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Relationships among; soil organic matter (SOM), the feeding activity of the soil-dwelling scarab larva, Costelytra zealandica (White) (Coleoptera: Melolonthidae), amber disease and soil numbers of its causal agent, Serratia entomophila (Enterobacteriaceae), were studied. C. zealandica larvae may cause severe damage to pasture roots and reduce ryegrass and clover production. Entomopathogenic strains of S. entomophila are being used in a biocontrol programme in New Zealand as they induce inhibition of larval feeding activity and larval death 1–3 months from the onset of infection. A mature (38-year-old) and a young (4-year-old) pasture from Canterbury, New Zealand, were chosen for this study. Both pastures had the same soil type, very similar agronomic practices but different ages and therefore SOM contents. Soil from both sites was collected and amounts of C and N of different fractions of SOM were measured. Organic matter was 7.59% and 4.41% in the mature and young pastures respectively. Total C and N in soil and most fractions of SOM were significantly higher in the mature pasture than in the young pasture. Total C and N present in cold and hot water extractions combined, representing the labile SOM fraction, showed 45% less C and 37% less N in the soil from the young pasture than in the soil from the mature pasture. In both soils, approximately 10% of the total C and N was present in the labile SOM fractions. Populations of soil-borne indigenous bacteria, S. entomophila, were estimated in fresh and air-dried samples from both pastures. Soils from the two pastures contained a significantly different number of S. entomophila cells. A more than ten times higher population was present in fresh soil from the mature pasture compared with fresh soil from the young pasture. However, levels of S. entomophila decreased significantly when the soil was air-dried for experimental purposes. An experiment was designed to explore the interactions occurring among SOM quantity and quality, S. entomophila performance as a biocontrol agent and simulated root feeding activity of early third instars of C. zealandica. Larvae were placed individually in pots containing air-dried soil from one or other of the two pastures (n = 10 per treatment). The experimental pots were inoculated at three dose rates of a pathogenic strain of S. entomophila. The control pots were treated with nutrient broth free of S. entomophila. All pots were incubated in the laboratory under the same experimental conditions. Larval feeding activity was measured using pieces of carrot root. All pots were examined for infection, mortality, feeding rate and gain in live weight of each larva after 15 and 30 days. The mature pasture was associated with significantly higher amber disease and mortality than the young pasture. Also, a significantly higher gain in larval weight was observed in the young pasture soil, together with a higher rate of carrot consumption by larvae. It can be concluded that the content of labile SOM in both pastures may account for the differences observed in this study and could have a buffering effect on plant damage caused by soil-dwelling scarab larvae.

Effects of the herbicide metsulfuron-methyl on soil microorganisms and their activities in two soils were evaluated under laboratory conditions. Measurements included their populations, soil respiration, and microbial biomass. In the clay soil, bacterial populations decreased with increasing concentration of metsulfuron-methyl during the first 9 days of incubation but exceeded that of the control soil from day 27 onward. In the sandy loam soil, the herbicide reduced bacterial populations during the first 3 days after application, but these increased to the level of untreated controls after 9 days' incubation. Fungal populations in both soils increased with increasing metsulfuron-methyl concentrations, especially in the sandy loam soil. CO 2 evolution was stimulated in both soils in the presence of the herbicide initially, but decreased during days 3 to 9 of the incubation period before increasing again afterward. The presence of metsulfuron-methyl in the soil increased microbial biomass, except in sandy loam soil at the first day of incubation.

The major inputs of nitrogen (N), phosphorus (P) and sulphur (S) as fertilizer and biological N2 fixation, and the major removals of these nutrients in harvested products (grain, meat and wool) for each year of the rotation of three pairs of farms were calculated. The farms were under a mixed cropping system of farming, common to the study area, in which grazed grass/white clover pasture and/or grass and white clover seed crops are grown in rotation with arable crops. One of each pair of farms was managed conventionally and the other was under an alternative organic or biodynamic system. The nutrient status of soils, harvested grain and pasture herbage were also measured along with the organic matter content and enzyme activities of the soils. Nutrient budgets (inputs minus outputs) for N, P and S on the conventional farms were generally balanced or positive so that the supply of these nutrients is unlikely to be limiting production. Nitrogen budgets were positive at all three alternative farms with biological N2 fixation accounting for most or all of the N input. One alternative farm had positive P and S budgets because of additions of compost, phosphate rock and elemental S. By contrast, at the other two alternative farms, net removal of P, and in one case S, occurred. In the other case, the S budget was balanced by one application (per rotation) of S fertilizer to the pasture. At these two sites, concentrations of grain N, P and S were lower than those at conventional sites and pasture herbage P and S concentrations were below recommended critical concentrations. Levels of total S and P and available P in soils were also lower on the alternative than conventional farms. Production on these alternative farms is relying on soil reserves of P and S, and additions of P and S will be required in the future to sustain current production levels. Organic C content and arylphosphatase, arylsulphatase and urease activities tended to be higher under alternative than conventional pastoral management. This was attributed to the longer pastoral phase under alternative (3–4 year) than conventional (1–2 year) management resulting in a small build up of organic matter. However, organic C content and enzyme activities were similar under conventional and alternative systems during the arable phase suggesting that conventional management had no adverse effect on soil biological activity.

Quaternary loess deposits containing charcoal and in situ organic matter constituents from Banks Peninsula, New Zealand, were subjected to various physical and chemical treatments before radiocarbon assay. A stepwide procedure was used in which each component was radiocarbon dated before and after the treatments were applied. The criterion adopted for judging the effectiveness of a treatment is an increase in the radiocarbon age of loess layer. On this basis the oldest and therefore the most reliable date was obtained from the intra-loess charcoal and its humic acid extract. By comparison, the radiocarbon ages of organic matter constituents of the whole or partitioned loess were much younger, and are considered to represent only average ages for the particular layers concerned. No advantage was gained by dating the carbon-enriched clay-humus fraction as opposed to whole loess samples. There is an apparent conflict between our dates and current interpretation of loess stratigraphy and chronology in the South Island of New Zealand, which requires further investigation. This uncertainty apart, the upper layers of multiple loess deposits are clearly much older than earlier reports indicate, and it follows that the correlation of these deposits with late-glacial events both within and beyond New Zealand is even more tenuous and unreliable than previously thought to be the case.

Six New Zealand topsoils of widely different origins and properties were subjected to 6m HC1 hydrolysis and the distribution of N fractions and amino acids were determined qualitatively and quantitatively. Of the total-N in the soils studied 83–91%, was hydrolysable with 6 m HCl. The largest proportion of the hydrolysable N was α-amino acid N (38– 42%). followed by hydrolysable-unknown N (HUN) (14–24%), and NH 4 + -N (14–22%). A significant proportion (25–50%) of the HUN fraction was accounted for by the non α-amino acid-N. Oxidative (3% H 2 O 2 ) hydrolysis released N-phenoxy amino acid-N and possibly N-compounds which were complexed with phenols and sugars. All soils had a similar amino-acid composition with a predominance of acidic amino-acids.

The effects of 5 different nitrogenous fertilisers (ammonium sulphate, ammonium sulphate + N-serve, potassium nitrate, poultry manure, and urea) each at 5 application rates (0, 150, 300, 450, or 600 kg N/ha) on the total nitrogen (N) and nitrate content of 2 varieties of spinach (Spinacea oleracea L.) and 1 variety of beetroot (Beta vulgaris L.) were evaluated in a pot experiment using Wakanui silt loam soil. The nitrification inhibitor, N-serve, was used to retard the microbial conversion of ammonium to nitrate. Total N and nitrate N generally increased with increasing rates of N applied. Potassium nitrate application resulted in the highest N uptake levels, and poultry manure application gave the lowest. N-serve depressed N uptake at 600 kg N/ha applied. Plants accumulated nitrate to a level potentially hazardous to health at only the highest rate (600 kg N/ha) of potassium nitrate, ammonium sulphate, and urea applied. Differences between the 2 varieties of spinach tested were not significant.

Humus samples derived from peat, moss or ornithogenic sources in the Antarctic continent have been examined by 13 C nuclear magnetic resonance techniques. The 13 C spectra show that the humus has undergone very little chemical modification. A fulvic acid fraction from a moss derived soil is almost entirely α- and β-glucose. The results also show that lignin is not a necessary precursor for aromatic components in soils. It is suggested that the aromaticity and carbohydrate content of certain soils is governed by the low temperature which influences the degree of humification.

Soil NH + 4 -N and NO − 3 -N at five soil depths (0–10, 10–20, 20–40, 40–60, 60–80 cm) and some environmental variables were measured in a field trial under fallow and wheat for 9 months. Significant linear and quadratic relationships were obtained relating soil NH + 4 -N, NO − 3 -N, NH + 4 -N + NO − 3 -N, and NH + 4 -N + NO − 3 + total-N uptake by wheat to soil heat accumulation (temperature), moisture, and rainfall. R 2 values generally decreased with soil depth and the maximum value (37%) was obtained for NO − 3 -N changes in the topsoil (0–10 cm). Although a considerable amount of variation in the inorganic values recorded is not included in the equations, our results suggest that the development of the above relationships particularly of the quadratic type are useful to predict crop requirements for N by measurement of environmental variables in the field.

The C 2 H 2 reduction (A.R.) assay was investigated for quantitative measurement of symbiotic N 2 fixation in established legume-based pastures under field conditions. It was found that the rate of C 2 H 4 production was relatively constant for approx 6 h. For an accurate estimation of the N 2 fixing activity, many field samples are required to overcome the errors due to the inherent spatial distribution of white clover ( Trifolium repens L.) within the pasture. Furthermore, it is necessary to physically integrate the day-to-day and diurnal variations in the N 2 fixing activity of the legume to obtain a reliable estimate of the rate of C 2 H 4 production and hence symbiotic N 2 fixation. The A.R. assay and an 15 N technique were compared for measuring symbiotic N 2 fixation in established pastures. A 3 h incubation in the A.R. assay gave the best estimate of symbiotic N 2 fixation relative to the 15 N technique. The 1 h incubation over-estimated and the 6 h incubation under-estimated the rate of symbiotic N 2 fixation.

The effect of Gigaspora margarita an endomycorrhiza—forming fungus, on the growth and chemical composition of perennial ryegrass plants grown at three concentrations and two sources of N were studied. The yield of plant tops was significantly depressed by mycorrhizal infection. Mycorrhizal plants had higher concentrations of free NH 4 + (and, consequently, higher cation excess concentrations), suggesting an impairment of protein synthesis possibly resulting from an inhibited supply of C. Total oxidizable C, soluble sugar content and C/N ratios were lower in mycorrhizal plants, suggesting that the mycorrhizal fungi were competing with the host for photosynthetically-derived C, consequently causing growth depressions. A possible mechanism of this competition is discussed.

Selected horizons of three present-day New Zealand soils and paleosols underlying them were studied, using standard soil chemical and mineralogical methods of the New Zealand Soil Bureau and a sensitive amino acid method. The chemical and mineralogical data obtained contributed little to the recognition of buried soils. Amino acid-nitrogen levels, on the other hand, showed significant differences between the various soil horizons. In all cases, they decreased with depth, except that whenever a paleosol occurred there was a definite and significant increase with respect to that present in the overlying horizon. Differences in amino acid levels between horizons were found to be valuable as indicators for the presence of paleosols that have been identified in the field. In addition, they confirmed the pedological differentiations of buried soil horizons.

Humic and fulvic acids from several sources were separated into three spectral types depending upon their infrared absorption characteristics. Those belonging to Type I showed equally strong bands at 1720 and 1600 cm−1, with no discernible absorption being evident at 1640 cm−1. A distinguishing characteristic of the preparations giving spectra of Type II was a very strong 1720 cm−1 band, a shoulder at 1650 cm−1, and the absence of a 1600 cm−1 band. The preparations of Type III showed pronounced bands indicative of proteins and carbohydrates. Observed spectral changes in the 1700-1600 cm−1 region indicated that the humification process consisted, in part, of a loss of COOH groups and a change in the environment of CO from the free or weakly H-bonded state to strongly chelated forms.

Concern has been expressed (Rasmussen er nl., 1976; Crutzen and Ehhalt, 1977; Bremner and Blackmer, 1978; Cicerone et al., 1978) about possible detrimental effects to the earth’s ozonosphere due to a suggested increase in tropospheric N,O. This increase could result from the expanding use of artificially-manufactured nitrogenous fertilizers. In pastoral agriculture in a number of countries (e.g. New Zealand and Australia) high concentrations of N are constantly being voided as urine on pastures by grazing animals. This may present a situation for NzO production and release to the atmosphere. Whereas artificial fertilizers are normally applied by broadcasting or banding, sheep and cattle urine is voided in discrete patches in which the concentration of applied N frequently exceeds the equivalent of 1000 kg haa’ (Doak, 1952; Barlow, 1974). Under these conditions soil pH increases and high concentrations of NOT-N can accumulate. Such effects may give rise to chemodenitrification routes for subsequent NzO release (Nelson and Bremner, 1970). Nitrous oxide fluxes from urine patches in grazed pastures have not been studied extensively, mainly because of the difficulty in measuring the very small amounts of N20 released in air samples. Using the highly sensitive electroncapture gas chromatograph method (Rasmussen et al., 1976) we report long-term release rates of N,O from nitrogenous fertilizers and sheep urine applied to grazed pasture blocks and short-term release rates from laboratory incubation of pasture soils. Our results demonstrate a positive stimulation of initial N,O release when sheep urine was applied to the soil compared with similar applications of ammonium sulphate and urea. An established ryegrass (Lolium perenne L.) white clover (Trifolium repens L.) grazed pasture in the Lincoln College Sheep Stud Farm was used. The soil is a Templeton silt loam (Cox et ul., 1971) a Dystric Ustochrept. It has the following properties: pH (1: 2.5 water) = 6.2, total N =0.31x, NOT-N = 26 peg gg’, NH:-N = 45 fig g’, organic C = 4.2%, field capacity = 34%. Eight blocks (165 x I65 x 150 mm) of soil complete with undisturbed pasture herbage were cut from the site and fitted into 5 1 polypropylene containers. These were transferred to a laboratory window-box and maintained there under ambient lighting and temperature conditions (20°C) for 45 days. During this period watering (to 32% average moisture capacity-see Fig. 1) was carried out. All pasture blocks except the controls received on each of 3 occasions 0.5 g N as either ammonium sulphate, urea or sheep urine in lOOmI of water: equivalent approximately to 200kgNhaa’, giving a total application of about 600 kgN ha-‘. Control pasture blocks received 100 ml of distilled water. Duplicates of each treatment were used. The sheep urine was collected from cannulated Romney ewes, analysed for pH (7.1) total N (1.37 g lOOmI-‘) and urea-N (1.26 g 100 ml-‘) and stored frozen till required. Subsequent analysis upon thawing showed no chemical changes associated with these N fractions. Nitrous oxide fluxes were measured using an intermittent enclosure technique in which air-tight lids were fitted to the polypropylene containers and the released N,O allowed to accumulate in the enclosed headspace (approx. 1 1). The lid was closed for about 1 h, during which time at least 2 air samples (I ml) were removed using a gas-sampling valve (Carle 8 port) and analysed for N,O. The analytical system consisted of a Varian 2800 gas chromatograph fitted with a 3 m x 3 mm O.D. stainless steel column of Porapak Q maintained at 20°C. This was connected to a PyeUnicam linearized pulsed electron-capture detector maintained at 35OC. The carrier gas was O,-free Nz at a Bow rate of 50 ml min’. Adequate separation of NzO from the potentially interfering gas CO, was achieved (Cicerone et al., 1978): their retention times being 195 s and 242 s respectively. The primary standard calibration gas was a 104 ~1 NzO 1-l in N2 gas mix (Matheson, U.S.A.). Secondary NzO-air standards were prepared by diluting known volumes of the primary standard gas with known volumes of compressed air. N,O peak areas were calculated automatically on a Varian Aerograph Model 408 integrator. To study initial N,O release rates under non-saturated soil aerobic conditions, small scale incubations were performed. Samples of air-dry soil (10 g

Some statements referring to our work on 13 C NMR of humic and fulvic acids have been recently reported in this journal by Ruggiero and co-workers. They are discussed in order to avoid possible misinterpretations.