Root distribution and water uptake patterns of corn under surface and subsurface drip irrigation

Information on root distribution and uptake patterns is useful to better un derstand crop responses to irrigation and fertigation, especially with the limited wetted soil volumes which develop under drip irrigation. Plant wate r uptake patterns play an important role in the success of drip irrigation system design and management. Here the root systems of corn were characteri zed by their length density (RLD) and root water uptake (RWU). Comparisons were made between the spatial patterns of corn RWU and RLD under surface an d subsurface drip irrigation in a silt loam soil, considering a drip line o n a crop row and between crop rows. Water uptake distribution was measured with an array of TDR probes at high spatial and temporal resolution. Root l ength density was measured by sampling soil cores on a grid centered on cro p row. Roots were separated and an estimation of root geometrical attribute s was made using two different image analysis programs. Comparisons of thes e programs yielded nearly identical estimates of RLD. The spatial patterns of RWU and RLD distributions, respectively normalized to the total uptake a nd root length, were generally similar only for drip line on a crop row, bu t with some local variations between the two measures. Both RLD and RWU wer e adequately fitted with parametric models based on semi-lognormal and norm al Gaussian bivariate density functions (Coelho and Or, 1996; Soil Sci. Soc . Am. J. 60, 1039-1049).