By Neal Kinsey
By using detailed measurements and specifically formulated procedures for controlling nutrient excesses and deficiencies in soils, it is possible to define, measure and manage soil fertility to help grow crops of the highest quality.
Whether trees, vines or cane crops, when it comes down to fertility, there are three very specific considerations that woody plants need to perform at their very best. The same is true for vegetables, grasses, legumes and small grain crops. Those needs are adequate water infiltration, proper environment for soil life and the correct amount of nutrients to supply that life and the crop via plant root uptake.
It is a big mistake to consider that just adding enough fertilizer to grow the crop is what determines soil fertility. There is far more to it than that, and if not correctly understood this can be very costly to those trying to survive and profit from such land. On the other hand, once these principles are understood and put into practice, it is like finding the road map to building up land for achieving its top performance.
Top fertility begins with soils that “drink in the water” — not those that are so hard that water is unable to penetrate and runs off as a source of erosion instead. Even on “flat” fields, whichever way the water moves, soil nutrients move with it. This is because soil colloids, the tiniest and yet most fertile clay particles, and the soil humus are so small that they will be picked up and eroded away first.
Is there anything growers can do about poor soils? Are you just stuck with that soil if a general fertility program will not suffice to solve the problem? Though much of agriculture seems to imply that this is the only real choice (because the farmer or grower is told it is too expensive to correct the soil) that does not have to be the case.
Adding carbonaceous materials, growing cover crops, using composts and manures and other conservation methods can help, but if any of these are considered as the initial key to lasting success, that is like the old saying about “getting the cart before the horse.”
The place to start is to consider and deal with the “science” of the soil as quickly as possible. That means providing exactly the right environment for the soil organisms, from microbes to earthworms, and all the other organisms that work to feed the plant. Soil scientists say this soil life is equivalent to the weight of an average sized cow in the soil under each acre of ground. This life in the soil eats first and the plants we are growing then get to choose from what is left.
In other words, the plants eat at the second table. When there is not a sufficient amount to supply the needs of both the soil and the plant, it is the plant that suffers. A good example is how soil organisms confiscate nitrogen needed to break down crop residues. They get first choice and if there is too little there, the plant will suffer a nitrogen deficiency.
Still, when soil organisms are placed into a hostile environment, they have trouble thriving and possibly even surviving. This is where the science of the soil again takes precedence. It now has to do with the proper amount of air and water the soil contains, as compared to the content of minerals and organic matter. This relates to the physical structure of the soil — or soil physics.
The soil needs plenty of room for supplying the needs of the living organisms that must survive there, including plant roots. That room or space must provide the needed air and water as well as sufficient soil and plant nutrient sources. To provide the most beneficial environment for the life of the soil requires 25 percent as air space, 25 percent for water, 45 percent for soil nutrients and 5 percent for organic matter.
But there is another aspect of soil science that has to be considered in order to provide this ideal physical structure. It has to do with the chemistry of the soil. The lack of proper emphasis on this aspect of soil science is why most of agriculture does not accomplish building the proper environment for soil life, including the plant roots that should be correctly feeding our crops.
The makeup of soil fertility should be based on the chemistry of the soil because only with the correct soil chemistry can the optimum physical structure (which determines the environment for life in the soil) be achieved.
Without a proper relationship between the soil minerals, which determines how they will react with one another, the physical structure will be lacking in a soil. There will not be the proper amount of air and water in relation to the mineral and organic matter content. Hence, the “house” or proper living conditions for all of the soil organisms will be lacking. That soil is not the “living soil” it needs to be. Now whatever we try to grow there suffers as a result. This is the real life-giving aspect of soil fertility.
Once the science is right, then you can consider and stress the differences that fertilizers and soil amendments can provide to keep the life in the soil functioning as it should, including the nuances of fertility needs for wine grapes or table grapes, versus raspberries or blackberries, versus almonds or walnuts, or whatever else is to be produced there.
Until this point is reached, the basics of topsoil performance to grow whatever crop you have in mind are still limiting. The sooner these can be corrected, the sooner each soil will be able to achieve its absolute top potential in terms of both yield and quality. Even though many other soil-building programs can help make improvements, the greatest limitations to top performance of all productive land is the lack of the right chemistry, which determines the right physical structure, which will then provide the ideal environment for the life in the soil and consequently what the producer wants to grow.
Utilizing a detailed soil analysis, combined with available GPS technology, now makes it possible to accurately determine exact requirements for each specific nutrient as required for significant variations in the soils of every vineyard, orchard or field. This technology is used to accurately measure, map for sampling and correctly fertilize for specific soil differences.
By understanding the subtleties of each different soil and the consequences that nutrient deficiencies or excesses will cause for walnuts, wine grapes, vegetables or any other crop to be grown on that land, potential problems can be identified and prioritized and appropriate solutions proposed.
On-site consultations should also be considered from time to time as they can prove useful to help ensure that growers are correctly using the best proven methods to achieve and maintain established needs.
About Neal Kinsey
Neal Kinsey has worked as a soil fertility specialist in his home state of Missouri since 1973, with clients in all 50 states and at least 70 other countries. He also conducts training courses for interested farmers and growers each year as well as on-farm consultations. He is a contributor to Acres U.S.A. magazine and author of Hands-On Agronomy.