Cultivar differences in spatial root distribution during early growth in soil, and its relation to nutrient uptake - a study of wheat, onion and lettuce

A study was made to quantify early root development, soil exploitation and nutrient uptake in spring wheat, onion and lettuce, and their variation among cultivars. The goal was to study genetic variation in root traits making cultivars better adapted to organic production systems or other low-input systems. Six cultivars of each species were grown in transparent tubes to allow direct observation of early root growth. The tubes were 0.3 m deep, and 0.24 m in diameter. By placing the plants close to the edge rather than at the centre of the tubes, we could quantify the spatial distribution of the root systems as well as the general root growth and nutrient uptake. Root growth of wheat and lettuce was faster than root growth of onion, and onion showed little capacity for horizontal root system development. Significant variation in early root growth and horizontal spread of the root system was found among cultivars of all three species. In general, cultivars with strong growth and high volume of soil exploitation showed higher average nutrient concentrations. Early shoot growth, root growth and nutrient uptake are intrinsically linked, making it difficult to determine whether improved root growth was the primary cause of improved performance. However, we did find cultivars where the strong root growth and superior root distribution seemed to be the driver for improved overall growth.