LEAF-let, the thrice-yearly newsletter for S & S Seeds

In the next figure, the rain or irrigation has stopped. The soil has begun to dry out. Capillary action begins as the tiny channels formed by the fine soil particles regain their porosity. Water rises toward the surface of the soil.

If seeds are sown and lie on a bare soil surface, in the absence of precipitation, sun and air movement dry the seeds even if they were previously watered. Moisture, that a germinating seed needs constantly, cannot reach the seed. Water that migrates to the surface evaporates. Under these conditions germination can fail completely.

To properly germinate, seeds should be surrounded by moist soil. So why not furrow the soil, bury the seeds and wet it down? To take full advantage of water's tendency to rise to provide moisture between waterings, the soil should not be disturbed. If the soil compaction is broken, the particles are separated and the water has no way to move upward.

If the soil layer containing the seeds becomes too coarse from tilling, the seeds are isolated from moisture rising to the surface. Water reaching the seeds then depends on water passing downward from irrigation or rain.

There are several problems with germinating seeds this way. The high water use is not only wasteful, it's impractical. Overwatering will also leach nutrients out of the soil, nutrients that are necessary to starting a good growth. In some areas where soil and water are high in salts, excess water will build up the salts in the soil. Salty soil hinders the seed's ability to take up water through osmosis.

Using the Elements

The fact that capillary action and molecular adhesion are stopped by coarse material can be put to use in helping seeds germinate.

The bottom figure shows an ideal condition. The seeds are sown and pressed into the bare soil using a roller. A coarser top dressing is laid over the seeds.

Water Works Wonders

Water passes down through the top dressing and seeks its lowest level, wetting the seeds as it passes. The top dressing protects the wet seeds from being dried out by sun and wind. Water rises through the undisturbed soil and reaches the level of the seeds where it stops. The top dressing, being coarser, won't support further rise so water collects at the boundary between the soil and top dressing where the seeds are. Germination is enhanced and the plants get a healthy start.

Balance

Moisture balance is necessary for proper germination. Lots of water may not be enough if it doesn't reach the seeds. Regular watering that replaces water runoff and evaporation will assure a good start for lawns, turfgrass or any other planting.