Lighting is one of the ways Mother Nature nourishes plants, trees, and forests. The Eindhoven-based company VitalFluid has mimicked that process: by simulating the effect of one of these lightning bolts, it is now possible to fertilize greenhouse crops in a sustainable way. The method could also be used for crop protection in the near future.
CEO Paul Leenders founded the company VitalFluid in 2014 out of his previous company in response to a project with TU/e, Wageningen University & Research, Radboudumc, and several companies from Nijmegen, the Netherlands. In this article, they provide an update on their trials.
Figure 1. Tomato crop (Roterno) for the VitalFluid (left) and reference treatment (right) at 13-10-2021
The crop in the VitalFluid treatment looks healthy and clearly has enough nitrogen available for uptake (left side of Figure 1), as it is readily supplied by the technology. The fruits showed some potassium deficiency, but by increasing the dosage of potassium this was restored. In the drain of the reference treatment, no nitrate was measured, indicating that the conversion of organic nitrogen into mineral N (NH4 + and NO3 -) was relatively slow. In nature, around 10% of fixed nitrogen is produced by lightning flashes. VitalFluid has taken this natural process to a reactor, for disinfection of water and fixation of nitrogen, so-called Natural Nitrogen.
A lightning flash is produced with electricity, creating plasma from air (78% N2, 21% O2). In this plasma, nitrogen and oxygen are turned into reactive components and led through the water. The reactive components that occur give the water temporary disinfecting properties, and after these reactions nitric acid (HNO3) will be fixed in the water. Nitric acid can be used for the fertigation of greenhouse crops. All mineral N is likely taken up by the plants which resulted in complete depletion of the root zone. The total quantity of N being available is not sufficient to cover the demand, which is shown in the crop as N-shortage symptoms: the plants have smaller and fewer leaves, and the leaves are paler green (right side of Figure 1).
Figure 2. Cumulative yield (kg/m2) for the VitalFluid (VF) and the reference (BIO) treatment.
To avoid a complete standstill of the plants in the reference, Chilean nitrate (NaNO3) was added to the organic nitrogen fertilizers, to compensate for the lack of microbial production of nitrate, which is possibly due to a lack of oxygen in the root zone. It was observed that the substrate is relatively wet and the O2 consumption by the roots, in addition to the microbiology, likely depleted the oxygen concentration completely. In addition, it might also be possible that the required microbial community could not have settled properly, which is a general problem of substrates. All in all, the too low activity or presence of the microbiology in the rootzone caused suboptimal conditions and low productivity of the crop.
Additional lighting
As the available amount of daylight is already strongly decreasing, SON-T lights are switched on to elongate the days and increase the total amount of light. This option is not possible in USDA-organic cultivation but was inevitable in this trial due to the starting date of the cultivation.
Recirculation of nutrient solution
Complete recirculation of drain water (no discharge) is achieved in the VitalFluid treatment. The addition of chili nitrate, containing high amounts of sodium, in the reference treatment causes the sodium concentration to increase rapidly, forcing the researchers to discharge the drain water of the reference treatment so no recirculation can be applied.
Results
The first harvest was on September 8, and the yield of the VitalFluid (VF) and the reference (BIO) treatments are shown in Figure 2. Yields were equal for both treatments until September 23, but crop development was quite different. The VitalFluid crop clearly had enough nitrate available for growth, whereas the reference crop was affected by the shortage of nitrogen, resulting in a decrease in productivity for this treatment.
For more information:
Wageningen University & Research
www.wur.nl