Soil organic matter changes according to the application of organic and mineral fertilizers within long-term experiments

摘要

Within the long-term field experiments at IOSDV Jable near Ljubljana (subalpine climate, heavy hydromorphic silt loam) and at IOSDV Rakican (Pannonian climate, sandy silt), the impact of organic matter management system and mineral nitrogen fertilization on the soil organic matter content was studied in the period 1998-2008. The following management systems were selected: system A - no organic matter, system B - farmyard manure ploughing in, system C - straw/catch crop ploughing in. Four different mineral N rates (NO, Nl, N2, N3) were evaluated. During the three-year crop rotation, maize, wheat and barley (or, alternatively, oats) were sown each year. The annual balance of C_(org) was calculated on the basis of the quantity of added organic and mineral fertilizers, considering the quantity of C_(org) in the soil. In system A, at both locations, fertilizing with the highest amount of mineral N resulted in a higher C_(org) content. At both locations, positive effect of organic fertilization on the increase of the C_(org) content was registered where management systems with organic matter (i.e. systems B and C) applied, while statistically significant impact of mineral N on a higher C_(org) content was determined only in system C. Within all three systems, the highest C_(org) values were reached when the highest mineral N application volume was used. After 11 years, the C_(org) content in system A decreased irrespective of the mineral N fertilization at both locations. At IOSDV Jable, a small decrease of the C_(org) content was measured in BNO, while all other treatments at IOSDV Jable and at IOSDV Rakican resulted in an increased C_(org) content. The average absolute value of difference among the C_(org) contents in 2008 and 1998 in all ten treatments at IOSDV Jable was 1.8 t/ha C_(org), while at IOSDV Rakican it amounted to 3.5 t/ha C_(org), which indicates a major influence of management system on the soil with a smaller clay content.