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One of our main activities is interpretation of soil, petiole and leaf test results. Although the test results of a wide variety of farm types are interpreted, we specialise in a number of horticultural crops (grapes/olives/stonefruit and pipfruit).

The interpretation includes comments on the findings, and fertiliser recommendations. For selected crops we add specific information such as deficiency and toxicity symptoms for that crop (in many cases with pictures), the role of specific nutrients in that crop etc..
In addition, when reporting on soil sample results, background information is added relating to soil testing and soil fertility. An example of a soil report can be seen by clicking here.

Soil testing provides a tool for soil and crop management. It provides information that is needed to be able to formulate a soil and plant nutrient management program. However it only provides part of the information required. Additional information such as petiole/leaf test results that reflect plant nutrient uptake, planting density, varieties and rootstocks, as well as information about the subsoil, annual rainfall etc., are required for effective soil and plant nutrient management.
In many cases soil and plant nutrient management is haphazard and reactive (often only based on soil and leaf sample results or visual observations).
Integrating soil and leaf data with other important parameters (varieties/rootstock characteristics) will provide a much better foundation for developing soil/plant management. It will help understand what the strengths and weaknesses of a particular block are, and enable the grower to address problems in a structural rather than haphazard way.
Having the integrated information in the one database will help predict effects of dry or wet seasons, and will help decide on the best type of corrective or preventative action if required.

Soil test information is only one part of the picture. Same with a leaf or petiole test.
Putting them together, and understanding interactions between soil and plant, as well as the different nutrients and soil pH and organic matter, will allow you to make some real progress.
It will also facilitate monitoring over time and comparing between blocks, an almost hopeless task when comparing piles of soil test and leaf test results, each on different piece of paper.

In the case of vineyards, this system can be linked to yield and juice or must data, making it even more powerful.

In our opinion this integration of information should be the goal of most horticultural growers. This is an area where AgConsult has taken the lead by developing specific software for the purpose.

SOIL TESTS

In most cases soils samples are collected by consultants or reps who are trained in sampling procedures. If growers prefer to take their own samples we can assist in determining which areas to sample and instructions about the actual sampling itself.

Most labs can test a wide variety of different soil parameters. If you are serious about soil management it is only logical that more than just the basic parameters (pH, phosphorus, calcium, magnesium and potassium) are tested. In most cases we recommend you include sulphates, a second phosphorus test (There are a number of potential problems with the standard Olsen test used in NZ), organic matter, exchange capacity, boron etc..

Interpretation of soil tests result requires an understanding of the meaning and shortcomings of individual test results. For instance:
The Olsen phosphorus test can give “false” results if lime has been applied recently or if Rock phosphate has been used.

High magnesium in terms of me/100 grams or as MAF units does not mean much if you are dealing with a high exchange capacity soil with high potassium levels. In case like that the Magnesium base saturation percentage is a better indicator.

The effect of pH and organic matter on iron uptake is very dramatic. What looks like a good result may not be quite as good (or vice versa) when considered in relation to the other parameters.

Not many individual growers or fertiliser reps have enough experience to interpret (comprehensive) soil test data. To a lesser extent this even applies to petiole and leaf tests.

For instance petiole nitrate levels seem to contradict petiole total N levels. In virtually all such cases these differences tell a story and are not contradictory but rather explanatory.

This is an area where we have specialised in over the last 15 years.

Depending on the crop you may need to consider a subsoil sample as well as a topsoil sample. The subsoil sample is usually taken pre planting, for instance in vineyards. It can help predict potential problems related to high soluble salt levels in the subsoil, high chlorides or boron, high clay content, poor structure, high potassium etc...

Example of Vineyard Soil Test (pre-planting) - click to enlarge

note: some elements in this test are part of a standard trace element
package (Cobalt & Selenium) but have no direct relevance to grapevines

PLANT TESTS
(LEAF & PETIOLE)

Monitoring plant health and nutrient uptake is best done through petiole and/or leaf testing. There are prescribed procedures for most crops which give instructions as to how samples should be collected and at what times.

When we receive the results from the lab, we will make a report discussing the results and containing recommendations for corrective (or in some cases preventive) action where required.

BIOLOGICAL TESTS

There is probably no grower or farmer who is not aware of the importance of biological activity in the soil. Instinctively we all recognise that a soil teeming with diverse communities of microbes, insects etc. is a better soil to grow in, than a soil that is devoid of any life. The organisms in the soil help improve and maintain structure, suppress pathogens and help release nutrients. Yet, yet until recently, it was difficult to mange the health of your soil because of a lack of understanding and information. There was no easy way of assessing soil health or soil biological activity.

Laboratories have been able to measure levels of phosphorus calcium etc., but that is only part of what makes your plant grow in the soil. In the last decades significant developments in the fields of microbiology and soil science have led to a better understanding of what relationships exist in the soil between the soil, plants and the millions of microbes, and other organisms. In addition techniques have now been developed to routinely measure some of these organism communities.

BIOLOGICAL SOIL TESTS ARE NOW AVAILABLE
Work done at Oregon State University and other institutes in this field meant that tests for some important soil health and soil biological activity are now on offer. This has allowed us to explore relationships between soil biological parameters and crop performance. Examples are the importance of mycorrhizal fungi for some crops, and whether a specific crop grows better in a bacterially dominated soil or in a fungally dominated soil.

WHAT USE IS A BIOLOGICAL TEST?
From previous international work, it is now clear that what is a good biological activity for one soil, is not necessarily good biological activity for another soil. Some crops prefer a soil that is dominated by fungal activity, some crops prefer a soil that is dominated by bacterial activity. This knowledge obviously affects management. Of particular interest are tests for mycorrhizal fungi on vine roots >research/mycorrhiza

There can be no effective management without knowledge and information. Before we can manage our soils according to the optimum requirement for a specific crop we need to know what it is that crop prefers, and in many cases we might want to know what the present status of the soil is. For instance grapevines prefer to grow in soils that are slightly dominated by fungal activity. They also form (like most crops) mutually beneficial (symbiotic) relations with certain types of fungi whereby the fungi live on the roots of the plants, extending outwards into the surrounding soil. In exchange for carbohydrates from the plant, it sources nutrients and water and in addition produce other metabolites that benefit grape quality and provide protection against certain soil root pathogens. These fungi are called mycorrhizal fungi. Such symbiotic relationships are very important for the vines and have a bearing on the size and quality of the final crop.
It is now possible to measure whether this soil has a suitable fungal:bacterial ratio, and by sending in some root samples we can determine whether the roots has good colonisation of mycorrhizal fungi, and of which type of mycorrhizal fungi.
If the results show that there is a problem we can adapt our management to correct it. By understanding how fertiliser, weed management, application of herbicides and pesticides and soil cultivation affect soil biological activity, we can manipulate the soil biological parameters towards where we want them to produce good quality crops with healthy plants in a soil that helps suppress diseases and maintains good soil structure and organic matter/humus.

HOW CAN YOU GET TO KNOW THE BIOLOGICAL SIDE OF YOUR SOIL?
AgConsult Ltd works with a number of companies throughout New Zealand that can take the samples and send them to us. Please contact us for your nearest agent. Alternatively, you can send the soil or root sample directly to use, contact us first regarding instruction on how to take the samples and how to send them to us.

SAMPLE REPORT

Click the image below to open an animated tour through a sample AgConsult report.(200k)