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Rapport2007Öppen tillgång

Broddharvning på våren i höstvete: inverkan på ogräs, kväveomsättning och skörd : slutrapport från försök 2003-2005

Myrbeck, Åsa; Rydberg, Tomas


Within organic farming, chemical weed control is prohibited and is generally being replaced by different tillage practices. At the same time the supply of sufficient amounts of nitrogen is often a problem within organic fanning. In cereal crops, harrowing is considered to be one of the most important mechanical weeding techniques. The loosening and aerating of the soil produced by harrowing should potentially enhance nitrogen mineralization. Furthermore, harrowing could enhance the soil structure and water content, since tillage is generally known to positively affect these soil factors through mechanisms such as crust breaking and enhanced tillering in cereals. This study investigated the effects of mechanical weed control in the spring on weeds, nitrogen mineralization and yield of winter wheat. Weed control was carried out when the crop had 2-3 leaves. Three different implements were tested on two soils differing in clay content for three consecutive years: A Väderstad Crosskill roller, an s-tine harrow and a spring tine harrow, and compared with untreated controls. Soil mineral nitrogen in the 0-10 and 10-20 cm layers and total nitrogen content of the crop were determined on several occasions for calculations of net nitrogen mineralization in the soi1. The numbers and weight of weeds were recorded one month after harrowing and at the time of harvesting. Grain yield was measured at harvest. The amount of dicotyledonous weeds was reduced by harrowing. On the soils with the lower clay content, weed numbers were reduced to between 50 and 82% of those in the control, while on the soil with the higher clay content they were reduced to between 42 and 82% of those in the control. On average, the best effect on the lighter clay soils was achieved by use of the s-tine harrow, while on the heavier clay soils the Väderstad Crosskill roller and the spring-tine harrow had the best weed control effect. In the harrowed treatments, the average mineral N content in the 0-30 cm layer was enhanced by only 0.4 kg ha?¹. At the same time the N uptake in the crop was reduced by approximately the same amount due to the crop suffering mechanical damage, and calculations of net nitrogen mineralization showed no increase in N mineralization after harrowing. Despite annual variations, harrowing in general had a positive effect on grain yield. Comparing the different implements, the best yields on the lighter clay soil were achieved by use of the spring tine harrow, which increased the yield compared with the control by an average of 5% in two years out of three (2002-2005). The best results on the heavier clay soils were achieved by use of Väderstad Crosskill roller, which gave a 5% yield increase compared with the control, while the use of spring tine harrow and s-tine harrow caused a yield reduction of about the same magnitude. On both soil types, the use of an s-tine harrow had a negative effect on wheat yield, probably due to a high degree of mechanical damage to the crop


jordbearbetning; broddharvning; höstvete; ogräs; kväveomsättning; skörd; skorpbrytning; vattenhalt; kvävemineralisering

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Rapporter från Jordbearbetningsavdelningen, Sveriges lantbruksuniversitet
2007, nummer: 111
Utgivare: Institutionen för markvetenskap, Jordbearbetningsavdelningen, Sveriges lantbruksuniversitet