Foliar sampling

This author recommends a minimum plot size of 4 rows x 200 ft for each treated plot. Foliar sampling would occur on the middle two rows with a 10-ft buffer on each end. Soil sampling would occur on each side of the middle two rows with a 10-ft buffer on each end. The 180-ft rows should be divided into 60-ft replicates designated as A, B, and C. The untreated plot should be 2 rows x 50 ft. For tree crops, 3 rows x 14 trees should be treated. The middle row should be sampled excluding the first and last trees. 

After the foliar samples have been collected they are placed on wet ice and brought back to a facility for dislodging. The goal of the dislodging procedure is to extract the residue present on the leaf surface that is available for transfer from the leaf. Residues that have been absorbed into the plant matrix would not be available for transfer. The best practice is to dislodge the residue within 4 h of collecting the sample. 

Black, K.G. and R.A. Fenske (1996). Dislogeability of Chlorpyrifos and Flonrescent Tracer Residues on Turf Comparison of Wipe and Foliar Sampling Techniqnes, Arch. Environ. Contam. Toxicol, 31, 563-570. 

Brockley, R.P. 2001. Foliar sampling guidelines and nutrient interpretive criteria for lodgepole pine. Extension Note, British Columbia Ministry of Forests, Victoria, B.C. 8 pp. 

Diazinon SOW was applied by air blast sprayers in accordance with typical application practices for orchards. Application began in March and continued until early-to mid-July. Dormant sprays typically contained diazinon in an oil mixture. Aqueous emulsions were applied as foliar sprays thereafter. Eqmpment was calibrated to provide an application rate of 3.4 kg active ingredient (a.i.)ha At least five applications were made at approximately 2-week intervals. During these applications, 233 samples were taken from spray tanks across the four treatment fields to estimate the application rate in PA, and 244 samples were collected in WA. 

A 25-g sample of <150- o.m control soil was placed into each of six jars for fortification. Three samples were fortified at each of two concentrations of oxamyl. Soil samples were fortified on the same days and at the same levels as the foliar... 

Extracts of gloves, extracts of foliar dislodgeable residue and absolute foliar residues, and filters containing thiophanate-methyl were analyzed by reversed-phase HPLC and ultraviolet detection at 254 nm (Engel, 1988). The LOD was 50 mg/L for extracts of filters and gloves, and 10 mg/L for leaf samples. Recovery was > 90%, and the "between days" CV of the analytical chemical method was < 5%. 

Figure 11. Carbofuran residue in high volume air samples taken above rice paddies treated by foliage spray (0) or by foliar spray followed by granular broadcast treatment (A) (51) (each point = 8 hr of sampling at 623 L/min)...

In spite of the sensitivity of the determination, because of the low concentrations of cadmium in most environmental samples, the element is still often preconcentrated. For example, discrete nebulization flame AAS has been used to measure foliar cadmium after extraction of the APDC complex into chloroform.15 Cobalt was extracted at the same time. Many other solvent extraction procedures have been described.1 Alternatively resins such as a chelating polydithiocarbamate resin have been employed to concentrate cadmium prior to determination.16 Extractions onto solid phase materials for preconcentration may be made more convenient by automation, for example using flow injection methodology.17... 

Cowell, J.E., S.A. Adams, J.L. Kunstman and M.G. Mueth (1993). Comparison of foliar and turf dislodgeable residue sampling techniques, in Pesticides in Urban Environments, K.D. Racke and A.R. Leslie (Eds), ACS Symposium Series 522, American Chemical Society, Washington, DC, USA, pp. 100-112. 

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