Australia’s greenhouse gas emissions from agriculture in 2022 were 67.8 million (M) tonnes (t) of carbon dioxide equivalent (CO2-e), amounting to 12.9% of total emissions. Erupted methane (CH4) from ruminant animals comprised 42% of agricultural emissions. By 2030, the Australian Government aims to reduce total emissions by 43% from the 2005 level. The primary policy instrument for achieving this reduction is the Emissions Reduction Fund (ERF) in which there are two main pathways for agriculture – emission avoidance through suppression of CH4 emissions and soil carbon sequestration (SCS) through approved projects. Although agriculture since 2014 has promised 15.2 Mt of abatement, by April 2022 it has delivered only 1.1 Mt. Examples are given of potential abatement by SCS for pasture and cropping land in different rainfall zones. Methods of suppressing CH4 emissions have yet to be scaled up commercially and proven for grazing animals. The main constraints on SCS are the unreliability of Australian rainfall, the high cost of project management relative to the value of a C credit, and the opportunity cost of maintaining an approved land management for at least 25 years.

Soil carbon sequestration (SCS) is a key priority in the Australian government's Long-Term Emissions Reduction Plan. Under the government's Emission Reduction Fund (ERF), farmers are encouraged to change to a management practice that will increase their soil carbon (C) stock and earn Australian Carbon Credit Units (ACCUs). The projections of net C abatement nationally range from 17 to 103 Mt carbon dioxide equivalent annually up to 2050. This huge range reflects the uncertainties in achieving net SCS due to biophysical constraints, such as those imposed by the paucity and variability of Australian rainfall and the difficulty of measuring small changes in soil C stock. The uptake by farmers is also uncertain because of compliance costs, opportunity costs of a practice change and the loss of business flexibility when a farmer must commit to a 25-year permanence period. Since the program's inception in 2014, only one soil C project has been awarded ACCUs. Nevertheless, an increase in soil C is generally beneficial for farm productivity. As a voluntary C market evolves, the government is expecting that farmers will sell their ACCUs to businesses seeking to offset their greenhouse gas emissions. The risk is that, in buying cheap offsets, businesses will not then invest in new energy-efficient technologies to reduce their emissions at source.

There is an extensive literature on the role of soil physicochemical factors such as rate of water supply, N supply and soil temperature in wine terroir expression, especially for dry-grown vines. Other recent literature invokes the possibility of unique strains of the natural yeast Saccharomyces cerevisiae influencing must fermentations to produce distinctive aroma profiles in wines. Others suggest that the composition of the soil microbiome at particular sites can influence vine growth, fruit composition and wine characteristics to create a microbial terroir. Because terroir is a multifactor concept, no general quantitative relationships between one or more soil properties and the distinctive characteristics of wine from a particular site have been identified; rather a unique combination of soil factor values interacts with local climate, grape variety, vintage, canopy management, and winemaker technique to determine a site’s terroir. However, with modern methods of sensing spatially referenced values of environmental and other variables at high resolution, terroirs can be mapped. This provides a platform for monitoring terroirs over time and recording how they respond to changes in environmental factors or to manipulations in the vineyard and winery.

Emeritus Professor Robert White, from the Faculty of Veterinary and Agricultural Sciences at The University of Melbourne, discusses the practicalities of grapegrowers earning net income from carbon credits by managing soil organic carbon.

In Australia, orthodox soil scientists dealing with land management and alternative practitioners who promote ‘regenerative agriculture’ have not been communicating and engaging effectively with each other. Over many years, scientists in the Commonwealth Scientific and Industrial Research Organization (CSIRO), state departments and universities have made significant achievements in mapping soil distribution, describing soil behaviour and identifying key soil properties and processes that are fundamental to healthy soil function. However, many alternative practitioners are dismissive of these achievements and highly critical of orthodox soil science. Yet many of the tools of soil science are essential to conduct evidence-based research towards elucidating how and why the exceptional results claimed by some alternative practitioners are achieved. We stress the importance of effective engagement and communication among all parties to resolve this ‘clash of cultures’.

This paper illustrates the benefits of long-term monitoring of soil and vine health in Craggy Range’s Te Muna vineyard in the Martinborough region of New Zealand. The soils at Te Muna are formed on two river terraces. The higher and older terrace, planted to Pinot Noir, is very gravelly; the lower and younger terrace, planted to Sauvignon Blanc, contains more silt and very fine sand. Both terraces are freely drained. Soil pH, organic C and available P were monitored in selected blocks on both terraces. Under current management that includes cover crops and sheep grazing in winter, soil organic C has been stable for 10 years. Because of the regular application of RPR and intermittent liming, soil pH (water) has risen from c.5.5 to 6.5–7. Values for soil available P, measured by Olsen bicarbonate and Mehlich-3 extractions, diverged over time. The Olsen test indicated satisfactory P levels: conversely, the Mehlich test showed P values rising to very high levels, confirming Western Australian experience that this acid extraction is unsuitable for soils treated with RPR. Petiole and leaf blade P concentrations confirmed these results, but they showed greater interannual variation than the soil P measurements. Overall, the long-term sustainability of the vineyard should be assured.

How much C can be stored in agricultural soils worldwide to mitigate rising carbon dioxide (CO2) concentrations, and at what cost? This question, because of its critical relevance to climate policy, has been a focus of soil science for decades. The amount of additional soil organic C (SOC) that could be stored has been estimated in various ways, most of which have taken the soil as the starting point: projecting how much of the SOC previously lost can be restored, for example, or calculating the cumulative effect of multiple soil management strategies. Here, we take a different approach, recognizing that photosynthesis, the source of C input to soil, represents the most fundamental constraint to C sequestration. We follow a simple "Fermi approach" to derive a rough but robust estimate by reducing our problem to a series of approximate relations that can be parameterized using data from the literature. We distinguish two forms of soil C: 'ephemeral C', denoting recently-applied plant-derived C that is quickly decayed to CO2, and 'lingering C,' which remains in the soil long enough to serve as a lasting repository for C derived from atmospheric CO2. First, we estimate global net C inputs into lingering SOC in croplands from net primary production, biomass removal by humans and short-term decomposition. Next, we estimate net additional C storage in cropland soils globally from the estimated C inputs, accounting also for decomposition of lingering SOC already present. Our results suggest a maximum C input rate into the lingering SOC pool of 0.44 Pg C yr−1, and a maximum net sequestration rate of 0.14 Pg C yr−1 – significantly less than most previous estimates, even allowing for acknowledged uncertainties. More importantly, we argue for a re-orientation in emphasis from soil processes towards a wider ecosystem perspective, starting with photosynthesis.

Grapevines must have 16 of the 118 known elements to grow normally, flower, and produce fruit. These essential elements, listed in table 3.1, are also called nutrients and as such are divided into • Macronutrients, which are required in relatively large concentrations • Micronutrients, which are required in smaller concentrations Box 3.1 discusses the different ways of calculating nutrient concentrations in soil, plants, and liquid. Vines draw most of their nutrients from the soil, and so table 3.1 also shows the common ionic form of each element in soil. Ions, the charged forms of elements, are introduced in box 2.4, chapter 2. For example, carbonic acid (H2CO3), which is a compound of carbon (C), hydrogen (H), and oxygen (O), dissociates in water into the ions H+ and HCO3−. This is a chemical reaction that can be written in shorthand form as . . . H2CO3 ↔ H+ + HCO3− . . . The double arrow shows that the reaction can go either forward (to the right) or backward (to the left), depending on the concentrations of H+ and HCO3− relative Concentration (symbol C)a is the amount of a substance per unit volume or unit weight of soil, plant material, or liquid. For example, the concentration C of the element nitrogen (N) can be expressed as micrograms (μg) of N per gram of soilb, noting that . . . 1 μg N/g = 1 mg N/kg = 1 part per million (ppm N) (B3.1.1) . . . An amount is the product of concentration and weight. For example, the total amount of N of concentration C (measured in μg/g) in a soil sample of 100g is . . . 100C μg or 0.1C mg (B3.1.2) . . . Because all soil and plant materials contain some water, analyses are best expressed in terms of oven-dry (o.d.) weights. The o.d. weight of a soil sample is obtained by drying it to a constant weight at 105ºC; for plant material the drying temperature is 70ºC. The amount of a nutrient is often expressed per hectare (ha) of vineyard.

Data for cropping and pastoral enterprises in south eastern Australia were used in a cost-effectiveness analysis to assess the feasibility of abating greenhouse gas (GHG) emissions through storing soil carbon (C) as soil organic matter under the Australian government's Carbon Farming Initiative. We used the C credit value for 2013-14 of $24.15 per tonne of CO2-equivalent (CO2-e) and a C storage rate of 0.5 tonne C/hectare/year for conversion of cropland to pasture. Given that a change of enterprise is driven primarily by farmer returns, we found that none of the changes were feasible at current prices, with the exception of wheat to cattle or sheep in an irrigated system, and dryland cotton to cattle or sheep. Given that our model scenario assumed the most favourable economic factors, it is unlikely that increased soil C storage through a change from cropping to pasture can make a significant contribution to abating Australia's CO2 emissions. However, of greater concern to society is the methane emissions from grazing cattle or sheep, which would negate any gain in soil C under pasture, except for a switch from dryland cropping to sheep.

Chapter 3 gives examples of how grapevines, being woody perennials, have the potential to develop extensive, deep root systems when soil conditions are favorable. One of the most important factors governing root growth is a soil’s structure, the essential attributes of which are • Spaces (collectively called the pore space or porosity) through which roots grow, gases diffuse, and water flows • Storage of water and natural drainage following rain or irrigation • Stable aggregation • Strength that not only enables moist soil to bear the weight of machinery and resist compaction but also influences the ease with which roots can push through the soil The key attributes of porosity, aeration and drainage, water storage, aggregation, and soil strength are discussed in turn. Various forces exerted by growing roots, burrowing animals and insects, the movement of water and its change of state (e.g., from liquid to ice) together organize the primary soil particles—clay, silt, and sand—into larger units called aggregates. Between and within these aggregates exists a network of spaces called pores. Total soil porosity is defined by the ratio . . . Porosity = Volume of pores/Volume of soil . . . A soil’s A horizon, containing organic matter, typically has a porosity between 0.5 and 0.6 cubic meter per cubic meter (m3/m3)—also expressed as 50% to 60%. In subsoils, where there is little organic matter and usually more clay, the porosity is typically 40% to 50%. Box 4.1 describes a simple way of estimating a soil’s porosity. Total porosity is important because it determines how much of the soil volume water, air, and roots can occupy. Equally important are the shape and size of the pores. The pores created by burrowing earthworms, plant roots, and fungal hyphae are roughly cylindrical, whereas those created by alternate wetting and drying appear as cracks. Overall, however, we express pore size in terms of diameter (equivalent to a width for cracks). Table 4.1 gives a classification of pore size based on pore function.

Any reduction in soil quality as a consequence of production practices, through processes, such as erosion, salinisation, sodicity, acidity and structural decline, threatens the long-term sustainability of winegrape production. Monitoring of soil quality is thus needed to identify when degradation is occurring in order to allow management intervention. This review examines the suite of biological indicators available for this purpose and the potential for their adoption as part of a minimum dataset by industry. Physical and chemical indicators are discussed in a companion paper. Many groups of organisms and various biological processes have been used as indicators of soil quality in research programs. There is a lack of consensus, however, on which are the key indicators for extensive monitoring programs, and little information is available on threshold values to aid data interpretation. At present, only soil organic carbon (together with labile carbon), potentially mineralisable nitrogen and microbial biomass can be recommended for measuring the biological aspects of soil quality in Australian viticulture. Although newer molecular methods have been developed to elucidate the community structure and genetic profiles of groups in the soil biota, and thus supplement measurements of microbial biomass, these methods are not readily available through commercial laboratories. Moreover, with the exception of tests for some pathogenic organisms, these measurements have not yet been linked to soil functions influencing grapevine growth and nutrition and so are not suitable for routine monitoring of vineyard soil quality.

Background and Aim A long-term trend in early ripening of winegrapes in southern Australia has been attributed to an increasing growing season temperature, soil drying linked to global warming and crop management. However, the 5x5-km cell size used used in the continental-scale model to derive soil properties was too coarse for the study vineyards of 0.216?ha. This paper aims to test the modelling conclusions using long records of annual rainfall for sites as close as possible to the experimental vineyards. Methods and Results If prolonged soil drying has occurred, it should be correlated with a decrease in annual rainfall, given that actual evapotranspiration should change little as the effect of increased atmospheric carbon dioxide concentration compensates for the effect of temperature increase on evaporation. Analysis of the longest, most complete Bureau of Meteorology records showed a highly significant decrease in rainfall (27?mm/decade) at Margaret River, but paradoxically no significant early ripening. Conversely, significant earlier ripening on the Mornington Peninsula was associated with a significant increase in rainfall (8.5?mm/decade). Conclusion Although growing season temperature and crop management to reduce yields may have contributed to earlier ripening, the case for an effect of prolonged soil drying was not supported. Significance of the Study The output of simulation models describing complex biological systems needs to be tested wherever possible against experimental data and observations. Also, the scale of modelling should be appropriate to the system being studied, especially for soil, which has marked spatial variability.

For many years, the poor physical and hydraulic properties of the soils in south-western Victoria have restricted crop production due to waterlogging. In this region of predominantly winter rainfall, raised beds have become popular with farmers to overcome these difficulties; however, little has been reported on the hydrology of raised beds compared with other tillage systems for cropping in the rain-fed environment of south-western Victoria. This study measured rainfall characteristics, runoff volumes, and soil properties such as the soil water content, bulk density, and hydraulic conductivity for three tillage treatments (raised beds, conventional cultivation, and deep cultivation) over 6 years on a Sodosol at a field site near Geelong, Victoria. Runoff was regressed against rainfall variables such as the amount per event, hours of rainfall, rainfall intensity, and maximum rainfall intensity to determine the significance of any differences between the treatments. The relationship between runoff and rainfall amount was best described with an exponential model. Raised beds significantly increased the amount of runoff relative to the other treatments when above-average rainfall was received, but there was little difference in runoff in years of below-average rainfall. No consistent effect of runoff on crop biomass was detected nor could any differences in runoff be attributed to differences in soil water content, hydraulic conductivity, and bulk density between treatments. The most important factor appeared to be the furrows between the raised beds, which acted as conduits for the flow of surface water during the larger storm events. During such events, runoff is an important hydrological process in cropping land in south-western Victoria.

Sewage sludge is a valuable source of organic matter, N, P and certain micronutrients that have beneficial effects on plant growth and biomass production. However, sanitary regulations often require the stabilization of sewage materials prior to applying them to soils as biosolids. Environmental regulations also demand appropriate management of biosolid-N to avoid groundwater contamination. Because stabilization processes usually make sewage sludge less putrescible, we hypothesized that the mineralization rates of organic-N from stabilized biosolids would be affected. Therefore, this study aimed to evaluate the mineralization of five biosolids in two soils a sandy Spodosol and a clayey Oxisol. Digested sludge, composted sludge, limed sludge, heat-dried sludge and solar-irradiated sludge were mixed with soil samples at a concentration of 32.6 mg N/kg soil (1.0 dry t/ha of digested sludge) and incubated at 25 degrees C in a humidity chamber for 23 weeks. Results showed that the stabilization processes generally slowed the release of mineral-N in soils relative to the digested sludge from which the biosolids originated. However, increments in the levels of mineral-N were more influenced by soil type than by the type of stabilization process applied to the sewage sludge. Mineralization rates were up to 5-fold higher in the Oxisol than in the Spodosol soil, and as a result, organic-N in biosolids mineralized 10-24% in Spodosol and 23-52% in Oxisol. Any appropriate plan for the management of biosolid-N for plant use should consider the interaction between soil type and biosolid type.

1Catedra de Quimica General e Inorganica, Department of Natural Resources and Environment, School of Agriculture, University of Buenos Aires, Avenida San Martin 4453, C1417DSE Buenos Aires, Argentina 2University of Brasilia, Caixa Postal 04.401, 70910-970 Braśilia, DF, Brazil 3Department of Plant, Soil and Environmental Sciences, University of Florence, Piazzale delle Cascine 28, 50144 Florence, Italy 4Centro de Estudios Ambientales del Mediterraneo (CEAM), C/Charles R. Darwin 14, Parque Tecnologico, 46980 Paterna, Spain 5Department of Biology, Tula State University, Lenin Avenue 92, Tula 300012, Russia

The essential water and N fluxes for irrigated wheat-maize systems were quantified in a one hectare plot in Fengqiu County in the North China Plain (NCP). A spatially-referenced, process model (WNMM) was developed to simulate key water, carbon and nitrogen dynamics, crop growth and agricultural management practices. An agricultural decision support tool (ADST) based on WNMM dynamically coupled to a geographical information system (GIS) was developed to provide best management practices (BMPs) for irrigation and fertilizer use county-wide. Adoption of BMPs would reduce annual N fertilizer use by 20-23% and provide annual water savings of AUD10-45 per ha for no significant change in crop yield. The potential net benefits of the project were estimated at AUD216 million.