Concepts and methods for studying interactions of roots and soil structure

Abstract

The central concept in present-day root ecological studies in agriculture is that reduced or improved root development may decrease or increase the efficiency of using water and nutrients and thus aggravate or reduce negative environmental impacts of agriculture. The normal root development of many agricultural crops is such that chemical fertility of the soil has to be so high that residues of NO 3 and P in the soil remain at harvest which are close to or higher than those acceptable to meet environmental standards on quality of ground- and surface water. Poor soil structures, with a large fraction of the soil at a relatively large distance to the nearest macropore or crack, may affect root penetration and functioning, and thus lead to even higher residues of macronutrients at harvest. If roots are not able to penetrate the matrix of the aggregates a clustered root distribution in the cracks is the result. Negative effects on nutrient and water uptake efficiency of non-regular root distribution and incomplete root-soil contact can now be estimated from the Root Position Effectivity Ratio, R per. Aeration of roots depends on the (maximum) distance between root tissue and the nearest “breathing section”, where part of that root is in contact with air-filled macropores or cracks, on the air-filled porosity of the root and on protection against leakage of oxygen out of the root. Methods are discussed for measuring: distance in pixel images, root distribution pattern on maps, synlocation of roots and other map features, root-soil contact, root position effectivity ratio, air-filled root porosity and continuity of air channels, and dynamics of root growth and decay.