Nitrogen use planning

Nitrogen fertiliser is a valuable resource for most New Zealand pastoral farms, whether dairy or drystock. Additional pasture grown by the use of nitrogen fertiliser typically costs less per kilo of dry matter than other supplements.

However, nitrogen fertiliser use is often reactive, rather than planned. This can result in its use being less than optimum.Developing an annual plan for nitrogen fertiliser use will help maximise the gains from this valuable resource.

Benefits of nitrogen planning

Developing a nitrogen plan requires some initial work at the start of the year, but it can result in a number of benefits, including:

• A steadier feed supply
• Less need to bring in feed at critical times
• Reduced stress for staff and stock
• Greater chance of fulfilling the farm’s production potential

Farmers who have a nitrogen plan for the forthcoming year are in a much better position to apply nitrogen fertiliser well before a feed deficit. This is a significant advantage, as pasture requires sufficient time to respond to nitrogen fertiliser.

Figure: Typical pasture response rates to nitrogen fertiliser, by season. Actual rates will depend on farm-specific conditions.

Developing a nitrogen plan

The following steps can be used to develop a nitrogen plan for any type of pastoral farm.

• Plot grass growth (or typical DM/ha levels) on a month-by-month calendar
• Add in the average monthly soil temperature and soil moisture data for the farm
• Mark in critical feed times, e.g. mating, lambing or calving, weaning
• Identify feed deficits - compare the critical feed needs to grass growth or typical DM/ha levels
• Identify times when extra conserved feed could be generated. Consider whether you need to plan for a particularly long, cold winter or dry summer
• Mark in times when there are other needs for nitrogen, e.g. for new pasture or crops
• Soil test to see if existing soil nitrogen levels can meet demand especially for forage crops (e.g. available N test).
• For each feed deficit or nitrogen application need, determine the best time to apply nitrogen fertiliser and rate to use. Take into account the estimated nitrogen response (kg DM/kg N applied) and the time it will take to achieve this response. Select a product that will deliver the necessary amount of nitrogen, reduce the risk of nitrogen loss and/or supply other productionlimiting nutrients at this time

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