SOIL SAMPLING (DEPTH) IN VINEYARDS

 

It’s that time of the year again.  Soil sampling to be done soon!  An issue that keeps coming back relates to the depth at which samples are taken.  Traditionally in New Zealand horticulture and viticulture, samples were collected from 0 – 150 mm depth.  In general, the medium ranges used are based on this sample depth.  It is important to realise this, as taken shallower or deeper samples will affect the results.  In most situations, fertility in the top 50 mm of soil is higher than at lower depth.

So, whatever sample depth is used, it is important to document the depth at which samples were collected.

I like playing with numbers on days off, and some time ago we looked at the relationship between soil levels and vine nutrient levels (in particular the major elements).  We selected a number of vineyards in Marlborough, Hawkes Bay, Martinborough and Western Australia.  They were all vineyards for which we had extensive data, over a range of years, and the soil data included topsoil and subsoil data.  It is important to note that all the vineyards were on relatively low CEC or stony soils.

What we found was really interesting.  The correlation between tissue (petiole/blade) and soil levels was stronger for subsoil levels than for topsoil levels.  This was even the case in vineyards where the topsoil was tested from 0-300 mm.  The correlation (with subsoil levels) was stronger for samples at veraison than at flowering.

Is this surprising?  Yes and no.  Yes, because the general practice is to test only the top 150 mm.  And medium ranges are generally based on this sample depth.  Few vineyards are also testing subsoils.

On the other hand, everyone that has dug a hole and looked at vine roots will know that only a small portion of the vine roots will be found in the 0-150mm zone.  Few vineyards are located in high summer rainfall areas; dry soil conditions during summer are common.  The topsoil dries out long before subsoil levels dry out, so it is not surprising that especially under summer conditions, vines rely more on subsoil nutrition.  This could explain the stronger correlation at veraison between subsoil levels and tissue levels.

In my view this is not surprising at all.  It is common sense, and we have been promoting subsoil testing for a long time for exactly these reasons.

So, what should you test this year?  If you haven’t done a subsoil test yet, do one now.  They don’t need to be repeated annually, levels in the subsoil generally won’t change much over time.

And for the topsoil samples?  I suggest you sample 0-200 or 0-300 mm depending on the depth of the topsoil.  If there is a clear change in colour at 200 mm (or there about) sample down to that change in soil colour.  Always document the depth at which the samples were collected.

We have more detailed suggestions/instructions for sampling available if you are interested.  Contact us and we will send you a pdf file on sampling.

In another blog we will talk about what you should test for.  In the meantime happy digging!

Zones Active in Integrape

As from today we have added some extra functionality to Integrape.  Although this may not be important for all vineyards, it will certainly help the vineyards with a large number of blocks.In most vineyards we only test some monitor blocks (soil/petiole etc) rather than each block separately.  Often we may test different blocks from year to year.  This makes it more difficult to look for trends over time.  It also makes it more difficult for day to day management.To solve some of these issues we have introduced zones.   A zone is a group of blocks with similar characteristics.  It could be grouping blocks based on the variety grown there, or represent blocks on the same soil type.  Typically they get the same fertiliser.

    Screenshot 1 –showing one of the individual Pinot Gris blocks in Block View  When in Integrape, you can choose the zone view (instead of the block view).  The zone view is based on all data from the blocks in that zone which are then averaged per report.  You wills till have the individual block data, simply switching back to block views will get you the actual results for the individual blocks.

Screenshot 2 –showing the average of all the Pinot Gris blocks in Zone view   

   Screenshot 3 – In Geo mode Zone view groups likewise blocks into zones.  The zones may represent different varieties planted, or blocks grouped together for management purposes (fertiliser/fertigation etc.).  If blocks were not tested at that particular time, they will still be represented by the average result from the blocks that were tested in that zone.

Integrape 2.0 is LIVE!

It has taken slightly longer than we expected, but Integrape 2.0 has gone LIVE this morning.

This way it is easy to digest huge amounts of information quickly.“A picture is worth a thousand words” may apply here in slightly adapted form; “a picture is worth a thousand test result values”. I know I am not the only one that experiences the limitations of brain power when trying to interpret multiple Excel worksheets full of numbers.

Integrape screenshot, Demo: Yield

New (nutrient) Profiles have been added, and more will be added soon.

One of the new Profiles is the Salinity Profile. It combines all parameters relating to salinity issues. Salinity is generally not a big issue in general in New Zealand, but the increased demand for land in Marlborough has meant that vineyards are moving into newer areas. One of those areas in Marlborough is characterised by the heavier soils and high sodium and salinity levels, especially in the subsoils.This needs management that is adapted to the soil conditions. The first thing is to find out the conditions of the soil.Test the topsoil and subsoil before planting. Testing the top 15 cm is not going to tell you much.It is woefully inadequate to base planting decisions and management decisions on only a shallow topsoil test. Vine roots do not restrict themselves to the top 15 cm of soil. In summer the topsoil dries out and vines increasingly source water and nutrients from the subsoil.

Having all the topsoil and subsoil data in one graph, combined with petiole and blade levels of sodium and chloride, will help assess the salinity situation and management responses to it.

It has been shown that Sauvignon Blanc can grow here successfully under the right management, and can produce some surprisingly good quality wine. However there are parcels of land where sodium, chloride and/or boron are too high resulting in vine death and yield depression. In a later blog we will discuss these issues in more detail.

Another new Profile is the ‘Vine’ Profile, which shows vine related parameters (pruning weights, bunches/vine, bunch weights, cane diameter etc. The profiles can be personalised to show the tests/parameters that you want to see there.

We will keep you posted regarding further developments.

Problems in the OLSEN P soil test department

For a long time now, the Olsen P test has been considered the “official” New Zealand test to measure available phosphorus. The decision to use the Olsen test was made some decades ago, based on local field trials. However there are a number of concerns in relation to the Olsen P test. This may be the “official” test that does not mean to say that it is always the best test to use. The concerns relate to the Olsen P test at low soil pH levels, when soils are tested where lime has been applied in the months prior, and where Rock Phosphate has been used as a phosphorus input.
For now, I just want to talk about the situation where Rock phosphate has been used. The use of Rock Phosphate (often called RPR – Reactive Phosphate Rock) has increased significantly in the last few years. Indeed, virtually all our clients are now using RPR in their base fertiliser (instead of more soluble forms of phosphorus). The use of RPR is more sustainable, reduces leaching, RPR can be used by organic growers, and it is more compatible with the promotion of beneficial mycorrhizal fungi in the soil than soluble phosphorus, especially applied at higher rates. More about the use of RPR in another Blog one day. This time of the year most growers are doing their annual soil tests. We increasingly see not shown the type of increase expected. Yet petiole and blade testing confirms the improved phosphorus status. See for instance the screenshot below (Vineyard names and block names have been blocked out). The green dot well below the target line (100%) represents the Olsen P result of 7 ug/L; well short of the target. The yellow brown line at the top is the Bray P level, well above target. The same applies to the blue line; representing petiole phosphorus at flowering over a number of years; well above target.

Integrape screenshot – phosphorus profile.

RPR has been used in this ( Marlborough) vineyard for the last 7 years or so. This is typical in many parts of Marlborough, where the soil test may show Olsen P levels of only 6 or 8 ug/L of plant available phosphorus (medium range 15-40 ug/L), yet petiole and blade levels are well into the medium range. I have a test in front of me right now from an organic vineyard in Hawkes bay; Olsen P is well below the medium range at 12 ug/L, however the Resin P test from the same sample shows a level of 56 mg/kg in the middle of the medium range (40-75 mg/kg). The problem with the Olsen P test in this case is that the test does not pick up plant available P compounds from RPR like the plant can. The test underestimates the quantity of PLANT-available phosphorus. The more RPR has been applied, or the longer a grower has been using RPR, the bigger this discrepancy can be. Thus is all well documented, and should be recognised by any competent consultant. There has been some talk about introducing correction factors, but that was not the answer. In our opinion, growers should simply ask the laboratory to do a Resin P test in addition to the standard soiltest. The resin P test works on a different principle, and much better reflects the levels of available phosphorus where RPR has been used. The Bray P test used by some laboratories is probably also more reliable as an indicator than the Olsen P test in these situations. Let’ put this in context; there is no perfect soil test for any element. The resin P test, the Mehlich 3 and the Bray P all have their limitations, just as the Olsen P test has. However in these circumstances (where RPR has been used), it makes a lot of sense to ask for a second opinion” using one of the more suitable tests for soils where RPR has been used. Quite a bit of work has been done with the Resin P test, and there are even some voices for the resin P test to take over as the “official P test”. To me, at this point, it just makes sense to test both; especially if you have applied RPR.