Putting the WOW into seed sowing

Putting the WOW into seed sowing

There are many possible reasons why renovation of greens (and fairways) may be undertaken. These include a desire to improve playing surfaces by addressing existing problems such as poor drainage, or surface trueness; improve the surfaces ability to respond to environmental limitations for example by using more modern cultivars adapted to the conditions in a particular location; or to repair any damage to the playing surface caused by maintenance activities, play or by stressful growing conditions.

In highly managed environments like golf courses the practices used to provide good quality playing surfaces can already antagonise the health of the plant. This year many areas of the UK have also experienced drought conditions this summer alongside high light and heat levels, significantly increasing the number of stressors on plant growth. Whilst cool season grass plants are able to survive periods of high temperature and low moisture through a process of summer dormancy, the plants will be weakened following this experience and some may not survive. Renovations may, therefore, be even more important for some this year in order to rectify some of the damage caused by the stressful growing conditions experienced.

With all this in mind, sowing and over-seeding are often essential aspects of renovation of greens and fairways, so it is important to understand the factors that lead to successful germination and establishment: water, oxygen, and warmth.

1. Water

If kept in suitable conditions, dormant seeds can remain viable for many years. In fact, one experiment has found that some viability can be retained for more than 100 years (Telewski & Zeevaart, 2002). That is not to say that you should store your grass seeds for 100 years, but it does highlight just how resilient seeds can be. Water is needed to break seed dormancy and initiate germination. The initial phases see the seeds begin to swell and soften followed by the emergence of tiny root hairs from the seed (Figure 1). Water continues to be a key requirement, preventing the emerging seedling from drying out before it can connect with moisture in the soil and become established.

During the early autumn months there is a high chance of sufficient rainfall to prevent emerging seedlings from drying out and enabling the young grass plant to build a strong root system while the temperature remains mild. Moist conditions are also experienced in the spring months, making this an alternative option for sowing seed. However, in the spring we are, in theory, heading more quickly towards increasing dryness leaving the plants with less time to build up resilient root systems that will enable the plant to survive through dry conditions and other environmental challenges.

2. Oxygen

The energy for seeds to germinate comes from the respiration process in which oxygen from the air reacts with the seeds stored sugar reserves to release energy enabling cells to divide and grow. The amount of oxygen held in the pore spaces of a soil can be reduced if it is waterlogged, compacted, or has a hard surface (Figure 2). For this reason, good soil preparation is essential. For example, aerating to reduce compaction and improve drainage, and scarification to remove layers of thatch that can build up.

Correct sowing depth also helps to ensure the seedlings have enough energy for the initial establishment phase before leaf growth enables the plants to begin converting energy from sunlight themselves (Table 1). To further assist this process, the use of a plant growth regulator restricts growth of existing turf to give new seedlings a better chance of competing for available light.

 Table 1 - Optimum sowing depth and temperature range for different grass species

3. Warmth

Warmer soil temperatures increase the speed of enzyme reactions and processes such as cell division leading to faster germination and establishment. Each grass species has a slightly different range of preferred temperatures for germination (Table 1).

Soils have a higher heat capacity than air, particularly when moist due to the even greater heat capacity of water. This means that soils can effectively act like a storage radiator, taking time to build up heat initially but over time storing the residual solar energy. As a result, the soil will be much cooler in the spring than in the autumn even if air temperatures are similar because there has not been sufficient time to build up residual heat. Germination therefore tends to be slower in the spring than it would be later in the year.

Whatever the impacts of this season’s weather, maintenance and play on your surfaces take time to consider your aims before renovating and always think about the requirements of establishing seeds because they can only germinate once.

References:

Telewski, F. W. & Zeevaart, J. A. D., 2002. The 120-yr period for Dr. Beal's seed viability experiment. 89(8), pp. 1285-8.

Dr Abigail Graceson - Technical Manager, Agrovista Amenity