The vineyards are growing fast now with the increase in temperature. Most of the canopy management practices has been done. All that is left is crop control and then a quick holiday before the start of the 2011 harvest season.
Weeds seem to be a major problem for the past three years. This is mainly due to the spring and summer rains, which we are not used to. This pose a big threat for dryland vineyards like ours, specially in a dry year that we are experiencing this year. Not only does it take up essential moisture, but some weeds excrete toxic elements that can negatively impact on the vineyards.
Downy Mildew is under control up to this stage. There are some places in Cabernet Sauvignon and Mourvedre where there are some damage to the bunches, but it is hardly 1%. The spraying programmes were followed very strictly this year, and with great results.
I foresee a good harvest, but to make it excellent we will need about another 40mm rain. But we'll see what happens.
Nothing exciting happened this week. So what do I write about. Its been a while since I posted useful information. So I came across some photos I took last year in a vineyard. This was the most amazing piece of land. Fertile, rich in humus and had earthworms as big as baby snakes, but small in comparison to the worm you'll see in the video!!
So, what makes these guys so important for me to write about? Its just worms right? Right?
Not really. Here is the deal on earthworms:
There are approximately 2700 different kinds of earthworms. The South African Giant Earthworm grows to be up to 6.7 meters (22 feet) and is the largest earthworm known. The record-setting specimen was found beside a road in William's Town, South Africa, in 1967. The worms normally grow to only about 1.8 meters (6 feet).
Earthworms prefer neutral to alkaline soils. They travel underground by means of waves of muscular contractions. The whole burrowing process is aided by the secretion of lubricating mucus. Their tunnels aerate the soil and contributes to overall soil health.
Furthermore, earthworms converts large amounts of organic matter (e.g. dead leaves) into rich humus, improving soils fertility and structure. The worms breaks pieces of organic matter off, eats it and during the digestive phase it gets mixed with dirt and digestive enzymes. It is then excreted and the deposits can been seen on the soil surface as little granular heaps of soil called "worm casts" or "vermicasts".
Research has show that fresh earthworm casts are 5 times richer in available Nitrogen, 7 times richer in available Phosphates and 11 times richer in available Potassium than the surrounding upper 6 inches (150 mm) of soil. The casts has better porosity, aeration, drainage and moisture holding capacity than normal compost. This has an enormous impact on the immediate soil environment, especially surrounding the root system.
Having this information, we try to add as much organic material to the soil as possible. This is done by putting straw in the vineyards, or compost. The more organic material you have in the soil, the more food there is for the earthworms to digest and to convert into more useful nutrition.
Here are the guys I photographed in the vineyards:
Tipping is part of canopy management and involves removing the top 2cm of the growth tip of a shoot. There are several reasons for tipping a vineyard.
Early in the season, vineyards that grow unevenly gets tipped to give the slower shoots a chance to catch up. By removing the growth tip you temporarily change the flow direction of nutrients and water in that shoot from upwards to downwards. This means that the other shoots gets a chance to grow to the same length so that you have a more uniform canopy.
This change of trans location direction also helps the shoot to attach firmer in the base eye. This helps the shoot to withstand wind a bit better.
Tipping also helps create side shoots. This is new growth with new leaves, which means new photosynthetic stations. It is important not to tip too early. You want to have a minimum of 5 leaves above the second bunch. Anything less will create a side shoot below the bunch and that shoot will take more energy away from the bunch.
Lastly tipping is done late in the season to stop/control vegetative growth in the vigorous blocks. This is to force the plant to contribute most of its water and nutrients to the bunches instead of new growth. Ideally, a vineyard block should be managed so that no tipping is necessary after Véraison (the onset of ripening visible through the change of color of the grape berries).
Tipping can be done with manual labour (the best way - better control as to the amounts taken off) or mechanically.
Here is a mechanical tipping mechanism.
That is pretty much the info you need on tipping. Here is a picture of a little warrior of the vineyard to end this post...
Soil preparation started on Tuesday. The soil is a sandy-loam soil, with a suitability rating of 7/10 for vineyards. It has a 50% coarse laterite layer from 45cm - 90cm. The area is 4ha big and will be planted with Carignan.
Soil preparation starts off with soil sampling - chemically and physically. Then the soil needs to get "loosened". This is to break the compacted zones and is done with a big ripper. A normal tractor cant be used for this and we usually use a D9 or D8 Caterpillar bulldozer for this job.
The importance of soil preparation must never be under estimated. It is the one chance you have to give the vineyard a better root developing chance and to set your chemical imbalances right to a reasonable depth. Once the vineyard is planted it is very difficult to do adjustments deeper that 30cm.
In this case we use a D8R Caterpillar. For the technical people you can read the specifications on this dozer here.
I don't have much more to say on this topic now, but the pictures are pretty much self explanatory.
Yes, it's that time of the season again. Unpredictable weather, flowering time and stressed farmers. Last year was an absolute nightmare for the South African wine industry with regards to this disease. This year we are prepared, but it is still a very dangerous and active threat.
Downy Mildew, Plasmopara viticola, overwinters in leaf debris as oospores and are immune to any fungicides. As soon as the temperature rises in spring time, (above 10 degrees Celsius ) accompanied by a minimum of 10mm rain, these spores germinate. They are now called zoospores. These spores penetrate the cells on the leaves at an early stage (6-8 square cm). As soon as this infection has taken place, the first symptoms are visible.
Primary signs are the formation of yellow "oily" stains on the front surface of the leaf which are visible 6-13days after infection.
Once the zoospores are dispersed they swim to the stomata, enter by forming germ tubes and invade inner plant tissues.
Secondary infection is associated with the production of more spores, visible at the back of the leaf. The germination or these spores are dependent on the availability of moisture and humid conditions.
Weather predictions play an integral role in the control strategy of Downy Mildew. Spraying before rain gives substantially better control than spraying after the rain.
Warning systems are in place to warn the respective wine growing areas when favourable conditions will occur.
The damage to the grapes obviously doesn't lay in the effect it has on the leaves, but rather in the bunches. If Downy Mildew progresses to the bunches, it has devastating effects. The berries dries out completely and the whole bunch can die. This is why preventative control is very important.
To the left are close ups of the zoospores.
Here are some photos of the damage Downy Mildew inflicted on a Cabernet Sauvignon block in the 2010 harvest.
