Adrian Bass | University of Glasgow (original) (raw)

Papers by Adrian Bass

Agriculture, Ecosystems & Environment, 2015

The addition of organic amendments to agricultural soils has the potential to increase crop yield... more The addition of organic amendments to agricultural soils has the potential to increase crop yields, reduce dependence
on inorganic fertilizers and improve soil condition and resilience. We evaluated the effect of biochar (B), compost (C) and co-composted biochar (COMBI) on the soil properties, crop yield and greenhouse gas emissions froma banana and a papaya plantation in tropical Australia in the first harvest cycle. Biochar, compost and COMBI organic amendments improved soil properties, including significant increases in soil water content, CEC, K, Ca, NO3, NH4 and soil carbon content. However, increases in soil nutrient content and improvements in physical properties did not translate to improved fruit yield. Counter to our expectations, banana crop yield (weight per
bunch) was reduced by 18%, 12% and 24% by B, C and COMBI additions respectively, and no significant effect was observed on the papaya crop yield. Soil efflux of CO2was elevated by addition of C and COMBI amendments, likely due to an increase in labile carbon for microbial processing. Our data indicate a reduction in N2O flux in treatments containing biochar. The application of B, C and COMBI amendments had a generally positive effect on soil properties, but this did not translate into a crop productivity increase in this study. The benefits to soil nutrient content, soil carbon storage and N2O emission reduction need to be carefully weighed against potentially deleterious effects on crop yield, at least in the short-term.

A portable Wavelength Scanned-Cavity Ring-Down Spectrometer (Picarro L2120) fitted with a diffusi... more A portable Wavelength Scanned-Cavity Ring-Down Spectrometer (Picarro L2120) fitted with a diffusion sampler (DS-CRDS) was used for the first time to continuously measure δ 18 O and δ 2 H of stream water. The experiment took place during a storm event in a wet tropical agricultural catchment in northeastern Australia. At a temporal resolution of one minute, the DS-CRDS measured 2160 δ 18 O and δ 2 H values continuously over a period of 36 h with a precision of ±0.08 and 0.5‰ for δ 18 O and δ 2 H, respectively. Four main advantages in using high temporal resolution stream δ 18 O and δ 2 H data during a storm event are highlighted from this study. First, they enabled us to separate components of the hydrograph, which was not possible using high temporal resolution electrical conductivity data that represented changes in solute transfers during the storm event rather than physical hydrological processes. The results from the hydrograph separation confirm fast groundwater contribution to the stream, with the first 5 h of increases in stream discharge comprising over 70% pre-event water. Second, the high temporal resolution stream δ 18 O and δ 2 H data allowed us to detect a short-lived reversal in stream isotopic values (δ 18 O increase by 0.4‰ over 9 min), which was observed immediately after the heavy rainfall period. Third, δ 18 O values were used to calculate a time lag of 20 min between the physical and chemical stream responses during the storm event. Finally, the hydrograph separation highlights the role of event waters in the runoff transfers of herbicides and nutrients from this heavily cultivated catchment to the Great Barrier Reef.

The isotope signatures registered in speleothems during tropical cyclones (TC) provides informati... more The isotope signatures registered in speleothems during tropical cyclones (TC) provides information
about the frequency and intensity of past TCs but the precise relationship between
isotopic composition and the meteorology of TCs remain uncertain. Here we present
continuous δ18O and δ2H data in rainfall and water vapour, as well as in discrete rainfall
samples, during the passage of TC Ita and relate the evolution in isotopic compositions to
local and synoptic scale meteorological observations. High-resolution data revealed a close
relationship between isotopic compositions and cyclonic features such as spiral rainbands,
periods of stratiform rainfall and the arrival of subtropical and tropical air masses with changing
oceanic and continental moisture sources. The isotopic compositions in discrete rainfall
samples were remarkably constant along the ~450 km overland path of the cyclone when
taking into account the direction and distance to the eye of the cyclone at each sampling
time. Near simultaneous variations in δ18O and δ2H values in rainfall and vapour and a
near-equilibrium rainfall-vapour isotope fractionation indicates strong isotopic exchange between
rainfall and surface inflow of vapour during the approach of the cyclone. In contrast,
after the passage of spiral rainbands close to the eye of the cyclone, different moisture
sources for rainfall and vapour are reflected in diverging d-excess values. High-resolution
isotope studies of modern TCs refine the interpretation of stable isotope signatures found in
speleothems and other paleo archives and should aim to further investigate the influence of
cyclone intensity and longevity on the isotopic composition of associated rainfall.

The continuous real-time analysis, at 30-s intervals, of precipitation at an Australian tropical ... more The continuous real-time analysis, at 30-s intervals, of precipitation at an Australian
tropical location revealed extreme and rapidly changing d18O and dD values related
to variations in moisture source areas, transport paths and precipitation histories.
The range of d18O (19.6% to +2.6%) and dD (140% to +13%) values from
5948 measurements of nine rain events over 15 days during an 8-month period at
a single location was comparable with the range measured in 1532 monthly
samples from all seven Australian Global Network of Isotopes in Precipitation
stations from 1962 to 2002. Extreme variations in d18O (8.7%to 19.6%) and dD
(54% to 140%) were recorded within a single 4-h period.
Real-time stable isotope monitoring of precipitation at a high temporal resolution
enables newand powerful tracer applications in climatology, hydrology, ecophysiology
and palaeoclimatology.

Combined measurements of salinity and the oxygen/hydrogen stable isotope composition of marine wa... more Combined measurements of salinity and the
oxygen/hydrogen stable isotope composition of marine
waters can characterise processes such as freshwater mixing,
evaporation, precipitation and sea-ice formation.
However, stable isotope data with high spatial and temporal
resolution are necessary for a detailed understanding
of mixed water bodies with multiple inputs. So far analysis
of d18O and dD values in water has been a relatively
expensive, laboratory-based technique requiring collection
of discrete samples. This has greatly limited the scope and
scale of field research that can be undertaken using stable
isotope analysis. Here, we report the first continuous
shipboard measurements of d18O and dD values in water by
diffusion sampling-cavity ring-down spectrometry. Combined
with continuous salinity recordings, a data set of
nearly 6,000 measurements was made at 30-s intervals
during a 3-day voyage through the Great Barrier Reef
Lagoon. Our results show that continuous shipboard measurement of d18O/dD values provides additional discriminatory power for assessing water mass formation processes and histories. Precise identification of river plumes within the Great Barrier Reef Lagoon was only possible because
unique d18O/dD–salinity relationships of individual plumes
were measured at high spatial and temporal resolution. The
main advantage of this new technique is the ability to
collect continuous, real-time isotope data at a small fraction
of the cost of traditional isotope analysi s of discrete
samples. Water d18O and dD values measured by diffusion
sampling-cavity ring-down spectrometry and laboratorybased
isotope ratio mass spectrometry have similar accuracy
and precision.

Measurement of soil-respiredCO2 at high temporal resolution and sample density is necessary to ac... more Measurement of soil-respiredCO2 at high temporal resolution and sample density is necessary to accurately identify sources and quantify effluxes of soil-respired CO2.A portable sampling device for the analysis of δ13C values in the field is described herein. CO2 accumulated in a soil chamber was batch sampled sequentially in four gas bags and analysed by Wavelength-Scanned Cavity Ring-down Spectrometry (WS-CRDS).A Keeling plot (1/[CO2] versus δ13C) was used to derive δ13C values of soil-respired CO2. Calibration to the δ13CVienna Peedee Belemnite scale was by analysis of cylinder CO2 and CO2 derived from dissolved carbonate standards. The performance
of gas-bag analysis was compared to continuous analysis where the WS-CRDS analyser was connected
directly to the soil chamber. Although there are inherent difficulties in obtaining absolute accuracy data for δ13C values in soilrespired CO2, the similarity of δ13C values obtained for the same test soil with different analytical configurations indicated that an acceptable accuracy of the δ13C data were obtained by the WS-CRDS techniques presented here. Field testing of a variety of tropical soil/vegetation types, using the batch sampling technique yielded δ13C values for soil-respired CO2 related to the dominance of either C3 (tree, δ13C = −27.8 to −31.9 ‰) or C4 (tropical grass, δ13C = −9.8 to −13.6 ‰) hotosynthetic pathways in vegetation at the sampling sites. Standard errors of the Keeling plot intercept δ13C values of soil-respired CO2 were typically <0.4 ‰ for analysis of soils with high CO2 efflux (>7–9μmolm−2 s−1).

Dissolved inorganic carbon (DIC) represents a significant component of both the terrestrial and o... more Dissolved inorganic carbon (DIC) represents a significant component of both the terrestrial and oceanic carbon
cycles. An instrument for the continuous and automated analysis of dissolved inorganic carbon in the field
is described. The analyzer is designed to allow collection of high-resolution (sub hourly) DIC data over prolonged
field deployments without the need for labor-intensive maintenance and monitoring. The instrument
sequentially acidifies an aliquot of water in gas permeable tubing through which CO2 diffuses into a gas tight
chamber and is quantified by an infrared gas analyzer. The instrument is accurate to ± 0.04 mM with a detection
limit of 0.01 mM. Comparisons with conventional head space equilibration techniques using mass spectrometry
yielded a good correlation differing by 0.016 ± 0.014 mM. Deployment in a tropical estuary and freshwater
rainforest catchment revealed the dynamic nature of inorganic carbon cycling in these aquatic systems.
DIC concentration was found to track the mixing of fresh and salt water well in the tropical estuary (as indicated
by conductivity measurements), and comprised a significant component of dissolved carbon export from
the estuary catchment. DIC totalled 24 ± 6% of the total carbon export from the rainforest catchment and varied
between 0.04 and 0.13 mM over a 4-d period. The dynamic nature of DIC in the two environments illustrates
the pressing need for the continuous and high-resolution data our instrument provides.

RATIONALE: Quantifying the processes that control dissolved inorganic carbon (DIC) dynamics in aq... more RATIONALE: Quantifying the processes that control dissolved inorganic carbon (DIC) dynamics in aquatic systems is
essential for progress in ecosystem carbon budgeting. The development of a methodology that allows high-resolution
temporal data collection over prolonged periods is essential and is described in this study.
METHODS: A novel sampling instrument that sequentially acidifies aliquots of water and utilises gas-permeable ePTFE tubing to measure the dissolved inorganic carbon (DIC) concentration and d13CDIC values at sub-hourly intervals by Cavity Ring-down spectrometry (CRDS) is described.
RESULTS: The minimum sensitivity of the isotopic, continuous, automated dissolved inorganic carbon analyser (ISOCADICA) system is 0.01 mM with an accuracy of 0.008 mM. The analytical uncertainty in d13CDIC values is proportional to the concentration of DIC in the sample. Where the DIC concentration is greater than 0.3 mM the analytical uncertainty is 0.1 % and below 0.2 mM stability is < _ 0.3 %. The isotopic effects of air temperature, water temperature and CO2 concentrations were found to either be negligible or correctable. Field trials measuring diel variation in d13CDIC values of coral reef associated sea water revealed significant, short-term temporal changes and illustrated the necessity of this technique.
CONCLUSIONS: Currently, collecting and analysing large numbers of samples for d13CDIC measurements is not trivial, but essential for accurate carbon models, particularly on small scales. The ISO-CADICA enables on-site, high-resolution determination of DIC concentration and d13CDIC values with no need for sample storage and laboratory analysis. The initial tests indicate that this system can offer accuracy approaching that of traditional IRMS analysis.

Modelling limnetic carbon processes is necessary for accurate global carbon models and stable iso... more Modelling limnetic carbon processes is necessary for accurate global carbon models and stable isotope analysis can provide
additional insight of carbon flow pathways. This research examined the spatial and temporal complexity of carbon cycling in a large temperate lake. Dissolved inorganic carbon (DIC) is utilised by photosynthetic organisms and dissolved oxygen (DO) is used by heterotrophic organisms during respiration. Thus the spatial heterogeneity in the pelagic metabolic balance in Loch Lomond, Scotland was investigated using a combined natural abundance isotope technique. The isotopic signatures of dissolved inorganic carbon (δ13CDIC) and dissolved oxygen (δ18ODO) were measured concurrently on four different dates between November 2004 and September 2005. We measured isotopic variation over small and large spatial scales, both horizontal distance and depth. δ13CDIC and δ18ODO changed over a seasonal cycle, becoming concurrently more positive (negative) in the summer (winter) months, responding to increased photosynthetic and respiratory rates, respectively. With increasing depth, δ13CDIC became more negative and δ18ODO more positive, reflecting the shift to a respiration-dominated system. The horizontal distribution of δ13CDIC and δ18ODO in the epilimnion was heterogeneous. In general, the south basin had the most positive δ13CDIC, becoming more negative with increasing latitude, except in winter when the opposite pattern was observed. Areas of local variation were often observed near inflows. Clearly δ13CDIC and δ18ODO can show large spatial heterogeneity, as a result of varying metabolic balance coupled with inflow proximity and thus single point sampling to extrapolate whole lake metabolic patterns can result in error when modelling large lake systems Whilst we advise caution when using single point representation, we also show that this combined isotopic approach has potential to assist in constructing detailed lake carbon models.

Understanding the effects of trophic status and dissolved organic carbon concentration (DOC) on l... more Understanding the effects of trophic status
and dissolved organic carbon concentration (DOC) on
lake carbon cycling is essential for accurate ecosystem
carbon models. Using isotopically labelled substrates
we assessed spatial and temporal variability in bacterial
respiration (BR) and algal primary production (PP) in
two trophically, morphometrically and hydrologically
different basins in LochLomond, a large temperate lake
in Scotland. GIS modelling was used to construct a
whole lake balance for bacterial production/respiration
and PP, and from this the proportion of heterotrophy
fuelled by allochthonous carbon was estimated. We
tested the hypotheses that trophic status and DOC
concentration affect the balance between PP and BR
and examined which is the more significant driving
factor. Additionally we estimated the percentage of BR
that is fuelled by terrestrial carbon. PP varied seasonally
and showed inter-basin homogeneity. BR was greatest
in the mesotrophic south basin in autumn, which
corresponded to measured peak DOC input, though
over an annual cycle no relationship was observed
between BR and DOC concentration. The PP:BR ratio
was 0.37 ± 0.30 and 0.3 ± 0.45 in the north and south
basins, respectively, assuming a bacterial growth
efficiency of 0.1. We have found that allochthonous
carbon potentially supports a substantial quantity of
pelagic production, even during periods of high photosynthesis.
Less productive systems are thought to be
dominated by heterotrophic processes. However, we
have found that the mesotrophic basin of a large lake to
be as heterotrophic as its neighbouring oligotrophic
basin, an observation that has implications for our
understanding of modelling of the role of lakes in
linking the terrestrial-atmospheric carbon cycle.

This study presents baseline data on the physiochemical properties and potential uses of macroalg... more This study presents baseline data on the physiochemical properties and potential uses of macroalgal (seaweed) biochar produced by pyrolysis of eight species of green tide algae sourced from fresh, brackish and marine environments. All of the biochars produced are comparatively low in carbon content, surface area and cation exchange capacity, but high in pH, ash, nitrogen and extractable inorganic nutrients including P, K, Ca and Mg. The biochars are more similar in characteristics to those produced from poultry litter relative to those derived from ligno-cellulosic feedstocks. This means that, like poultry litter biochar, macroalgal biochar has properties that provide direct nutrient benefits to soils and thereby to crop productivity, and will be particularly useful for application on acidic soils. However, macroalgal biochars are volumetrically less able to provide the carbon sequestration benefits of the high carbon ligno-cellulosic biochars.

In small catchments with rapid flood pulses, detailed temporal data are essential because high-di... more In small catchments with rapid flood pulses, detailed temporal data are essential because high-discharge events can be measured in hours and days, rather than weeks and months. Using high-resolution (15 min) sampling, we studied the dynamics of aquatic dissolved and particulate organic carbon (DOC and POC) export through episodic discharge events in a small pristine rainforest catchment in northeast Australia between November 2009 and March 2010. High temporal resolution using this instrumentation requires extensive calibration with
concurrent field sampling. The concentration of DOC and POC peaked during times of high stream discharge, reflecting an increased mobilization of soil-water carbon stocks. DOC was the major form of organic carbon in the stream (, 70% of the total carbon export). The majority of total organic carbon exported from the catchment
(84%) occurred during significant discharge events (discharge . 50 L s21), which occurred only 9% of the time. Export of DOC and POC totaled 195 and 68 kg km22 month21, respectively, with a DOC:POC ratio of 2.9 6 0.9. If this subcatchment was sampled at weekly intervals the lateral export of carbon would have been
underestimated by between 49% and 78% for DOC and POC, respectively. Preliminary d13C and molar C:N values of the dissolved and particulate matter suggest that during discharge events, less microbially processed material from the upper soil layers dominated organic matter export, with the opposite being true in nonflood conditions. Not only will the quantities of organic matter exported change in different discharge conditions, but the source and quality may also shift. This study reveals that a field-portable instrument for DOC and POC quantification can yield robust, high-temporal-resolution carbon budget estimates, though detailed, site-specific calibration is essential.

Cavity ring-down spectrometers,with automated sampling interfaces, were deployed to allowmeasurem... more Cavity ring-down spectrometers,with automated sampling interfaces, were deployed to allowmeasurements of water isotopes (δ18O, δD) and dissolved inorganic carbon (δ13CDIC) stable isotope ratios at high temporal resolution along a transect from New Zealand to the Antarctic continental shelf. Measurements every 10 min for δ18O and δD, 15 min for DIC yielded 2499 and 2289 discrete measurements respectively. High resolution data enabled the delineation of water mass boundaries as well as revealing insights into surface hydrological and biological processes. δ18O, δD, and δ13CDIC decreased southwards, dropping by approximately 1.0‰, 7.0‰, and 0.5‰, respectively. Though the decline in δ13CDIC with latitude was generally linear, the drop in δ18O and δD was punctuated by areas of rapid, significant change corresponding to the Sub-Tropical, Sub-Antarctic and Polar Fronts. North of the Sub-Antarctic Front (approx. 54.5°S) the dominant control on water and DIC isotopes was the precipitation–evaporation balance and the contribution of upwelling waters, respectively. Further south, in close proximity to the sea ice and on the Antarctic shelf, water isotope values were more variable and predominantly influenced by the melting/freezing of sea-ice coupled to inputs from glacial/snow melt water. Local increases in δ13CDICwere likely due to photosynthetic enrichment of the DIC pool. Using this newinstrumentation has provided one of the most comprehensive oceanic transect data sets yet achieved and illustrates the potential of these methods to delineate discrete water masses and advance our knowledge of both water and inorganic carbon cycling processes in the ocean. This methodology, combining high-resolution isotopic measurements with hydrographic data, has significant benefits in modelling water mixing in locations with multiple sources and controlling processes.

Globally, Dissolved Inorganic Carbon (DIC) accounts for more than half the annual flux of carbon ... more Globally, Dissolved Inorganic Carbon (DIC) accounts for more than half the annual flux of carbon exported from terrestrial ecosystems via rivers. Here we assess the relative influences of biogeochemical and hydrological processes on DIC fluxes exported from a tropical river catchment characterized by distinct land cover, climate and geology transition from the wet tropical mountains to the low lying savanna plains. Processes controlling changes in river DIC were investigated using dissolved organic carbon (DOC), particulate organic carbon (POC) and DIC concentrations and stable isotope ratios of DIC (13CDIC) at two time scales;
seasonal and diel. The recently developed Isotopic Continuous Dissolved Inorganic Carbon Analyser (ISO-CADICA) was used to measure diel DIC concentration and 13CDIC changes at a 15 minute temporal resolution. Results highlight the predominance of biologically mediated processes (photosynthesis and respiration) controlling diel changes in DIC. These resulted in DIC concentrations varying between 3.55-3.82 mg/L, and 13CDIC values ranging from -19.7±0.31 to -17.1±0.08 ‰. In contrast, at the seasonal scale we observe wet season DIC
variations predominantly from mixing processes, and dry season DIC variations due to both mixing processes and biological processes. The observed wet season increases in DIC concentrations (by 6.81 mg/L) and 13CDIC values of river water (by 5.4 ‰) largely result from proportional increases in subsurface inflows from the savanna plains (C4 vegetation) region relative to inflows from the rainforest (C3 vegetation) highlands. The high DIC river load during the wet season results in the transfer of 97% of the annual river carbon load. Therefore, in this gaining river there are significant seasonal variations in both the hydrological and carbon cycles, and there is evidence of substantial coupling between the carbon cycles of the terrestrial and the fluvial environments. Recent identification of a substantial savanna carbon sink in wetter years in the recent past does not take into account the possibility of a substantial, rapid, lateral flux of carbon to rivers and back to the atmosphere.

This study investigated the effects of biochar and compost, applied individually or together, on ... more This study investigated the effects of biochar and compost, applied individually or together, on soil fertility, peanut yield and greenhouse gas (GHG) emissions on a Ferralsol in north Queensland, Australia. The treatments were (1) inorganic fertilizer only (F) as a control; (2) 10 t ha1 biochar + F (B + F); (3) 25 t compost + F (Com + F) ha1; (4) 2.5 t B ha1 + 25 t Com ha1 mixed on site + F; and (5) 25 t ha1 cocomposted biochar-compost + F (COMBI + F). Application of B and COMBI increased seed yield by 23% and 24%, respectively. Biochar, compost and their mixtures significantly improved plant nutrient availability and use, which appeared critical in improving peanut performance. Soil organic carbon (SOC) increased
from 0.93% (F only) to 1.25% (B amended), soil water content (SWC) from 18% (F only) to over 23% (B amended) and CEC from 8.9 cmol(+)/kg (F only) to over 10.3 cmol(+)/kg (organic amended). Peanut yield was significantly positively correlated with leaf chlorophyll content, nodulation number (NN), leaf nutrient concentration, SOC and SWC for the organic amendments. Fluxes of CO2 were highest for the F
treatment and lowest for the COMBI treatment, whereas N2O flux was highest for the F treatment and all organic amended plots reduced N2O flux relative to the control. Principal component analysis indicates that 24 out of 30 characters in the
first principal component (PRIN1) individually contributed substantial effects to the total variation between the treatments. Our study concludes that applications of B, Com, B + Com or COMBI have strong potential to, over time, improve SOC, SWC, soil nutrient status, peanut yield and abate GHG fluxes on tropical Ferralsols.

Diurnal variations in aquatic systems may be a major factor influencing carbon cycling. However, ... more Diurnal variations in aquatic systems may be a
major factor influencing carbon cycling. However, few
studies have examined diurnal variation on floodplains and
wetlands, especially in the tropics. Stable isotope analysis
of dissolved inorganic carbon (d13CDIC) provides insight
into the driving factors behind diurnal physio-chemical
variability, but to date, the manual collection of large
sample numbers at high temporal frequency has been
prohibitive. Here, we report one of the first, high-resolution
isotopic studies of d13CDIC on a tropical floodplain using
acidification-interface cavity ring-down spectrometry.
Water samples were analysed for d13CDIC and other water
quality parameters at 15-min intervals for 24 h. Our results
show significant diurnal variation in both DIC concentration
and d13CDIC. Maximum DIC concentration, recorded
overnight, was approximately 100 % greater than during
the day. Maximum DIC concentration coincided with
minimum d13CDIC as a result of shifting autotrophic/heterotrophic
balance. Changes were significant over small
time scales and showed CO2 gas evasion estimates could
vary by as much as 50 % based on measurements taken
less than 5 h apart. These data show that to accurately
evaluate the role of tropical floodplains in global carbon
dynamics, a comprehensive understanding of diurnal variation
will be essential.

Deteriorating soil fertility and the concomitant decline in agricultural productivity are major c... more Deteriorating soil fertility and the concomitant decline in agricultural productivity are major concerns in many parts of the world. A pot experiment was conducted with a Ferralsol to test the hypothesis that application of biochar improves soil fertility, fertiliser-use efficiency, plant growth and productivity, particularly when combined with compost. Treatments comprised: untreated control; mineral fertiliser at rates of 280 mg nitrogen, 70 mg phosphorus and 180 mg potassium pot–1 (F); 75% F + 40 g compost pot–1 (F + Com); 100% F + 20 g willow biochar pot–1 (F + WB); 75% F + 10 g willow biochar + 20 g compost pot–1 (F +WB+ Com); 100% F + 20 g acacia biochar pot–1 (F + AB); and 75% F + 10 g acacia biochar + 20 g compost pot–1 (F +AB + Com). Application of compost with fertiliser significantly increased plant
growth, soil nutrient status and plant nutrient content, with shoot biomass (as a ratio of control value) decreasing in the order F + Com (4.0) > F +WB+ Com (3.6) > F +WB (3.3) > F +AB+ Com (3.1) > F +AB (3.1) > F (2.9) > control (1.0). Maize shoot biomass was positively significantly correlated with chlorophyll content, root biomass, plant height, and specific leaf weight (r = 0.99, 0.98, 0.96 and 0.92, respectively). Shoot and root biomass had significant correlations with
soil water content, plant nutrient concentration, and soil nutrient content after harvesting. Principal component analysis (PCA) showed that the first component provided a reasonable summary of the data, accounting for ~84% of the total
variance. As the plants grew, compost and biochar additions significantly reduced leaching of nutrients. In summary, separate or combined application of compost and biochar together with fertiliser increased soil fertility and plant growth.
Application of compost and biochar improved the retention of water and nutrients by the soil and thereby uptake of water and nutrients by the plants; however, little or no synergistic effect was observed.

Agriculture, Ecosystems & Environment, 2015