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An approach for estimating when soils will reach maximum nitrogen storage (2004)

Schipper, L.A. ; Percival, H.J. ; Sparling, G.P.

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 20 (2004), 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. Net accumulation of organic nitrogen in soil is constrained by the amount of organic matter and its minimum C:N ratio. Our objective was to estimate the potential for New Zealand soils to continue accumulating nitrogen within the soil organic pool. We calculated total carbon and nitrogen in the top metre of 138 representative soil profiles from the New Zealand National Soils Database. Carbon in these mainly pasture soils was assumed to be at steady state. The maximum nitrogen storage capacity was estimated by calculating the amount of nitrogen stored under assumed minimum soil C:N ratios of either 9, 10 or 11. The storage capacity remaining was determined as the difference between the amount of nitrogen currently stored and the maximum storage capacity. The length of time before a soil profile will reach the maximum capacity for nitrogen storage was calculated assuming net accumulation of 20, 50 and 100 kg N ha−1 yr−1. A C:N ratio of 9 (giving most storage capacity) and a conservative accumulation rate of 20 kg N ha−1 yr−1 showed that 12% of these soils would be at maximum storage within 40 years. A C:N ratio of 10 and a storage rate of 50 kg N ha−1 yr−1 would result in 54% of the soils reaching maximum storage within the next 40 years. As the capacity for nitrogen storage in soils declines, nitrate leaching is likely to increase with associated risk to the environment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00369.x

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Soil and solution chemistry under pasture and radiata pine in New Zealand (1997)

Parfitt, R.L. ; Percival, H.J. ; Dahlgren, R.A. ; [et al.]

Springer

Plant and soil 191 (1997), S. 279-290

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ISSN: 1573-5036

Keywords: acidification ; carbon ; carbon dioxide ; nitrogen ; pasture ; Pinus radiata ; sea salt

Source: Springer Online Journal Archives 1860-2000

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

Notes: Abstract The conversion of hill country pasture to exotic forest plantations is occurring rapidly (70,000 ha yr−1) in New Zealand. Impacts of this land-use change on soil properties, soil fertility, and water quality are only beginning to be investigated. This study examines the effects of radiata pine (Pinus radiata) on soil and soil solution chemistry, in a region of low atmospheric pollution, 20 years after plantation establishment, assuming that the pasture and pine research sites had comparable soil properties before planting pine. The primary effects of conversion on soil chemistry were a decrease of organic carbon in the mineral soil that was balanced by an accumulation of the surface litter layer, a decrease in soil N, soil acidification, and increased pools of exchangeable Mg, K, and Na. Soil solution studies revealed a large input of sea salts by enhanced canopy capture of sea salts that contributed to much larger solute concentrations and elemental fluxes in the pine soil. Sea salts appear to accumulate in the micropores of pine soil during the dry summer period and are slowly released to macropore flow during the rainy season. This results in a progressive decrease in solute concentrations over the period of active leaching. While chloride originating from sea salt deposition was the dominant anion in the pine soil, bicarbonate originating from root and microbial respiration was the dominant anion in the pasture soil. Carbon dioxide concentrations in the soil atmosphere were 12.5-fold greater in the pasture soil than in the pine soil due to greater rates of root and microbial respiration and to slower diffusion rates resulting from wetter soil conditions in the pasture. Although elemental fluxes from the upper 20 cm of the soil profile were substantially greater in the pine soil, these losses were compensated for by increased elemental inputs resulting from nutrient cycling and enhanced canopy capture of sea salts.