Regional sustainability in table grape production on saline soils
A study was done in South Africa to investigate the state of the soil salt content and its effect on plant growth on a regional rather than a point basis. The study site went through a development phase since 1996 of establishing new vineyards each year. This provided an excellent opportunity to investigate soil characteristics, plant vigour and their relationship since the start of development. Soil samples were taken and trunk circumferences were measured. The soil properties included in the investigation were soil clay percentage, ECe, soil pH value and time since initial irrigation. Exploratory data analyses were done and variograms were drawn for all data. Kriging was used to map the variables and multiple regression analysis was used to investigate their relationships on a regional basis. A number of useful observations were made. Trunk circumference as an index of growth showed a negative correlation with ECe and a positive correlation with soil pH. Trunk circumference reflected a positive growth cycle when compared with time since development. Regression analysis showed that trunk circumference as an indicator of vigour could be confidently predicted through knowledge of the vine age, soil pH and ECe and reflected upon measurement and prediction of sustainability in grape production. This approach has widespread applications for agricul ture in terms of dealing with variation in a landscape and dealing with water supply problems. Methodology that uses a regional approach rather than a point approach in management could enhance the ability to increase profitability and ultimately improve water management.