Vineyard Nutrient Management
Conditions Affecting Nutrient Availability to Grapevines
Conditions affecting nutrient availability to grapevines include soil properties such as pH, organic matter, and texture, as well as environmental factors like moisture, temperature, and light, as well as the biological activity of microbes. These factors influence the chemical form of nutrients, their movement in the soil, and their ability to be absorbed by plant roots. Soil pH is a critical factor, as it determines whether nutrients are soluble and available. In acidic conditions, some nutrients become toxic, while in alkaline conditions, others become less available. Other factors include soil structure, soil texture, and the presence of beneficial microorganisms, such as mycorrhizal fungi. Antagonistic effects can arise from the excess of one nutrient or from abiotic stresses, including heat and drought.
The Concept of the Limiting Factor
The law of the minimum states that plant production can be no greater than that level allowed by the growth factor present in the lowest amount relative to the optimum amount for that factor. This growth factor, be it temperature, nitrogen, sulfur, or water supply, will limit the amount of growth that can occur and is therefore called the limiting factor. This is similar to the adage that a chain is only as strong as its weakest link. If a factor is not the limiting one, increasing it will do little or nothing to enhance plant growth.
Soil and Water Conditions
Soil pH
Soil pH affects the solubility of minerals and, consequently, their availability. Soil pH values between 6.0 and 7.0 provide optimal nutrient availability in vineyard soils (Figure 16.10). At a low pH, beneficial elements such as molybdenum (Mo), phosphorus (P), magnesium (Mg), and calcium (Ca) become less available to vines. Other elements, such as aluminum (Al), iron (Fe), and manganese (Mn), may become more available, and Al and Mn may reach levels that are toxic to vines. In highly alkaline soils, the mineral nutrients iron and zinc become less available, resulting in nutritional problems, such as iron chlorosis, in grapevines.
Soil Texture
Sandy soils have many large pores, making water movement and drainage more rapid. This often results in the leaching (i.e., loss) of mobile nutrients such as nitrate. Where sands are water-repellent, water movement is slow, and nutrient availability at depth is usually poor. Generally, these soils have low levels of organic matter, resulting in a low fertility status. Sandy soils retain a low amount of water for vine use, which can make irrigation scheduling and nutrient application via fertigation difficult. The cation exchange capacity (CEC) of sandy soils is generally low.
Soil Compaction
Soil compaction can limit or completely restrict root penetration, effectively reducing the volume of soil that is accessible to the plant, including nutrients and water (Goldammer, 2026). To limit soil compaction, avoid entering the vineyard when it is too wet, and minimize the weight per axle by decreasing load weight and/or increasing tire surface area in contact with the soil.
Soil Moisture
Soil water content is critical not only for supplying the crop’s water needs but also for dissolving nutrients and making them available to the plant. Excess water in the soil, however, depletes oxygen and builds up carbon dioxide levels. While oxygen is necessary for roots to grow and absorb nutrients, high levels of carbon dioxide are toxic.
Soil Temperature
Temperature plays a crucial role in regulating the rate of soil chemical processes that make nutrients available for plant growth. Under cool soil temperatures, chemical reactions and root activity decrease, rendering nutrients less available to the vines. Cool air temperatures can lower evapotranspiration, reducing the convective flow of water and nutrients from the soil to the roots.
Nutrient Mobility in Soils
Nutrients differ in their mobility in the soil, which affects their susceptibility to leaching loss. As a good general rule, ammonium (NH4⁺), potassium (K⁺), calcium (Ca2⁺), and magnesium (Mg2⁺) are more mobile than the micronutrients (Cu2⁺, Fe2⁺, Fe3⁺, Mn2⁺, and Zn2⁺).
Water Quality
Water quality affects crop nutrient availability through its impact on soil pH, salinity, and the presence of toxic elements. High or low pH can make certain nutrients unavailable, while high salinity can damage roots and hinder water and nutrient uptake.
Vine Management
Rootstock Selection
Grapevine rootstocks significantly influence nutrient availability by affecting the uptake and transport of minerals like nitrogen and potassium, which are essential for vine growth and yield. Rootstocks can differ in their genetic background, leading to variations in nutrient absorption efficiency, with some rootstocks being better at absorbing certain nutrients than others.
Fertilizer Antagonisms
For optimum growth, it is not enough to have an abundance of available nutrients. Grapevine nutrients also need to be made available in the correct ratios to one another. This is because specific elemental fertilizer ions compete with others for uptake. Such a thing occurs with plant nutrients, in the soil or in the root zone. Many chemical reactions occur in the root zone; some are beneficial to the plants, while others may be detrimental to plant nutrition. Chemical interactions can enhance or interfere with the uptake of certain elements, depending on the concentration of other elements and whether they are synergistic or antagonistic.
Weather and Climate
Weather impacts crop nutrient availability through temperature and precipitation, with high temperatures accelerating nutrient release but also causing leaching and stress, while low temperatures slow microbial activity and nutrient uptake. Excessive rainfall leads to nutrient leaching, particularly for mobile nutrients like nitrogen, while drought reduces soil moisture, limiting nutrient movement to roots. Extreme heat stress can also directly decrease nutrient content in plants by disrupting uptake processes, even if nutrients are available in the soil.
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