Plant Tissue Testing
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Soil testing can provide an estimate of plant nutrient availability in a soil. However, soil testing cannot predict the quantity of nutrients a plant or crop will actually use because many factors other than soil fertility levels are involved in plant nutrition. Only through plant tissue analysis can we assess the plant鈥檚 nutritional status and determine how well the soil is supplying the plant鈥檚 nutritional requirements. Plant tissue analysis cannot replace a good soil testing program; however, plant tissue analysis can provide additional information on plant nutrient status not obtained from soil analysis.
In theory, plant tissue testing is quite simple. Plant samples from a field are collected and the nutrient levels determined after the plant tissue has been digested or extracted in a solution. Generally, only those plant portions growing above ground are sampled, although underground parts are sometimes sampled. Frequently, only specific plant parts (leaves or petioles, for example) are sampled. After nutrient levels are measured, the plant鈥檚 nutritional status can be determined by comparing the measured levels with standard levels that have been previously determined through field research. Alternatively, when a field contains both healthy and unhealthy plants, samples can be taken from both and a comparison of nutritional levels can be made. Nutritional problems frequently can be identified by this process.
In reality, there are a number of factors that make plant tissue testing far more complicated than suggested. Plant nutrient concentrations are affected by plant age, plant part and sometimes by variety even in a healthy plant. These influences must be taken into consideration.
As a plant ages, the proportions of the various types of structures change. Young plants are very succulent, with a high proportion of water in the tissues. When the plant gets older, water content decreases, the proportion of cell walls increases and the plant may become woody. The different plant structures vary in plant nutrient content. Concentrations of some nutrients (N, P, K, Cu, Zn) tend to decrease as plants age, while the concentrations of others (Ca and Mn) often increase. Unfortunately, the rates in which these tissues change are difficult to quantify. Therefore, it is extremely important to know the plant鈥檚 growth stage (or age) when sampled if the composition is to be compared to 鈥渟tandardized鈥 levels. There are commonly recommended growth stages for sampling and standard nutrient stages. Samples taken from plants at different growth stages are not easily evaluated.
Just as plants of various ages differ in nutrient content, different plant parts may contain varying levels of plant nutrients. For example, the wood and the leaves of a tree contain very different nutrient levels. Similarly, stems, leaves, roots and fruits of non鈥搘oody plants may have distinct nutrient concentrations. Therefore, it is critical when taking a plant tissue sample that the plant structure collected is the one for which standard values are known. In small plants, the whole above鈥揼round portion of the plant is usually sampled. In older plants, the most common sampling method is to collect the youngest fully expanded (grown to its full size) leaf, or to take the petioles (leaf stems) associated with those leaves. For plants requiring leaf sampling, the petiole is usually not included. Petioles are often used for sampling water鈥搒oluble (nitrate and phosphate) rather than total nutrients because the petiole is the conducting tissue where nutrients travel from the stem to the leaf. The recommended plant part for sampling should be determined for each specific plant (see Table 1.)
If a field contains both healthy and unhealthy plants, these sampling guidelines are less critical. One can remove a sample from both healthy and unhealthy plants, making sure that the same plant part is taken in both. The healthy plant can be used as the standard value to compare against the unhealthy plant. This type of comparison may be less ideal than it appears because the physiological age of the two plant groups differ. It is not uncommon for an unhealthy plant to mature at a different rate than a healthy one. For example, an unhealthy plant may bloom much earlier than its healthy counterpart. Therefore, although two plants may have been planted at the same time in the same field, their physiological age, or stage of development, may not be the same. This can make direct comparison difficult. It is helpful if soil samples are collected from healthy and unhealthy areas when tissue samples are collected.
Plant tissue samples should be taken from plants representative of the sampling area. Dead or damaged plants, those with insect or disease problems, those at the end of rows or in edge rows, or plants that differ significantly from those in the rest of the planting should not be sampled. Plants that have been recently sprayed with foliar fertilizers should be avoided. It is important that at least the recommended number of plants is sampled to ensure that a representative sample is obtained. If the recommended sample size is 25 mature leaves, all leaves should be taken from separate plants. In addition, the sampled plants should be randomly selected from a field, not concentrated in one area.
Try to sample clean leaves. Plants analyzed for iron or aluminum should first be washed quickly in a mild (2 percent) detergent solution. Fresh tissue samples must be dried rapidly at 150掳 to 175掳F until all water is removed (a kitchen oven on the warm setting will suffice). Drying at higher temperatures may destroy plant tissues; drying at lower temperatures will not stop biological activity. Tissue samples will dry best in open containers, cloth bags or opened paper bags. Samples should be dried immediately following sampling. If this is not possible, samples may be refrigerated for short periods of time prior to drying.
Tissue samples are ground to powder in the laboratory, then put into a liquid form for analysis. One of several methods may be used. Often plant tissues are digested in acid solutions. The tissue may be directly digested in boiling acid or it may be ashed in a furnace prior to acid digestion. Sometimes soluble nutrients are extracted from plant tissue in water or in salt or dilute acid solutions. Selection of appropriate methodology depends on the specific analysis to be conducted.
Results from analyses are most frequently compared directly to previously determined standard values. Standards are established for nutrient concentration ranges adequate for healthy plant growth; these are called sufficiency ranges. By comparing the results of a plant tissue analysis with these standards, the nutritional status of the test crop can be established. Sufficient nutrient concentration ranges for most crops grown in 蜜桃影像 are presented in Table 2.
In some cases, the levels of soluble nutrients in petiole tissues provide more sensitive parameters for nutritional diagnoses than leaf analyses. Diagnostic values for petiole nutrient levels are given in Table 3.
Table 1. Recommended plant part and growth stage for selected crop plants.
Crop | Number of Plants Sampled | Plant Part | Stage of Growth |
---|---|---|---|
Alfalfa | 12 | Top 6 inches | Prior to bloom |
Barley | 25 | Whole top1 | Emergence of head from boot |
Beets | 20 | Most recently mature leaf 2 | At maturity |
Bluegrass | Clippings | 4鈥6 weeks after last cut | |
Broccoli | 12 | Most recently mature leaf | At heading |
Bromegrass | 25 | First mature stem w/leaves | At maturity |
Brussels sprouts | 12 | Most recently mature leaf | At maturity |
Cabbage | 15 | Whole tops | 2鈥6 weeks old |
Cabbage | 12 | Wrapper leaf | 2鈥3 months old |
Canola | 20 | First fully mature leaves | At flowering |
Carrot | 15 | Most recently mature leaf | 惭颈诲鈥搒别补蝉辞苍 |
Carrot | 15 | Oldest leaf | At maturity |
Cauliflower | 12 | Most recently mature leaf | At heading |
Celery | 12 | Most recently mature leaf | 贬补濒蹿鈥揼谤辞飞苍 |
Chinese cabbage | 12 | First fully developed leaf | 8鈥搇eaf stage |
Chinese cabbage | 12 | First fully developed leaf | At maturity |
Clover, red | 15 | Whole top | Prior to bloom |
Clover, alsike | 20 | Whole top | At first flower |
Clover, white | 50 | Leaves | Prior to bloom |
Romaine lettuce | 12 | Wrapper leaf | At maturity |
Head lettuce | 12 | Wrapper leaf | Heads half鈥搒ize |
Oats | 25 | Whole top | Emergence of head from boot |
Potato | 25 | Most recently mature leaf | Plant 12 inches tall |
Potato | 25 | Most recently mature leaf | Tubers half鈥揼rown |
Raspberry | 50 | Most recently mature whole leaves | Flower bud start |
Strawberry | 25 | Most recently mature whole leaves | At flowering |
Tall fescue | 20 | Clipping | 5鈥6 weeks after last cut |
Timothy | 25 | Whole top | Early bloom |
Turnip | 12 | Most recently mature leaf | 惭颈诲鈥揼谤辞飞迟丑 |
1 Whole top is the entire above ground portion of the plant.
2 Most recently mature leaf is the youngest fully developed leaf.
Table 2. Nutrient sufficiency ranges for selected crop plants.1
Nutrient | Alfalfa | Barley | Beets | Bluegrass | Broccoli |
---|---|---|---|---|---|
% | |||||
Nitrogen | 2.95鈥5.00 | 1.75鈥3.00 | 4.00鈥5.50 | 2.60鈥3.50 | 3.20鈥5.50 |
Phosphorus | 0.24鈥0.70 | 0.20鈥0.50 | 0.25鈥0.50 | 0.28鈥0.40 | 0.30鈥0.75 |
Potassium | 2.00鈥3.50 | 1.50鈥3.00 | 2.00鈥4.50 | 2.00鈥3.00 | 2.00鈥4.00 |
Calcium | 1.20鈥3.00 | 0.30鈥1.20 | 2.50鈥3.50 | ________ | 1.00鈥2.50 |
Magnesium | 0.16鈥1.00 | 0.15鈥0.50 | 0.30鈥1.00 | 0.40鈥0.48 | 0.23鈥0.75 |
Sulfur | 0.23鈥0.50 | 0.15鈥0.40 | 鈥斺赌 | 0.16鈥0.24 | 0.30鈥0.75 |
ppm | |||||
Boron | 20鈥80 | 鈥斺赌 | 30鈥85 | 鈥斺赌 | 0鈥100 |
Copper | 6鈥30 | 4.25 | 5鈥15 | 鈥斺赌 | 5鈥15 |
Iron | 31鈥250 | 鈥斺赌 | 50鈥200 | 鈥斺赌 | 70鈥300 |
Manganese | 21鈥200 | 18鈥100 | 50鈥250 | 鈥斺赌 | 25鈥200 |
Molybdenum | 1.0鈥5.0 | 0.11鈥0.18 | |||
Zinc | 20鈥70 | 20鈥70 | 15鈥200 | 鈥斺赌 | 35鈥200 |
Nutrient | Brome grass | Brussels sprouts | Cabbage 2鈥6 wks | Cabbage 2鈥3 months | Canola |
---|---|---|---|---|---|
% | |||||
Nitrogen | 2.00鈥3.50 | 2.20鈥5.50 | 3.00鈥5.00 | 3.00鈥5.00 | 2.50鈥4.00 |
Phosphorus | 0.25鈥0.35 | 0.26鈥0.75 | 0.35鈥0.75 | 0.30鈥0.75 | 0.25鈥0.50 |
Potassium | 2.00鈥3.50 | 2.00鈥4.00 | 3.50鈥6.00 | 3.00鈥5.00 | 1.50鈥2.50 |
Calcium | 0.25鈥0.40 | 0.30鈥2.50 | 3.00鈥4.50 | 1.10鈥3.50 | 0.50鈥4.00 |
Magnesium | 0.14鈥0.30 | 0.23鈥0.75 | 0.50鈥2.00 | 0.24鈥0.75 | 0.20鈥1.50 |
Sulfur | 0.17鈥0.30 | 0.30鈥0.75 | 鈥斺赌 | 0.30鈥0.75 | 0.25鈥0.50 |
ppm | |||||
Boron | 10鈥20 | 30鈥100 | 25鈥75 | 25鈥75 | 30鈥80 |
Copper | 5鈥10 | 5鈥15 | 5鈥15 | 5鈥15 | 2.7鈥20 |
Iron | 50鈥100 | 60鈥300 | 30鈥200 | 30鈥200 | 20鈥200 |
Manganese | 40鈥80 | 25鈥200 | 50鈥200 | 25鈥200 | 15鈥100 |
Molybdenum | 鈥斺赌 | 0.25鈥1.00 | 鈥斺赌 | 0.4鈥0.7 | 鈥斺赌 |
Zinc | 20鈥50 | 25鈥200 | 25鈥200 | 20鈥200 | 15鈥70 |
Nutrient | Carrots mid-season | Carrots mature | Cauliflower | Celery | Chinese Cabbage |
---|---|---|---|---|---|
% | |||||
Nitrogen | 1.80鈥3.50 | 3.00鈥3.50 | 3.00鈥4.50 | 2.50鈥3.50 | 4.50鈥5.50 |
Phosphorus | 0.20鈥0.50 | 0.20鈥0.40 | 0.33鈥0.80 | 0.30鈥0.50 | 0.50鈥0.60 |
Potassium | 2.00鈥4.30 | 2.90鈥3.50 | 2.60鈥4.20 | 4.00鈥7.00 | 7.50鈥9.00 |
Calcium | 1.40鈥3.00 | 1.00鈥2.00 | 0.70鈥3.50 | 0.60鈥3.00 | 3.00鈥5.50 |
Magnesium | 0.30鈥0.53 | 0.25鈥0.60 | 0.24鈥0.50 | 0.20鈥0.50 | 0.35鈥0.50 |
ppm | |||||
Boron | 29鈥100 | 30鈥75 | 30鈥100 | 30鈥50 | 23鈥75 |
Copper | 4.5鈥15 | 5鈥15 | 4鈥15 | 5鈥8 | 5鈥25 |
Iron | 50鈥300 | 50鈥300 | 30鈥200 | 20鈥40 | 31鈥200 |
Manganese | 60鈥200 | 60鈥200 | 25鈥250 | 200鈥300 | 25鈥200 |
Molybdenum | 0.5鈥1.5 | 0.5鈥1.4 | 0.5鈥0.8 | 鈥斺赌 | 鈥斺赌 |
Zinc | 20鈥250 | 20鈥250 | 20鈥250 | 20鈥50 | 30鈥200 |
Nutrient | Alsike Clover | Red Clover | White Clover | Romaine Lettuce | Head Lettuce |
---|---|---|---|---|---|
% | |||||
Nitrogen | 3.00鈥4.50 | 4.5鈥5.0 | 3.50鈥4.50 | 3.50鈥5.00 | |
Phosphorus | 0.25鈥0.50 | 0.20鈥0.60 | 0.36鈥0.45 | 0.45鈥0.80 | 0.40鈥0.60 |
Potassium | 1.50鈥3.00 | 2.20鈥3.00 | 2.00鈥2.50 | 5.50鈥6.20 | 6.00鈥9.60 |
Calcium | 1.00鈥1.80 | 2.00鈥2.60 | 0.50鈥1.00 | 2.00鈥2.80 | 1.40鈥2.25 |
Magnesium | 0.30鈥0.60 | 0.21鈥0.60 | 0.20鈥0.30 | 0.60鈥0.80 | 0.36鈥0.70 |
Sulfur | 鈥斺赌 | 0.26鈥0.30 | 0.25鈥0.50 | 鈥斺赌 | 鈥斺赌 |
ppm | |||||
Boron | 15鈥50 | 30鈥80 | 25鈥50 | 25鈥60 | 23鈥50 |
Copper | 3鈥15 | 8鈥15 | 5鈥8 | 5鈥25 | 7鈥25 |
Iron | 50鈥100 | 30鈥250 | 25鈥100 | 40鈥100 | 50鈥175 |
Manganese | 40鈥100 | 30鈥120 | 25鈥100 | 11鈥250 | 20鈥250 |
Molybdenum | 鈥斺赌 | 0.50鈥1.00 | 0.15鈥0.25 | 鈥斺赌 | 鈥斺赌 |
Zinc | 15鈥80 | 18鈥80 | 15鈥25 | 20鈥250 | 25鈥250 |
Nutrient | Oats | Potatoes 12-in. plants | Potatoes tubers 陆 grown | Raspberry plants |
---|---|---|---|---|
% | ||||
Nitrogen | 2.00鈥3.00 | 4.50鈥6.50 | 3.00鈥4.00 | 2.20鈥4.00 |
Phosphorus | 0.20鈥0.50 | 0.29鈥0.50 | 0.25鈥0.40 | 0.30鈥0.50 |
Potassium | 1.50鈥3.00 | 2.40鈥3.90 | 3.20鈥4.10 | 1.40鈥3.00 |
Calcium | 0.20鈥0.50 | 0.76鈥1.00 | 1.50鈥2.50 | 0.80鈥1.50 |
Magnesium | 0.15鈥0.50 | 0.36鈥0.49 | 0.49鈥0.54 | >0.30 |
Sulfur | 0.15鈥0.40 | 鈥斺赌 | 鈥斺赌 | 鈥斺赌 |
ppm | ||||
Boron | 鈥斺赌 | 25鈥50 | 40鈥70 | 25鈥75 |
Copper | 5鈥25 | 7鈥20 | 7鈥20 | 3鈥50 |
Iron | 40鈥150 | 50鈥100 | 40鈥100 | |
Manganese | 22鈥100 | 30鈥250 | 30鈥250 | 30鈥250 |
Molybdenum | 0.2鈥0.3 | 鈥斺赌 | 鈥斺赌 | 鈥斺赌 |
Zinc | 15鈥70 | 45鈥250 | 30鈥200 | 25鈥100 |
Nutrient | Strawberry plants | Tall Fescue | Timothy | Turnips |
---|---|---|---|---|
% | ||||
Nitrogen | 2.50鈥4.00 | 3.20鈥3.80 | 0.53鈥1.68 | 3.50鈥5.00 |
Phosphorus | 0.21鈥1.00 | 0.34鈥0.45 | 0.11鈥0.18 | 0.33鈥0.60 |
Potassium | 1.30鈥3.00 | 2.80鈥4.00 | 1.14鈥1.70 | 3.50鈥5.00 |
Calcium | 1.00鈥2.50 | 鈥斺赌 | 0.09鈥0.35 | 1.50鈥4.00 |
Magnesium | 0.25鈥1.00 | 鈥斺赌 | 0.06鈥0.25 | 0.30鈥1.00 |
Sulfur | 鈥斺赌 | >0.15 | 鈥斺赌 | 鈥斺赌 |
ppm | ||||
Boron | 23鈥50 | 鈥斺赌 | 1鈥10 | 30鈥100 |
Copper | 6鈥50 | 鈥斺赌 | 7鈥45 | 6鈥25 |
Iron | 50鈥200 | 鈥斺赌 | 22鈥54 | 40鈥300 |
Manganese | 70鈥200 | 鈥斺赌 | 11鈥35 | 40鈥250 |
Zinc | 20鈥200 | 鈥斺赌 | 24鈥62 | 20鈥250 |
1Standard values are for plant parts and growth stages specified in Table 1.
Table 3. Sufficiency levels for nitrate, phosphate, and potassium in petioles and leaf midribs of selected crop plants.
Crop | Stage of Growth | Plant part | Nitrate鈥 N (ppm) | Phosphate鈥 P (ppm) | Potassium (%) |
---|---|---|---|---|---|
Broccoli |
惭颈诲鈥揼谤辞飞迟丑 First buds |
Midrib of YML1 |
>9000 >7000 |
>4000 >4000 |
>5.0 >4.0 |
Brussels sprouts | 惭颈诲鈥揼谤辞飞迟丑 | Late growth Midrib of YML |
>9000 >7000 |
>3500 >3000 |
>5.0 >4.0 |
Chinese Cabbage | Heading | Midrib of wrapper leaf | >9000 | >3500 | >4.0 |
Carrot | 惭颈诲鈥揼谤辞飞迟丑 | Petiole of YML | >10000 | >4000 | >6.0 |
Cauliflower | Head forming | Midrib of YML | >9000 | >5000 | >4.0 |
Celery | 惭颈诲鈥揼谤辞飞迟丑 | Near mature Petiole of YML |
>9000 >6000 |
>5000 >3000 |
>6.0 >5.0 |
Head Lettuce |
Heading Harvest |
Midrib of wrapper leaf |
>8000 >6000 |
>4000 >2500 |
>4.0 >2.5 |
Potato |
贰补谤濒测鈥搒别补蝉辞苍 惭颈诲鈥搒别补蝉辞苍 Late season |
Petiole of fourth leaf from the growing tip |
>19000 >15000 >8000 |
>2000 >1600 >1000 |
>12.0 >9.0 >6.0 |
1 YML 鈥 youngest mature (fully expanded) leaf.
Nutritional diagnoses can give important information about the condition of a crop; however in the case of an annual crop, it may be too late to effectively remedy nutritional problems. Nevertheless, even when irreparable damage has been done, diagnostic nutritional information can be extremely valuable. If tissue analyses reveal shortages of nutrients routinely applied in a fertilization program (nitrogen, phosphorus or potassium), this may be an indication that the fertilization regime being used is inadequate for that crop. The next time the crop is grown at that location, fertilizer application rates should be adjusted. If tissue analyses reveal shortages of secondary or micronutrients, soil test information should be consulted and consideration should be given to various means of correcting the problem before the field is planted again. When dealing with perennial crops, adjusting fertilization practices can be made at almost any time. Action taken late in the season may not improve that season鈥檚 yield, but performance in subsequent years should be enhanced.
Information from plant tissue tests cannot replace that from soil tests; the two practices provide complementary data. By combining information from the two sources, one gets a clearer picture of the ability of a soil to provide adequate nutrition and of the crop to use nutrients. Both should be considered integral parts of a complete nutrient monitoring program.
References
The information contained in Tables 1鈥3 was derived from the following publications:
Dow, A.I. 1980. Critical nutrient ranges in Northwest crops. Western Regional Extension Publication No. 43.
Evanylo, G.K. and G.W. Zehnder. 1988. Potato growth and nutrient diagnosis as affected by systemic pesticide growth stage. Communications in Soil Science and Plant Analysis 19:1731鈥1745.
Gardner, B.R. and J.P. Jones. 1975. Petiole analysis and the nitrogen fertilization of Russet Burbank potatoes. American Potato Journal 52:195鈥200.
Geraldson, C.M. and K.B. Tyler. 1990. Plant analysis as an aid to fertilizing vegetables. In Soil Testing and Plant Analysis, ed. R.L. Westerman. Madison, WI: Soil Science Society of America.
Jones, J.B. Jr., B. Wolf, and H.A. Mills. 1991. Plant Analysis Handbook. Athens, GA: Micro鈥揗acro Publishing, Inc.
Kelling, K.A. and J.E. Matocha. 1990. Plant analysis as an aid to fertilizing forage crops. In Soil Testing and Plant Analysis, ed. R.L. Westerman. Madison, WI: Soil Science Society of America.
Kleinkopf, G.E. and D.T. Westermann. 1982. Scheduling nitrogen applications for Russet Burbank potatoes. University of Idaho Current Information Series No. 367.
MacKay, D.C., J.M. Carefoot, and T. Entz. 1987. Evaluation of the DRIS procedure for assessing the nutritional status of potato (Solanum tuberosum L.). Communications in Soil Science and Plant Analysis 18:1331鈥1353.
Redshaw, E.S. 1990. Plant tissue testing. Agri鈥揻ax, Alberta Agriculture. Agdex 100/08鈥1.
Sanchez, C.A., H.W. Burdine, and V.L. Guzman. 1989. Soil testing and plant analysis as guides for the fertilization of celery on histosols. Soil and Crop Science Society of Florida Proc. 49:69鈥72.
Sanchez, C.A., G.H. Synder, and H.W. Burdine. 1991. DRIS evaluation of the nutritional status of crisphead lettuce. HortScience 23:274鈥276.
Walworth, J.L., R.G. Gavlak, and J.E. Muniz. 1990. Effects of potassium source and secondary nutrients on potato yield and quality in Southcentral 蜜桃影像. University of 蜜桃影像 Fairbanks, Agricultural and Forestry Experiment Station, Research Progress Report No. 18.
Westfall, D.G., D.A. Whitney, and D.M. Brandon. 1990. Plant analysis as an aid in fertilizing small grains. In Soil Testing and Plant Analysis, ed. R.L. Westerman. Madison, WI: Soil Science Society of America.
Williams, C.M.J. and N.A. Maier. 1990. Determination of the nitrogen status of irrigated potato crops. I. Critical nutrient ranges for nitrate鈥搉itrogen in petioles. Journal of Plant Nutrition 13:971鈥984.
Steven Seefeldt, Extension Faculty, Agriculture and Horticulture. This publication was originally prepared by James L. Walworth, former Soil Scientist, University of 蜜桃影像 Agriculture and Forestry Experiment Station, Palmer.
Reviewed June 2015