echard

From Ancient Greek ἔχω (ékhō, “to hold”) + ἄρδω (árdō, “to water, to irrigate”).

echard (plural echards)

(dated) The portion of water in a sample of soil that is not available to vegetation.
- 1905, Arthur Tansley, The New Phytologist, page 238:
  The echard of a given habitat is experimentally ascertained by isolating a block of soil by impermeable plates, allowing it to dry slowly and determining its water-content at the time when the plants growing on it are wilting irrecoverably
- 1951, John Smith, Distribution of Tree Species in the Sudan in Relation to Rainfall and Soil Texture:
  Grasses sprout on the sands long before the early rains have restored the echard of adjoining clays and given a surplus as chresard which can initiate grass growth.

English