EFFECTS OF NUTRIENT AVAILABILITY AND SUBSOIL BULK DENSITY ON CORN YIELD AND NUTRIENT ABSORPTION

Abstract

A 4-yr study was conducted to determine the extent to which soil fertility and subsoil bulk density limit corn yields at the Elora Research Station. In one treatment, soil was replaced to a depth of 1 m with a highly fertilized soil:peat:perlite artificial medium (AM). Two other main treatments consisted of the natural soil with either a recommended fertility (RF) or a very high fertility (VHF) treatment. Plots were irrigated using a trickle system. Corn (Zea mays L.) yields on the artificial medium were the same as those on the VHF treatment in all 4 yr. This was unexpected because of a high subsoil bulk density (1.5 Mg m−3 in the Bm and 1.8 Mg m−3 in the Ck horizons). Grain dry matter yields on the VHF treatment were considerably higher than those on the RF treatment (7.8 compared to 5.3 t ha−1) and were higher than the average yield (6.1 t ha−1) on the best treatment in a previous long-term fertility experiment at Elora. The response appeared to be due to all three macronutrients. Some response to N and K was expected, but the response to P, which was a major portion of the total response, was unexpected. It is concluded that subsoil bulk density is not a significant limitation on this soil when adequate water and nutrients are provided. The marked response to phosphorus application above recommended rates may indicate a need to re-evaluate the fertility requirements of high-yielding corn hybrids. Key words: Soil bulk density, corn yield, nutrient absorption, phosphorus, fertility