These bulbs in trays are forced, they are special ones.
From the big fields they take the cover off this week starting, straw nowadays, in earlier days reed was used. But at this moment there is hardly a green leaf to see.
After they have ploughed the earth in autumn and fertilized, the sandy soil is not so fertile, little bulbs are planted and covered with straw for protected the bulbs and against blowing away of the sandy soil. In the winter, january and february taken off the straw and add thin cow manure again to stop the earth blowing away from the always blowing westenwind. Than in spring it will be getting warmer and more light so bulbs are growing fast, than flowering and than 'koppen' take the flowers off, because all the energy has to stay in the bulb, making little ones. the leaves and stems stay in the soil: they give the food. In summer lifting the bulbes out of the soil 15 june-15 aug, drying, take rest of roots of, pellen with tulips or holding with hyacinths. Grades for the sizes, count them, look for diseases and sell. the little ones keep for next year.
That is in short the whole process. Did not border to mention all the fertilise stuff.