Plant nutrient tests and soil analysis are used to diagnose nutrient requirements and provide information for adjusting fertiliser programmes. SAP analysis measures the nutrient concentration in the sap and can be used to forecast nutrient deficiencies.
A SAP analysis can tell you the current uptake of nutrients and nutrient deficiencies and / or excesses long before visible symptoms first appear in the grass. It serves to highlight the nutrients which the grass is able to use for growth at that moment. It can also indicate nutrient imbalances in the soil and provide information for selecting fertiliser.
Factors effecting mineral uptake
- Soil pH
- Nutrient Imbalances
- Release of fertilisers
- Soil structure
- Root development
- Soil microbial life
- Climatic conditions; temperature, light & moisture
Nutrient Uptake
There are two kinds of nutrients in plants, dissolved salts which relate to current uptake for plant development and fixed nutrients found in organic compounds and these are much less available for plant development. The SAP test mostly measures dissolved salts.
A SAP analysis will quickly show highs and lows of nitrogen inputs. This nutrient is a major limiting factor to healthy grass growth. It is an essential component of amino acids and proteins that are the building blocks of grass growth. It is also a vital component of chlorophyll, which is required for carbohydrate formation (photosynthesis) and this is essential for turning the grass green. Under poor growing conditions, such as low soil temperatures, nitrogen mineralisation and availability can be a major limiting factor to grass growth. This can be readily identified in the SAP analysis.
Plants readily take up nitrogen in the form of nitrate and ammonium. Nitrate is converted to amino acids and proteins. At certain times of the year, high nitrate can encourage luxurious growth resulting in the production of larger weak cells. This is often accompanied with low sugar production. Over stimulation from nitrate accumulation should be managed.
When roots cannot deliver NPK or other nutrients the plant will use its reserves. Consistent healthy growth is only achieved when the grass has a balanced nutrient uptake. A strong healthy sward can prevent other issues such as attack from pests and disease. A SAP analysis can be an invaluable tool in the nutrient management process.
Sampling Procedure
Timing
First sample to be taken in the early spring, at the start of rapid growth or when a problem is suspected throughout the year.
Subsequent samples should be taken at 2-4 week intervals after any corrective application is made.
Samples
Samples of the clippings should be taken from the grass box as soon as possible after early morning cut. Please take as large a sample as the sample bag will allow. All samples should be placed into the plastic bags provided and protected from heat and light as quickly as possible, but do not freeze.
Avoid
- Sampling within 5 days of a nutrient application
- Sampling within 2 days of a chemical application
- Taking the sample after 10:30am
- Diseased or dean grass
- Soil Contamination of the sample
- Sampling within 2 days of a chemical application