Do wine grapes growing on more fertile soil produce better wines?
By Neal Kinsey, Kinsey Agricultural Services
There is ongoing debate about whether a consistent and realistic method can be used when consulting with growers for grape vineyards to measure and systematically build soil fertility for improved wine grape production. While some argue that the concept is too broad to establish an effective program, practical evidence using detailed soil nutrient analyses suggests more in-depth consideration could provide further essential information.
Across various wine regions in North America, Europe, Australia, New Zealand, and South Africa, vineyard owners and managers have utilized information from such a program with notable success from as far back as the 1980’s and 90’s.
Furthermore, do wine grapes growing on more fertile soil produce better wines? Some think not, but is that a correct assumption? The plan for writing this column is to provide sensible answers to soil nutrient needs and related problems based on over 50 years of actual measurable vineyard experience that has helped successfully deal with such questions. The intent is to help growers in building up vineyard productivity and grape quality by making use of actual experience at solving such problems from widely varied circumstances that relate to all types of vineyard soil.
Most grape growers would likely agree that they have certain soils that grow better grapes than others. But under equal circumstances, by considering what can be shown as the foundational nutrient needs in some of the top vineyard soils in various parts of the world, could those soils that are not already as good do just as well by providing them with those same nutrient levels?
And even so, when a certain soil does or does not seem to be the best soil on the property for growing grapes, is it possible that the measured fertility needs can be employed to prescribe and achieve even higher desirable qualities? And in turn, can such measured fertility be proven useful for measuring and providing a basic foundational key to natural soil health and the resulting soil quality required for growing better wine grapes?
When a grower knows what is desired, but is still not sure how to achieve it, first consider working out and establishing a proper baseline. Devise a plan to see what the fertility levels show to be in the soils that are already producing the best grapes. If there are vineyard soils that have already proven themselves in terms of better quality and production, use those as a starting point.
Once the baseline for good and bad soils have established that the testing you plan to use is a reliable program that can be counted on for measuring the needed fertility in the vineyard, what considerations should receive the greatest attention for building a sensible fertility program for a specific approach to the many variations in typical vineyard soils?
Great emphasis in recent times is being placed on soil quality for growing grapes and rightly so. But what matters most in terms of soil quality in vineyards? Some may say it is water movement, to others it is better aeration, or perhaps friability, or soil microbiology. But ultimately, all of these are positively affected by what nutrients the soil already contains and those applied as fertilizers and soil amendments.
There are three basic aspects of science that should be used as keys to determine whether each soil performs poorly, above average or at its best. The real key to top quality for any soil is its biological activity. The soil is the plant’s stomach. Therefore, accurately feeding the soil provides needed nourishment for the vines! The best soil is living soil. To put “life” in your wines requires “life” in your grapes which comes from abundant life in the soil. In just an average soil that life is enormous (more on that in an upcoming column) and includes everything from the growing plant roots, to earthworms, to soil microbes.
For soil biology to be at its best in each soil requires good physical structure, which assures adequate pore space for a balance of air and water in the soil. But if soils are lacking the proper physical structure, this in turn has a negative effect on plant roots and soil organisms that are needed for the most productive, healthy soils and plants. The question then should be what can be done to obtain the aeration and moisture needed for vineyard soils that do not already have them? And is there a way to measure and determine such needs?
In general, programs based on soil testing used for establishing a vineyard fertilization program to improve soil fertility do not focus on actual soil nutrient needs. The excuse normally used is that correcting and feeding the soil is too expensive. General soil testing is designed to encourage feeding the plants, not the soil. To achieve optimum results where quality matters even more than production the nutrient content of each vineyard soil must not be neglected.
Here is another key for determining vineyard soil health and quality. The mineral make-up of each soil determines its physical structure. And this mineral make-up must be measured using the basic principles of soil chemistry. So, soil biology (life in the soil) depends on soil physics (proper physical structure to provide a balance of aeration and moisture content) which is determined by soil chemistry (the proper mineral make-up) to grow the best vines and grapes.
When a given soil has sufficient nutrient make-up to grow grapes well, there are four elements that will provide the principal influence on the structure of that soil. They are the same four elements that most influence the soil pH in a range that will grow the best grapes. When a vineyard soil contains the proper amount of these four mineral nutrients, that soil will be the most friable, it will take in water properly, and it will have the proper air and water to encourage and maximize life in the soil. Those four elements are calcium, magnesium, potassium and sodium.
In other words, the soil chemistry determines the proper physical structure of every soil which is needed to build the “house” or a “proper environment” for the biology. In over 50 years of examining soil samples from thousands of soils for grape growers this is what can be determined time after time. When soils already possess the proper nutrients levels, those are the soils that perform the best. These soils grow the healthiest vines and provide the best quality of grapes for making wine. For soils that do not have this ability, to the extent that the required nutrients can be measured and supplied to match up with the fertility of the top producing soils, those soils too can be built up to produce top quality grapes.
Dr. William Albrecht taught the meaning of true nutrient balance for winegrape soils. One of his major principles was always to feed the soil and let the soil feed the plant. But to accomplish that purpose, the soil first had to have the proper nutrient relationships. This is what is meant when referring to balanced soil. And that balance was ascertained by first taking soil tests to see what each type of soil required.
Observable differences in the growth of plants on any soil, including differences in native vegetation, in the color of the soil or in slope – any obvious differences – when large enough to fertilize separately should be sampled separately. In areas that are different but too small to treat separately, stay out of those areas and do not mix that soil with other soil being sent for testing. Such differences can indicate nutrient differences in many cases. Soil taken from such areas and mixed with other areas would not correctly reflect what should be done to either one in terms of proper fertility needs.
Specific nutrient requirements to correct each individual soil needs to be identified. In every soil, if there is too little of one nutrient, there will be too much of something else. And this is the real key to soil balancing. When you supply any nutrient, the soil has too little of, as that nutrient increases some other nutrient will decrease accordingly. As a rule, that decrease will most affect and reduce whatever other element that soil has in excess. In other words, the first key to soil balance is to supply any nutrient shortage which begins reducing whatever that soil contains that is too excessive.
Every soil is different and depending on the circumstances will require its own set of requirements. This is where a detailed soil analysis is a necessity for solving the specific problems of each soil. And finding those solutions should be the first order of business for anyone working with the fertility for vineyard soils.
Working with wine grape soils and using the same exact testing methods for analyzing them from the middle 1970’s right up to the present has provided decades of useful information that continues to reveal positive answers to the questions posed above. And in case after case, from the best to the worst, analyzing soils using the same exact methods year after year has verified how fertility levels have been shown to establish an extremely important part in providing winegrape quality as well as production.
A soil test should define the necessary parameters to enable a consultant or fertilizer dealer to determine the good from the bad. Then from the test results tell why that is the case, even when not seen with the eye. If that is not possible, then how reliable can any advice based on those tests be for helping the soil in question?
An important point here is that when a vineyard soil is sampled correctly, an accurate detailed soil analysis should enable the identification of the best soils, the average soils and the worst soils for winegrape production. This is what makes it possible to evaluate vineyard soils and to rebuild the poor areas. But even more, if those areas that are producing the best grapes on the property are grown in soils that are lacking what the best vineyards have been shown to possess in terms of fertility, no matter how well they are doing, they can still do better.
Time after time, the vineyards that produce the highest quality grapes and wines have been shown to possess a specific set of nutrient relationships, arranged in a definite pattern, and no matter how well the reputation may already be, when the critical nutrients are still not shown to be present in the correct proportions, conditions can still be improved with the correction of each soil’s required nutrient levels.
What makes the most difference and why in terms of soil fertility and how is it best achieved? This type of information is what will be considered in various ways in this column in the months ahead. Comments and questions regarding content are encouraged.
For more information
contact…
Neal Kinsey
Kinsey Agricultural Services
573 683-3880
