Why use fertilisers??

Why do farmers apply fertiliser?  All living organisms require some basic chemical elements to function i.e. to build DNA, cells walls etc  The major elements required are; –nitrogen, phosphorus, potassium, sulphur, calcium and magnesium

Why do farmers use fertiliser?  To over come nutrient deficiencies  To replace nutrients transferred: –off farm in production i.e. milk, meat, wool,crops –to unproductive areas of the farm i.e. effluent ponds, tracks

 If any one of these elements is deficient – grass will not grow –or will not grow as well as it could

What are the environmental problems associated with fertiliser application?  Phosphate runoff –Approximately 80% of the phosphate in our waterways comes from agricultural runoff  Nitrate leaching –A study in the late 80’s indicated that up to 20% of ground wells in Taranaki and Waikato had over 10mg/l nitrate –The recommended maximum level is 11.3mg/1

These affect water quality  By causing algal blooms and excessive weed growth which –stops us drinking it –stops recreational activity –stops us eating the fish –and kills aquatic life

How do excess nutrients get into waterways?  Direct application –animals depositing directly in waterways –fertiliser spreaders applying too close to waterways  Erosion –pugging & compaction  Runoff –surface runoff –sub-surface runoff  Leaching

Nitrate Leaching  Dairy cattle numbers have gone from 2.9 million to 4.1 million in 2001  N fertiliser use has gone from 117,000 tonnes of N in 92/93 to 333,000 tonnes in 01/02  What are the current figures?  A cows urine patch contains the equivalent of kg N/ha

Nitrate Leaching cont..  At normal rates of application leaching losses from nitrogen fertilisers are typically 5-10% of nitrogen applied.

What can be done to minimise the environmental effects One option - Design a fertiliser plan for each farms specific needs. –This includes:  Nutrient budgeting  GPS Soil & Herbage testing  Farm Environment Maps  Using environmentally fertilisers

Sustain – an example of a more environmentally friendly fertiliser  Sustain is urea that has been coated in Agrotain & Sulphur. –Sustain reduces leaching losses of nitrogen. –And also reduces ammonia volatilisation losses to the atmosphere

Sustain  Agrotain slows the breakdown of the urea. –Urea breaks down over 0-2 days –Sustain breaks down over 0-10 days  Slowing the breakdown of urea gives the plant more opportunity to take up nitrogen therefore leaving less nitrogen available to be leached.