oa Agrochemophysica - The response of grapes to a manipulation of the soil-plantatmosphere continuum : I : growth, yield and quality responses

Volume 12, Issue 4
  • ISSN : 0302-7112



A group of twelve lysimeters was used to study the effects of five different soil water regimes varying between 0 and � lOOkPa soil water potential, on the yield, fruit quality and vegetative growth of grapevines over two seasons. The treatments were applied separately during two growth stages according to a central composite rotatable statistical model with two x-variables denoting the two growth stages, thus enabling predictions of optimum treatment combinations for the different response parameters. The majority of the parameters were highly correlated to soil water regime. Yield was strongly influenced by the soil water potential, even though the maximum stress applied was not severe. The first growth stage, which extended from budbreak to the start of fruit ripening, had a dominant effect on yield in general, and an optimum combination regime of 82/12 (Phase 1/Phase 2) in terms of per cent available moisture is predicted. The optimum for yield in terms of soil water potential is predicted at �5 ,3 / �27,5 kPa. The quality parameters were influenced by the treatments in both growth stages, and the effects were opposing. A wet soil water regime during Phase 2 (ripening stage) had a positive influence on ent and berry quality, while a wet regime during Phase 1 had detrimental effects on sugar/acid ratio, berry-cracking and the number of loose berries after cold storage. The predicted optimum in terms of quality is set at 70/85 per cent available moisture or �15,0/ �5,0 kPa soil moisture potential. Shoot and root growth, stem circumference, leaf surface area, as well as stomatal concentration, were strongly affected by the soil water regime during Phase 1, and a wet regime is favourable. Phase 2 had very little effect on the vegetative growth. All the evidence points to a combination regime of 70/85 % available moisture (Phase 1 /Phase 2) producing the best results in terms of all the growth and physiological parameters nvestigated.

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