Total monetary value of agricultural exports is a terrible way to measure output. It doesn't take into account: 1. Re-exports (Rotterdam is the largest port in Europe) 2. Specialisation in the production of certain goods (i.e. high imports and exports) 3. The high price of agricultural goods in Europe, driven by high trade barriers. 4. Low domestic consumption compared to more populous nations.
For a better analysis of the monetary value of Dutch agricultural exports see here: https://www.cbs.nl/en-gb/news/2018/03/dutch-agricultural-exp...
Note for example the 22.5 billion Euros in re-exports of agricultural goods.
90% reduction in water usage is also hard to judge without looking at changes in other advanced agricultural nations.
It would be more interesting to see the yields per-hectare the Dutch are achieving compared to other advanced agricultural nations.