Die gebruik van operdwalle om 'n marginale, hidromorfe grond se fisiese toestand vir wingerdbou te verbeter

[摘要] ENGLISH ABSTRACT: Viticulture is increasingly extended to marginal soils including low-lying waterlogged soils.These soils demand Special soil management practises such as ridging.Ridging entails the heaping of the top soil in continuous bands to create favourable rootingconditions above restrictions in the deeper soil layers. This practise has been used with varyingdegrees of success, mainly because farmers used their own and sometimes wrong techniques.This research was undertaken to determine which method of ridge construction and ridge dimensions would offer optimal conditions for vine root growth.Results show that the active growing season can be devided in two periods if the soil iswaterlogged during early spring. Ridging induces favourable soil physical conditions during thewet and waterlogged first part of the season. Due to the increase in depth to the water table,dryer, warmer and better aerated soil conditions prevail during this period. These favourablegrowth conditions reflect clearly in the shoot growth tempo and leaf water potential.Low soil water content and high soil temperatures in the ridged soil had a negative on vinegrowth during the second part of the season. However, according to the total shoot growth theeffect of the initial favourable soil physical conditions dominated these negative effects.Although the unridged soil contained more available soil water during· the later stages of thegrowing season, it could not compensate for the poor growth during the beginning of theseason. The deterimental effects due to low soil water content and high soil temperatures inridges can be overcome with additional practices such as irrigation and mulching.The soil physical properties did not differ with respect to ridges of different height and width andtherefore no differences in vine reaction could be measured. The increase in depth to the watertable improved soil physical conditions to the same extent in all the ridged treatments. However,due to practical considerations, the double row ridges are recommended. Firstly, a wide troughis obtained to allow free tractor traffic without damaging the ridges. Secondly, 3700 vines can beplanted per hectare if the distance between two adjacent ridges amounts to 4,5 m, i.e. a plantspacing of 1,2 m x 1,2 m x 4,5. This is significantly more than 2700 when a conventional narrowspacing of 1,2 m x 3,0 m is used with single row ridges. Thirdly, if microjets are used, only oneirrigation line is needed for every two vine rows which implicates a financial advantage. During construction of ridges tractor traffic should be avoided on the loose soil to preventcompaction. Unstable soil should not be used for ridge construction since it may lead to run-offof rain and irrigation water. Additional soil preparation in the form of ripping to a depth of 600 mmis sufficient if the soil is to be ridged. Ripping enchances drainage if it is done in the correct slope direction. The loosened soil does not dry out to the same extent as the overlying ridged soil. Vine roots in the additional loosened soil will buffer the vineyard against dessication.Ridging impairs normal viticultural practises and it is therefor only recommended where conventional deep soil preparation and drainage cannot be done with permanent success.

[发布机构] Stellenbosch University