Potato Petiole Guide for Nutrient Testing

Potato Petiole Sampling and Guidelines

Sampling potato petioles and analyzing then is a very effective way to refine and verify if your potato fertility program is working well. Petioles are commonly sampled as opposed to whole plant parts as in other crops. The petiole, being basically the stem that connects the leaflets, acts like a straw for nutrients traveling to the leaves. Thus sampling the petioles gives on a flow rate of nutrients.

Sampling Techniques

Sample between 9 a.m. and 4 p.m. so the plant is actively growing
Sample between 20 and 50 plants depending on the thickness of the petioles
sample a representative area of the field: Not too close to the edges, road and any other non-normal area. In a center pivot field this means in the middle towers.
Cross rows of plants to minimize any influences with fertilizer applications.
Sample the 4^th or 5^th fully expanded leaf or about midway down the plant. This location will change in indeterminate varieties that keep growing.
Pull the whole leaf off, then strip the leaflets off petiole.
Sample until you have about an 1 inch diameter bundle of petioles
Place samples in a paper bag (never plastic) that is labeled well for the lab and keep in a cool place.
Ship to the lab for analysis as quickly as possible.
Request a complete analysis early and late season. In between, nitrate and phosphate analysis may be sufficient to chart a plants progress. Two samples are always needed to know the tend in a nutrients availability.

Interpreting the Results

Sufficiency levels of nutrient change over the season, so it is important to evaluate the lab results based on crop stage. Varieties vary greatly in sufficiency levels as well. Below are tables to interpret petiole analysis results.

Nitrates

Varieties

60 Days After Planting (ppm)

70 Days After Planting (ppm)

90 - 100 Days After Planting (ppm)

100 to 120 Days After Planting (ppm)

Norkotah, Norgold, Yukon Gold, Frontier, Norkotah Texas Lines

High:38,000

Low:28,000

High:36,000

Low:25,000

High:25,000

Low:15,000

High:10,000

Low:5,000

Alpha, Crestone, Century, Centennial, Any New Variety

High:40,000

Low:30,000

High:32,000

Low:23,000

High:30,000

Low:20,000

High:10,000

Low:5,000

Sangre and other Reds

High:35,000

Low:25,000

High:20,000

Low:10,000

High:15,000

Low:6,000

High:0

Low:0

Nugget, Chipeta, Norkotah CO Line 3

High:32,000

Low:20,000

High:25,000

Low:15,000

High:14,000

Low:8,000

High:6,000

Low:5,000

Russet Burbank

High:30,000

Low:20,000

High:28,000

Low:18,000

High:25,000

Low:13,000

High:10,000

Low:5,000

Phosphates

Phosphate sufficiency levels are the same for all varieties more or less and it is a straight line down in levels across the season. The table below summarizes the desirable levels.

Plant Stage	Desirable Petiole level of Phosphorus in ppm
60 Days After Planting	3500
90 days After Planting	2200
115 days After Planting	1000

Micronutrients

Again desirable petiole levels don't vary much from variety to variety, but the vary across the growing season. Use the tables below to interpret your petiole lab results.

MICRONUTRIENT GUIDELINES
	P %	Ca %	Mg %	S %	Cu ppm
LOW	0.3	0.5	0.25	0.07	2
HIGH	0.45	1.5	0.5	0.15	5
EARLY SEASON PETIOLE REPORT

LOW	0.25	0.5	0.25	0.07	2
HIGH	0.35	1.5	0.5	0.15	5
MID SEASON PETIOLE REPORT
LOW	0.1	0.5	0.25	0.07	2
HIGH	0.15	1.5	0.5	0.15	5
LATE SEASON PETIOLE REPORT
MICRONUTRIENT GUIDELINES
	K %	Zn ppm	Fe ppm	Mn ppm	B ppm
LOW	9.5	15	90	30	20
HIGH	12	50	300	100	50
EARLY SEASON PETIOLE REPORT
LOW	8.5	15	60	30	20
HIGH	11	50	300	100	50
MID SEASON PETIOLE REPORT
LOW	6	15	40	30	20
HIGH	8	50	300	100	50
LATE SEASON PETIOLE REPORT

Note: This information should only be used as a guide. Adjustments for local conditions must always be made.

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