Wednesday, July 21, 2010

Soil saturation and weather related stress

This summer's weather has presented many challenges due too heavy rainfall and warm temperatures. Although daytime temperatures have been a little warm, the night time temperatures are 10-12 degrees warmer than normal. Then throw in high humidity and we start see signs of stress. Our push-up greens have 2" of sand with heavy clay base underneath. The heavy rainfall coupled with heavy soil, warmth and high humidity have lead to anaerobic soil conditions. Anaerobic soil conditions persist when prolonged saturated turf does not allow for gas exchange in the root zone. The heat, water and lack of oxygen make the roots die off and plants start to look unhealthy or die. Many of our wettest greens are starting to show signs of decline. Many of you may have noticed greens like front of #4, middle of #6, middle of #11, #12, #13, #16, and bottom #17 at differing points this summer look thin and unhealthy. In a situation like #6 green the area affected is in the low spot in the middle of the green. This area holds water and does not allow oxygen into the soil. Also on days of warmth these areas become hotter due to the amount of water directly below the surface. The water, heat, humidity, lack of air movement and lack of sand in the profile cause roots to die or die back closer to the surface. #13 is a great example of a green that receives little air movement even on windy days. All of these scenarios produce a situation where plant health especially the roots are negatively affected. The picture to the left is taken from the middle of #6 green in the low area mentioned above. The soil temperature in the middle of #6 green at noon today, July 21st, is 91 degrees. Keep in mind it is only 80 degrees air temperature currently. How can this be?? Water heats up faster than air, which in turn heats up the saturated soil and has a negative impact on the roots (suffocates). On a side note #13 green in the low area is 92 degrees. Whereas "good" greens like #9 and #10 are 84 degrees some 6-10 degrees cooler. So under these anaerobic soil conditions a few problems can arise. One is wet wilt, where the soil is so saturated that all the pore space is devoid of oxygen and root health is comprimised. Under heat and windy days this can be prevalent. Scald is another situation that can cause damage and is similar to wet wilt in that it causes damage under heat, wind, and intense sunlight. Because the turf is saturated the soil heats up at an alarming rate as direct sun causes turf decline. And lastly anytime you have situations of heat, humidity and moisture you are going to have intense disease pressure particularly on turf that is already weak or growing in a poor environment.

So what options do we have that can help in the fight against root loss, thinning greens and turf death? Almost weekly greens have been needle tined (aka venting) with the aerator in the picture to the right. Venting is the process of using small diameter solid tines (.2") that do not affect play much but allow for the exchange of oxygen in anaerobic soil situations. Other options we have chosen is skipping mowing and or rolling after heavy rain events. Although the soil is extremely saturated light syringing on days with heat, intense sunlight or wind will also cool the plant off so that it can function properly. Lets note that syringing is not watering but cooling off the surface of the plant during these "extreme" conditions. Long term solutions involve amending the soil profile with sand. This is being done bi-weekly to help modify our soil profile. Deep tine aeration with 10-12" tines along with a solid core aeration program will over time help alleviate the problem. Another factor is the amount of trees that surround many of our greens complexes. These trees inhibit air movement, which is a large part of the problem with many of the greens at Ridgeway. Selective cutting of trees that do nothing but rob Ridgeway of having consistently good putting surfaces is necessary part of our greens management program.

In summary needle tining (venting), skipping of mowing(after heavy rain), skipping verticutting, topdressing during stress and light syringing after periods of no rain will help keep these areas alive. Long term solutions involve selective cutting of trees, consistent topdressing when weather allows, and the combination of deep tining/core aeration will greatly improve conditions on the putting surfaces by allowing increased drainage and air movement.