Zealand Soils Research Articles

Fractionation of zinc in some New Zealand soils

The amounts and forms of zinc in twenty surface soils from Canterbury and Southland, New Zealand were determined using a sequential fractionation scheme. Total soil zinc concentrations ranged from 38.1 mg#lbkg‐1 to 113.8 mg#lbkg‐1. Although the proportions of zinc found in individual fractions varied between soils, on average approximately 3% occurred as exchangeable zinc, 5% as organic‐bound zinc, 9%, 18%, 24% was associated with manganese, amorphous iron and crystalline iron oxides, respectively, and 40% was in the residual fraction. In a group of soils formed in greywacke alluvium or loess, exchangeable zinc was inversely related to soil pH. Within the same group of soils, those of similar age with greater concentrations of total and organic‐bound zinc were present in imperfectly‐ and poorly‐drained soils compared with well‐drained soils. Zinc extracted from the soils with a range of reagents used to assess ‘plant available’ zinc was correlated strongly with the concentrations of zinc present in the exchangeable and organic‐bound zinc fractions.

Structural vulnerability of New Zealand soils

Some New Zealand soils withstand intensive cultivation and support continuing high production and yet maintain essential soil physical qualities of infiltration, aggregation, and aeration. In other soils, essential soil qualities deteriorate rapidly under the impact of even moderately intensive management practices. Our objective was to estimate the inherent susceptibility of New Zealand soils to physical degradation by focusing on structural vulnerability. We took a deductive approach by reviewing the available information on the structural stability and physical degradation of New Zealand soils. We identified 4 soil attributes that are well represented in the national soils database and are most likely to control structural vulnerability: (i) stabilising short-range-order oxy-hydroxides of aluminium and iron as estimated by phosphate retention, (ii) total organic carbon content, (iii) clay content, and (iv) wetness. The 4 attributes were standardised and transformed and a simple structural vulnerability index (SV) was devised. We determined SV for all mineral soils in the national soils database. The results provide a ranking of soil groups according to their structural vulnerability. We concluded that the index may be used as a first approximation rating of the structural vulnerability of New Zealand soils to aid resource management.

Desorption of native and added zinc from a range of New Zealand soils in relation to soil properties

Compared with zinc (Zn) sorption, there is very little information on the effect of soil properties on Zn desorption from soils. In this study, desorption of native and added Zn from 7 Canterbury (NZ) soils was determined using a technique involving repeated equilibration of soil in 0·01 M Ca(NO3)2. The concentrations and patterns of desorption of both native and added Zn varied between the different soils. Greater concentrations of native Zn were desorbed from surface soils than from subsoils, and greater concentrations of added Zn were desorbed from subsoils than from their corresponding surface horizons. Correlation analysis showed that cation exchange capacity (CEC) and organic carbon (C) were the dominant soil variables contributing towards sorption or desorption of Zn. However, simple linear regressions involving CEC or organic C explained only 48–62% of the total variation in Zn sorption or desorption from the different soils. Multiple regression analysis indicated that cumulative native Zn desorption (expressed as percentage of DTPA-extractable Zn) was strongly related to CEC and the content of Mn oxides, which in combination explained 80% of the variability between soils. Regression analysis also showed that CEC plus Mn oxides and pH explained 91% of the variability in Zn sorption between the soils; whereas for added Zn desorbed (%), CEC plus pH and crystalline Al oxides explained 93% of variability in added Zn desorption.

Chemical soil conditions in pristine Nothofagus forests of New Zealand as compared to German forests

In many German forest soils low base saturation of CEC in deeper soil layers was reported and acidic deposition is seen as the major cause of these findings. To test this hypothesis we sampled 5 New Zealand forest soils from pristine beech (Nothofagus fusca, N. menziesii, N. solandri) sites under climatic and geological conditions comparable to higher elevations in Germany. The soils developed from granite and greywacke. Soil samples were analyzed for pH and the exchangeable cations were extracted with 1M NH4Cl. The base saturation of all soil profiles was very low, even in deeper layers and was thus similar to the patterns found in many German forest soils. The pH was generally higher in the New Zealand soils as compared to Germany. The reason for the depletion of base cations in deeper soil layers of New Zealand forest soils is most likely the leaching of base cations with HCO3- resulting from the dissociation of carbonic acid in connection with high amounts of seepage. Thus, under high rainfall conditions, the low base saturation found in deeper layers of forest soils cannot exclusively be attributed to the effects of acidic depositions and land use. ei]Section editor: R F Huettl

Chemical soil conditions in pristineNothofagus forests of New Zealand as compared to German forests

In many German forest soils low base saturation of CEC in deeper soil layers was reported and acidic deposition is seen as the major cause of these findings. To test this hypothesis we sampled 5 New Zealand forest soils from pristine beech (Nothofagus fusca, N. menziesii, N. solandri) sites under climatic and geological conditions comparable to higher elevations in Germany. The soils developed from granite and greywacke. Soil samples were analyzed for pH and the exchangeable cations were extracted with 1M NH4Cl. The base saturation of all soil profiles was very low, even in deeper layers and was thus similar to the patterns found in many German forest soils. The pH was generally higher in the New Zealand soils as compared to Germany. The reason for the depletion of base cations in deeper soil layers of New Zealand forest soils is most likely the leaching of base cations with HCO3- resulting from the dissociation of carbonic acid in connection with high amounts of seepage. Thus, under high rainfall conditions, the low base saturation found in deeper layers of forest soils cannot exclusively be attributed to the effects of acidic depositions and land use. ei]Section editor: R F Huettl

Towards a National Landslide Information Base for New Zealand

ABSTRACTLandslides constitute a problem as a natural hazard, as a factor in land development decisions, and as a major process in the depletion of New Zealand's soil resource. There are compelling social, economic, and legislative reasons for obtaining and accessing information on landslide activity. As a way of improving a currently weak information base, recommendations are given for establishing an information system appropriate to specific management functions.

The effect of strong hydroxide solutions on the stability of aggregates and hydraulic conductivity of soil

SummaryThe effect of two hydroxides (NaOH and KOH) and two chlorides (NaCl and KCl) on aggregate stability and saturated hydraulic conductivity (Ks) was studied in three New Zealand soils using concentrations (0.003, 0.03, and 0.3 m) typical of the range of pH found in strongly alkaline industrial liquid wastes. The different solutions were used as pretreatments prior to aggregate stability measurements and as influent solutions for Ks measurements.The concentration of hydroxide appeared to be the most important factor affecting aggregate stability and KS in all soils. Aggregate stability and Ks decreased with increasing hydroxide concentration, but were generally unaffected by chloride solutions. Relative Ks decreased to <2.5% of initial kS with all hydroxide concentrations, but the time until a decrease ocurred depended on concentration. In contrast, relative kS remained > 100% with chloride solutions, but decreased substantially when distilled water replaced the chloride solutions. Differences in aggregate stability and Ks due to the cation present (either Na+ or K+) appeared to be very small. A surface crust formed in the upper 1 cm of the soils leached with hydroxide solutions. This surface crust had substantially less organic carbon than the upper 1 cm of soil from the cores leached with chloride.A two‐stage process explains the decrease in ks when strongly alkaline solutions are applied to soil. First, organic matter dissolution decreases aggregate stability, with the rate of organic matter dissolution depending on hydroxide concentration; and second, increased repulsion of soil particles (due to increased pH) causes movement of dislodged particles into pore spaces, resulting in decreased Ks.

Sorption of cupric, dichromate and arsenate ions in some New Zealand soilds

Concentrated solutions of copper (Cu2+), dichromate (Cr2O2−7) and aresenate (AsO43−) ions (CCA solutions) are used extensively in the New Zealand timber preservation industry. These ions are therefore, potential soil pollutants at timber treatment sites. Sorption of these three ions was examined by the surface and sub-surface horizons of two free-draining New Zealand soils over a range of soil solution pH values.

Weathering trends in terrace deposits up to 350,000 years old in northeast Southland, New Zealand

Gravelly floodplain deposits and six terrace treads in the Waimea Plains, northeast Southland, New Zealand, range in age from ca. 1000 years old to 350,000 yr old. Deposits are progressively more weathered with increasing parent material age. Soils developed in them are classified as Recent Soils, Brown Soils and Ultic Soils in the New Zealand Soil Classification and Udifluvents, Dystrochrepts, Haplohumults, Hapludults and Paleudults in the USDA Soil Classification (Soil Taxonomy). The youngest soils are slightly acid. Those developed in deposits 35,000–70,000 yr old are strongly acid. In soils in deposits 160,000 yr old and older, that have weathered in two or three interglacial periods, including the present one, pH and total exchangeable bases values are higher than in soils in younger deposits. The higher pH of the soils in older deposits is attributed to release of cations by stone weathering. Soils developed in deposits up to 70,000 yr old have clays dominated by mica and chlorite. Stones in these soils are at most weakly weathered, and the < 2 mm fraction contains 2–13% clay and 63–95% sand. Weathering of older deposits has destroyed the fabric of most stones. The < 2 mm fraction of soils developed in deposits 250,000–350,000 yr old contains 34–38% clay and 20–24% sand; clays are dominated by kaolin-group and mica-smectite minerals and 60% of the total Fe in the < 2 mm fraction is in secondary forms. Two phases of weathering are distinguished: a phase of approximate duration 100,000 yr in which most weathering and leaching occurs in the matrix, which becomes increasingly acidified; and a phase from 100,000 to 350,000 yr which is dominated by cation release from stones, reversal of the acidification trend, and breakdown of stone fabric.

Measurement of plant-available cadmium in New Zealand soils

Several methods of measuring plant-available cadmium (Cd) were compared using soils that had accumulated Cd under normal New Zealand agricultural practices (low total Cd concentrations, and phosphatic fertiliser as the dominant Cd source). The study encompassed 9 New Zealand soils with different Cd input histories. Cadmium was extracted from these soils by demineralised water, 0.05 M Na2EDTA, 1 M NH4OAC (pH 7), 0.01 M CaCl2, and 0.05 M CaCl2 and quantified by differential pulse anodic stripping voltammetry (DP-ASV) and graphite furnace atomic absorption spectrophotometry (AAS). The DP-ASV measures the free Cd ion and that associated with labile complexes, but not large organic Cd complexes. Extractable Cd levels were compared with those which are plant-available, as determined by pot studies (lettuce). The 0.01 M CaCl2-extractable Cd measured by AAS and 0.05 M CaCl2-extractable Cd measured by DP-ASV gave the best estimate of plant availability of Cd.

Leaching of copper, chromium, and arsenic through some free-draining New Zealand soils

Concentrated toxic solutions of copper, chromium, and arsenic (CCA) are used extensively in the New Zealand timber preservation industry. A 2% w/v solution containing cupric, dichromate, and arsenate ions was leached through undisturbed soil monolith lysimeters containing the surface and subsurface horizons of 2 free-draining New Zealand soils. The resulting breakthrough curves were successfully modelled using the Gompertz equation for biomass growth. Differences between soil horizons in the fitted Gompertz parameter values were related to differences in soil physical and chemical properties affecting leaching. Results were compared to those from a previous study investigating pulse leaching of a concentrated CCA solution of similar ion ratio using the same soils. Generally, solution leaching produced breakthrough curves influenced more by the soil's physical structure and less by kinetic processes (i.e. sorption and diffusion). This was in part due to the high metal concentrations of the CCA solution and the decreased contact time between soil and solute in the solution leaching experiment. The relative ease of solute ion breakthrough increased in the order copper &lt; arsenate &lt; dichromate. The study suggests that further research is required to assess management implications for spills of these heavy metal ions to soils to prevent leaching or runoff to ground and surface water.

Historic Measurements of Radiocarbon in New Zealand Soils

Extensive measurements of radiocarbon have been used in New Zealand since the mid-1960s to follow carbon (C) movement and turnover in soils. We present here unpublished radiocarbon (14C) measurements on a range of eight New Zealand soils with details of the sites, ecosystems, climates, soil descriptions and associated analytical data. An overview is also given of published 14C measurements on soils, and the use of these measurements to model soil C turnover.

Natural reseeding of caucasian clover (Trifolium ambiguum) in tussock grasslands

The potential of natural reseeding to increase the density of caucasian clover (Trifolium ambiguum M.Bieb.) swards in tussock grassland environments was investigated. Rates of pollination were high on all sites and viable seed was produced by mid March on sites ranging in altitude from 600 to 1100 m a.s.l. Hard seed, expected to survive passage through the grazing animal and germinate in the dung, was present. Rhizobia that effectively nodulate caucasian clover are absent from New Zealand soils and nodulation of seedlings and rhizome roots is dependent on spread of inoculant rhizobia in the soil. Lateral movement of rhizobia in soil did not exceed 6 cm per year, only slightly less than recorded rates of rhizome expansion. There was no evidence of movement of rhizobia in wind-blown dust or on sheep's hooves. Natural reseeding has the potential to 'thicken-up' swards of caucasian clover, but the slow spread of rhizobia indicates that nodulation failures will limit the extent of spread into unsown areas. Keywords: caucasian clover, reseeding, rhizobia, rhizomes, Trifolium ambiguum

Effects of high pH solutions with large monovalent cation concentrations on cation exchange properties

Disposal of strongly alkaline industrial liquid wastes, which contain large monovalent cation concentrations, by means of land treatment systems is becoming increasingly common. This study investigated the effects of solutions with large monovalent cation concentrations and high pH on cation exchange properties in four New Zealand soils with different clay mineralogies. The soils were shaken with a range of concentrations (0–0.3 M) of NaOH, KOH, NaCl, and KCl. Cation exchange capacity (CEC) and exchangeable cations (Ca2+, Mg2+, K+, and Na+) were measured following shaking and washing procedures. Although the hydroxide solutions dissolved significant amounts of organic matter from all soils, there was still a net increase in CEC measured at all hydroxide concentrations. The magnitude of the CEC increase was dependent on hydroxide concentration. The increase in CEC is attributed to newly generated negative charge on surfaces which possess variable charge (i.e. pH dependent) characteristics such as edge sites of clay minerals, sesquioxides, and the undissolved organic matter remaining in the soil. In contrast to hydroxide solutions, no increase in CEC was measured in chloride-treated samples. Increases in the concentration of all treatment solutions resulted in increases in the exchangeable ion concentration of the index cation used in the treatment solution (either Na+ or K+) and decreases in concentration of the other three exchangeable cations. In general, higher exchangeable sodium percentage (ESP) values were measured in samples treated with NaOH than samples treated with NaCl at all concentrations. Similarly, higher exchangeable potassium percentage (EPP) was measured in samples treated with KOH than samples treated with KCl at all concentrations. The higher ESP and EPP values recorded when hydroxide solutions were used as treatments are attributed to the newly generated negative charges being counter-balanced by the monovalent index cation present in the treatment solution. It is suggested that existing equations commonly used to predict ESP and EPP values are unsuccessful for accurately predicting changes when soils are treated with hydroxide solutions, due to their inability to account for the newly generated exchange sites. The equations did, however, adequately predict the effects of both chloride solutions on ESP and EPP.

Relationships between soil solution aluminium and extractable aluminium in some moderately acid New Zealand soils

This work investigates the relationship between soil solution aluminium (Al) and extractable Al in some New Zealand soils giving high extractable Al levels, yet with pH(H2O) values ≥ 5.2. Total Al in 1 M KCl extracts ranged from 0.8 to 11.6 cmol(+)/kg, and in corresponding 0.02 M CaCl2 extracts from 0.002 to 0.39 cmol(+)/kg. Soil solutions had low total Al concentrations, ranging from &lt; 0.5 to 12.5 µM, with &lt; 10% of the Al in the monomeric Al form as determined by the chromeazurol S colorimetric method. There was a poor correlation between Al in soil solution and that extracted by either 1 M KCl or 0.02 M CaCl2. The measured monomeric Al concentrations in the soil solutions did not exceed levels corresponding to Al toxicity threshold activities set at 10 or 2 µM, related to a range of pasture plant tolerances, whether based on the activity of Al3+ species alone, or on the sum of the individual activities of Al3+, Al(OH)2+ and Al(OH)2+ species. The high 1 M KCl-extractable and 0.02 M CaCl2-extractable Al values provided a misleading indication of potential Al toxicity status, probably due to the generation of artificially high extracted Al concentrations from these particular types of soils.

Selenium status of New Zealand infants fed either a selenium supplemented or a standard formula

New Zealand soils are deficient in the essential micronutrient, selenium. New Zealand infants have low selenium levels at birth and experience a further decline if fed cows milk based formula. This study examined the selenium status of infants fed with a new commercially available selenium supplemented formula. Forty-four newborn infants, whose mothers wished to formula feed, were randomized in an open controlled trial to be fed a commercially available selenium supplemented cows milk formula (containing 17 micrograms Se/L) or an unsupplemented formula (containing 4.6 micrograms Se/L). Cord, 1 and 3 month blood samples were obtained for selenium status (plasma and red cell selenium and glutathione peroxidase) and thyroid function. Mean plasma selenium and glutathione peroxidase values were significantly higher in supplemented than unsupplemented infants at 1 month (unpaired t-tests; P < 0.0001 and P = 0.001 respectively) and 3 months (P < 0.0001 and P = 0.0005). Analysis within treatment groups between time points (paired t-tests) showed that selenium supplementation prevented the fall in plasma selenium from birth to 1 month seen in unsupplemented infants and was associated with a rise in levels between 1 and 3 months (P = 0.002). Supplementing cows milk formula with selenium to replicate the levels found in breast milk is nutritionally sound. Feeding from a few days of age with a formula containing 17 micrograms Se/L in infants with low selenium status at birth is sufficient to cause a rise to 80% of adult levels at 3 months of age.

A simple kinetic approach to derive the ecological dose value, ED 50, for the assessment of Cr(VI) toxicity to soil biological properties

Three New Zealand soils of contrasting texture, organic matter content and cation exchange capacity (CEC) were amended with K 2Cr 2O 7 solutions, spanning two concentration ranges, 0–5 μmol Cr(VI) g −1 soil and 0–50 μmol Cr(VI) g −1 soil. Samples were assayed for phosphatase, sulphatase and urease enzyme activities, and for basal respiration, microbial biomass C, dimethyl sulphoxide(DMSO)-reducing activity and denitrification, 3 and 60 d after amendment. Extractability of Cr(VI) from similarly amended samples was measured from 0 to 100 d. Cr(VI) proved to be strongly inhibiting of most of the biological properties and in most instances inhibition was explained by one or both of two simple Michaelis-Menten kinetic models. The first of these (Model 1) simulated fully competitive kinetics and the second (Model 2) simulated partially competitive kinetics. A single inhibition constant, similar to ED 50 as conceptualized in previous studies, could usually be calculated for each property in each soil. The properties could be ranked in the following order of decreasing sensitivity to Cr(VI): denitrification > DMSO-reduction > sulphatase activity ≈ biomass C > phosphatase activity > urease activity > respiration. For the most sensitive property, denitrification, ED 50 values range from 63 to 730 nmol Cr g −1 soil. Soil mineral surface area, organic matter content and CEC influenced the sensitivity of properties between soils. Although the extent of inhibition often diminished with time, the differences were generally much smaller than the observed decline in extractability of Cr(VI), indicating that a persistent, long-term inhibition, outlasting the Cr(VI) itself, had occurred.

Contribution of organic matter and clay minerals to the cation exchange capacity of soils

Abstract The cation exchange capacity (CEC) at pH 7 was measured for samples of 347 A horizons and 696 B horizons of New Zealand soils. The mean CEC was 22.1 cmolc/kg for the A horizons and 15.2 cmolc/kg for the B horizons. Multiple regressions were carried out for CEC against organic carbon (C), clay content, and the content of seven groups of clay minerals. The results, significant at p <0.001, were consistent with most of the CEC arising from soil organic matter. For the samples of A horizon, the calculated CEC was 221 cmolc/kg per unit C and for the B horizons was 330 cmolc/kg C. There was also a contribution from sites on clay minerals. Multiple regression indicated that smectite had a higher CEC (70 cmolc/kg) than other minerals but it was not as high as that of type smectites; kaolin minerals had the lowest CEC. There was a significant effect of interaction between organic matter and some clay minerals on the CEC. Samples from B horizons containing allophane had lower CEC than those not containing ...

Influence of the number of rhizobia on the nodulation and establishment of Trifolium ambiguum

Rhizobium leguminosarum bv. trifolii in New Zealand soils is ineffective on Trifolium ambiguum and inoculation with an effective strain of rhizobia is essential for nodulation. We investigated the effect of inoculation on the establishment of oversown T. ambiguum (cv. Monaro) in different tussock grassland environments. Peat-based inoculant was applied to seed at a range of rates, in a gum arabic-lime pellet, and when sown 1 day after inoculation the number of rhizobia ranged from 0.2 × 10 3 to 260 × 10 3 seed −1 Over the 9 sites, seedling nodulation progressively increased from 5% up to 66% as the number of rhizobia seed −1 increased. Seedling establishment at the end of the first year was directly related to nodulation. These results have important practical implications in improving the establishment of this legume, as the number of rhizobia required to maximize nodulation is higher than that obtained by inoculation at the recommended rate.

The effect of hydroxide solutions on dissolution of organic-carbon in some New Zealand soils

The disposal of high pH, hydroxide-based, liquid wastes using land treatment systems is becoming increasingly common in New Zealand. For effective disposal of high pH liquid wastes to land, it is necessary to understand the effects of different hydroxide-based solutions on organic carbon dissolution to ensure soil physical properties are not adversely affected. Single-step and multi-step extraction experiments were designed to investigate the effect of high pH solutions on organic carbon dissolution in four New Zealand soils. In the single-step extraction experiments, soil was shaken with varying concentrations of NaOH and KOH (0.003, 0.01, 0.03, 0.1 and 0.3 M) at a 1:5 soil to solution ratio for 18 h. Organic carbon dissolution occurred at very low concentrations and increased linearly with hydroxide concentration, with up to 45% of the total initial organic carbon dissolved when 0.3 M NaOH was used. KOH dissolved slightly less organic carbon than NaOH, indicating that a cation difference occurred. When the anion was changed to chloride, the amount of organic carbon dissolved was very small (&lt;2% of total initial organic carbon) for all concentrations, indicating that the hydroxide anion was most important in causing organic carbon dissolution. Multi-step experiments involved repeatedly shaking soil with fresh hydroxide extracting solutions, and showed that the difference between NaOH and KOH in dissolving organic carbon decreased as the number of extractions increased. The cumulative amount of organic carbon dissolved increased from about 45% after a single-step extraction to about 75% after five extractions. Organic carbon dissolution with different solutions tended to be higher in an allophanic soil, but similar in soils dominated by phyllosilicate clay minerals. The results indicate that factors such as the chemical composition of the liquid waste and soil type need to be considered prior to land disposal to prevent adverse effects on soil physical properties.