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Pore characteristics and hydraulic properties of a sandy loam supplied for a century with either animal manure or mineral fertilizers
Author(s) -
Schjønning P.,
Iversen B.V.,
Munkholrn L.J.,
Labouriau R.,
Jacobsen O.H.
Publication year - 2005
Publication title -
soil use and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.709
H-Index - 81
eISSN - 1475-2743
pISSN - 0266-0032
DOI - 10.1111/j.1475-2743.2005.tb00398.x
Subject(s) - loam , manure , environmental science , agronomy , mineral , soil science , soil water , biology , ecology
Application of organic residues to soil is generally assumed to improve soil tilth. Only few studies have reported the long‐term effects on the more subtle aspects of soil porosity, and no reports have considered the potential effects of organic amendments on the pore system in the subsoil. We sampled undisturbed soil cores (100 cm 3 and 6280 cm 3 ) using metal cylinders in differently fertilized plots in the long‐term field experiment at Askov Experimental Station, Denmark. We selected the 0–60 cm soil layer of plots dressed for a century with either mineral fertilizers (labelled NPK) or animal manure (labelled AM) and unfertilized plots (UNF) as a reference. Both fertilization treatments were studied at two levels of nutrient application: ‘normal’ (labelled ‘1’) and 1.5 times ‘normal’ (labelled ‘1½’). Water retention, air permeability and air diffusivity were measured on the small cores, and we used the large cores for measuring near‐saturated and saturated hydraulic conductivity. In the plough layer, the AM and NPK soils displayed identical pore volumes in size fractions that were larger as well as smaller than 30 μm, while the UNF soil had a significantly smaller volume of pores < 30 μm. No clear trends were found in treatment effects on pore organization as calculated from air diffusivity and air permeability measurements. No significant differences in hydraulic conductivity were found in the plough layer. For the subsoil below ploughing depth, significantly larger macropore volumes and near‐saturated hydraulic conductivities were found for soil of plots receiving the larger (‘1½’) amount of nutrients compared with the ‘normally’ dressed soil. This effect was independent of fertilization system (AM or NPK). We attribute the larger volume of macropores to the improved root growth conditions in the soil with the higher nutrient level. We conclude that addition of animal manure at rates realistic in agriculture has only a modest effect on soil pore characteristics of the plough layer soil compared with the use of mineral fertilizers. For the subsoil below ploughing depth, a high level of nutrient application may increase soil macroporosity and near‐saturated hydraulic conductivity, but the origin of nutrients is of no significance.