Impact of tillage on root systems of winter wheat

There is relatively little information about root growth response under different tillage systems in cool temperate regions. In a 5-yr field trial at two sites [loamy silt (1995-1999) and sandy loam soils (1996-2000)] in the Swiss midlands, the effect of tillage intensity [no-tillage (NT) and conventional tillage (CT)] on the morphology and distribution of winter wheat (Triticum aestivum L.) roots at harvest was studied for 3 yr (1997-1999). The root length density (RLD), mean root diameter (MD), and relative length per diameter-class distribution of the roots were determined using washed roots from soil cores taken from the row and the midrow. Averaged across all the other factors, NT resulted in a slightly lower RLD and a slightly larger MD compared with CT. However, compared with CT, the RLD was higher in the upper soil layer (0 to 5 cm), similar from 5 to 10 cm, and lower from 10 to 30 cm in NT. The tillage effect disappeared below 30 cm. This tillage-induced difference in root distribution was more and more marked from 1997 to 1999. In the row, the MD was greater from 0 to 15 cm, was similar down to 25 cm, and was smaller from 25 to 50 cm in NT compared with CT while below 50 cm, the MD was hardly affected by tillage intensity. However, MD in the midrow was usually significantly higher from 0 to 10 cm under NT than under CT.