide some guidance for establishing soil chronosequences and interpreting obtained data. Concepts related to the soil system, soil body, and soil-forming factors are introduced, and advantages and disadvantages of different types of soil chronosequences are pointed out. The question of whether soil formation reaches steady-state is raised, leading to the conclusion that some soil properties achieve steady-state whereas others do not, and that soil formation as a whole may only rarely reach a kind of near steady-state. The influence of climate and relief, and associated three-dimensional water and material fluxes in landscapes, are addressed, and concepts related to pedogenic processes, soil properties, and energy and matter transfers as drivers of soil formation are discussed. Feedback systems and thresholds in soil development are highlighted, the concept of progressive vs regressive pedogenesis is introduced, and potential shortcomings of soil chronosequence studies are addressed. Implications of each of the mentioned concepts for soil chronosequence studies are pointed out. Additional keywords: chronofunctions, pedogenesis, soil development, soil properties, soil sequences. Received 9 October 2014, accepted 21 May 2015, published online 17 August 2015, Introduction Numerous soil chronosequences have been studied over the last four decades. These studies provide valuable information on soil-forming processes and their rates; however, caution is required to avoid interpreting [...]