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Publication #HS1123

Plant Part Selection and Preliminary Sufficiency Ranges for Sap Testing Interpretation of Greenhouse Herbs 1

Robert C. Hochmuth, Eric H. Simonne, Lei Lani L. Davis, and Wanda L. Laughlin2

“Quick test” kits have been used for testing plant sap nitrate nitrogen (NO3-N) and potassium (K). These tests have been widely used in the Florida vegetable industry since the early 1990s (Fletcher et al., 1993; Hochmuth, et al., 1988; Hochmuth, 2003; Hochmuth et al., 2003; Vann et al., 1993). The objective is to use portable testing equipment that can be taken to the field by growers to assess the nutrient status of the crop. One of the most popular “quick tests” has been the Cardy meters, one for NO3-N and one for K. A drop of plant sap is placed on calibrated electrodes and the concentration of NO3-N or K is read on a digital scale. Consult the publication entitled “Calibrating sap-testing meters” (Studstill et al., 2006) for a detailed description of how to properly use these meters.

Recent interest has increased in herbs as an alternative crop throughout Florida. Production of herbs has increased both in the field and greenhouses. Greenhouse hydroponic herb production, primarily basil, increased from near zero acres in 1988 to nearly 20 acres in 2004 (Tyson et al., 2004). Several studies with herbs have been conducted from 2000-2006 at the UF/IFAS North Florida Research and Education Center—Suwannee Valley near Live Oak, Florida (Stapleton and Hochmuth, 2001). Many of the studies evaluated various nutrient programs for producing high-quality fresh herbs using hydroponic systems. These studies provided several opportunities to document observed sap concentration of NO3-N and K in the plant sap of basil (Ocimum basilicum), cilantro (Coriandrum sativum), dill (Anethum graveolens), spearmint (Mentha spicata), and oregano (Origanum vulgare) (Table 1). These concentrations represent target nutrient levels based on repeated tests and under growing conditions that resulted in adequate yield and quality.

Sap testing is typically done on petioles because they are easily identifiable succulent organs and they yield usable volumes of sap when pressed. However, herbs may not have large identifiable petioles. Botanically, petiole is defined as "leaf stalk," petiolule as "leaflet stalk" and vein as "strand of fibrovascular tissue in a leaf or other laminar structure" (Radford et al, 1968). Hence, the plant part used to develop the target nutrient concentrations (Table 1) should be also used for routine analysis (Figures 1–6). A minimum of 20 plants should be sampled for routine analysis in order to ensure a representative sample. When a problem is suspected, take two separate samples, one from symptomatic, and one from healthy plants.

Figure 1. 

Leaf parts of basil, dill, mint, oregano, and cilantro selected for sap collection. (Plant parts may not anatomically correspond to a petiole. Using the same leaf part in routine sap testing is necessary if the typical ranges presented above are to be used. The arrow marks plant part used for sap testing.)


Credit:

UF/IFAS


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Figure 2. 

Basil leaf part used for sap collection and analysis. (The arrow marks plant part used for sap testing.)


Credit:

UF/IFAS


[Click thumbnail to enlarge.]

Figure 3. 

Cilantro leaf part used for sap collection and analysis. (The arrow marks plant part used for sap testing.)


Credit:

UF/IFAS


[Click thumbnail to enlarge.]

Figure 4. 

Dill leaf part used for sap collection and analysis. (The arrow marks plant part used for sap testing.)


Credit:

UF/IFAS


[Click thumbnail to enlarge.]

Figure 5. 

Spearmint leaf part used for sap collection and analysis. (The arrow marks plant part used for sap testing.)


Credit:

UF/IFAS


[Click thumbnail to enlarge.]

Figure 6. 

Oregano leaf part used for sap collection and analysis. (The arrow marks plant part used for sap testing.)


Credit:

UF/IFAS


[Click thumbnail to enlarge.]

References

Fletcher, J., R. Hochmuth and G. Hochmuth. 1993. Calibration of N and K fresh sap quick-test procedures for polyethylene-mulched peppers. Proc. 24th Natl Agricultural Plastics Congr. 24:147–152.

Hochmuth, G. J., P. R. Gilreath, E. A. Hanlon, G. A. Clark, D. N. Maynard, C. D. Stanley, and D. Z. Hamon. 1988. Evaluating plant N status with plant sap quick-test kits. Proc. Tomato Institute. Fla. Coop. Ext. Serv. Spec. Series. SS-VEC 801:6–14.

Hochmuth, G. 2003. Plant Petiole Sap-Testing for Vegetable Crops. Cir 1144. 6 pp. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/CV004

Hochmuth, R., D. Dinkins, M. Sweat, and E. Simonne. 2003. Extension Programs in Northeastern Florida Help Growers Produce Quality Strawberries by Improving Water and Nutrient Management. HS-956. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/HS190

Radford, A.E., H.E. Ahles and C. Ritchie Bell. 1968. Manual of the vascular flora of the Carolinas, the University of North Carolina Press, Chapel Hill, N.C. 1183 pp.

Stapleton, S. C., and R. C. Hochmuth. 2001. Greenhouse production of several fresh-cut herbs in vertical hydroponic systems in north central Florida. Pro. Fla. State Hort. Soc. 114:332–334.

Studstill, D., E. Simonne, and R. Hochmuth, and T. Olczyk. 2006. Calibrating Sap-Testing Meters. HS328. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://ufdc.ufl.edu/IR00002738/00001

Tyson, R. V., R. C. Hochmuth, E. M. Lamb, E. McAvoy, and T. Olczyk. 2004. Greenhouse vegetables in Florida's mild winter climate – 2004 update. Acta Hort 654: 37–40.

Vann. C. D., R. C. Hochmuth, and G.J. Hochmuth. 1993. Watermelon N and K petiole sap testing. Proc. 1993 Watermelon Inst. Fla. Coop. Ext. Serv. Special Series SS-HOS-003.

Tables

Table 1. 

Leaf part used and corresponding plant sap concentrations of nitrate-nitrogen and potassium ranges typically found in several greenhouse herbs. (See Fig.1 for illustration)

Crop

Plant Part Sampled

Fresh Plant Sap Concentrations z,y

NO3-N

(mg/L)

K

(mg/L)

Basil

Most recently matured leaf petiole

1000–2000

1000–2000

Cilantro

Newest 4–6 inch section of vein after all leaves removed

1500–2500

3500–5500

Dill

Newest 4–6 inch section of vein after all leaves removed

1000–1500

3500–5500

Spearmint

Newest 4–6 inch section of vein after all leaves removed

1500–2500

1000–2000

Oregano

Newest 4–6 inch section of vein after all leaves removed

2000–3000

2500–3500

ZPlant sap was expressed from the designated plant part and placed on Cardy meters for nitrate-nitrogen and potassium.

Y1 mg/L = 1ppm

Footnotes

1.

This document is HS1123, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date November 2007. Reviewed October 2016. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Robert C. Hochmuth, regional specialized Extension agent and center director; Eric H. Simonne, professor, Horticultural Sciences Department; Lei Lani L. Davis, Extension program assistant; and Wanda L. Laughlin, greenhouse manager; UF/IFAS Suwannee Valley Agricultural Extension Center, Live Oak, FL 32060.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow directions on the manufacturer's label.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.