Record drought and heat are making seedling establishment a serious challenge – Turfgrass Science at Purdue University

Record drought and heat are making seedling establishment a serious challenge

After the extremely stressful summer conditions of 2010 many thin areas in cool-season lawns have been reseeded to restore turf density and improve appearance.  Regardless of environmental conditions, establishing a turf from seed is a challenge and the process is as much art as it is science. Seedling establishment requires two steps, germination and development. Success for both processes relies heavily on two major factors; temperature and moisture. Higher temperatures cause both to occur more quickly but without sufficient attention to soil moisture a new seeding can fail quickly.

Providing the “right” amount of moisture during seedling establishment is truly an art. Initially it is desirable to keep the seedbed as moist as possible, almost to the point of saturation (but not quite). The goal during this phase is to ensure that moisture is not limiting and the objective is to get the seed to “pop”. The purpose of supply water during this time is so that seed can imbibe the water which helps to engage various enzymes inside the seed. As this occurs various biochemical processes are initiated which are essential to the formation of the first roots and shoots. In practical terms, it is imperative to continue to supply a small quantity of moisture regularly (realize that applications may occur > 5 times daily). Additionally, it is important to recognize that there are species differences with regard to speed of germination. For example, the fescues and ryegrasses will normally germinate in < 7 days. By contrast, Kentucky bluegrass takes > 7 days and sometime > 21 days. Thus, it is essential to keep the seed as moist as possible to avoid any delays in germination which ultimately will affect seedling development, and turf coverage. Note: for some open and exposed sites a mulch material  like straw, geotextile fabrics, etc.  may be helpful in conserving moisture at the soil surface.

Once you are fairly certain that most of the seed you have planted has indeed “popped” it is okay to begin gradually reducing the number of irrigation cycles but DO NOT LET NEW SEEDLINGS DRY OUT or you will start the process all over again. Remember that seedling roots are very small, perhaps only a few millimeters deep and although you may be watering less frequently you may need to supply  slightly more water to keep up with seedling water loss. Generally it is a good idea to keep the upper soil profile moist to the touch but not saturated. The new roots need some oxygen in the soil pores to properly develop.

Unfortunately there are no “set guidelines” for how much water to supply during establishment. The only suggestions we have during this process is to regularly monitor soil moisture by sight/feel and pay attention to prevailing environmental conditions. This is the “art” of seedling establishment and requires careful daily monitoring. Obviously on sunny, warm, breezy days the seed and seedlings will be more prone to desiccation, whereas on a calm, overcast day the seedbed may remain moist with only a few irrigation cycles. Regardless, it is imperative to closely monitor soil moisture and weather conditions to ensure rapid establishment. Hopefully Mother Nature will take pity on lawns throughout Indiana and provide some very much needed rainfall, SOON!!!

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