Gør jorden let at bearbejde. Lars J. Munkholm Institut for Agroøkologi Aarhus Universitet

Transkript

1 Gør jorden let at bearbejde Lars J. Munkholm Institut for Agroøkologi Aarhus Universitet

2 Problemer med såbedskvalitet Hovedbudskaber: Jordens bearbejdbarhed/smuldreevne er meget påvirket af dyrkningen Tilførsel af organisk stof og skånsom trafik og jordbearbejdning er vigtige virkemidler Foto: Janne Aalborg Nielsen

3 Disposition Hvad er smuldreevne? Hvad påvirker smuldreevnen? Hvordan kan man bestemme smuldreevnen? Opsummering

4 Smuldreevne/bearbejdbarhed Hvad er det? God smuldreevne = let at bryde store knolde, svært bryde små aggregater Hvad siger det noget om? Jordens evne til at danne et passende såbed ved jordbearbejdning Behov for energi til jordbearbejdning

5 Hvad afhænger smuldreevne af? Jordtype Vandindhold Organisk stof Pakningsgrad

6 Smuldreevne vs. vandindhold 1,2 Smuldreevne God 1 0,8 0,6 0,4 Tør grænse Vindue i vandindhold Våd grænse Vindue i vandindhold lig tid til rettidig jordbearbejdning Dårlig 0,2 0 Tør Vandindhold Våd Munkholm et al, 2011

7 Smuldreevne vs. vindue i vandindhold HUG NPK Ugødet tør våd optimal Vandindhold g 100g -1 Munkholm et al., 2002

8 Smuldreevne vs. organisk stof Smuldreevne indeks Askov jorde Rothamsted jorde Kulstofindhold (g 100g -1 ) Schjønning et al., 2009

9 Organisk stof og energiforbrug 10-20% reduktion i energiforbrug ved pløjning i canadiske og engelske forsøg (McLaughlin et al., 2002; Watts et al., 2006)

10 Effekt af pakning og intensiv harvning Vægtet middel knoldstørrelse (mm) cd c a Effekt af org. stof b c d 0 MIN-REF MIN-ROT MIN-PAC ORG-REF ORG-ROT ORG-PAC Behandling Abdollahi et al, 2014

11 Undgå den onde cirkel Lavt kulstofindhold Lille tilførsel af org. stof Intensiv jordbearbejdning Dårlig smuldreevne Lav strukturstabilitet Hård ved udtørring Lille vindue i vandindhold 11

12 Hvad kan gøres? Strukturopbygning/stabilisering Organisk stof tilførsel Halm, husdyrgødning, sædskifte, efterafgrøder Kalkning Trafik Undgå kørsel på våd jord Dæktryk Jordbearbejdning Optimeret rettidighed Behovsbestemt intensitet 12

13 Visuel vurdering - VESS metoden 13

14 Structure quality Size and appearance of aggregates Visible porosity and Roots Appearance after break-up: various soils Appearance after break-up: same soil different tillage Distinguishing feature Appearance and description of natural or reduced fragment of ~ 1.5 cm diameter Sq1 Friable Aggregates readily crumble with fingers Sq2 Intact Aggregates easy to break with one hand Sq3 Firm Most aggregates break with one hand Mostly < 6 mm after crumbling A mixture of porous, rounded aggregates from 2mm - 7 cm. No clods present A mixture of porous aggregates from 2mm -10 cm; less than 30% are <1 cm. Some angular, non-porous aggregates (clods) may be present Highly porous Roots throughout the soil Sq1 Smuldrende Most aggregates are porous Roots throughout the soil Macropores and cracks present. Porosity and roots both within aggregates. Fine aggregates The action of breaking the block is enough to reveal them. Large aggregates are composed of smaller ones, held by roots. Sq5 Meget kompakt High aggregate porosity Low aggregate porosity Aggregates when obtained are rounded, very fragile, crumble very easily and are highly porous. Aggregate fragments are fairly easy to obtain. They have few visible pores and are rounded. Roots usually grow through the aggregates. Sq4 Compact Requires considerable effort to break aggregates with one hand Mostly large > 10 cm and sub-angular non-porous; horizontal/platy also possible; less than 30% are <7 cm Few macropores and cracks All roots are clustered in macropores and around aggregates Distinct macropores Aggregate fragments are easy to obtain when soil is wet, in cube shapes which are very sharp-edged and show cracks internally. Sq5 Very compact Difficult to break up Mostly large > 10 cm, very few < 7 cm, angular and non-porous Very low porosity. Macropores may be present. May contain anaerobic zones. Few roots, if any, and restricted to cracks Grey-blue colour Aggregate fragments are easy to obtain when soil is wet, although considerable force may be needed. No pores or cracks are visible usually. Ball et al., 2007; Guimaraes et al., 2011

15 Opsummering Jordens smuldrevne er vigtig i forhold til såbedskvalitet og meget påvirket af vandindholdet og dyrkningen. Sæt gang i den gode cirkel. Tilførsel af organisk stof, skånsom trafik, behovsbestemt jordbearbejdning gør jorden let at bearbejde. Følg udviklingen i marken.

16 Tak for opmærksomheden