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Effect of Gypsum and Drought Stress on Maize (Zea mays L.). I. Growth, Light Absorption and Yield¹

An experiment was designed to study the effect of gypsum and drought stress on growth, water status and yield with maize (Zea mays L.). Water status was assessed under field conditions by measurements of relative turgidity (RT) at noon. No stress was defined as RT greater than 90% — drought stress as RT less than 90%. A nostress crop was compared with a crop drought stressed for a period of 20 days during male meiosis and with a crop drought stressed during grain filling (after pollination to maturity). These treatments were set out in a randomised block design with a further comparison between the untreated sodic clay soil (control) and the same soil treated with gypsum.

Gypsum and no-stress conditions stimulated tiller production so that the final effective plant densities were above optimum. The no-stress treatments produced large amounts of dry matter but this was channelled into sterile tillers rather than into grain. Drought stress during male meiosis stunted growth, stunted tassel development, reduced chlorophyll content and light absorption (during the period of stress) but, overall, was not very detrimental to grain yield. Drought stress during grain filling reduced grain yield by 50%; grain weight was reduced and a very high proportion of photosynthate went into sterile tillers.

Key Words: Water stress • Meiosis • Ameliorant • Relative turgidity • Relative water content • Irrigation • Corn

² Present address: Agricultural Research. Station Leeton N.S.W. 2705, Australia.

Received for publication October 17, 1970.