Shallow water table effects on photosynthesis and corn yield

The effect of water-table management practices on leaf photosynthesis and corn yield was investigated under two different field conditions in 1989 and 1990. In one field, water-table depths were maintained at 0.3, 0.6, and 0.9 m in field lysimeters during the growing season. In the other field, average water-table depths of 0.2, 0.3, 0.6, 0.9, and 1.1 m were maintained through subirrigation. Photosynthesis measurements were made regularly during the growing season, and yield data were collected at harvest. In 1989, a relatively dry year, photosynthesis rates were higher at shallow water-table depths than at deep water-table depths. In 1990, a very wet year, photosynthesis rates were not significantly different for water-table depths between 0.3 and 0.9 m, but rates decreased significantly for water-table depths shallower than 0.3 m. Statistical analysis indicates that water-table effects on photosynthesis rates were not consistent. However, effects of various water-table depths on photosynthetic water-use efficiency (PWUE) were highly significant in both dry and wet seasons. Corn yields increased with increasing water-table depths. At water-table depths of 0.2 to 0.3 m, corn yield decreased significantly. In both dry and wet seasons, effects of water-table treatments on grain yield were highly significant and significant relationships were obtained between PWUE values and yield.