There’s are a number of factors that can impact on herbicide performance in the turf grass environment. Many of the herbicides used in agriculture are also used in turf management although their use differs with regard to application. In an agricultural system pre emergent herbicides are often applied to bare soil and not watered in. This means they are subjected to a number of extremes that can impact on the results. In the turf grass situation the majority of the time there is a full grass cover and water is often not limiting. This means that factors such as volatility and photo- degradation are significantly less likely to occur. However, in the turf grass situation it is highly likely that factors such as leaching and thatch content are going to play a much more important role than in the agricultural situation. This is a brief outline of what factors can impact on turf grass herbicide performance. All the references are linked within the document. For a more detailed look at this topic check out https://gilbasolutions.com/cracking-the-code-factors-shaping-herbicide-performance-34/

1. 2023 What influences herbicide
performance?
Or how to stop wasting $$
Useful links
Adjuvants
Pre emergents 1, 2, 3

2. 1. Adsorption: Some of the herbicide
gets adsorbed onto the soil, making it
less mobile.
2. Degradation: Over time, natural
processes like photodegradation and,
moisture, breaks down the herbicide.
3. Soil pH
4. Temperature
5. Rainfall
6. Moisture
7. Humidity

3. For a herbicide to work it needs three things:
Good contact
Poor contact will give poor
results.
Hairy and waxy leaves can
impact on herbicides
Length of contact
If it isn’t in contact for
long. Poor results.
Rain after application
Site of action
Must be able to move to
where it actually works.
Actively growing

4. Challenges deep-dive
Soil Factors
● CEC
● Organic matter
● Texture
● pH
Climatic Factors
● Humidity
● Temperature
● Amount of light
● Moisture

5. Soil Texture
● Most important for soil
applied herbicides
● High levels of clay and OM >
adsorption

6. CEC
● soils ability to adsorb positively
charged compounds
● fine-textured, high-organic
matter soils have larger CEC’s
than coarse, low-organic
matter soils
Injury symptoms caused by the residual effect of oxyfluorfen on
sorghum. Injury symptoms caused by the residual effect of oxyfluorfen
on sorghum at 0, 15, 30, 45, 60, 90, 120, 150, 180, and 200 days after
application (DAA) of the herbicide in comparison with the control
treatment (C), in soils in the region of Curitibanos-SC: Ultisol (clay), Rio
Paranaíba-MG: Oxisol (clay), and Oratórios-MG, Brazil: Inceptisol
(loamy sand).

7. pH
● influences water solubility,
adsorption, and hydrolysis
● triazines
● sulfonylureas
● Imidazolinones
● glyphosate

8. Temperature
● Couch grown at high
temperatures retains 3x
more glyphosate than at
low
temperatures.
● In general, uptake and
translocation of foliar herbicides
increases with increasing
temperature

9. Rainfall
● Pre-emergent herbicides can
vary dramatically in how they
behave after rainfall
Active Water
Solubility
(mg/L)
Soil
Adsorption
Capacity
Koc
Soil
Movement/
Leaching
Rating
S-metolachlor 530 100 High
Pendimethalin 0.275 25455 Very Low
Prodiamine 0.013 13000 Very Low
Propyzamide 15 200 High

10. Soil moisture
● Crowsfoot control increases
with increasing soil moisture
● Best at > 20% VMC and lowest
at < 12% VMC.
● Diclofop activity reduced at low
soil moisture

11. Humidity
● RH effects glufosinate -
ammonium
● Best results under high RH
● Use an adjuvant in low RH
conditions.
● Potential for spray drift
increases

12. Light
● A 44% loss in 3 days due to
photodegradation of some pre -
emergent herbicides, when used
on bare soil and not watered in.
● In a turf setting, 10% loss was
within 7 days when not watered
into the turf.
Useful links
Adjuvants
Pre emergents 1, 2, 3