Potato Petiole Analysis: Staying on Track from Emergence and Beyond

After the initial sigh of relief that tubers are in the ground and emerged, comes the concern to keep them on track to meet your tonnage and quality commitments at the end of the season – which may be cold, hot, wet or dry and everything in between. Maintaining growth to meet your target yields can be done but not in the absence of information and this is where regular petiole analysis comes to the fore.

Why Carry Out Petiole Analysis on Potatoes?

Highly Accurate Measure of Plant’s Current Nutritional State

Highly accurate measure of plant’s current nutritional state – the petiole is the main nutrient ‘highway’ of the plant connecting the roots and leaves and therefore analysis of them provides an accurate picture of nutrient levels within the plant at that given time.

Proactive Nutrient Management

Proactive nutrient management – petiole nutrient analysis provides real-time insight into the plant’s nutrient status. It can identify ‘hidden hunger’ – nutrient deficiencies that are not yet visible in the field – allowing growers to act before yield is limited and damage becomes difficult to correct.

Enables In-Field Corrective Actions

Enables in-field corrective actions – the real-time analysis leads to the opportunity to take decisions to correct in-field deficiencies or not, but the decision is based on facts. The decision can be made before the deficiency has incurred irreversible yield and quality damage.

Optimising Yield and Quality

Optimising yield and quality – regular monitoring helps maintain optimal nutrient supply during critical growth stages such as tuber initiation and bulking, which directly affect marketable yield. Nutrition levels also influence other quality parameters such as skin finish, dry matter levels, bruising resistance – all important factors to consider.

Optimising Input Volumes and Costs

Optimising input volumes and costs – by measuring nutrient supply levels and comparing them to growth stage demand allows growers to optimise their inputs, by ensuring that supply and demand are evenly matched. Over-application of nutrients can be just as detrimental to crops as deficiencies, while also being a costly waste of money and time.

Effectively Using Petiole Analysis

Sampling Method

Sampling method – Select the 3rd or 4th fully emerged leaf of the plant – the 3rd or 4th leaf is selected because it is fully formed and it has all the nutrients it should have. Then take your leaf with the leaflets and the petiole down the middle, and strip the leaves off, leaving just the petiole. Do this every 10 paces or so down one row and then move across the field some distance and come back up another until you have collected about 40.

When taking samples, it is important to remember that they need to arrive at the lab ‘as fresh as possible’ to prevent sample decay. This is best achieved by taking samples Sunday-Wednesday and posting immediately to avoid them sitting either in a post box or sorting office over a weekend period, especially in hot weather.

Sample Timings

Sample timings – Sampling needs to be undertaken early enough in the season to be able to make meaningful nutritional adjustments. Ideally after tuber initiation and as bulking begins.

Translating Results into Actions

Translating results into actions – single figure analysis results are meaningless unless they can be interpreted into easily understandable data. This is best achieved when combined with a full soil analysis and variety growth stage nutrient demand figures.

When sampled correctly and combined with soil analysis and variety-specific nutrient demand information petiole sampling is the most accurate way of establishing a crop’s in-season nutritional health.

Providing growers with solid information on which to weigh up the cost, yield and quality benefits of nutrient interventions in a season which offers very few certainties.

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