Distribution of roots and root length density in a maize/soybean strip intercropping system

In a field experiment in the Yellow River Basin conducted in 2007 and 2008, it was found that, under full irrigation, the roots of maize not only penetrated deeper than those of soybean but also extended into soybean stands underneath the space between inner rows of soybean. The roots of soybean, however, were confined mainly to the zone near the plants. Horizontal growth of the roots of both the crops was confined mainly to the soil layer 16–22 cm below the surface, a layer that lay above an existing plough pan. Root length density (RLD) was much higher in the top layer (0–30 cm deep) and in the zone closer to the plants. The exponential model proved suitable to describe the RLD vertically and horizontally in both sole cropping and in intercropping.