Dr. Schittenhelm, why are you looking for alternative energy crops in the first place?
For some time now, there have been lots of additional maize varieties in our fields and they are being used for biogas production. That much maize is not good in terms of sustainable agriculture. Alternatives are needed for agrobiodiversity, soil fertility and water protection.
What is the cup plant particularly good at?
Exactly that: Bringing diversity into agriculture and ensuring sustainability. Once sown, the cup plant can be used for many years, as it’s a permanent crop. This results in a cycle that eats up less of the soil. Additionally, the cup plant has a deep and dense root system, which gives the soil more support, especially during heavy rainfall on slopes. And last but not least, one of its strengths is that it has flowers and therefore is beneficial to bees and other insects in the period after the rapeseed flowering season.
What about the cup plant’s main job? How good is its biomass yield?
In good conditions, the cup plant produces a similar biomass yield to maize. It compensates for the approximately 15% lower methane yield with lower costs, saving on seed, tractor diesel, fertiliser and pesticides during cultivation. And on top of that, something which is very important for nature conservation and water protection; no tillage is required.
What effect does this have on the nitrogen content in the soil?
After maize is harvested, there is usually a lot of nitrogen left in the soil that can leach out when it rains in winter. That’s not good for our water sources. The situation after the cup plant harvest is different because in the autumn the plant sprouts again to knee-height after being harvested, so the mineral nitrogen still present in the soil is absorbed by the cup plant and is thus protected from leaching. The re-sprouting is also then a free green fertiliser.
A wide range of crops is important for sustainable agriculture.
Dr. Siegfried Schittenhelm
Recent research has shown that large amounts of organic matter accumulate under the cup plant during the long periods of downtime and soil regeneration. Only after the permanent crop has been ploughed up and the field has been reintegrated into the farm’s crop rotation does mineralisation result in a high nitrogen resupply. This then makes smart nitrogen management necessary.
So should the cup plant replace maize?
No, not at all. Maize is a great crop. It has an extremely high yield and hardly has any diseases. It’s not a matter of displacing it, but reducing maize to a reasonable level is a good goal to have. A wide range of crops is important for sustainable agriculture.
What do you recommend for the first year of cultivation?
In the first year after sowing, the cup plant only grows to about half a metre high and does not have a very high yield at all. In order to get something out of the first harvest, it is best to grow it as a nurse crop with maize. This means a permanent cup plant crop can be established in combination with a biomass harvest of maize. The plant, over the years, then grows up to three metres tall with lots of flowers and large leaves. The cup plant loses its lower foliage in the almost light-proof stands, but this is also beneficial, as the resulting leaf scattering promotes soil life like earthworms and therefore soil fertility.
The amount of water required is comparatively high, not least because of the large leaf area. To produce the same amount of dry matter, the cup plant needs 50% more water than maize does. The cup plant should therefore be grown where there is sufficient water available – be it through high rainfall, high soil water storage, or a connection to groundwater. The cup plant is not recommended as an intercrop in a crop rotation due to the high seed costs.
How should the cup plant be fertilised?
For nutrient recycling, fertilisation should be done by using fermentation residues from biogas plants.
And over how much area is the plant currently being grown?
I can only speak for Germany, where we have about 6,000ha this year. Demand has increased recently; its cultivation here is considered an ‘ecological priority area’ and is promoted by the EU as part of ‘greening’.
The superpowers of the cup plant
- High mass yield for energy production
- Once planted, it can remain in the same field for 15+ years
- Protects against water erosion by eliminating tillage
- Crop protection is hardly necessary
- Provides insects and birds with a quiet place in the field and food
- Up to 150kg/ha of honey can be harvested from one hectare of cup plant
- The stalk fibres can also be used to make paper and sustainable packaging
Characteristics of the cup plant
- It is a perennial which has a lot of flowers
- It needs a lot of water