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One-Degree Increments in Soil Temperatures Affect Maize Seedling Behavior¹

ABSTRACT

One-degree differences in soil temperatures, ranging from 12 to 35C, induced changes in the growth and nutritional behavior of maize seedlings (Zea mays L.) amounting to as much as 30 to 40% per degree. An improved system was developed to provide the precise environmental control required. The system provided for nearly isothermal control of soil temperatures even when soil and air temperatures differed by as much as 15C. The system also provided for uniform control of air temperature within ±0.7C and relative humidity within ±1% throughout the growing region in the 2 by 2.75 by 2 m growth chamber.

With each degree increase in soil temperature from 12 to 26C, total seedling dry weights were an average of 20% greater than weights at each previous soil temperature and an average of 12% smaller with each degree increase from 26 to 35C. Nutritional status, leaf lengths and numbers, stem lengths, and root numbers also were very dependent upon soil temperature. Of special interest, a soil-temperature-dependent disorder resembling Ca deficiency was observed in the maize shoot. Also, the uptake of B was uniquely different from that of other elements. Surprisingly, the same total uptake of B occurred regardless of the soil temperature below 21C.

The desirability of rigidly controlling soil temperature in pot experiments and the importance of minor changes in soil temperature on plant behavior have been clearly demonstrated.

¹ Contribution from the US Soils Laboratory, Soil and Water Conservation Research Division, ARS, USDA. Beltsville, Md.

² Research Soil Scientist.

Received for publication February 19, 1969. Accepted for publication May 13, 1969.