SOIL STRUCTURE PROBLEMS IN TULIP CULTURE

The production of tulip bulbs is more difficult on silt and clayey soils than on sandy soils, due to the less favourable physical properties of the former. Many silt soils are liable to slaking and puddling, which makes them denser in rainy winters. Under these conditions, many bulbs die off in the winter or growth is retarded in the spring and summer. In addition, the mechanical planting and harvesting sometimes gives difficulties on clayey soils.

The physical properties of these soils were found to be closely related to soil texture, lime status, organic-matter percentage, and drainage. For successful cultivation, these properties must satisfy certain criteria, the most important of which are: (a) the ground-water level in the autumn and winter should be more than 1 m below the soil surface; (b) the organic-matter content should be at least 2 per cent in soils containing 15 to 20 per cent clay, some lime, and some medium-coarse sand. On soils with a higher clay content, a poor lime status, or fine sand, the organic-matter content must be higher.

The physical properties of soil are also affected by tillage. It was found that heavy clay soils must be tilled in early autumn and in such a way that a rather fine seed bed is obtained, whereas silt soil must be tilled as late as possible in order to obtain a rather coarse seed bed.