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Comparison of Long-Term Organic and Conventional Crop–Livestock Systems on a Previously Nutrient-Depleted Soil in Sweden

^a Dep. of Soil Science, Swedish Univ. of Agricultural Sciences, P.O. Box 7014, SE-750 07 Uppsala, Sweden
^b Enbärsväg 8, SE-761 63 Norrtälje, Sweden

View larger version (26K): [in this window] [in a new window]   Fig. 1. The 6-yr crop rotations of the organic and conventional systems including cover crops. Both rotations were grown 3 times during the experimental period of 18 yr. Note that the organic system included 3 cover crops and an in-sown forage crop acting as a cover crop, but the conventional included only one in-sown forage crop.

View larger version (28K): [in this window] [in a new window]   Fig. 2. (A) Soil pH values (H2O), (B) exchangeable P, and (C) exchangeable K concentrations in the plow layer (0–0.3 m) of the Bjärröd soil (1979–1999). Data points without bars represent pooled samples; bars represent standard errors of triplicate samples.

View larger version (13K): [in this window] [in a new window]   Fig. 3. Changes in organic carbon in soils of the organic and conventional systems over three crop rotations (± standard error, n = 3). Open symbols represent modeling results and filled symbols observed soil measurements.

View larger version (21K): [in this window] [in a new window]   Fig. 4. Yearly dry matter yields in the organic (), control (), and conventional () systems over three 6-yr crop rotations (±SE, n = 3). The weed biomass in the conventional system and control (data not shown) was very low due to herbicide treatment.

View larger version (15K): [in this window] [in a new window]   Fig. 5. Concentrations of inorganic N in leachate from the organic and conventional systems (1990–1993). N concentrations were significantly higher in the organic treatment in the year 1992 (P = 0.02), but there was no difference between treatments in the years 1990 and 1993.