Aggregate water-stability, particle-size and soil solution properties in conducive and suppressive soils to Fusarium wilt of banana from Canary Islands (Spain)

The influence of several soil properties on soil conduciveness or suppressi veness to disease caused by the soil fungus Fusarium oxysporum f. sp. cuben se was studied in seven field plots of banana plantations, situated in Tene rife and Gran Canaria islands (Canary Islands, Spain). In each plot, soil s amples were taken in conducive and suppressive areas to Fusarium wilt. Wate r-stable aggregates (WSA: 200-2000 mum diameter), soil particle size, and s elected soil solution characteristics [pH, electric conductivity (EC) and s oluble Na] were determined in the samples. Aggregate water-stability was hi gher in soils of conducive areas than in suppressive areas. The percentage of WSA in the conducive areas ranged from 460 to 330 g kg(-1), while in the suppressive areas the maximum value was 285 g kg(-1) and the minimum was 1 50 g kg(-1). The soils had high clay content and the EC and soluble Na tend ed to be higher in suppressive areas than in conducive areas. Soil solution pH was lower in conducive areas (except sites 1 and 9). Our data provide e vidence that in different soil areas of the same plot, the structural stabi lity of aggregates, presumably controlled in part by the clay fraction, sol uble Na concentration and EC, is of great importance for the conduciveness or suppressiveness to banana wilt caused by Fusarium oxysporum f. sp. cuben se of the soils studied. Finally, we hypothesize that a greater stability o f the aggregates forming anaerobiosis could partly explain most of the avai lable Fe found in soil areas where the disease was severe, at least in thes e types of soils. (C) 2001 Elsevier Science Ltd. All rights reserved.