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Open access

Taru Sandén, Georg J. Lair, Jeroen P. van Leeuwen, Guðrún Gísladóttir, Jaap Bloem, Kristín Vala Ragnarsdóttir, Markus Steffens and Winfried E.H. Blum

Summary

In order to study the soil aggregate distributions and soil organic matter (SOM), we sampled top- and subsoils in four intensively farmed croplands (two organic (Org-OB and Org-LA), and two conventional (Con-OB and Con-LA)) on Haplic Chernozems located in Marchfeld in the east of Vienna (Austria). Soil structure and SOM quantity, quality and distribution between free and occluded particulate organic matter and aggregate size fractions (<20 µm, 20-250 µm, 250-5000 µm) were studied by following a density fractionation procedure with low-energy ultrasound treatment. The relation of the soil physicochemical (e.g., particle size distribution, pH, organic carbon, total nitrogen) and biological properties (e.g., fungal biomass, active fungi) with stable soil aggregate size fractions and SOM was studied. The mean weight diameter (MWD) showed no significant difference between all studied sites and was between 3.8 mm and 10.0 mm in topsoils and between 6.7 mm and 11.9 mm in subsoils. In topsoils, the contents of calcium-acetate-lactate (CAL)-extractable P, active fungal biomass, dithionite-extractable Fe and sand were significantly positively correlated with the amount of the macroaggregates and with the MWD. We observed that most soil organic carbon, depending on soil texture, was stored in the microaggregate size classes <20 µm and 20-250 µm.

Open access

Heide Spiegel, Teresa Mosleitner, Taru Sandén and Johann G. Zaller

Summary

Organic fertilization has been shown to benefit soil biota. A field experiment was established in 1991 at the AGES experimental research station Ritzlhof to investigate the effects of long-term fertilization on soil biota and crop yields. Experimental plots were cultivated using a crop rotation with maize, wheat, barley, and pea. Eight treatments consisted of compost application (urban organic waste, green waste, cattle manure, and sewage sludge compost). Composts were applied exclusively (organic) or amended with mineral nitrogen (N) fertilizers (80 kg N ha−1, organic-mineral) and compared to 0 (control) and mineral (40, 80, and 120 kg N ha−1) fertilization. Earthworm activity and biomass, litter decomposition, crop growth, and yield parameters were investigated under winter barley (Hordeum vulgare L.) in 2014 after uniform mineral fertilization and 1.5 years after the last compost application. Earthworm activity was significantly increased under long-term organic-mineral fertilization compared to the control, whereas earthworm biomass was unaffected by compost application. Litter decomposition rate was highest in the control. Only barley stem growth was affected by fertilization, whereas other barley parameters including yield were unaffected. The results showed that long-term fertilization affects soil biota even if compost is not applied every year.