Impact of tillage on maize rooting in a Cambisol and Luvisol in Switzerland

Soil conditions under no-tillage (NT) are often unfavorable for the growth of maize roots in comparison to conventional tillage (CT). In 1997 and 1999, the impacts of tillage on the morphology and spatial distribution of maize (Zea mays L.) roots at anthesis were investigated in a 5-year field trial at two sites (loamy silt and sandy loam soils) in the Swiss midlands. Four soil cores, perpendicular to the maize row, were taken to a depth of 100 cm in each plot; the root length density (RLD), the mean root diameter (MD), and the relative length per diameter-class distribution (LDD) of the roots were determined.

Roots were longer and thinner in 1999 than in 1997. The RLD was significantly higher and the MD was smaller on the loamy silt than on the sandy loam. The RLD and MD decreased with the distance from the plant row. Most of the maize roots, about 80% of the total root length, were in the layer from 0 to 40 cm, with maximum values from 5 to 10 cm; the thickest roots were in the soil layer from 10 to 50 cm. Significant differences in RLD with increasing distance from the row of plants were found in the top 30 cm.

Averaged over the whole soil profile, RLD was higher and MD was smaller under CT than under NT. The impact of tillage on RLD and MD interacted with spatial factors and years. Within the soil profile, RLD was significantly higher under NT than under CT at a depth of 5 cm, whereas it was higher under CT than under NT below 10 cm. Below 50 cm, there was no difference in RLD between the tillage systems. In a horizontal direction, MD was consistently higher in the row and lower in the mid-row under NT than under CT.

Our results show that differences in maize root growth between tillage systems, which were reported in previous studies, persist until anthesis. The accumulation of maize roots near the soil surface in NT suggests that subsurface-banding of starter fertilizer is a more efficient way of applying fertilizer (particularly immobile nutrients such as phosphorus) compared with broadcasting in order to supply sufficient nutrients for NT maize.