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Timing of Phosphorus Management for Optimal Potato Production

Timing is a critically important aspect of nutrient management. It impacts everything from crop health, to return on investment, to the environment. It is no wonder that the ‘right time’ is one of the four pillars of nutrient management, including the right rate, right source, and right placement.


For any nutrient, one of the main goals is to have the nutrient release and availability align with plant uptake as closely as possible. There needs to be sufficient nutrient availability for crop demand over the growing season, while minimising soil nutrient loss.


Consider the timing aspect of phosphorus management for potato production. Phosphorus is an important nutrient for both potato yield and tuber quality.


Potatoes can utilise a considerable amount of P compared to other crops, for example, a 45 T/Ha crop could use 30Kg of P per hectare.


The majority of this P uptake occurs during the bulking growth stages, more than 40 days after emergence and continues into late bulking. The peak daily P uptake also occurs in the latter part of the season, meaning that the daily P uptake requirements are highest during bulking.


But how does phosphorus fertiliser timing match up with this nutrient uptake? We know the recommended phosphorus application timing is generally at planting or early in the new season, which seems ironic given the peak uptake occurs much later in the season.


We also know that traditional P fertilisers are highly water soluble, dissolving quickly into the soil solution where they can undergo chemical reactions that can later limit the P availability to plants (calcium, aluminum and iron are the most common elements that tie up P).


If applications are done in a timely manner before tissue levels have dropped, in season applications can be of some help, but with P having limited mobility in the soil, this is not as effective, especially as the roots are not close to the surface. When soil P concentrations fail to meet peak P demands, tuber size, yield and health can be diminished.


Considering a liquid alternative

Liquid P complexes can address the issues associated with late season applications as they are more mobile within the soil, avoid the ‘lock up’ experienced in certain soils and have some foliar absorption.


ECTOL - STARTER is such a product, offering a mixture of protected Phosphorus, Nitrogen and Potassium (14:12:2) that is safely applied in-furrow. It will not ‘burn’ sensitive seeds or seedlings. The Phosphorus complex avoids immobilisation and lock-up of Phosphorus in acid soils and reduces the loss on Nitrogen from leaching and Phosphorus as run-off­.


A trial conducted in Tasmania, where late application of P in the form of ECTOL STARTER was used, demonstrated significant yield increases. Download trial report here.


To find out more, contact the team at ECTOL today.


J H McKay

Ref: Potato Grower 2014

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