Management of Vineyard Soils
Salt-affected Vineyard Soils
Primary salinization occurs naturally where the soil parent material is rich in soluble salts, or in the presence of a shallow saline groundwater table. Salt-affected soils often occur on irrigated vineyards, especially in arid and semiarid regions, due to insufficient leaching, improper irrigation, poor drainage, or irrigation water high in salts
Properties of Salt-Affected Soils
Salt affected soils can be categorized into three groups depending on the total soluble salts and the amount of sodium salts.
- Saline soils – salt problems in general
- Sodic soils – sodium problems
- Saline-sodic soils – problems with sodium and other salts
These categories are defined using defined numerical criteria (e.g., EC, SAR, ESP, and pH) as shown in Table 19.6.
Salts generally found in saline soils include sodium chloride, calcium chloride, gypsum, magnesium sulfate, potassium chloride, and sodium sulfate. Calcium and magnesium salts are usually at a high enough concentration to offset the negative soil effects of sodium salts.
Sodic soils are low in soluble salts but relatively high in exchangeable sodium relative to calcium and magnesium. Sodic soils generally have a pH value between 8.5 and 10 or even higher. They are characterized by their poor physical structure and slow permeability, causing vine productivity to be limited.
Saline-sodic soils are soils that have chemical characteristics of both saline soils (EC greater than 4 mmhos/cm and pH less than 8.5) and sodic soils (ESP greater than 15).
Soil Sampling after Planting
After planting, soil sampling and salinity analysis should be routinely conducted every 2 to 3 years in the vineyards that have been planted on marginal soils or where water of marginal quality is used for irrigation. Routine evaluation of soil salinity assists with making decisions about irrigation and soil and water amendments. Year-to-year sampling should be done at the same time each season with respect to rainfall patterns and irrigation scheduling.
Sampling Soil at Multiple Depths
Sampling soils and analyzing for soil salinity at multiple depths will help the grower in understanding salt distribution and accumulation patterns within the root zone and also help in assessing the effectiveness irrigation management for controlling salinity
Managing Saline Soils
The first step in managing salt-affected soils is to determine the problem and identify its cause or source. If salt problems are suspected or likely, soil and water samples should be collected on an annual basis and analyzed for EC, ESP and/or SAR, and pH.
Most vineyards are typically planted on well-drained soils, irrigated with good quality water, and receive enough rainfall in the winter to leach the salts below the root zone. However, if salt build-up continues salts can be moved below the root zone by applying more water than the vine needs. This method is called the leaching requirement method. Fall is the best time for a large, planned leaching event because nutrients have been drawn down.
Managing Sodic Soils
Sodic soils usually are the most expensive to reclaim and, in many situations, reclamation is not economical. The reclamation procedures discussed here can improve sodic soils, but many years or decades of good soil and crop management are required to fully remediate a sodic soil.
Reclamation of sodic soils is different than with saline soils; excess sodium must first be replaced by another cation and then leached. Calcium is required for sodic soil reclamation, as it will displace sodium and reduce the ESP and SAR. The most common form of calcium used for this purpose is gypsum. Gypsum is used because it is calcium-rich, dissolves at high pH, and does not contain elements or compounds that might interfere with reclamation.
There are several options in applying amendments to treat sodic soils. Adding amendments directly to the water is ideal for managing soils with slow water infiltration rates where crusts have formed on the soil surface. Solution-grade gypsum injected as a slurry at controlled rates is the most common method of adding calcium to irrigation water. Liquid formulations of acid-forming amendments may also be injected, but be certain as previously mentioned that soil lime is present.
Managing Saline-sodic Soils
Saline-sodic soils containing high concentrations of both salts and sodium (Na+) are managed using both management processes described above for saline and sodic soils.
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