While maize rooting depth at anthesis varies from around 0.7 m to close to 1 m, approximately 90% of the root system is recovered from the top 0.3 m of soil (Dwyer et al., 1996). In the 0–25 cm topsoil layer, the RLD of 478 was one- to threefold more than that of Wu312 at 93 DAS, also the RLD of 478 in the subsoil layer from 25 to 55 cm deep was higher than that of Wu312, when plants had the largest root dry weight and root length. Better root development is favourable for N acquisition. On the other hand, the difference in RLD between the two genotypes was larger than that for RDWD especially in the topsoil profile (Fig. 7; Supplementary Figs. 2 and 3). The results indicated that 478 had longer
lateral roots than Wu312. Fine roots have a positive effect on N uptake rate for Kentucky bluegrass, while there is no relationship
between the thick ones (diameter >0.5 mm) and N uptake rate
(Sullivan et al., 2000). In a field experiment with 10 maize cultivars,
nitrate depletion and root length densities in the subsoil layer are
closely correlated