Epifluorescence imaging of electrochemically Switchable Langmuir-Blodgett films of Nafion

Reforestation of riparian zones is increasingly practiced in many regions for purposes of biodiversity conservation, bank stabilisation, and improvement in water quality. This is in spite of the actual benefits of reforestation for recovering underlying soil properties and function remaining poorly understood. Here we compare remnant riparian rainforest, pasture and reforestation plantings aged 2-20 years in an Australian subtropical catchment on ferrosols to determine the extent to which reforestation restores key soil properties. Of the nine soil attributes measured (total nitrogen, nitrate and ammonium concentrations, net nitrification and ammonification rates, organic carbon, bulk density, fine root biomass and water infiltration rates), only infiltration rates were significantly lower in pasture than remnant riparian rainforest. Within reforestation plantings, bulk density decreased up to 1.4-fold and infiltration rates increased up to 60-fold with time post-reforestation. Our results suggest that the main outcome of belowground processes of early reforestation is the recovery of the soils' physical structure, with potential beneficial ecosystem services including reduced runoff, erosion and associated sediment and nutrient loads in waterways. We also demonstrate differential impacts of two commonly planted tree species on a subset of soil properties suggesting that preferential planting of select species could accelerate progress on specific restoration objectives

Responses of soil organic carbon, aggregate diameters, and hydraulic properties to long-term organic and conventional farming on a Vertisol in India

Organic matter management can improve soil structural properties. This is crucial for agricultural soils in tropical regions threatened by high rainfall intensities. Compared to conventional farming, organic farming is usually deemed to increase organic carbon and improve soil structural properties such as stability and permeability. However, how much, if any, buildup of organic carbon is possible or indeed occurring also depends on soil type and environmental factors. We compared the impact of seven years of organic farming (annually 13.6 t ha−1 of composted manure) with that of conventional practices (2 t ha−1 of farmyard manure with 150–170 kg N ha−1 of mineral fertilizers) on soil structural properties. The study was conducted on a Vertisol in India with a two-year crop rotation of cotton soybean wheat. Despite large differences in organic amendment application, organic carbon was not significantly different at 9.6 mg C g−1 on average in the topsoil. However, the size distribution of water-stable aggregates shifted toward more aggregates <137 μm in the organic systems. Cumulative water intake was lower compared to the conventional systems, leading to higher runoff and erosion. These changes might be related to the lower pH and higher exchangeable sodium in the organic systems. Our results indicate that higher application of organic amendments did not lead to higher soil organic carbon and associated improvement in soil structures properties compared to integrated fertilization in this study. Chemical properties may dominate soil aggregation retarding the uptake and integration of organic amendments for sustainable agricultural intensification in tropical, semiarid climates

Plastic properties

Application of a force to soil can result in an elastic, non-permanent, deformation that only lasts while the force is applied or a plastic, permanent deformation that persists after the load is removed. The latter may, or may not result in a decrease in the soil volume. How easily and how much the volume changes is determined by the soil's plasticity. It is an important factor influencing ease and outcome of soil tillage operations. Soil plasticity is caused by the lubricating film of water surrounding soil particles that allow the soil to change shape without rupturing upon application of forces. As an inherent soil property it is governed primarily by the surface area of the soil particles. Plasticity increases with increasing clay content, activity of clay minerals, position of the adsorbed cations in the lyotropic series and organic matter content

Changing tillage management practices and their impact on soil structural properties in north-western New South Wales, Australia

A study was conducted in 1998 in north-western New South Wales to assess how changes in tillage practices and farmers’ perceptions of ‘good’ or bad’ paddocks relate to soil structural properties. Forty landholders were visited and interviewed to obtain background information on their current and past management practices, crops and cropping systems used, and what they expect in the future. The majority of the soils were Vertosols (78%), with some Kandosols and a few Chromosols. Conventional tillage was practised on 63% of the fields surveyed. Conservation tillage (minimum or zero-tillage) was only practised on swelling clay soils. On these soils 26% of the fields had been converted from conventional to conservation tillage during the past 3 years, while on 14% of the fields conservation tillage had been practised since they were brought into crop production (3–10 years previously). Saturated hydraulic conductivities on the farmed black Vertosols with a history of conventional tillage were lower than those of the virgin sites, but increased after conversion from conventional to conservation tillage. Fields that were brought into cropping during the last 10 years using conservation tillage only had higher saturated conductivities than the virgin sites. There was little effect of cropping history on saturated hydraulic conductivity on the grey Vertosols. Soil organic carbon on the control sites was always greater than on the corresponding cultivated sites, regardless of whether conventional or conservation tillage was practised. Tillage history did not affect any of the measured soil chemical properties. Platyness of soil structure was a clear indicator for wheel-induced compaction. Platy structure was not shown on any of the swelling clay soils at the never-cultivated sites, and tended to be more frequent on the ‘poor’ sites. This was most pronounced for the grey Vertosols, where 80% of the ‘poor’ and 50% of the ‘good’ sites were platy, and on the black Vertosols, with 42% and 31% respectively. The overall close agreement between platyness and the farmers’ perceptions of ‘good’ and ‘poor’ sites indicated that platyness has an impact on soil productivity and that soil compaction continues to be a limiting factor for crop production. We also concluded that black Vertosols respond better to conservation tillage than grey Vertosols, possibly due to their greater resilience and better ability to self-ameliorate. The absence of conservation tillage adoption on non-swelling clay soils in this region (at the time of the study) may reflect the length of time required before conservation tillage improves soil structure and, ultimately, yield

Gamma Irradiation with 50 kGy Has a Limited Effect on Agronomic Properties of Air-Dry Soil

International collaboration on agronomy projects often requires the shipment of soil samples between countries to conduct analyses. However, quarantine regulations in numerous countries restrict the importing of soil samples unless they are sterilized, or analysis is carried out only in quarantine facilities, which greatly increases cost. Yet, sterilization is only an option if it does not change the soil properties. There is conflicting information about the effect of irradiation on soil chemical properties. To assess the effect of gamma irradiation on some soil chemical properties, one hundred randomly selected air-dried (40 °C) soil samples were split into two samples. One sample was left untreated and the other sample was irradiated with 50 kGy as prescribed by Australian biosecurity regulations. Commonly measured agronomic soil chemical properties were then measured and results from the non-irradiated samples were compared to the irradiated samples. The results show no effect of irradiation on soil cation exchange capacity, exchangeable cations, total carbon and nitrogen content, and DTPA-extractable Zn. Small (&lt;5%) but statistically significant effects of irradiation were observed for pH (1:5 water), electric conductivity (EC1:5), DTPA-extractable Cu, Fe and Mn, and Colwell P. The irradiation effects on Fe were greater in the topsoil than subsoil. Considering that irradiation-induced changes to soil chemical properties were below 5%, gamma irradiation can be considered a suitable method to sterilize air-dried soil to meet import requirements, without affecting the interpretation of soil fertility reports

Sustaining soil fertility in support of intensification of Sweetpotato cropping systems

Sweetpotato is the most important food and cash crop in the Highlands of Papua New Guinea (PNG). However, low tuber yield due to declining soil fertility, unsustainable cultivation practices as well as yield-limiting virus infestations are\ua0 increasing problems threatening food security. Sustainable, farmer-adoptable soil fertility management strategies are needed to satisfy the increasing demand for sweetpotato. This is now of particular importance with the projected rapid adoption of high yielding, virus free (Pathogen Tested, PT) sweetpotato varieties. Over the past 4 years several on-stationand on-farm trials showed that substantial yield increases of over 40% are possible from a combination of using PT material and applying fertiliser, either in mineral or organic form