Soil properties and fertility of Ashley Dene: The challenge

Extracted from Chapter One: The early years. This part chapter describes the formation of the soil types and properties found on Ashley Dene

Effects of plantation forest species on soil properties

Large scale afforestation of grasslands has occurred in New Zealand. Detailed investigation of changes in soil properties over time following establishment of different tree species is necessary to understand the impacts of this land-use change on soil nutrient dynamics and availability. A field trial was established in 1999 comprising 4 replicate plots of three commercial tree species (Pinus radiata, Eucalyptus nitens, Cupressus macrocarpa). Soil samples were taken from each plot prior to tree planting and after 5 years growth (2004). Analyses of samples taken in 1999 showed that the topsoil (0-5 cm) had a low pH (5.1), with low to medium levels of total carbon (5.01%), nitrogen (0.43%), phosphorus (630 mg/kg), sulphur (510 mg/kg) and exchangeable base cations (7.52 cmolc/kg). Results for comparison between samples taken in 1999 and 2004 revealed a decrease in total C, N, P, S and exchangeable Ca and Mg confined to the 0-5 cm soil depth. The reductions were generally greater under P. radiata than E. nitens and C. macrocarpa. In contrast, inorganic and plant available Olsen P levels increased under all species. These findings confirm that afforestation of grassland has a major short-term impact on soil properties and processes

Effects of plantation forest species on soil properties

A poster showing significant depletion of topsoil P over 10 years following establishment of plantation forest on grassland was mainly attributed to enhanced mineralisation of readily extractable organic P due to a combination of factors including decomposition of pasture residues, tree uptake, and the actions of mycorrhizal fungi associated with tree roots

Increasing phosphate rock availability using a lupin green manure crop

Legumes have been shown to increase the dissolution and utilisation of phosphate rock (PR) phosphorus (P) compared with non-legumes because of their acidifying effect on the rhizosphere. A promising agronomic approach for optimising nutrient availability in organic cropping systems appears to be the integration of legume green manures (GM) into the cropping rotation. A field experiment was conducted to study the combined effect of legume growth (in terms of improved P utilisation from PR) and subsequent organic matter additions (green manure incorporation) on crop growth compared with a corresponding winter fallow system. Three rates of PR (0, 60, 120 kg P/ha) were applied in autumn before sowing of lupin green manure and maize as the crop. A fourth PR treatment involving the application of 60 kg P/ha as PR in spring, before maize sowing was also employed. The objective of the study was to quantify the impact of preceding lupin (green manure), treated or not treated with PR, on a subsequent maize crop, and to evaluate winter fallow and green manure effects in terms of P availability. The observed improvements in maize yields following green manuring and PR application of approximately 1.5t/ha and the 3.1-5.3 kg/ha increase in P uptake by maize in the first season were due to a combination of P release into soil solution following the mineralisation of organic P additions via the lupin GM and increased solubilisation of residual P due to rhizosphere and possible mycorrhiza colonisation processes

Natural regeneration of soil physical conditions following the establishment of permanent pasture on a structurally degraded soil

Oral presentation at the 20th World Congress of Soil Scienc

Changes in soil cadmium concentrations with time following cessation of phosphorus fertilizer inputs

Cadmium (Cd) can accumulate in soil from the application of phosphorus fertilizer. However, there is little information on what happens to soil Cd concentrations when Cd inputs stop. This study used soil and pasture samples collected from a long-term field trial to measure changes in Cd concentrations in soil for 22 yr after Cd inputs from fertilizer had stopped and assessed whether the application of nitrogen (N) (50 kg ha¯¹ yr¯¹) could increase plant uptake of Cd and reduce soil Cd concentrations. It was found that there was no significant change in total or labile soil Cd (1 M CaCl₂ extractable) concentrations after Cd inputs stopped. The application of N did not significantly (P <.05) increase dry matter yield or increase Cd solubility. As a result, N did not enhance plant uptake of Cd. A mass balance that included Cd loss via plant uptake and Cd leaching confirmed they were insufficient to result in a detectable decrease in soil Cd concentration over the 22-yr interval of the trial. It appears that even an acid soil with low amounts of carbon (2.67%), iron/aluminum oxides, and clay can still strongly retain Cd, preventing Cd depletion from the soil, despite stopping Cd inputs and trying to enhance plant uptake of Cd from the application of N fertilizer

Italian ryegrass swards reduce N leaching via greater N uptake and lower drainage over perennial ryegrass cultivars varying in cool season growth rates

Pasture mitigation strategies are needed to reduce the negative effects of nitrate (NO₃⁻) leaching from intensive pastoral livestock production systems. We explored the capability of pasture grasses with different cool season (winter–early spring) growth rates to reduce NO₃⁻ leaching and increase N uptake. Following a single urine application of 700 kg N ha⁻¹, NO₃⁻ leaching loss and N uptake by Italian ryegrass and four perennial ryegrass cultivars of varying seasonal growth (heading dates from –7 to +20 days), either undersown with/without Italian ryegrass, were quantified in a 12 month lysimeter study. Italian ryegrass cv. Tabu had lower NO₃⁻ –N leaching loss and drainage, and greater N uptake and DM yield than perennial ryegrass varieties. Italian ryegrass total N leaching loss (143 kg N ha⁻¹ yr⁻¹) was 46–33% less (P < .05) than early and mid-season maturing Tyson, Arrow and AberDart perennial ryegrass. Italian ryegrass total N uptake (463 kg N ha⁻¹) was 1.2–1.4 times greater than all other grass sward types. Overall, perennial ryegrass pure swards had similar N uptake and N leaching. Late-season maturing One 50 perennial ryegrass showed significantly reduced (P < .05) total N leaching loss. Undersowing Italian ryegrass into established perennial ryegrass swards resulted in lower NO₃⁻leaching and greater N uptake than non-undersown perennial ryegrass swards, though not significant. Results confirm Italian ryegrass is a useful pasture grass option for reducing annual N leaching loss. Cool season perennial ryegrass varieties appear not to influence soil N uptake and leaching loss

Effects of long-term grassland management on the chemical nature and bioavailability of soil phosphorus

Relationships between the relative solubility of soil phosphorus (P) and short-term plant P uptake were investigated using soils obtained from a field trial that had been maintained under contrasting mowing regimen (no mowing, mowing with clippings left, mowing with clippings removed) for 15 years. In a glasshouse pot experiment, P uptake by red clover and Italian ryegrass was found to be 40% lower for the clippings removed treatment compared with the no mowing treatment, which was consistent with the fact that concentrations of readily extracted inorganic P were 42% lower in the clippings removed treatment soil. However, P uptake was 51–54% higher for the clippings left treatment soil compared with no mowing, despite the fact that levels of readily extracted soil inorganic P were similar in both treatments. This indicated that biological and biochemical processes associated with enhanced mineralisation of organic P and turnover of P through the microbial biomass made a greater contribution to increased plant P uptake in the clippings left soil compared with the other treatments. These findings highlight the importance of soil biological processes in determining the P nutrition and productivity of managed grasslands

Improvement of degraded soil physical conditions following the establishment of permanent pasture

Conventional cultivation practices are known to degrade the physical properties of soils. The objective of this study was to measure changes in soil physical conditions following the establishment of permanent pasture (perennial ryegrass/white clover) on a structurally degraded soil. The physical regeneration of the topsoil was monitored over a 4-year period using a visual structure evaluation method as well as more widely used physical measurements of soil quality (e.g. soil bulk density, macroporosity, water infiltration rates, and earthworm numbers). Over the first four years of permanent pasture, there was a significant increase in macroporosity and decrease in soil bulk density from year one to year four following pasture establishment. Earthworm numbers increased from 120 m⁻² to between 440 and 620 m⁻², and water infiltration rates more than doubled after year two. However, the Peerlkamp method was not sensitive enough to detect visual changes in soil structure over the study period