Rainfall Interception by Corn Plants. First Part : Development of a Method to Quantify the Stemflow in Corn.

When rain falls in a crop, it is redistributed into three elements, namely stemflow, throughfall, and plant storage. While the throughfall reaches the soil in a similar way to unmodified rainfall, the stemflow concentrate the water towards the root zone and the water stored in the plant surface evaporates. This suggests that the interaction of rainfall with vegetation influences processes of great concern to environmental scientists and engineers such as evapotranspiration, rainfall-runoff relationships, distribution of soil moisture, soil erosion, ground water quality, and others. Our work was done in two stages. The first was purely qualitative, when the interaction of rainfall with the crop was observed for different stages of plant development. The second stage involved the development of an instrument to measure the stemflow rate and accumulation. The design of the stemflow meter was based on a tipping bucket rain gauge modified to collect the water flowing on the stem of the plant instead of rain. We installed the prototype in a fully developed plant and a regular rain gauge in the vicinities of the field to be used as reference. There is no consensus in the current literature on how to compare the volumetric stemflow rate to rain gauge data. We show some methods and propose one that we consider suitable for fully developed plants. So far our results suggest that the stemflow accounted for almost 90% of the total rainfall, being an important element of the partitioning of rainfall by the considered plant. It is to be noted that our experiment is in early stages and our results reflect the behavior of one single plant and cannot be generalized to the whole field and to other stages of development. A complete experiment with independent measurements of stemflow, throughfall, rainfall and other variables is yet to come.