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Plant Analysis: An Important Tool in Turf Production
C. Owen Plank and R.N. Carrow1
One of the major factors affecting the growth of turfgrass and turf quality is its nutritional status. The nutrient status of turfgrass is often an "unseen" factor, except
when the concentration of a nutrient becomes so acute that it adversely affects the desired growth characteristics, or deficiency or toxicity symptoms appear on the grass.
Plants require specific amounts and balances of nutrients for optimum growth and reproduction. A deficiency of one essential nutrient or an imbalance between two nutrients during a
critical growth stage can reduce the desired growth characteristics. The extent this effect may have on growth is related to the degree of nutrient deficiency or imbalance. In some cases a deficiency or a toxic
level of a nutrient can cause total plant failure in a very short period of time.
As a result of modern technology, the nutrient status of turfgrass can be rapidly assessed through plant analysis techniques. Plant analysis is a process in which plant samples are
collected from a plant at a specified time during the growing season and analyzed for various essential nutrients. The nutrients of primary concern are: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca),
magnesium (Mg), sulfur (S), manganese (Mn), iron (Fe), boron (B), copper (Cu), and zinc (Zn). In addition to the analyses, most plant analysis programs also include an evaluation of the analytical data to determine
whether an element is low, sufficient, or high.
One should not confuse plant analysis or plant tissue analysis with tissue testing. As noted in a later section plant analysis is conducted in a laboratory using wet chemistry
methodology or a combination of wet chemistry and combustion methodologies. Tissue testing is conducted in the field, and the process includes conducting colorimetric procedures on freshly extracted tissue sap using
test papers, vials, and color charts. An advantage for this type of analysis is that it provides immediate results and has a lower cost than wet chemistry and combustion methods. However, these tests are not
quantitative and are limited to nitrate (NO3), phosphate (PO4), and potassium (K) analyses (Jones et al., 1991).
USES OF PLANT ANALYSIS
Plant analysis can be used by turf managers to:
- Confirm suspected nutrient deficiency symptoms;
- Verify toxicities;
- Reveal hidden hunger; i.e., plants show no visible symptoms, but the nutrient content is low enough to reduce growth or affect quality characteristics;
- Aid in evaluating the efficiency of applied fertilizers;
- Assist in formulating fertilization practices, and
- Monitor the nutrient status of plants throughout the growing season to determine whether each nutrient is present in sufficient concentration for optimum growth characteristics.
Plant analysis is a proven and effective means of predicting fertilizer needs for many crops. However, it does not completely replace a soil test. Soil and plant analysis serve
different purposes and when properly used they compliment each other in providing detailed information for maximizing the efficiency of fertility programs.
Soil testing is based on the concept that the concentration of a particular nutrient in a given volume of soil reflects whether or not the nutritional level of that soil is adequate
for optimum crop growth or production. Plant analysis is based in part on the concept that the amount of a specific nutrient in the plant tissue is related to the plant availability of that element in the soil.
However, plant analysis also reflects nutrient uptake conditions in the soil. Soil properties such as compaction, impervious layers or poor drainage may inhibit the uptake of nutrients by plants. Or a low
concentration of one nutrient in the plant may result from the excessive application of another nutrient. Conversely, favorable soil physical properties and optimum soil moisture may accentuate nutrient uptake even
though the soil may not have an abundant supply of nutrients.
As a result of these soil-plant interactions, there are certain instances when contradictions occur between soil and plant analysis results. For example, assume turf is growing on a
soil in which the soil tests revealed a medium level of extractable magnesium. A plant analysis from the area a few weeks later indicates that magnesium is low. Immediately, the validity of the test results are
questioned, which is an absolutely normal response. However, a closer examination of the plant analysis results revealed that the calcium and potassium concentrations of the turf were high. Upon checking the
information supplied on the history sheet accompanying the plant analysis results, it was noted that calcitic limestone had been used as the liming material and a high rate of potassium was applied in the fertilizer
program. As a result of these two management practices, the level of calcium and potassium in the soil were sufficient to reduce the uptake of magnesium.
This is one example of how soil testing and plant analysis can be used together for making better nutrient management decisions. Plant analysis can also be used to supplement a soil
testing program. It is particularly useful in distinguishing between nitrogen and sulfur deficiencies in turf as deficiency symptoms of the two elements are similar. Plant analysis offers an excellent means of
delineating which element is deficient (which cannot be ascertained through soil testing). If this distinction is not made properly and the wrong corrective treatment is applied, plant growth can be affected
appreciably.
In the case of most turfgrasses, a soil analysis prior to active growth in the fall or spring makes it possible to determine whether limestone, phosphorus, potassium, or magnesium
applications will be needed. Plant analysis of the turfgrass during the growing season will indicate if the applied materials were effective and whether the preplant prediction by soil analysis was correct.
In order for a plant analysis program to be successful it must include the following essential components:
- A representative sample of the area in question
- Proper sample preparation for analysis
- Accurate analysis of the sample
- Correct interpretation of the results
- Proper recommendations based on the analytical data and historical information supplied with the sample
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Acknowledgements
1Associate Professor and Professor, The University of Georgia, Crop & Soil Science Department, Athens, GA 30602-7272 and Griffin, GA 30223-1797,
respectively.
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