Factors affecting grass growth Flashcards
What are the 4 main factors that affect grass growth?
Light
Temperature
Water
Nutrient levels (mainly nitrogen)
In what conditions does grass grow best?
Grass grows best at low altitudes with sufficient (but not too much) summer rainfall. The soil is best when it is deep and moist
Describe the seasonal growth patterns of grass
- starts in mid March, when the temperature starts to rise during the day, and there is increasing sunlight (both amount and intensity)
- steadily rises and peaks in mid spring, at about 100kg DM/ha/day. It is still wet during spring, which benefits growth
- growth may dip in mid-late summer due to lack of rainfall during July and August
- often there is another peak of growth during September, when it is warm and wet enough to allow growth
- growth usually stops in early November and will ‘hibernate’ during the winter. Slow growth of the roots may still happen, unless the soil is frozen
What is affecting the typical grass growth patterns?
Climate change
What is the effect of light on grass growth?
- low light levels = low photosynthesis = low growth energy levels = low growth rate
- a reduction in light for even short periods has an impact on grass growth
- short term fluctuations in light intensity are covered by stored energy in the sheath base and growing leaves
- roots are very sensitive to reduction in light intensity - this can affect the nutrient uptake from the soil, water uptake from soil and the overall plant stability as the roots do not grow and reach down into the soil
- low light levels lead to 5 fold reduction in shoot weight and 30 fold reduction in root weight
What is the effect of physiological ageing on grass growth?
The cells within the plant change as it ages - an old plant has a thick cell wall with high levels of lignin and a large vacuole. This gives more structure and strength but makes it less digestible .
How can grass be stressed? What effect does this stress have?
- may be cut, grazed or temperatures changes
- grazing as a form of management does more damage to the grass and reduces nitrogen levels (but causes less stress than cutting)
- cutting stresses the plant more and it uses its remaining energy to try and repair itself. The shorter it is cut the more desire it has to grow back and the more severe the reaction
What are the effects of water on grass growth?
Water stress (drought/too much water) reduces leaf appearance. This leads to reduced tiller production and lower productivity and less ground cover
What are the benefits of good drainage?
- improves quality of ground
- access to ground earlier in the year (when it is wetter)
- quantity of grass produced improves
Why is nitrogen important?
Essentially more nitrogen = higher production.
This input of nitrogen may be from artificial fertilisers, organic fertilisers or legumes.
Optimising the nitrogen levels can double grass DM production
At what temperature does grass start to grow?
5 degrees Celcius
What should be considered when choosing fertiliser?
- soil type
- soil nutrient status (normally looks at nitrogen, phosphorus and potassium)
- pH of soil
What is the ideal soil pH for grass to grow?
6-6.5 (very slightly acidic)
What do the optimum levels of nitrogen depend on?
- the grass growth site class
- management system used (cutting or grazing)
- previous years’ fertilizer policy
- use of organic manur
- presence of/value place upon clover
- Optimum may be between 0-400kg N/ha
What is the role of potassium and phosphorus?
They work alongside nitrogen in supporting roles - especially for root development
- grass does not give any response to nitrogen where K and P were not present
- K is essential, particularly in the flowering stages and there is limited growth without
- P is good for cell division and early growth - it is deficient in clay and area of heavy rain
- Sulphur works similarly to P
