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Nitrate leaching from a small, underdrained, grassland, clay catchment (1986)

Haigh, Rosalyn A. ; White, R.E.

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 2 (1986), S. 0

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ISSN: 1475-2743

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract. Losses of nitrogen in the tile drainflow from a clay soil (Evesham series) under grazed grassland were monitored during the 1982/83 and 1983/84 drainflow seasons. In 1982/83, 40% of the discharge had a NO3− concentration 〉 11.3 mgNl−1, while in 1983/84 concentrations were always 〉 20 mgNl−1. Total N lost by leaching was 17.5 and 48.7 kg ha−1 in 1982/83 and 1983/84 respectively, which was equivalent to 9 and 43% of the fertilizer applied. The marked difference in N losses for the two seasons was attributed to differences in the quantity and timing of N fertilizer applications, the dryness of the preceding summer and the duration and density of stocking.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1475-2743.1986.tb00683.x

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Frequency distributions and spatially dependent variability of ammonium and nitrate concentrations in soil under grazed and ungrazed grassland (1987)

White, RE ; Haigh, Rosalyn A ; Macduff, Jh

Springer

Nutrient cycling in agroecosystems 11 (1987), S. 193-208

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ISSN: 1573-0867

Keywords: ammonium ; fertilizer ; grazing ; lognormal ; nitrate ; spatial dependence

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The frequency distributions of soil NO 3 - and NH 4 + concentrations under grazed and ungrazed grassland were found to be lognormal, irrespective of time of year or soil depth. The variance and skewness of the sample values increased with stocking density and use of N fertilizer. An analysis of the spatial dependence of the variability using the semivariogram showed a high ‘nugget’ variance, even when three sample values from each sampling point were averaged. Most of the variance was therefore short-range (occurring within a distance of 0.4 m), suggesting that the sample volume for soil mineral N measurement should be as large as is practicably possible. As an estimate of the average mineral N content, the geometric mean of the sample values consistently underestimated the true arithmetic mean of the population from which the same was drawn. The conventional estimate of the arithmetic mean for lognormally distributed samples values was satisfactory when the sample number was 〉 50 and the (log) variance 〈 0.75 (µg N cm−3). However, for data with larger variances, high coefficients of skewness and fewer observations, Sichel's estimator was a more efficient measure of the true population mean.