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Yield and Yield Components of Zea mays L. as Influenced by Artificially Induced Shade¹

Studies were made to determine the effects upon grain yield of light reduction, leaf and stem removal, and thinning of corn (Zea mays L.) plant populations at ear silk emergence. Grain yields per hectare were significantly reduced when 75 to 100% of the solar energy available to leaves located below the ear was intercepted by black polyethylene shades. Restricting light penetration to these leaves by 25 to 50% had little effect on per hectare grain yields. Leaf or stem removal reduced grain yields by 22 to 44%. Leaves located either below or above the ear leaf, (other leaves removed) were equally efficient the production of grain on a per unit of leaf area basis. Artificially shaded leaf tissues continued contributing to grain yield although with greatly reduced efficiency per unit leaf area. Removal of all tissues above the ear reduced ear weight 45%. Weight per 100 kernels was reduced as a result of leaf tissue removal. The largest kernel size reduction occurred when all tissues above the ear were removed. Induced shading had little or no effect on the air temperature or relative humidity in these treatments. Soil temperatures at a depth of 12 cm were 2 C higher in the check treatment than under 100% shade. Weed growth increased as light reaching the soil surface was increased through defoliation or plant population reduction.

² Former Research Assistant in Agronomy (now Area Extension Agent, Agronomy, Fremont, Ohio) and Professor.

Received for publication May 16, 1966.