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  • 1
    ISSN: 1432-0789
    Keywords: Carbon-dioxide production ; Climatic factors ; Microbial biomass ; Microbial nitrogen ; Mineral N flush ; Nitrogen mineralisation ; Pasture production ; Seasonal changes ; Water-soluble carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A 2-year study (1983–1984 to 1984–1985) was conducted to estimate temporal and seasonal changes and the effects of fertiliser on some soil chemical, biochemical and microbiological characteristics. The soil used was a Typic Vitrandept under grazed pasture. Soil samples were taken regularly to a depth of 75 mm from paired unfertilised and fertilised (500 kg ha− 30% potassic superphosphate) plots. Except for organic C, fertiliser had little or no effect on the characteristics measured. Organic C averaged about 9.2% in unfertilised soil and was about 0.3% higher in the fertilised soil. The size of the microbial biomass fluctuated widely in the 1st year (3000 μg C g−1 in February to 1300 μg C g−1 in September) but there was less variation in the 2nd year (range 1900 μg C g−1 to 2500 μg C g−1 soil). CO2 production values (10- to 20-day estimates averaged 600 μg of CO2-C g−1 soil) were generally higher in spring compared to the rest of the year. Water extractable C increased over winter and declined through spring in both years (range 50 μg C g−1 soil to 150 μg C g−1 soil). Mineral-N flush values were higher in summer (300 μg N g−1 soil) and lower in winter months (200 μg N g−1 soil). The pattern of variation of microbial N values was one of gradual accumulation followed by rapid decline. This rapid decline in values occurred in spring and autumn (range 130–220 μg N g−1 soil). N mineralisation and bicarbonate-extractable N showed no clear trend; these values ranged from 100–200 and 122–190 μg N g−1 soil, respectively. There was a significant correlation (0.1%) between N mineralisation and bicarbonate-extractable N in the late summer-autumn-early winter period (February–August) in both years but not in spring. These results and their relationships to climatic factors and rates of pasture production are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0789
    Keywords: Chitin ; Heterodera trifolii ; Meloidogyne spp. ; Nematodes ; Nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of soil amendment with crabshell chitin on the growth of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.), and on populations of soil bacteria, fungi, and plant-parasitic and free-living nematodes were investigated in a pot trial. Five soil samples were collected from Te Puke (Paengaroa Shallow Sand, a Typic Hapludand) and five from Hamilton (Bruntwood silt loam, an Aquic Hapludand), New Zealand. Subsamples of each soil were either amended with chitin or unamended and planted with white clover and ryegrass. The ryegrass shoot weight in amended soil was greater (P〈0.01), most probably due to N mineralised from chitin. A significantly lower (P〈0.01) root: shoot ratio of ryegrass in the amended soil also suggested improved N availability, and therefore less root mass was needed to support a given shoot mass. A reduction in nodulation was observed in 12-day-old white clover seedlings (P〈0.05) and also in 6-week-old seedlings (P〈0.01). The shoot weight of white clover was significantly lower (P〈0.05) in amended soil, possibly due to phytotoxic effects of chitin. Chitin increased (P〈0.01) the populations of bacteria and fungi by 13-fold and 2.5-fold, respectively. The cyst nematode of white clover, Heterodera trifolii, was significantly reduced in chitin-amended soil, possibly due to increased levels of chitinase produced by rhizosphere microorganisms. Two other plant-parasitic nematodes, Pratylenchus spp. and Tylenchus spp., were also reduced in ryegrass roots and in soil as a result of the chitin amendment. However, the total number of free-living nematodes increased 5.4-fold in amended soil.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0789
    Keywords: Key words Chitin ; Heterodera trifolii ; Meloidogyne spp. ; Nematodes ; Nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of soil amendment with crabshell chitin on the growth of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.), and on populations of soil bacteria, fungi, and plant-parasitic and free-living nematodes were investigated in a pot trial. Five soil samples were collected from Te Puke (Paengaroa Shallow Sand, a Typic Hapludand) and five from Hamilton (Bruntwood silt loam, an Aquic Hapludand), New Zealand. Subsamples of each soil were either amended with chitin or unamended and planted with white clover and ryegrass. The ryegrass shoot weight in amended soil was greater (P〈0.01), most probably due to N mineralised from chitin. A significantly lower (P〈0.01) root: shoot ratio of ryegrass in the amended soil also suggested improved N availability, and therefore less root mass was needed to support a given shoot mass. A reduction in nodulation was observed in 12-day-old white clover seedlings (P〈0.05) and also in 6-week-old seedlings (P〈0.01). The shoot weight of white clover was significantly lower (P〈0.05) in amended soil, possibly due to phytotoxic effects of chitin. Chitin increased (P〈0.01) the populations of bacteria and fungi by 13-fold and 2.5-fold, respectively. The cyst nematode of white clover, Heterodera trifolii, was significantly reduced in chitin-amended soil, possibly due to increased levels of chitinase produced by rhizosphere microorganisms. Two other plant-parasitic nematodes, Pratylenchus spp. and Tylenchus spp., were also reduced in ryegrass roots and in soil as a result of the chitin amendment. However, the total number of free-living nematodes increased 5.4-fold in amended soil.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 52 (1979), S. 305-309 
    ISSN: 1573-5036
    Keywords: Ammonium oxidising bacteria ; Most probable number ; Nitrification ; Nitrosomonas nubers ; Soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Most probable number of ammonium oxidising bacteria in soil has been estimated without the need to carry out chemical tests to determine the production of nitrite or nitrate in dilution tubes. The medium used contained phenol red which changes colour from pink to yellow as the oxidation of ammonium to nitrate decreases the pH. This makes it possible to determine growth visually. An incubation period of 8 weeks at 25°C was sufficient to obtain maximum estimates of ammonium oxidising bacteria in the soils tested.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 60 (1981), S. 177-186 
    ISSN: 1573-5036
    Keywords: Aluminium ; Bacteria ; Fungi ; Lime ; Mineralization ; Nitrogen ; pH ; Pot ; trial ; Ryegrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of rates of lime and nitrogen on the growth of ryegrass (Lolium perenne) was measured in a pot experiment using two yellow-brown earth steepland soils (pH 5.1 and 5.3). Nitrogen or raising the soil pH above 5.8–6.0 markedly increased growth on both soils. Negative lime×N interactions on both soils together with other data indicated that an increase in the rate of mineralization of N was the major effect of lime. Numbers of bacteria and fungi as measured by plate counts were not increased by liming and hence the increased rate of mineralization of N was attributed to increased microbial activity.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The rate of nitrification by soil aggregates at pH 5.5 and 7.5 was examined by a perfusion technique. Nitrification occurred at both levels of H-ion concentration but at the higher pH the rate of nitrification was greater. The population estimates of nitrifying bacteria were correspondingly greater at the high pH. Once the pH was lowered from 7.5 to 5.5, the nitrification rate decreased slowly with a corresponding decrease in the numbers of nitrifying bacteria. The distribution of nitrifying bacteria throughout soil aggregates was homogenous. The lower limit of pH for nitrification was 4.3.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The rate of nitrification by soil aggregates at pH 5.5 and 7.5 was examined by a perfusion technique. Nitrification occurred at both levels of H-ion concentration but at the higher pH the rate of nitrification was greater. The population estimates of nitrifying bacteria were correspondingly greater at the high pH. Once the pH was lowered from 7.5 to 5.5, the nitrification rate decreased slowly with a corresponding decrease in the numbers of nitrifying bacteria. The distribution of nitrifying bacteria throughout soil aggregates was homogenous. The lower limit of pH for nitrification was 4.3.
    Type of Medium: Electronic Resource
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