Graze food store fertility limiter

It may be necessary to add additional processes to the growth of pasture coming from simulated data or field records. This limiter allows you to specify an approximate fertility of the soil upon which the pasture is growing in addition to the values used in the pasture model. This is useful when the pasture model is not providing information on the nutritional content (nitrogen) of the growth. There are situations where the nitrogen content (and therefore protein, digestibility and nutrition) of the pasture will be reduced. This usually happens in years of above average rainfall where the pasture production exceeds the nitrogen freely available, or in months where with pasture growth resulting from aseasonal rainfall such as during the dry season. Rather than provide a detailed nitrogen model, we use a simplified approach by tracking the annual nitrogen used by pasture production and if this exceeds a set supply, the nitrogen content of all further growth is reduced by a set amount. This also provides a means of reducing the nitrogen content by the set amount for any growth occurring in specified months.

At present only one (the first) fertility limiter is considered for each pasture.

The following parameters are used to define this activity

Annual nitrogen supply

The annual supply of nitrogen in kg/ha before new pasture nitrogen content is reduced.

RequiredGreater than 0

Note: The Summary information for this component will determine the pasture biomass (kg/ha) that will grow before the limits are enforced based on the nitrogen content of the associated pasture.

First month of Annual pasture growth

This value determines the period over which annual growth and nitrogen use is calculated.

RequiredMonth of year

Nitrogen reduction to apply

The proportional reduction in new pasture nitrogen content when conditions are met (e.g. 0.2 will apply a 20% reduction in new growth N concentration). The nitrogen value assigned will still respect the minimum nitrogen content defined for the Graze food store type. A value of 1 would therefore cause total reduction in nitrogen content and set the value to the minimum nitrogen for the pasture.

RequiredProportionGreater than 0

The following components will add additional functionality to this limiter

Month range timer

Adding a Month range timer to this activity will force the reduction to be applied in the specified months. This allows for reduced nitrogen content in out-of-season pasture production such as aseasonal dry-season rainfall leading to pasture growth. This timer will cause the reduction regardless of the current remaining, annual, nitrogen supply.

Please contact developers if you require another style of timer to apply the fertility limiter.