scispace - formally typeset
Search or ask a question

Showing papers by "Karin Müller published in 2009"


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the long-term effect of the addition of organic carbon (C) on the macropore structure of topsoils and found that soil C management combats climate change directly by sequestering C and indirectly in the form of a reduction of N2O emissions.
Abstract: Summary We analysed the long-term effect of the addition of organic carbon (C) on the macropore structure of topsoils. For this purpose we compared the top 50 mm in the tree rows of an organic apple orchard with those in an adjacent conventional orchard with the same soil type, texture and previous land-use history in New Zealand. After 12 years the topsoils of the organic orchard had 32% more soil organic carbon (SOC) sequestered than those of the conventional, integrated orchard because of regular compost applications and grass coverage. We quantified the macropore structure (macropores = pores > 0.3 mm) of nine undisturbed soil columns (43 mm long, 20 × 17 mm in the plane) within each orchard using 3D X-ray computed tomography. The macroporosity (7.5 ± 2.1%) of the organic orchard soil was significantly greater than that of the integrated orchard (2.4 ± 0.5%). The mean macropore radius was similar in the organic and integrated systems, with 0.41 ± 0.02 mm and 0.39 ± 0.01 mm, respectively. The connectivity of macropores tended to be greater in the organic than in the integrated system, but this was not statistically significant. The pronounced soil C management in the organic orchard increased both the formation of macropores by roots and a larger fresh weight of anecic earthworms, and the stabilization of the macropore structure was increased by a larger aggregate stability and microbial biomass compared with those of the integrated orchard. We simulated the diffusion through the measured pore structures of segments of the soil columns. The segments had the length of the mean aggregate size of the soils. The relative diffusion coefficients at this aggregate scale were significantly greater in the organic (0.024 ± 0.0009) than in the integrated (0.0056 ± 0.008) orchard. In a regression analysis with both the porosity and connectivity of macropores as significant variables, 76% of the variability of the relative diffusion coefficients was explained in the integrated, and, with the porosity as the only significant factor, 71% of the variability in the organic orchard. We hypothesize that a greater relative diffusion coefficient at the aggregate scale would reduce nitrous oxide (N2O) production and emission in a wet soil and suggest that soil C management combats climate change directly by sequestering C and indirectly in the form of a reduction of N2O emissions, by creating more macropores.

75 citations


Journal ArticleDOI
15 Aug 2009-Geoderma
TL;DR: In this article, the generic filtering capacity of an aggregated soil for organic pesticides was defined as the capacity of the soil aggregates to take up pesticides from the soil solution, to adsorb them to the soil matrix, and to degrade them.

26 citations


Journal ArticleDOI
TL;DR: In this article, the impact of decreased organic carbon (SOC) on soil filtering capacity for pesticides was investigated using 2,4-D. The hypothesis was that in aggregated soils the filtering capacity of organic compounds depends on physical, chemical and biological properties at the aggregate scale, impacting water sorptivity, pesticide sorption and pesticide degradation respectively.
Abstract: Recently, the loss of soil organic carbon (SOC) has been reported for some pastoral NZ soils. The impact of decreased SOC on soil filtering capacity for pesticides was investigated using 2,4-D. The hypothesis was that in aggregated soils the filtering capacity for organic compounds depends on physical, chemical and biological properties at the aggregate scale, impacting water sorptivity, pesticide sorption and pesticide degradation respectively, and that these are related to the SOC content. Indicators for these properties were identified, namely the water repellency, SOC content, and microbial biomass and basal respiration rates. Two pairs of sites with the same soil type, texture, land-use and climatic conditions, but with significantly different SOC content within each of the pairs were selected. For hydrophobic soils, a SOC loss tended to have a negative impact on chemical and biological properties, but a positive impact on the physical filtering capacity of aggregates for 2,4-D.

1 citations