Agriculture

The following agricultural products are made available via MetService.

Seasonal Forecast

The seasonal forecast describes the general trends expected in the weather over the next two months. The forecast describes how weather conditions may depart from normal over the next two months: it does not describe any given day or days.

Regions are grouped together according to how they are expected to vary from normal, even though the actual resulting weather may well differ across a group. The forecast is best used for general guidance. Comparison of the forecast variations from normal with the normal for a particular location (your place) may assist with planning over the next couple of months.

Even though MetService expresses a confidence level in the forecast, we offer no guarantees: two months is a long way to look ahead.

The seasonal forecast is issued on the 10th of each month and is available on the Rural Section.

Facial Eczema

MetService operates a 14-day facial eczema risk potential service. This is based on forecasts of the elements that contribute to rapid spore growth (ground minimum temperatures of 12 degrees Celsius and above, and rainfall), not of spore counts.

The facial eczema risk model:

• Considers days in isolation
• Reduces spore growth in heavy rainfall and periods of extended dry even when minimum temperatures are forecast to be over 12 degrees Celsius
• Provides the "most likely outcome" for the fourteen day period
• Assumes the ground is flat: you will need to consider the additional risk of north facing slopes, ridges and lee of hedges.

Forecasts are updated daily by 6pm and are available through RD1.com.

Cow Heat Stress

The primary environmental factors associated with cow heat stress are:

• Air temperature
• Humidity
• Radiation
• Air movement

Cattle are homeotherms, which means they maintain a relatively constant deep body temperature (of about 38.6°C). Heat stress occurs when an animal's heat load exceeds its capacity to lose heat. The immediate response to heat stress is a reduction in feed intake, followed by a fall in metabolic rate to decrease the body's maintenance requirements. This helps to balance heat production with heat loss.

An index of heat stress can give an indication of the degree of stress likely to be experienced by dairy cattle.

Minimum protective measures can be viewed as insurance against possible milk production losses. These measures include:

• Provision of access to clean drinking water. Lactating cows typically require more than 100 litres/day and will drink between two to six times per day.
• Making afternoon milking times later, reducing the walking distance to the dairy, reducing the time spent in holding yards, minimising handling stress.
• Ensuring summer forages are of high quality. Feeds with a high structural component can increase the heat of fermentation in the rumen, increasing the heat load on the cow. Provide feed at night when it is cooler.
• Using paddocks with shade trees.
• Using sprinklers in the dairy to wet the cows' coats and thereby aid in evaporative cooling. (However, sprinkling can increase the humidity around the cows, especially when they are held close together. The effectiveness of sprinkling depends on the removal of water vapour by air movement, ideally by using a fan).

Drying Index

The drying index is based on the Penman-Monteith evapotranspiration equation. This uses forecast or actual air temperature, humidity, radiation and wind speed to calculate the evapotranspiration rate. Detailed forecasts, for many locations throughout New Zealand, of air temperature, humidity, radiation and wind speed are obtained from MetService's computer weather prediction model . However, please note that as this data is computer generated timing of events may differ from manually written MetService forecasts.

The Drying Index forecast is provided as:

1. The evapotranspiration rate, expressed as total millimetres per period.
One of the following text comments related to the evapotranspiration rate:


• 0 - 1mm POOR
• 1 - 2mm GOOD
• 3+mm EXCELLENT
2. A rainfall flag.

The presence of the rainfall flag indicates that more than 0.4mm is forecast for the period. There may be occasions where the evapotranspiration is forecast to be EXCELLENT but the rain flag is present. This is because of the timing of the forecast rain within the period; for example, evapotranspiration may be excellent for 5 of the 6 hours but rain (>0.4mm in total) is expected in the last part of the period.

The evapotranspiration rate refers to the loss of moisture from green grass shading ground that is not short of water. Therefore if the underlying soil is dry, the ET rate will be less than that forecast.

In the forecast, the day is divided into three periods:

• Morning: 6am - noon
• Afternoon: noon - 6pm
• Evening: 6pm - 6am

This is currently available in the metservice business package: MetConnect

Contact

For any questions that you may have about services we can offer, please contact us.