Managing Soil vs. Sand Sports Fields - Comparing Apples and Oranges
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As sports turf managers you will have many different sports fields to manage with a range of rootzones. Using the same management techniques on these different rootzones could lead to disaster. This article outlines the major differences involved in managing a soil base field vs. a sand based field.
One way to manage compaction on a soil based field is to control traffic. This can be achieved by having a practice field so that the field used for scheduled games receives less compaction. Proper irrigation management is a must. Avoid light, infrequent irrigation. You must be careful; if the turf roots are restricted to the top 0-5 cm due to compaction you may need to water more frequently so that the portion of the soil that contains roots does not dry out.
A sports turf managers major tool to fight compaction is soil cultivation. There are many different soil cultivation techniques that can help a compacted field. These include: solid tine coring, hollow tine coring, drilling, slicing, spiking and high pressure water cultivation. Core cultivation has many benefits. It increases water infiltration, increases soil aeration and increases root penetration. The increase in root penetration is very evident when you cut into an aeration hole. The newly formed white roots stand out. One draw back of core aeration on heavy textured soils is the soil on the walls of the soil core become more compacted for a period of time after core cultivation. There is also the risk on heavier soils of forming a cultivation pan. This is a compacted layer of soil at the depth of the cultivation tines. On soil based fields, core aeration of some form or cultivation is recommended at least twice per season.
One of the best ways to manage compaction is core cultivation followed by soil replacement. If the soil cores are removed and the core holes are filled with a properly specified sand, over time soil compaction will be minimized.
Compaction on properly constructed sand based rootzone is rarely a problem. Over time there may be a compacted zone that develops in the top 0-2 cm due to the accumulation of organic matter in that area from decaying turf roots. If this occurs, infrequent core aeration will alleviate the compaction.
Soil texture has a major influence on irrigation management and this is often the area that causes the sports turf manager the most trouble. Sand based rootzones have poor water holding capacity because only half of the pore space will hold water and the other half will be filled with air. They do, however, have deeper roots than a soil-based field. On a soil-based field there are many more micropores and usually much more water is held in the rootzone. There are two confounding factors however. The water in a soil-based field may be so tightly held by the soil that it is not available to the plant. Also, soil based fields tend to have shallow roots, so the roots may not be able to get at all the water in the soil. In the end, both rootzones may require the same amount of water at the same frequency but generally the sand based rootzone will require water more frequently than the soil.
Water infiltration is often a problem on soil based fields. They may not be able to absorb the amount of water delivered during one irrigation cycle. To get around this, a shorter cycle can be used and cycled twice at each irrigation. On the other hand, sand based rootzones, if they do dry out can become hydrophobic and at this point they are very difficult to almost impossible to re-wet.
Cation exchange capacity (CEC) is a relative measure of the soils potential fertility. The magnitude of the CEC depends on soil texture, types of minerals in the soil and the amount of organic matter. Sand has a very low CEC and soils have a high CEC. See Table 1. Typical CEC's of some soils below for some average CEC's.
Because of sands lower potential fertility, it will require a greater amount of fertilizer than a soil-based field. This is especially true during establishment where up to 1 lb. of nitrogen per 1000 sq. ft. may be required each growing week until turf is established. With sand fields there is also a greater potential for fertilizer to leach. It is important on sand rootzones to use a slow release form of fertilizer to minimize leaching and apply less fertilizer more often. Sand rootzones, especially during establishment have very few microbes in them. It is important at this stage not to use a fertilizer that relies on microbes to release nitrogen. Sand-based fields are generally lower in phosphorus than soil based field. Potash is more likely to leach from a sand-based field and they are more likely to require micronutrients than a soil-based field.
Soil-based fields will require less fertilizer, less often than sand. This is especially true on compacted fields where the addition of excess nitrogen decreases rooting and weakens the turf plants. Fertilizers that rely on microbial degradation are suitable for soil based rootzones. In general there is very little nutrient leaching from a soil-based field.
Thatch accumulates when the turf growth is greater than the soil's microbe ability to break down thatch. On sandy soils where there are fewer microbes there is a greater tendency for thatch to form. Thatch management on sand based fields is usually accomplished through topdressing with a topdressing that is the same as the rootzone. To manage thatch on a sand field the topdressing frequency and amount must match the turf growth so that there is no excess accumulation of thatch. On soil based fields thatch management is accomplished through core aeration. The greatest tool is core cultivation in conjunction with soil replacement, in other words, removing cores and replacing it with a proper sandy loam soil.
As you can see, sand and soil fields are very different beasts, requiring different management practices, which are summarized in Table 2. Hopefully, the information here will help you better understand what is happening below the turf and help you better manage the fields you have whether they are sand, soil or a combination of both.
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