Abstract

Early autumn cultivation of soil is known to stimulate nitrogen (N) mineralization and increase the risk of N leaching from arable land. This is due to mineralization of soil organic matter and high release of nitrate after mechanical disturbance at a time when soil temperature still allows high microbial activities. Nitrogen uptake in winter wheat is rather low, often not more than 10-15 kg ha⁻¹. Therefore, N mineralized due to conventional establishment of winter wheat is at risk of leaching during autumn and winter, especially if the preceding crop leaves a lot of N in the soil and in its crop residues, e.g. oilseed rape. This project studied the extent to which direct-drilling or shallow cultivation using Väderstad Carrier (5-7 cm) or stubble cultivation (10-12 cm) instead of conventional establishment after early moldboard ploughing could mitigate N mineralization during autumn, and how it affected crop establishment and yield. One-year field trials with three replicates were established at three Swedish sites in autumn 2002 and studied for three consecutive years. All four techniques for establishment of winter wheat (including direct-drilling) resulted in more soil mineral N in comparison with untreated soil. The increase after direct-drilling compared to no treatment varied between 5-36 kg N per hectare and was possibly explained by faster release of N from the oilseed rape residues. Two weeks after sowing, the soil profile contained on average 10, 5 and 7 kg less soil mineral N after direct-drilling than after moldboard ploughing in a light clay soil in Skåne, a light soil in Västergötland and a heavy clay soil in Uppland respectively. Shallow cultivation resulted in -3 kg, +11 kg and -10 kg less mineral N per hectare compared with moldboard ploughing in Skåne, Västergötland and Uppland respectively. In Skåne, soil mineral N increased with increasing tillage depth. At the two other sites, however, there was no clear relationship between tillage intensity and soil N content. In Västergötland shallow cultivation resulted in more soil mineral N than moldboard ploughing, while in Uppland direct-drilling resulted in more soil mineral N than shallow tillage. Comparing moldboard ploughing and shallow tillage, soil mineral N during autumn after establishment of winter wheat was more dependent on the timing of tillage than tillage method. Average values of all nine experiments showed that net mineralization was 8% lower after direct-drilling than after primary tillage and sowing (moldboard ploughing or shallow tillage), while compared to moldboard ploughing it was 20% lower. Reduced tillage, especially direct-drilling but also shallow tillage, increased the amount of weeds in spring compared with moldboard ploughing. However, these treatment differences disappeared after herbicide application in summer, and thus with normal spraying, the effect of reduced tillage on weeds was not a problem. Direct-drilling resulted in a 2% yield reduction compared with moldboard ploughing. The highest wheat yields were obtained after stubble cultivation and Väderstad Carrier. From an economic point of view, direct drilling or shallow cultivation to establish winter wheat is preferable to conventional moldboard ploughing.

Keywords

jordbearbetning; höstvete; oljeväxter; kvävenyttjande; nettomineralisering; mineralkväve; ogräs

Published in

Rapporter från Jordbearbetningsavdelningen, Sveriges lantbruksuniversitet
2008,
Publisher: Institutionen för markvetenskap, Jordbearbetningsavdelningen, Sveriges lantbruksuniversitet

Permanent link to this page (URI)

https://res.slu.se/id/publ/126000