Gas exchanges and growth of maize as affected by aeration porosity and soil compaction

Assuming that less than 10% aeration porosity is sufficient to ensure plant development, provided that other aspects of porous space remain functional, and the magnitude of this effect is dependent on soil density, the objective of this study were to evaluate the physiological and growth responses in corn plants submitted to different aeration porosities and compaction levels. The experiment was conducted in a greenhouse, in randomized block design in factorial arrangement (2 x 5), two densities: 1.6 and 1.7 Mg m - ³, five aeration porosity: 7, 8, 9, 10 and 12%, with five repetitions per treatment. For each density were made columns of soil in hydraulic press, and the aeration porosities were monitored by mercury tensiometers. The interaction between the factors had no effect on the analyzed variables. Aeration porosity lower than 10% did not cause significant reduction in gas exchange and plant growth values, while in higher porosity there was a limitation in CO 2 , fixation, and as a consequence, reduced photosynthesis, accompanied by a reduction in plant height and biomass production of the aerial part. At higher density, photosynthesis and SPAD index were higher, but the increase in biomass was smaller. It is concluded that aeration porosity greater than 10% are more limiting to plants, and the range between 7 and 10% generally reflects similar values. The highest levels of chlorophyll b and carotenoids in the highest density are adaptive responses to the stress condition.