Last year, European governments agreed to ban the use of mancozeb. The exact dates of the phase-out of sales and the period to use up stocks are not yet known, but 2021 will probably be the last year that mancozeb can be used. Because mancozeb also contains manganese (Mn) and zinc (Zn), this will affect crop protection as well as your fertilisation strategy. Both elements play an important role in keeping crops green and therefore productive. A deficiency can lead to increased sensitivity to diseases.
Manganese and zinc are both nutrients that are vital for essential processes in the crop, including photosynthesis. On sandy soils and/or soils with a high pH especially, there is poor availability of Mn and Zn, which means that uptake through the roots is often not sufficient. Whereas previously, applications of mancozeb automatically provided manganese and zinc, this source will no longer be possible in the future. This will make applications of a manganese/zinc foliar fertiliser an indispensable measure.
Each year, Soiltech conducts numerous trials to demonstrate the safety and effectiveness of its products. We recently received the results from trials that investigated the impact of the mancozeb ban, and how to compensate for its phasing out by using a a manganese/zinc foliar fertiliser.
To avoid problems with manganese and zinc in flower bulb cultivation, Soiltech set up a trial with tulips at the research centre Proeftuin Zwaagdijk. The plots in the trial were given a basic fertiliser treatment. As a reference, a trial plot was used that was set up and maintained according to usual crop protection practice (including applications of mancozeb,but not foliar fertilisers). In addition, a second reference plot (without foliar fertilisers) was included in the trial. This plot was treated with spray applications of crop protection products without mancozeb.
To fulfil the manganese and zinc demands, a further two plots were maintained like the mancozeb-free plot, with additional manganese (Optima Leaf-Mn+) and zinc (Optima Leaf-Zn+ ) provided by foliar fertilisers from Soiltech. The treatment on one plot alternated mancozeb (6x/year) and Optima Leaf-Mn+ and Optima Leaf-Zn+ (6x/year). The other plot was sprayed 12x with Optima Leaf-Mn+ and Optima Leaf-Zn+.
The graph below reveals some interesting findings:
Firstly, a significant yield decrease of up to 4.1% was apparent between the mancozeb-free regime and the regime that sprayed mancozeb 12x. This finding emphasises once again the impact the ban on mancozeb will have on your crop performance.
In addition, an increase of 8.1% was seen between the mancozeb-free spraying regime and the mancozeb-free spraying regime supplemented with Soiltech’s manganese and zinc foliar fertiliser. This demonstrates the importance of the additional manganese and zinc spray treatments when the authorisation for mancozeb expires. The plot where mancozeb was alternated with the additional manganese and zinc treatment performed even better.
The good results achieved by applying Optima Leaf-Mn+ and Optima Leaf-Zn+, encouraged Soiltech to examine the possibility of combining the two separate fertilisers into one product. This will enhance the ease of use while still achieving the same good results. This resulted in a product logically named: Optima Leaf-MnZn+.
Continuation of trials
As bulb cultivation is a two-year cycle, the bulbs harvested last year have been replanted and the same treatments will be applied in the coming growing season. We expect the differences observed in the past year to be even more pronounced in the coming year. We will also use dry matter analysis to determine how the bulbs react to the various fertilisation strategies.
In 2020, Soiltech also performed similar trials with manganese fertilisers in crops including potatoes and sugar beet. The results of these trials show a similar added value.