Bulbs in clay, was Soils and flower color

penstemon penstemon@Q.com
Wed, 20 May 2015 12:30:54 PDT

>Nothing could be further from the 
truth; tulips do best in a rather heavy clay-ish soil that goes dry in the 
summer. Put them in a lean, sandy soil and they won't thrive like they do in a 
heavier soil.

It’s probably the relative lack of air in heavy soils rather than any water-retentive properties (which only operate in mesic situations). In arid regions, clay is drier than sand. 
Most of the soil-water studies available online originate in regions with regular rainfall, so not really relevant here, or are directed toward crop irrigation, also not relevant. 

See Peterman, et al, Soil properties affect pinyon pine – juniper response to drought, in Ecohydrology 2012
(not only for the discussions of water in clay vs. coarse soils, but the fact that the definitely non-bulbous pinyon (Pinus edulis) is found on clay soils because of migration to such soils when precipitation rates were higher, 600 years ago). 

or Sala, et, al. Primary Production of the Central Grassland Region of the United States, Ecology, Vol. 69, no. 1 (1988)

“In dry regions, major losses of soil water occur via bare soil evaporation. However, where sandy soils occur, bare soil evaporation
is lower than in loamy soils because water penetrates deeper into the soil. Runoff also is lower in sandy soils than in loamy soils.”

or the online version of the Encyclopedia of Ecology, p.884. 

“Soil texture is of large importance as it affects both infiltration and the movement of wetting fronts. Fine-textured soils that are high in clay and silt fraction tend to impeded infiltration, in which wetting fronts move only very slowly, and surface evaporation after rainfalls can be very high. More-coarse-textured soil rich in sand fractions, as for instance sandy loams, are characterized by high infiltration rates and rapid percolation. For this reason, coarse-textured soils are often better for plant growth. As this is in contrast to soils in mesic areas where fine-textured soils are commonly considered to be superior for plant production, this is called the ‘inverse texture effect’”.  

Bob Nold
Denver, Colorado USA

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