Trials suggest water rates and application timing are central to higher tuber residue values, explains Nick Winmill, Agrii head of potato trials and research.

Trials commissioned by Sutton Bridge Crop Storage Research (SBCSR) and performed by SBCSR with support from Agrii found that higher water rates in combination with applications early or late in the day result in higher tuber residue values.

Maleic hydrazide has the potential to reduce sprout growth over long storage durations removing the need for post-harvest treatments that are, in comparison, relatively costly. Ensuring the crop absorbs sufficient active substance to have the desired effect while observing maximum residue levels, however, has been the subject of research.

A study in 2006 found that while the detected residues were often well below the maximum limit, there were instances that could be considered problematic. The authors found this to be a result of poor application practice. More information on conditions suitable for optimal application was therefore considered of value to growers.

A further trial by SBCSR and Agrii in 2021 (S1056) sought to consider the importance of humidity in promoting absorption.
Maintaining high humidity levels for a 24-hour period after application resulted in a three-fold and highly significant increase in tuber maleic hydrazide residue concentration. The effect was similar in both varieties used in trial – Taurus, and Innovator – but was within the permitted limit.

While such conditions are unlikely to occur in the field, they demonstrate that humidity is an important factor in optimising applications.
We know from earlier research that plant hydration is important to ensuring that maleic hydrazide is transported around the plant. This begins on the leaf and, it is proposed, that by extending drying time through higher humidity, the absorption time was also increased.

The results indicate that the timing of maleic hydrazide applications should also take account of drying conditions.

Yield differences between dry and humid conditions were not significant in either of the varieties used in the trial.

Progeny tubers from a selected pot of each variety used in the trial highlighted that there were no negative yield or size consequences of maleic hydrazide