Quantifying surfactant interaction effects on soil moisture

Quantifying surfactant interaction effects on soil moisture and turf quality.

ACIAR Improving soil health in support of sustainable development in the Pacific

The proposed project focuses on developing research-based indicators that growers and extensionists can use to assess soil health status (including key chemical, physical and biological variables), as well as extension approaches to communicate soil health.

Nutrient loss and water quality under extensive grazing in the upper Burdekin river catchment, North Queensland

Increased sediment and nutrient losses resulting from unsustainable grazing management in the Burdekin River catchment are major threats to water quality in the Great Barrier Reef Lagoon. To test the effects of grazing management on soil and nutrient loss, five 1 ha mini-catchments were established in 1999 under different grazing strategies on a sedimentary landscape near Charters Towers. Reference samples were also collected from watercourses in the Burdekin catchment during major flow events.Soil and nutrient loss were relatively low across all grazing strategies due to a combination of good cover, low slope and low rainfall intensities. Total soil loss varied from 3 to 20 kg haˉ¹ per event while losses of N and P ranged from 10 to 1900 g haˉ¹ and from 1 to 71 g haˉ¹ per event respectively. Water quality of runoff was considered moderate across all strategies with relatively low levels of total suspended sediment (range: 8-1409 mg lˉ¹), total N (range: 101-4000 ug lˉ¹) and total P (range: 14-609 ug lˉ¹). However, treatment differences are likely to emerge with time as the impacts of the different grazing strategies on land condition become more apparent.Samples collected opportunistically from rivers and creeks during flow events displayed significantly higher levels of total suspended sediment (range: 10-6010 mg lˉ¹), total N (range: 650-6350 ug lˉ¹) and total P (range: 50-1500 ug lˉ¹) than those collected at the grazing trial. These differences can largely be attributed to variation in slope, geology and cover between the grazing trial and different catchments. In particular, watercourses draining hillier, grano-diorite landscapes with low cover had markedly higher sediment and nutrient loads compared to those draining flatter, sedimentary landscapes.These preliminary data suggest that on relatively flat, sedimentary landscapes, extensive cattle grazing is compatible with achieving water quality targets, provided high levels of ground cover are maintained. In contrast, sediment and nutrient loss under grazing on more erodable land types is cause for serious concern. Long-term empirical research and monitoring will be essential to quantify the impacts of changed land management on water quality in the spatially and temporally variable Burdekin River catchment.

Implementation costs of Agricultural Management Practices for Water Quality Improvement in the Great Barrier Reef Catchments. CSIRO: Water for Healthy Country National Research Flagship

Executive summary. In this report we analyse implementation costs and benefits for agricultural management practices, grouped into farming systems. In order to do so, we compare plot scale gross margins for the dominant agricultural production systems (sugarcane, grazing and banana cultivation) in the NRM regions Wet Tropics, Burdekin Dry Tropics and Mackay Whitsundays. Furthermore, where available, we present investment requirements for changing to improved farming systems. It must be noted that transaction costs are not captured within this project. For sugarcane, this economic analysis shows that there are expected benefits to sugarcane growers in the different regions through transitions to C and B class farming systems. Further transition to A-class farming systems can come at a cost, depending on the capital investment required and the length of the investment period. Obviously, the costs and benefits will vary for each individual grower and will depend on their starting point and individual property scenario therefore each circumstance needs to be carefully considered before making a change in management practice. In grazing, overall, reducing stocking rates comes at a cost (reduced benefits). However, when operating at low utilisation rates in wetter country, lowering stocking rates can potentially come at a benefit. With win-win potential, extension is preferred to assist farmer in changing management practices to improve their land condition. When reducing stocking rates comes at a cost, incentives may be applicable to support change among farmers. For banana cultivation, the results indicate that the transition to C and B class management practices is a worthwhile proposition from an economic perspective. For a change from B to A class farming systems however, it is not worthwhile from a financial perspective. This is largely due to the large capital investment associated with the change in irrigation system and negative impact in whole of farm gross margin. Overall, benefits will vary for each individual grower depending on their starting point and their individual property scenario. The results presented in this report are one possible set of figures to show the changes in profitability of a grower operating in different management classes. The results in this report are not prescriptive of every landholder. Landholders will have different costs and benefits from transitioning to improved practices, even if similar operations are practiced, hence it is recommended that landholders that are willing to change management undertake their own research and analysis into the expected costs and benefits for their own soil types and property circumstances.

Persistence of bellyache bush (Jatropha gossypifolia L.) soil seed banks

Bellyache bush (Jatropha gossypifolia L.) is an invasive shrub that adversely impacts agricultural and natural systems of northern Australia. While several techniques are available to control bellyache bush, depletion of soil seed banks is central to its management. A 10-year study determined the persistence of intact and ant-discarded bellyache bush seeds buried in shade cloth packets at six depths (ranging from 0 to 40 cm) under both natural rainfall and rainfall-excluded conditions. A second study monitored changes in seedling emergence over time, to provide an indication of the natural rate of seed bank depletion at two sites (rocky and heavy clay) following the physical removal of all bellyache bush plants. Persistence of seed in the burial trial varied depending on seed type, rainfall conditions and burial depth. No viable seeds of bellyache bush remained after 72 months irrespective of seed type under natural rainfall conditions. When rainfall was excluded seeds persisted for much longer, with a small portion (0.4%) of ant-discarded seeds still viable after 120 months. Seed persistence was prolonged (> 96 months to decline to < 1% viability) at all burial depths under rainfall-excluded conditions. In contrast, under natural rainfall, surface located seeds took twice as long (70 months) to decline to 1% viability compared with buried seeds (35 months). No seedling emergence was observed after 58 months and 36 months at the rocky and heavy clay soil sites, respectively. These results suggest that the required duration of control programs on bellyache bush may vary due to the effect of biotic and abiotic factors on persistence of soil seed banks.

Chickpeas! Varietal performance, wet feet and root rot, virus and salinity effects in 2012, Ascochyta management, seed quality, issues in central Queensland and effects of desiccating too early with glyphosate on seed germination

Take home messages: Plant only high quality seed that has been germ and vigour tested and treated with a registered seed dressing Avoid poorly drained paddocks and those with a history of lucerne, medics or chickpea Phytophthora root rot, PRR; do not grow Boundary if you even suspect a PRR risk Select best variety suited to soil type, farming system and disease risk Beware Ascochyta: follow recommendations for your variety and district Minimise risk of virus by retaining stubble, planting on time and at optimal rate, controlling weeds and ensuring adequate plant nutrition Test soil to determine risk of salinity and sodicity – do not plant chickpeas if ECe > 1.0-1.3 dS/m. Beware early desiccation of seed crops – know how to tell when 90-95% seeds are mature

The Effect of Silica and Manure Addition into Suppressive and Conducive Soil on the Incidence of Fusarium Wilt Disease of Banana

Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of banana. One potential method to manage fusarium wilt of banana is by manipulating the nutrient status in the soil. This study was conducted to determine the quality of Foc suppressive and conducive soil, the influence of soil application of silica and manure on the incidence of fusarium wilt of banana. Surveys were conducted in five banana plantations in three provinces in Indonesia: Lampung-Sumatra, West Java and Central Java. From the five locations, one location (Sala-man-Central Java) was heavily infected by Foc, another location (NTF Lampung-Sumatera) was slightly infected by Foc, while the rest (Sarampad-West Java, Talaga-West Java and GGP Lampung-Sumatra) were healthy banana plantations without Foc infection. Labile carbon analysis showed that the Foc suppressive soil had greater labile carbon content than conducive soil. Also, the analysis of fluorescein diacetate hydrolysis (FDA) and ?-glucosidase showed greater microbial activity in suppressive soil than the conducive soil. Observations of the incidence of necrotic rhizome of Foc susceptible 'Ambon Kuning' (AAA) banana cultivar showed that in the suppressive soil taken from Sarampad West Java, the application of silica and manure helped suppress fusarium wilt disease development. In the conducive soil taken from Salaman-Central Java, silica and manure applications were not able to suppress disease incidence. The result of this study indicated that in suppressive soil, the application of silica can increase plant resistance to Foc infection, while manure application can increase soil microbial activity, and suppress Foc development.

Effect of water quality and season on the population dynamics of Cabomba caroliniana in subtropical Queensland, Australia

Cabomba caroliniana is a submersed aquatic macrophyte that originates from the Americas and is currently invading temperate, subtropical, and tropical freshwater habitats around the world. Despite being a nuisance in many countries, little is known about its ecology. We monitored C. caroliniana populations in three reservoirs in subtropical Queensland, Australia, over 5.5 years. Although biomass, stem length, and plant density of the C. caroliniana stands fluctuated over time, they did not exhibit clear seasonal patterns. Water depth was the most important environmental factor explaining C. caroliniana abundance. Plant biomass was greatest at depths from 2–4 m and rooted plants were not found beyond 5 m. Plant density was greatest in shallow water and decreased with depth, most likely as a function of decreasing light and increasing physical stress. We tested the effect of a range of water physico-chemical parameters. The concentration of phosphorus in the water column was the variable that explained most of the variation in C. caroliniana population parameters. We found that in subtropical Australia, C. caroliniana abundance does not appear to be affected by seasonal conditions but is influenced by other environmental variables such as water depth and nutrient loading. Therefore, further spread will more likely be governed by local habitat rather than climatic conditions.

Effect of water quality and season on the population dynamics of Cabomba caroliniana in subtropical Queensland, Australia

Cabomba caroliniana is a submersed aquatic macrophyte that originates from the Americas and is currently invading temperate, subtropical, and tropical freshwater habitats around the world. Despite being a nuisance in many countries, little is known about its ecology. We monitored C. caroliniana populations in three reservoirs in subtropical Queensland, Australia, over 5.5 years. Although biomass, stem length, and plant density of the C. caroliniana stands fluctuated over time, they did not exhibit clear seasonal patterns. Water depth was the most important environmental factor explaining C. caroliniana abundance. Plant biomass was greatest at depths from 2–4 m and rooted plants were not found beyond 5 m. Plant density was greatest in shallow water and decreased with depth, most likely as a function of decreasing light and increasing physical stress. We tested the effect of a range of water physico-chemical parameters. The concentration of phosphorus in the water column was the variable that explained most of the variation in C. caroliniana population parameters. We found that in subtropical Australia, C. caroliniana abundance does not appear to be affected by seasonal conditions but is influenced by other environmental variables such as water depth and nutrient loading. Therefore, further spread will more likely be governed by local habitat rather than climatic conditions.

Strategic tillage in no-till farming systems in Australia’s northern grains-growing regions: II. Implications for agronomy, soil and environment

In semi-arid sub-tropical areas, a number of studies concerning no-till (NT) farming systems have demonstrated advantages in economic, environmental and soil quality aspects over conventional tillage (CT). However, adoption of continuous NT has contributed to the build-up of herbicide resistant weed populations, increased incidence of soil- and stubble-borne diseases, and stratification of nutrients and organic carbon near the soil surface. Some farmers often resort to an occasional strategic tillage (ST) to manage these problems of NT systems. However, farmers who practice strict NT systems are concerned that even one-time tillage may undo positive soil condition benefits of NT farming systems. We reviewed the pros and cons of the use of occasional ST in NT farming systems. Impacts of occasional ST on agronomy, soil and environment are site-specific and depend on many interacting soil, climatic and management conditions. Most studies conducted in North America and Europe suggest that introducing occasional ST in continuous NT farming systems could improve productivity and profitability in the short term; however in the long-term, the impact is negligible or may be negative. The short term impacts immediately following occasional ST on soil and environment include reduced protective cover, soil loss by erosion, increased runoff, loss of C and water, and reduced microbial activity with little or no detrimental impact in the long-term. A potential negative effect immediately following ST would be reduced plant available water which may result in unreliability of crop sowing in variable seasons. The occurrence of rainfall between the ST and sowing or immediately after the sowing is necessary to replenish soil water lost from the seed zone. Timing of ST is likely to be critical and must be balanced with optimising soil water prior to seeding. The impact of occasional ST varies with the tillage implement used; for example, inversion tillage using mouldboard tillage results in greater impacts as compared to chisel or disc. Opportunities for future research on occasional ST with the most commonly used implements such as tine and/or disc in Australia’s northern grains-growing region are presented in the context of agronomy, soil and the environment.

Fertilising for yield and quality in sown grass pastures and forage crops

Sown pasture rundown and declining soil fertility for forage crops are too serious to ignore with losses in beef production of up to 50% across Queensland. The feasibility of using strategic applications of nitrogen (N) fertiliser to address these losses was assessed by analysing a series of scenarios using data drawn from published studies, local fertiliser trials and expert opinion. While N fertilser can dramatically increase productivity (growth, feed quality and beef production gains of over 200% in some scenarios), the estimated economic benefits, derived from paddock level enterprise budgets for a fattening operation, were much more modest. In the best-performing sown grass scenarios, average gross margins were doubled or tripled at the assumed fertiliser response rates, and internal rates of return of up to 11% were achieved. Using fertiliser on forage sorghum or oats was a much less attractive option and, under the paddock level analysis and assumptions used, forages struggled to be profitable even on fertile sites with no fertiliser input. The economics of nitrogen fertilising on grass pasture were sensitive to the assumed response rates in both pasture growth and liveweight gain. Consequently, targeted research is proposed to re-assess the responses used in this analysis, which are largely based on research 25-40 years ago when soils were generally more fertile and pastures less rundown.

Clays Can Decrease Gaseous Nutrient Losses from Soil-Applied Livestock Manures

Clays could underpin a viable agricultural greenhouse gas (GHG) abatement technology given their affinity for nitrogen and carbon compounds. We provide the first investigation into the efficacy of clays to decrease agricultural nitrogen GHG emissions (i.e., N2O and NH3). Via laboratory experiments using an automated closed-vessel analysis system, we tested the capacity of two clays (vermiculite and bentonite) to decrease N2O and NH3 emissions and organic carbon losses from livestock manures (beef, pig, poultry, and egg layer) incorporated into an agricultural soil. Clay addition levels varied, with a maximum of 1:1 to manure (dry weight). Cumulative gas emissions were modeled using the biological logistic function, with 15 of 16 treatments successfully fitted (P < 0.05) by this model. When assessing all of the manures together, NH3 emissions were lower (×2) at the highest clay addition level compared with no clay addition, but this difference was not significant (P = 0.17). Nitrous oxide emissions were significantly lower (×3; P < 0.05) at the highest clay addition level compared with no clay addition. When assessing manures individually, we observed generally decreasing trends in NH3 and N2O emissions with increasing clay addition, albeit with widely varying statistical significance between manure types. Most of the treatments also showed strong evidence of increased C retention with increasing clay additions, with up to 10 times more carbon retained in treatments containing clay compared with treatments containing no clay. This preliminary assessment of the efficacy of clays to mitigate agricultural GHG emissions indicates strong promise.