Due to the huge economic growth in the Western Cape, water is scarce. At Rijk’s Private Cellar we use our water as efficiently as possible, only irrigating when 100% necessary. To improve the quality of the grapes and save water, ” regulated deficit irrigation” is practised.
Regulated Deficit Irrigation (RDI)
To use RDI, you must have soils that dry out quickly. And drain well. Our shale soils do this. And you must be able to monitor the soil moisture in each block so you know when to irrigate. In the growing season, from 1st week September to harvest time, last week January, each blocks moisture content is monitored. Every Monday and Thursday of each week a complete visual inspection of each blocks growth, canopy and general health is recorded. Three holes per one hectare block down to 800mm are then dug. A handful of the soil is then “squeezed” and a score of zero for completely dry to 10 for completely saturated is recorded. This data is then downloaded onto the computer and evaluated. The amount of water to be irrigated is then determined depending on the cultivar and time of the growing season. Irrigation takes place at night to reduce the effect of wind and heat evaporation. This is a labour and time consuming task, starting at 6 am and finishing at 3 pm each day.
Why do we do all this?
In the growth stage of the vine and the bunch development each season, the vine needs water and nutrients from the soil to produce strong shoots with lots of leaves. The leaves are the “factory“ that the grapes need to produce excellent grapes. When the bunches reach “pea size “, cell multiplication takes place and the bunches get bigger, more juicy and sugar starts forming. At this point, depending on the cultivar, we stress the vine by restricting water and nutrients to the root zone.
The effect
By stressing the grapes between pea size and veraison, we get small tight bunches, small berries, reduced amounts of juice in the grape, and reduced tonnages. The ratio of juice to skins of the berry is also reduced. This results in thicker skins, giving ripe fruit flavours and fully concentrated grapes. And then picked in the cool of the night at optimum ripeness, the rewards of our efforts are reflected in the wines.
Dam Storage
The western cape has a Mediterranean climate. Winter rains and dry summers. We have registered water rights to extract water from 2 rivers in winter when the rivers are in full flow. This water would otherwise flow out to the sea. Our 2 dams have a total capacity of 250,000 cubic metres. The water is then pumped into the dams and then stored for the summer when all the required irrigation takes place. Due to the evaporation caused by sun and wind, one third of the water in the dam is lost. The usable amount of water therefore is reduced to 175,000 cubic metres. This is required for irrigation of the vineyards, and also for drinking.