In 2021 WENR started the field and pot experiments to test the agronomic effectivity of the liquid ammonium sulphate fertilising product (AS) produced by the Arjan Prinsen Farm (APF) in the Netherlands.

The field experiments have a simple factorial block design with calcium ammonium nitrate (CAN) as reference fertiliser and AS as test product.
Fertilising products were used following the 4R stewardship principles, i.e., CAN was scattered and AS was injected into the sod.
The testing is accompanied by monitoring changes in soil mineral nitrogen in spring and after the harvest to determine risks of nitrate leaching.

The field experiments are conducted on grassland and on arable land with silage maize on sandy soils and clay soils.
On grassland the experiments started in early April, on arable land in early May.
For these crops the weather was precocious, yielding a first cut grass of 6 – 7 ton dry matter/ha and a good germination of silage maize seeds.
Two groups, the project-group of Bio-based Fertilisers Achterhoek and the ministerial and provincial supervisory committee on the pilot Bio-based Fertilisers Achterhoek visited the field experiments on June 22 and showed great interest.
In April the pot experiments were started first by growing a grass sod of ryegrass or by germination of silage maize seed.
After establishing a thick grass sod or reaching the 3-4 leaf growth stage, the fertilisers were applied again following the principles of the 4R Stewardship: CAS was scattered and AS was injected.

Monitoring of greenhouse gas emissions by means of an acoustic gas-monitor started Immediately.
For the measurement of ammonia volatilisation, by using acid traps, separate pot experiments are planned. These will start in July.