Dry soils = demand for good soil moisture information

ICYMI: This week Derek Cameron and Joe Siebert both presented on the use of moisture sensors to avoid water stress.  

We are about to install 50x new moisture probes to get them operational before the grape and horticulture season begins. This is the highest amount in a month since we started the service back in 2007. 

There is huge interest in soil moisture levels!

This season we have been defient in rainfall. 

Consider the role evapotranspiration has in soil moisture. On many occasions so far this year the daily evapotranspiration rate has been higher than the daily rainfall.

We have a net loss of soil moisture when the daily evapotranspiration rate is greater than our daily rainfall. When rainfalls and it is less than the daily evapotranspiration rate it gets used up by plants or lost through evaporation and doesn’t increase soil moisture.

The volume of rainfall is not enough to go past the immediate topsoil.

We have a net loss of soil moisture through long periods of this year.

An measure of rainfall I have charted “effective rainfall” which is the daily rainfall vs. daily evapotranspiration - ABOVE. Unless the blue daily rainfall (mm) column is greater than the orange Evapotranspiration (mm) column than there was a net loss of soil moisture for that day. 

Irrigation at budburst is being recommended by many "in the know" to make up for this shortfall. 

Contact James Hook for more information - james@djsgrowers.com.au

Soil types of the McLaren Vale Wine Region

Sand (11% of the McLaren Vale Wine Region - mainly located in Blewitt Springs and McLaren Flat)

PIC: Sandy soil with clay and gravel at 1.0 metres depth. Did you know? Sandy soils generally have clay/gravel underneath, sometimes this is at greater than 3 m depth, and often vineyards on the tops of hills have more vigour than those at the bottom!

NOTES:

Topsoil: sandy with a gravelly and bleached horizon.

Subsoil: yellow and red sandy clay loam to clay.

Drainage: well drained but seepage can occur in the gravel layer above the clay, creating a subsoil waterlogging problem.

Natural fertility: Low. Cation capacity is low. Organic carbon is often very low. 

Salinity and sodicity issues: generally not an issue but localised salinity can be introduced by seepage water.

Black Heavy Clay - "Bay of Biscay" (7% of the McLaren Vale Wine Region)

PIC: Heavy black, cracking Biscay Clay.

NOTES:

Topsoil: black cracking clay (sometimes self-mulching) with increasing amounts of soft carbonate.

Subsoil: black clay grading to grey-green heavy clay.

Drainage: imperfect and leaching of salts can be an issue.

Natural fertility: deep and inherently fertile but difficult to work, especially when wet.

Salinity and sodicity issues: are possible in these soils with some naturally saline and/or sodic.  Irrigating with marginal water can make these problems worse.

Other: boron toxicity problems are possible in these soils.

Loam over red clay - "Urrbrae Loam" (26% of the McLaren Vale Wine Region)

PIC: The famous Urrbrae soil. 

Topsoil: silty loam to silty clay loam.

Subsoil: red clay with increasing soft carbonate at depth. 

Drainage: moderately well drained.

Natural fertility: deep and inherently fertile. 

Salinity and sodicity issues: soils are generally not naturally saline or sodic but problems can occur due to the accumulation of salt from irrigation water. Often vineyards with these soils are irrigated with bore water. 

Other: Main limitations are related to poor structure due to the high silt content of the surface soils and susceptibility of the upper part of the profile to compaction. These soils compact with repeated tractor driving. 

“Terra Rossa” like soil (20% of the McLaren Vale Wine Region) 

PIC: Terra rossa (means red soil in italian) soils occur many areas of the world. Compared to most clayey soils, terra rossa has good drainage characteristics. This makes it a popular soil type for food and wine production. Among other wine regions, it is found in La Mancha in Spain and the Coonawarra locally. 

Topsoil: clay loam increasing clay content.

Subsoil: highly calcareous clay loam to clay.

Drainage: well drained.

Natural fertility: moderate to high fertility. 

Salinity and sodicity issues:   SImilar to Urrbrae soil, salinity or sodicity problems can occur due to the accumulation of salt from irrigation water.

Sandy loam over brown clay - "Gilgai" (24% of the McLaren Vale Wine Region)  

PIC: Soil from near Rifle Range rd, between Willunga and McLaren Vale. 

Topsoil: grey massive sandy loam grading to bleached loamy sand.

Subsoil: brown mottled poorly structured clay with soft carbonate at depth.

Drainage: imperfectly drained. 

Natural fertility: shallow with moderate fertility. 

Salinity and sodicity issues: soils are not naturally saline but due to the poor drainage and sodic nature of the clay, salts can accumulate in the top clay layers and cause salinity issues.

Other: Water can perch on the poorly structured subsoil clay saturating the upper profile for up to several weeks after prolonged rain.

NOTES BY JAMES HOOK - DJ's

Iprodione update: change for Vintage 2019.

During the last growing season (2017/18) a European Union decision was taken to withdraw authorisations for plant protection products containing iprodione as an active constituent. You would know iprodione for its use as a late season Botrytis product for use in grapes (Rovral, Corvette, Ippon etc).

The latest information from the AWRI is that iprodione not be applied to wines targeted for export markets (published in their latest Dogbook), many wineries have now determined that products containing iprodione can no longer be applied to grapes destined for export.    

It is not recommended to use iprodione unless you are only selling wine domestically. 

Precision spreading in vineyards with Platfarm software

This video is about using DJ's application maps for precision spreading with Platfarm. 

To enquire about how precision spreading can improve your farm business ask Joe Siebert (as featured in this video) e= joe@djsgrowers.com.au. 

What to do after a dry summer?

After tough vintage, with a dry summer, the obvious reaction is to build up your vines. Many growers think of incorporating animal or chicken manure into the soil. They see piles of manure and think;  "I'm adding a lot of organic matter and goodness to the soil."

Manures are actually organic material, not organic matter. Manures need to be broken down by micro-organisms to work. Manures are unstable in the soil and as much as 90 percent of it disappears by decomposition.

A good test is to buy manure now and compost it for a year. Record the weight difference.

What you need is organic matter which is stable in your soil.

What's the difference between organic material and organic matter? Organic material is anything that was alive and is now in or on the soil. For it to become organic matter, it must be decomposed into humus. Humus is organic material that has been converted by microorganisms to a resistant state of decomposition.

Organic matter is stable in the soil. It has been decomposed until it is resistant to further decomposition.

Products that are fully composted are the equivalent to many tonnes of chicken or animal manure because it consists of Humic material and Organic Carbon both of which are stable and long lasting in your soil.

Creating management zones

DJ's Growers are able to help you create targeted managment zones within your vineyard using satellite images to quantify variabilty within your block. Specifically, we can provide you with satellite NDVI imagery for the 2017-18 growing season.

Once ground-truthed, we can help you develop prescription maps for variable rate inputs such as fertiliser, compost, or mulch or help you to perform targeted testing and diagnosis for other limitations within the site.

DJ's Growers can help you save money by targeting inputs specifically where you need them this winter, and by reducing hotspots for disease in your vineyard through the spring/summer months.
We can also help you make more money from your fruit by improving uniformity and fruit quality, and in optimising harvest maturity within the block.

Please view the short video below (click image) or send us an email to learn more about how we can help grape growers in McLaren Vale this winter with imaging and mapping.

Post Harvest Fertiliser and Irrigation in Grapevines.

Summary from GWRDC research.

A vineyard with leaf scorching at the point of harvest (E-L 38). 

The importance of the post-harvest period is largely determined by climate, variety, yield, and management prior to harvest. Vines will tolerate a season or two with limited post-harvest irrigation, but productivity will eventually be reduced if this continues over many seasons. Although beyond the scope of this module, the importance of long term planning needs to be emphasized if water shortages are expected to continue. This includes understanding that cropping levels, together with effective salinity management, are two key factors in determining the sustainability of vines with reduced water supply.

Uptake of other minerals may be equally important during the post-harvest period, but relative to nitrogen, a lot less is known as to their role as reserves. The cycling of nutrients, and thus ability to store and re-mobilize again in spring, depends on their mobility within the plant. This is high for all the macronutrients, except calcium, which has low mobility. With the exception on manganese, which is also low, all the other micro nutrients have intermediate mobility.

As a rough guide to the relative importance of different nutrient reserves (where such information exists), studies with whole mature vines have shown that about 50% of nitrogen and phosphorus in the new seasons canopy comes from stored reserves. Around 15% of potassium comes from reserves, but less than 5% of magnesium and calcium.

A considerable proportion of these nutrient reserves can be up-taken and stored in the post-harvest period the previous year, with about one third of the annual nitrogen and phosphorus requirements stored after harvest, and about 20% for magnesium and calcium, and 15% for potassium. As indicated by some macro nutrient level increases during the post-harvest period, the application of fertiliser during this period allows nutrient status to improve and reduces potential deficiencies in the following growing season. It has been shown, for example, that post harvest nitrogen application is reflected in the petiole concentration at flowering. Post-harvest nutrient applications may therefore make an important contribution to the growth and general health of vines in the following season.

Key points regarding nutrient reserves are:

• Like carbohydrates, grapevines require a supply of nutrients from stored reserves to support growth in early spring. Nitrogen in the roots and wood follows a similar pattern to carbohydrates (although much lower in concentration), and post-harvest applications will influence the nitrogen status of the vine in the following season.

• The role of other nutrient reserves is less well understood, but post-harvest uptake of phosphorus does appear to be important. To a lesser extent, magnesium, calcium and potassium uptake after harvest will also contribute to growth in the following spring. Little is known about the role of other nutrients carried over winter in grapevine tissues.

Sooty Mould in Olive Trees

At this stage of the season black olive scale can be seen on olive trees. The adult females are very easy to recognise on the olive tree stems. They are dome shaped dark black in colour and 2-5mm in size. Note also the co-responding sooty mould. 

Olive black scale and co-responding sooty mould.

During spring use copper fungicides to reduce the amount of sooty mould.

At this point of the season scale are dormant underneath their protective shell where they lay egg.

During the December and January cream coloured 'crawlers' hatch from these eggs and move up the stems. They usually settle along the veins of  young leaves. At this stage they don't have the impervious shell of the adult and can usually be killed with one or two applications of insecticidal oil about two weeks apart. It puts an oil film over the young 'crawler' and suffocates it. 

Spray oil during December to stop the crawlers.

If the crawlers are allowed to live, they will moult after about one month and then migrate to the young stems and twigs of the tree. Here they will mature and lay more eggs and their protective brown shells will be impervious to sprays.

Olive black scale. Squash the scale between your fingers to see if it is alive. If it is alive, then your fingers will be wet from the juices squeezed out. If it is dead  then your fingers will be dry and dusty.

Bad infestations of live mature scale may need spraying with an insecticide.

As the scale feeds they excrete is a sweet, sticky, 'honeydew'. A  fungus known as sooty mould feeds on this food and multiplies until the entire tree may be covered with the black sooty mould.

The leaves are coated with the black deposit so the sun's light can't  penetrate the leaves properly. Therefore photosynthesis can't take place efficiently. This results in a stunted  and unhealthy tree with poor crops.

To make the problem worse, sweet 'honeydew' on the leaves also attracts large  numbers of ants. Ants constantly move over the scale, they frighten away the small wasp parasites which in normal cases would  keep the scale under control. 

The good news is that healthy olive trees don't get the scale, sooty mould and ant infestation to any great extent. More good news is that heavily infested  trees are easily fixed.