Soil organic matter changes according to the application of organic and mineral fertilizers within long-term experiments | Spremembe vsebnosti organske snovi v tleh v odvisnosti od gnojenja z organskimi in mineralnimi gnojili znotraj trajnih poskusov

English. Within the long-term field experiments at IOSDV Jable near Ljubljana (subalpine climate, heavy hydromorphic silt loam) and at IOSDV Rakičan (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 (N0, N1, 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 Corg was calculated on the basis of the quantity of added organic and mineral fertilizers, considering the quantity of Corg in the soil. In system A, at both locations, fertilizing with the highest amount of mineral N resulted in a higher Corg content. At both locations, positive effect of organic fertilization on the increase of the Corg 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 Corg content was determined only in system C. Within all three systems, the highest Corg values were reached when the highest mineral N application volume was used. After 11 years, the Corg content in system A decreased irrespective of the mineral N fertilization at both locations. At IOSDV Jable, a small decrease of the Corg content was measured in BN0, while all other treatments at IOSDV Jable and at IOSDV Rakičan resulted in an increased Corg content. The average absolute value of difference among the Corg contents in 2008 and 1998 in all ten treatments at IOSDV Jable was 1.8 t/ha Corg, while at IOSDV Rakičan it amounted to 3.5 t/ha Corg, which indicates a major influence of management system on the soil with a smaller clay content.

Slovenian. V statičnem poskusu IOSDV Jable, blizu Ljubljane (predalpsko klimatsko območje, ilovnato meljasta hidromorfna tla) in IOSDV Rakičan (panonsko klimatsko območje, meljasto ilovnata tla) smo preučevali vpliv gospodarjenja z organskimi gnojili in vpliv gnojenja z mineralnimi dušikom na vsebnost organske snovi v tleh v letih 1998 do 2008. Vključeni sistemi gospodarjenja so bili: sistem A - gospodarjenje brez organskega gnojenja, sistem B - gnojenje s hlevskim gnojem, sistem C - zaoravanje slame/podorin. Preučevane so bile štiri stopnje gnojenja z mineralnim dušikom: N0, N1, N2 in N3. V triletnem kolobarju si sledijo koruza, pšenica, ječmen/oves. Letna bilanca Corg je bila izračunana na podlagi količin dodanih organskih in mineralnih gnojil, pri upoštevanju stanja Corg v tleh. Na obeh lokacijah je v sistemu A gnojenje z največjim odmerkom mineralnega dušika povečalo vsebnost Corg v tleh. Na obeh lokacijah je bil dokazan vpliv organskega gnojenja na povečanje vsebnosti Corg, v sistemih B in C, medtem ko je bil značilen vpliv gnojenja z mineralnim dušikom dokazan le v sistemu C. Najvišje vsebnosti Corg znotraj sistemov so bile pri obravnavanju z največjim odmerkom mineralnega dušika. Po enajstih letih se je vsebnost Corg v sistemu A na obeh lokacijah zmanjšala, ne glede na gnojenje z mineralnim dušikom. Vsebnost Corg je po enajstih letih narasla v vseh obravnavanjih sistemov B in C, razen pri obravnavanju BN0 v IOSDV Jable. Povprečna absolutna razlika vsebnosti Corg med letoma 2008 in 1998 znotraj vseh deset obravnavanj v IOSDV Jable je 1,8 t/ha Corg, v IOSDV Rakičan pa 3,5 t/ha Corg. Rezultati nakazujejo, da je vpliv različnega sistema gospodarjenja večji na lokaciji IOSDV Rakičan, kjer vsebujejo tla manjši odstotek gline.