Modification of soil aggregation by watering regime and roots growing through beds of large aggregates

Abstract

The influence of root growth and soil watering regime on aggregation was studied under controlled conditions. The study examined the influence of pea (Pisum sativum cv Greenfeast), ryegrass (Lolium rigidum cv Wimmera) and wheat (Triticum aestivum cv Kite) roots on changes in aggregation and on the properties of the aggregates. The soil was a non swelling red-brown earth which was either kept wet or was allowed to wet and dry during the experiment. Root growth increased the percentage of small sized aggregates (<18mm diameter), organic carbon, tensile strength and stability of aggregates in comparison with a non planted soil. Changes in aggregate size distribution and properties of the aggregates were related to root length density of the species and also to the soil watering regime. Root length density was in the order ryegrass > pea > wheat. Wetting and drying of soil increased the strength and stability of aggregates. Incubating aggregates allowed some roots to decompose but did not increase the strength or stability of aggregates compared with unincubated soil. The results of this experiment are of practical significance in soil structural management, and in studies of soil aggregation dynamics. It may be possible to use plant roots to alter the size and properties of aggregates.

Significance of tree roots for preferential infiltration in stagnic soils

“…Roots and other soil organisms affect soil structure, but the structure also influences root growth (Angers and Caron, 1998). Materechera et al (1994) showed that roots create pores, but could also fragment soil aggregates through penetration. These findings indicate that it is impossible to specify all preferential flow paths by means of root measurements.…”

Plant: soil interactions in temperate multi-cropping production systems

“…Plant roots further affect soil structural dynamics via root exudation (e.g. EPS), which can affect soil binding and adhesion (soil aggregation) directly or indirectly via microbial activity; and water uptake, which affects slaking (Materechera et al 1994;Angers and Caron 1998;Pierret et al 2011). Such processes result in general packing effects around the roots (Clemente et al 2005), which are involved in the formation of macropores (Young et al 1998), especially when deeprooted species are grown.…”

Exopolysaccharides produced by the symbiotic nitrogen-fixing bacteria of leguminosae

“…Furthermore, they are not pathogenic and produce large amounts of EPS. In figure 3 we illustrate the appearance of colonies characterized by aggregation process is related to several factors, such as the physical properties, climatic conditions and biological activities in the soil (Materechera et al, 1994;Bezzate et al, 2000).…”