Nutrient management in table and wine grapes by fertigation.

摘要

Under drip irrigation, the dense rootlet system that develops under the drip emitters is spread in an onion-shaped limited volume of soil. A gradient of soil water potential that varies between saturation in the pooling area under the drippers to wilting point at the edges of the wetted soil exists under frequent irrigation regimes. An opposite gradient of aeration consisting of high aeration at the periphery of the wetted soil to almost zero aeration under the drippers maintain simultaneous high water availability without interference with root aeration. Soluble mineral application by fertigation through drip emitters results in concentration gradients of the various elements according to their mobility in the wetted soil. Element such as K and P are slow movers and tend to concentrate near the pooling area, whereas nitrates and chlorides move fast and tend to concentrate at the edges of the wetted zone. The ability of individual roots to exchange water and minerals enables root growth and extension beyond the wetted soil zone. The composition and concentration of the soil solution can be monitored and controlled by the use of soil extractors and field kits for rapid analyses. Blade and petiole mineral analyses made at full bloom stage and before harvesting serve as an efficient tool for optimizing production and quality. Petiole analyses better reflect the mineral status of the vines. The control of NPK fertigation by means of soil extractors, blade and petiole analyses, and water availability significantly affect fruit bud fertility, sugar, pH, maturation time and fruit flavour.