Mapping the vertical distribution of maize roots in China in relation to climate and soil texture

Aims Optimizing water and fertilizer management for crops requires an understanding of root distribution. Maize (Zea mays L.) is currently the most widely planted cereal crop in China, yet the vertical distribution of maize roots across different regions remains unknown. The aims of this work were (i) to quantify the effects of climate and soil texture on the vertical distribution of maize roots, and (ii) to show the depth distribution of root biomass in China. Methods We used data of maize root biomass from 11 Chinese ecological stations with discontinuous observations from 2004 to 2014 to fit the regression coefficient beta for an asymptotic equation Y = 1 - beta(d), where d is the soil depth and Y is the proportion of root biomass from the surface to depth d. A statistical model was then developed to quantify the effects of climate and soil texture on the fitted beta values. Using the statistical model, we map the depth distribution of maize root biomass in China. Important Findings Maize root biomass in the 0-100 cm soil depth varied by an order of magnitude at different stations, from 64 to 268 g m(-2). Maize planted in sandy soils and/or maize with high accumulated temperature for development had higher root biomass and deeper rooting systems. The fitted beta values ranged from 0.785 to 0.977, which can be modeled by an integration of the accumulated temperature during the maize growing period and the soil clay and sand fractions (R-2 = 0.66, n = 50, P < 0.001). Up to 82% of maize planting regions in China showed shallower rooting systems where more than 90% and 95% of the root biomass occurred in the top 20 and 30 cm soil layers, respectively. Deeper rooting systems occurred in some temperate arid and temperate semi-arid regions, with less than 80% of the root biomass in the top 20 cm soil. Our findings highlighted the vertical distribution of maize roots, and underlined the spatial variability in the vertical distribution of roots across China's planting areas of maize.