J. McL. Bennett

Influence of lime and gypsum on long-term rehabilitation of a Red Sodosol, in a semi-arid environment of New South Wales

This paper determines the influence of lime and gypsum on the rehabilitation of a degraded sodic soil in a semi-arid environment 12 years after application. The aim was to assess rehabilitation strategies for sodic soils as alternatives to the application of gypsum alone. An experimental site was used where lime and gypsum combinations (L0G0, lime 0 t ha–1 and gypsum 0 t ha–1; L0G1, L0G2.5, L0G5, L1G0, L2.5G0, L5G0, L1G1, L2.5G1) had been applied 12 years prior, in 1994. An earlier study had reported on the effects after 3 years of the chemical ameliorants and tillage on a range of soil physical and chemical properties at the site. The current study, sampled in 2006, assessed the effects after 12 years of lime and gypsum on soil chemistry, stability, hydraulics, vegetative growth and soil respiration. Calcium, primarily from lime, was observed to have a major effect on soil health. Significant effects on soil chemistry were limited to increases in exchangeable calcium and decreases in exchangeable magnesium, although aggregate stability in water and hydraulic conductivity were significantly improved where L5G0 was applied. Vegetation patch width, total nitrogen and carbon, and soil respiration were significantly improved where lime had been added at 2.5 or 5 t ha–1. As no lime could be detected in the soil 12 years after application, it was deduced that lime had acted as a catalyst for increased functionality in soil and vegetation interactions. This increased soil functionality resulted in an increased rate of lime dissolution in the soil.

Adoption of Soil Health Improvement Strategies by Australian Farmers: I. Attitudes, Management and Extension Implications

Abstract Purpose: There is inconsistency in the design, understanding, implementation and monitoring of soil health programmes. Despite mounting scientific evidence for the credibility of certain soil health indicators, an increase in the reporting of programme benefits, and progress in communicating these benefits, many farmers remain hesitant to implement structured management plans and strategies tailored to address soil health. The purpose of this research is to investigate the proportion of Lachlan and Macquarie Valley landholders who implement a structured soil health programme and to better understand the role of extension in the management of these. Design: Non-parametric analysis of a mail-based survey supported with content analysis of landholder comments was used. Findings: Results suggests that the overall landholder attitude towards soil health management is positive, although soil health management programmes are often inconsistent, unstructured, or ad hoc. Ongoing communication between landholders, agronomists, extension agencies and scientists is shown to be vital in the adoption of soil health management programmes. Practical implication: By understanding landholder attitudes and management practices, as well as the role of extension, extension efforts can become more targeted and effective. Value: This article shows that soil health management is a primary focus of Australian farmers and elucidates the importance of extension efforts in management and planning. Areas where extension should be focussed are identified.

Adoption of soil health improvement strategies by Australian farmers: II. impediments and incentives

Abstract Purpose: Many farmers remain hesitant to implement structured management plans and strategies tailored to address soil health, irrespective of mounting scientific evidence for the credibility of certain soil health indicators, an increase in the reporting of program benefits and progress in communicating these benefits. Hence, the purpose of this research is to better understand the impediments associated with the adoption of such programs. Design: Non-parametric analysis of a mail-based survey supported with content analysis of landholder comments was used. Findings: This research highlights that impediments to the adoption of soil health programs are affected by region and that this is likely influenced by the availability, enthusiasm and motivation of surrounding environmental service providers. While the initial investment in soil health management is perceived as an impediment, landholders indicate that production longevity and long-term financial gain are achievable. Education is not viewed as an impediment by landholders, but cannot be ruled out as an impediment due to the increasing complexities of farming and the displayed knowledge of landholders. Practical implications: Impediments and incentives to the adoption of soil health management plans have been identified. This provides for strategic planning in promotion and adoption of such plans, as well as identifying priority issues of concern. Originality/Value: In investigating the impediments and incentives associated with adoption of soil health management plans, strategies for adoption can be formulated and pressing areas of concern are identified.

The Efficacy of Lime, Gypsum and Their Combination to Ameliorate Sodicity in Irrigated Cropping Soils in the Lachlan Valley of New South Wales

Two primary factors controlling dissolution rate of lime and gypsum chemical ameliorants are magnitude and frequency of water infiltration. Thus, it could be expected that longevity of these amendments is reduced under irrigated-systems, relative to dryland-systems. This paper examines efficacy of single and combined applications of lime and gypsum in two irrigated agricultural soils used for cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) production. Full-field, replicated experimental-strips consisting of control (L0G0) and combinations of 2.5 t/ha lime (L2.5) and/or gypsum (G2.5), and of 5 t/ha lime (L5) and/or gypsum (G5) were applied; there were seven treatments, that is, L0G0, L2.5G0, L0G2.5, L2.5G2.5, L2.5G5, L5G2.5, and L5G5. For both soils, exchangeable and soluble cation concentrations, cation exchange capacity (CEC), pH, electrical conductivity (EC), residual gypsum, aggregate stability in water (ASWAT), and crop production were measured 6 months and 2.5 years after amendment application. Exchange efficiency of calcium (Ca2+) applied as amendment was calculated after 6 months. Exchange of Ca2+ for sodium (Na+) was primarily attributable to gypsum, and generally at the higher rate at 6 months; effects did not persisting over 2.5 years. The EC effect of gypsum was not observed after 6 months or 2.5 years post-gypsum application and 12.85 ML/ha of infiltrating irrigation-water/rain. Results indicate using lime and gypsum singly, or in combination, at low agronomic rates is not necessarily viable for broadacre-irrigated-agriculture on alkaline clayey soils.

Influence of Gypsum Enhanced Chicken-Manure-and-Wheat-Straw Compost on Amelioration of an Irrigated Sodic Brown Vertisol – Laboratory Experiment

The use of gypsum to ameliorate soil sodicity is a typical practice in Australian agriculture. However, the longevity of ameliorative effect due to gypsum application is often short, due to the rate of dissolution and subsequent leaching by rainfall and/or irrigation. Gypsum was combined with chicken manure/wheat straw compost, during the composting process, in order to investigate the potential of creating a slow release source of calcium (Ca2+). A leaching column experiment was conducted using a Brown Vertisol treated with C0G0 (compost 0 t.ha−1, gypsum 0 t.ha−1), C0G5, C5G0, and C5G5. Columns were irrigated with 635 mm of irrigation water in total. C5G5 treated soil retained more Ca2+ and leached less Ca2+ than gypsum alone, decreased the exchangeable cation ratio and increased soil saturated hydraulic conductivity.

Pressurised Dewatering of Sugarcane Press Mud for Logistical Transport Efficiency and Industrial Reuse

Abstract Press mud, a by-product from sugar milling, has agronomic soil input value, but its transport distance from the mill site is limited by its high moisture content (75–80%). This results in over-application close to the mill, concentrating nutrient sources from a wider harvest region, and has potential for environmental harm. Moisture reduction methods have traditionally focussed on centrifuge techniques, but pressurised systems have been shown to have benefit in other waste industries. This work investigates a press-based system for the dewatering of press mud with sequential loading. Subsequently, the solid and filtrate components were assessed for agricultural land application value, with the solid further assessed for livestock feed value. The observed weight reduction was between 20 and 50%, which increased the viability of land application. Results suggest a combination of mill by-products (PM, ash and bagacillo) could result in a product that is more suitable for dewatering. The separated solids had potential for both land application and livestock feed, while the filtrate nutrient value was observed as low.