Soil aeration and crop growth in response to excess water

The general purpose of this study was to monitor the soil aeration status during flooded and unflooded conditions over the corn growing season, and to determine corn growth response to artificial flooding on both isolated field plots (specially constructed for controlling water-table elevations) and plots that drained naturally;To sample and analyze the soil atmosphere for oxygen (O[subscript]2) concentration, a new technique was developed and tested in laboratory columns and field plots. Laboratory testing showed that the new sampling technique was fast, reliable, and free of outside air contamination during sampling and analysis;Artificial flooding of soil reduced O[subscript]2 concentrations, redox potentials (Ehs), and oxygen diffusion rates (ODRs) below the critical levels at all the sampling depths resulting in inadequate soil aeration and restricted supply of O[subscript]2 to plant roots. High water tables occurring in plots with natural drainage, due to flooding of an adjacent isolated field plot, and increased wetness on the soil surface of all the experimental plots as a result of heavy rains, also caused a decrease in the values of these three aeration indicators used in this study. The relationships between the air-filled pore spaces in soil and the three aeration indicators suggested that an aeration porosity of 8 to 10% was necessary to have adequate aeration for good plant growth;Flooding corn at the early (36 days after planting), and the late (56 days after planting) vegetative stages resulted in poor crop growth (plant-canopy height and dry-matter production) and reduced grain yield. These two vegetative stages of corn growth, also gave the highest crop susceptibility (CS), and normalized crop susceptibility (NCS) factors for corn for the 1987 and 1988 growing seasons;The relationships between the stress-day index (SDI) and the relative yields of corn grown at the experimental site and a nearby undrained area indicated a linear decrease in relative yields with increasing soil wetness (SDIs)