Foliar application of nitrogen (N) may supplement soil-applied N in sweet cherry orchards. The proteinogenic amino acid L-proline is a potential source of organic N. However, little is understood about its uptake and effects on fruit quality. In this study, 15N-labelled L-proline was spray-applied to branches of the cultivar ‘Lapins’ either pre- or post-harvest. Leaves, fruit, and whole branches were sampled to investigate the uptake and allocation of foliar-applied N. Both treatments resulted in elevated 15N levels in leaves, with N derived from proline (%NDP) comprising 0.22% and 0.45% after pre- and post-harvest applications, respectively. The fruit was a sink for pre-harvest L-proline, with the highest %NDP in the pedicel (0.21%), followed by the skin (0.17%) and flesh (0.12%). Quality outcomes of smaller, darker fruit with lower stem retention indicate advanced maturity following L-proline application. Both pre- and post-harvest treatments resulted in the recovery of 15N in branches at late dormancy, with %NDP in bark (0.12%), buds (0.15%), and wood (0.02%) of the post-harvest treatment twice as high compared with those from the pre-harvest treatment. This study demonstrates proof of concept of the uptake of L-proline into the leaves of sweet cherry plants and translocation into the fruit and storage organs of the branch.

Optimizing the utilization of applied nitrogen (N) in fruit trees requires N supply that is temporally matched to tree demand. We investigated how the timing of N application affected uptake, allocation, and remobilization within 14-year-old “Gala”/M26 apple trees (Malus domestica Borkh) over two seasons. In the 2017–2018 season, 30 g N tree−1 of 5.5 atom% 15N–calcium nitrate was applied by weekly fertigation in four equal doses, commencing either 4 weeks after full bloom (WAFB) (pre-harvest) or 1-week post-harvest, or fortnightly, divided between pre- and post-harvest (50:50 split). Nitrogen uptake derived from fertilizer (NDF) was monitored by leaf sampling before whole trees were destructively harvested at dormancy of the first season to quantify N uptake and allocation and at fruit harvest of the second season to quantify the remobilization of NDF. The uptake efficiency of applied N fertilizer (NUpE) was significantly higher from pre-harvest (32.0%) than from the other treatments (~17%). The leaf NDF concentration, an indicator of N uptake, increased concomitantly only when pre-harvest N was applied. Pre-harvest treated trees allocated more than half of the NDF into fruit and leaves and stored the same amount of NDF into perennial organs as the post-harvest treatment. Subsequent spring remobilization of NDF was not affected by the timing of N fertigation from the previous season. A seasonal effect of remobilization was observed with a decrease in root N status and a reciprocal increase in branch N status at fruit harvest of season two. These findings represent a shift in the understanding of dynamics of N use in mature deciduous trees and indicate that current fertilizer strategies need to be adjusted from post-harvest to primarily pre-harvest N application to optimize N use efficiency. This approach can provide adequate storage N to support early spring growth the following season with no detriment to fruit quality.

Analyser-Based Phase-Contrast imaging (ABPCI) is a phase-contrast imaging method that produces high contrast images of weakly absorbing materials. However, it is only sensitive to phase variations lying in the diffraction plane of the analyser crystal (i.e in one dimension; 1-D), as it is highly sensitive to phase variations lying in the diffraction plane of the analyser crystal. In order to accurately account for and measure phase effects produced by the wavefield-sample interaction, ABPCI and other 1-D phase sensitive methods must achieve 2-D phase sensitivity. We applied an inclined geometry method to a Laue geometry setup for X-ray ABPCI through rotation of the detector and object about the optical axis. This allowed this traditionally 1-D phase sensitive phase contrast method to possess 2-D phase sensitivity. We acquired tomographic datasets over 360 degrees of a multi-material phantom with the detector and sample tilted by 8 degrees. The real and imaginary parts of the refractive index were reconstructed for the phantom.

The application of nitrate (NO3–) fertiliser is important worldwide in providing nitrogen (N) nutrition to perennial fruit trees. There is little information available on N losses to the environment from commercial cherry orchards, in relation to different timings of NO3– application. The emission of nitrous oxide (N2O) gas is an important greenhouse gas loss from NO3– application, being responsible for 6% of anthropogenic global warming and a catalyst for depletion of stratospheric ozone. In a commercial sweet-cherry orchard in southern Tasmania, we applied 373 g NO3–-N m–2 (equivalent to 90 kg NO3–-N ha–1) either pre- or post-harvest, or equally split between the two, to study the resultant N2O emissions. Emissions averaged 8.37 mg N2O-N m–2 day–1 during the pre-harvest period, primarily driven by a heavy rainfall event, and were significantly greater (P < 0.05) than the average 4.88 × 10–1 mg N2O-N m–2 day–1 from post-harvest NO3– application. Discounting the emissions related to the rainfall event, the resultant average 1.88 mg N2O-N m–2 day–1 for the rest of the pre-harvest emissions remained significantly greater (P < 0.05) than those post-harvest. Ongoing studies will help to build on these results and efforts to minimise N2O emissions in perennial tree cropping systems.

It doesn’t take a scientist to tell you that red cherries are a tangy, delicious treat. It does, however, take a scientist, or an inquisitive child, to ask what makes them red. Tasmanian Institute of Agriculture researcher Nadine Macha is hoping to find out more about a special kind of antioxidants called anthocyanins that do just that.

Enhanced efficiency nitrogen (N) fertilisers (EENFs) contain chemical urease or nitrification inhibitors, or physical barriers (e.g. polymer coating) to minimise the rapid build-up of nitrate (NO3-) in soils. They have the potential to improve N use efficiency and lower N2O emissions from soils. However, evidence of the efficacy of EENFs in warm, wet subtropical conditions is lacking. We therefore developed N response curves (0, 30, 60, 90, 120 and 150 kg N ha(-1)) for urea, polymer coated urea (PCU), 3,4-dimethylpyrazole phosphate (DMPP)-urea (Entec (R)), N-(n-butyl) thiophosphoric triamide (NBPT)-urea (Green urea (R)) and a carbon-coated urea (Black urea (R)) in subtropical, aerobic rice (Oryza sativa L) crops in two fields with contrasting soils (Gleysol and Histosol), and quantified N2O emissions from nil-N and 90 kg N ha(-1) treatments for all EENFs and urea. In the Gleysol, cumulative in-crop N2O emissions were relatively high (approximately 2 kg N2O-N ha(-1) season(-1) with 90 kg N ha(-1) applied) with no significant mitigation from any EENFs compared to urea. Grain yield data fitted with an exponential model indicated that 95% of the estimated maximum grain yield (6.8 t ha(-1) at 14% moisture) was achieved with 81 kg N ha(-1) for the urea treatment. The yield response curves for all tested EENF products did not differ significantly from the urea-N yield response curve. In the Histosol, cumulative in-crop N2O emissions were negligible (around 0.05 kg N2O center dot N ha(-1) season(-1)), with no significant difference (p < 0.05) between N fertiliser or nil-N treatments, and 95% of the estimated maximum grain yield (5.63 t ha(-1) at 14% moisture) was achieved with only 11 kg N ha(-1) for urea. There was no evidence that EENFs could achieve the maximum yield at a lower applied N rate. We hypothesised that the low soil pH of 4.9 (1:5 CaCl2 extract) may have inhibited nitrification in the Histosol, leading to low N2O emissions and a limited response to N fertiliser. Ultimately, the results of this study found no evidence that EENF products could improve agronomic N use efficiency or lower N2O emissions in the two aerobic rice crops studied.

Although there is growing evidence that the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) can lower soil nitrous oxide (N2O) emissions in temperate environments, there is little evidence of its efficacy in subtropical or tropical environments where temperatures and rainfall intensities are typically higher. We investigated N2O emissions in field-grown aerobic rice in adjacent fields in the 2013–14 and 2014–15 seasons in a subtropical environment. Crops were topdressed with 80 kg nitrogen (N) ha–1 before rainfall, as either urea, urea + DMPP (at 1.6 kg DMPP t–1 urea: ‘urea-DMPP’) or a blend of 50% urea and 50% urea-DMPP in the 2013–14 season, and urea, urea-DMPP or polymer (3 month)-coated urea (PCU) in the 2014–15 season. DMPP-urea significantly (P < 0.05) lowered soil N2O emissions in the 2013–14 season during the peak flux period after N fertiliser application, but had no effect in 2014–15. The mean cumulative N2O emissions over the entire growing period were 190 g N2O-N ha–1 in 2013–14 and 413 g N2O-N ha–1 in 2014–15, with no significant effect of DMPP or PCU. Our results demonstrate that DMPP can lower N2O emissions in subtropical, aerobic rice during peak flux events following N fertiliser application in some seasons, but inherent variability in climate and soil N2O emissions limited the ability to detect significant differences in cumulative N2O flux over the seasonal assessment. A greater understanding of how environmental and soil factors impact the efficacy of DMPP in the subtropics is needed to formulate appropriate guidelines for its use commercially.

While there is a growing body of literature suggesting that the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) can reduce N2O emissions from soils in temperate environments, there is little evidence of its efficacy in subtropical and tropical environments where temperatures and rainfall intensities are typically higher. We investigated N2O emissions in aerobic rice crops in a subtropical environment in late summer/autumn in 2014 and in an adjacent field in late summer/autumn in 2015. Crops received 80 kg/ha N as either urea, DMPP-urea, or a blend of 50 % urea and 50 % urea-DMPP in 2014, and urea, urea-DMPP or polymer-coated urea (PCU) in 2015. DMPP-urea significantly (P < 0.05) lowered soil N2O emissions in the 2013-14 season during the peak flux period after N fertiliser was applied, but had no effect in the 2014-15 season. The mean cumulative N2O emissions over the entire growing period were 190 g N2O-N/ha in 201314 and 413 g N2O-N/ha in 2014-15, with no significant effect of DMPP or PCU. Our results demonstrate that DMPP can lower N2O emissions in subtropical, aerobic rice crops during peak flux events following N fertiliser application in some seasons, but inherent variability in soil N2O emissions limit the chances of detecting significant differences in cumulative N2O flux over longer time periods. A greater understanding of how seasonal and/or soil factors impact the efficacy of DMPP in lowering N2O emissions following N fertiliser application in the subtropics is needed to formulate appropriate guidelines for its use commercially.

Numerous controlled-environment studies have found significant reductions in soil nitrous oxide (N2O) emissions following amendment of soil with woody biochar, but there is limited evidence to support these findings under field conditions. We evaluated N2O emissions from soils amended with 1) 5 t ha(-1) surface applied poultry litter; 2) 5 t ha(-1) incorporated poultry litter; 3) 5 t ha(-1) poultry litter + 11 t ha(-1) woody biochar; 4) 5 t ha(-1) poultry litter + 10 t ha(-1) woody mulch; 5) 4 t ha(-1) poultry litter biochar + 11 t ha(-1) woody biochar, in a coppiced Melaleuca plantation over two years. Melaleuca biomass, total soil carbon (C) and nitrogen (N) and soil C fractions did not differ among treatments 12 months after amendment. Woody mulch applied with poultry litter resulted in significantly lower N2O emissions compared to the incorporated and surface-applied poultry litter in the second season, but the addition of woody biochar had no significant impact on cumulative N2O emissions. However, N2O emissions per unit of N applied were significantly (P < 0.05) lower in the woody mulch and woody biochar treatments compared to poultry litter alone in the second season. In both seasons, cumulative N2O emission and N2O emissions per unit of N applied were significantly lower in the poultry litter biochar + woody biochar treatment, supporting the notion that pyrolysis of poultry litter is a management practice that could substantially reduce N2O emissions from the agricultural sector. (C) 2016 Elsevier B.V. All rights reserved.

Agricultural soils are the primary anthropogenic source of atmospheric nitrous oxide (N2O), contributing to global warming and depletion of stratospheric ozone. Biochar addition has shown potential to lower soil N2O emission, with the mechanisms remaining unclear. We incubated eucalypt biochar (550 °C) – 0, 1 and 5% (w/w) in Ferralsol at 3 water regimes (12, 39 and 54% WFPS) – in a soil column, following gamma irradiation. After N2O was injected at the base of the soil column, in the 0% biochar control 100% of expected injected N2O was released into headspace, declining to 67% in the 5% amendment. In a 100% biochar column at 6% WFPS, only 16% of the expected N2O was observed. X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces. We have shown increases in -O-C = N /pyridine pyrrole/NH3, suggesting reactions between N2O and the carbon (C) matrix upon exposure to N2O. With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents. Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O.

Employing x-ray computed tomography (mu-CT), we examined the impact of an oil mallee (OM) biochar, at concentrations of 0%, 1% and 5% (w/w), on soil structural traits in three soil types (Vertisol, Ferralsol and Arenosol). The biochar was pyrolysed at a maximum temperature of 550 degrees C, sieved to between 250 mu m and 2 mm prior to amending the soils, had an internal porosity of 75% (v/v) and an organic carbon (Corg) content of 60%. Soil structure was quantified, at a resolution of 70 pm, by measuring p,-CI' porosity, mean pore radius, fractal dimension and connectivity of the pore space. Addition of 5% OM biochar resulted in higher mu,-CT porosity (i.e. >70 pm) in the Vertisol (p <0.001), averaging 7.5, 9.1 and 13.4%, respectively, for 0, 1 and 5% biochar, with the Ferralsol having corresponding mu,-CT porosities of 6.2, 6.5 and 10.9%, the difference also being significant (p = 0.03) for 5% OM biochar amendment. Significant increases (p <0.05) in connectivity of the largest pore and mean pore radius were observed in all three soils containing 5% OM biochar and also in the Arenosol with 1% OM biochar. Over a 15-month incubation the Ferralsol containing 5% OM biochar showed increased p,-CT porosity (p <0.05) and fractal dimension (p <0.05), the latter indicating greater homogeneity of pore space distribution. Addition of OM biochar significantly decreased the rate of water loss through evaporation and drainage of all incubated soils (p <0.05) and reduced volumetric water content at field capacity in the two clay-rich soils. Soil with 1% OM biochar showed an increase in the rate of drainage in the Vertisol (p <0.05 at 0.02 MPa) and a 20% increase in the available water content of the Arenosol (p <0.05). It is hypothesised that the highly porous structure of biochar may have contributed to the changed water retention characteristics of the soils. This study highlights the potential for OM biochar to modify the structural characteristics of contrasting soils. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.