Organic manures are a valuable source of plant available nitrogen (N).
However, using either too much or too little N can adversely affect crop
yields and quality. By integrating manure and inorganic fertiliser N additions,
crop yields and quality will be optimised and pollution risks reduced.
WHAT IS MANNER?
MANNER is a decision support system that can be used to accurately predict the fertiliser nitrogen value of organic manures on a field specific basis. MANNER has been developed using results from the latest research, funded by DEFRA, on organic manure utilisation on agricultural land.
MANNER can be used either:
- in advance of applying manure to check the likely effect of a spreading policy, or
- to assess the actual fertiliser N value of a spread manure using manure application details and weather data.
- Type of organic manure being spread (e.g. cattle, pig, poultry or biosolids)
- The total N, readily available N and dry matter content of the manure. A laboratory analysis or on-farm test result is best, but if this is not available, MANNER has built-in 'typical' values
- Amount applied, either in metric or imperial units (e.g. tonnes/hectare or tons/acre)
- Date when the manure was spread
- Application method and whether incorporated into the soil (e.g. left on the surface or ploughed down after a given time)
- Soil type in the field
- Rainfall since spreading until the end of soil drainage (commonly
about the end of March). local rainfall data should be entered, but
if not known, MANNER has built in 'typical' values
MANNER ESTIMATES PLANT AVAILABLE NITROGEN SUPPLY BY ACCOUNTING FOR:
Ammonia losses to air
The ammonium (readily available) N content of manures can easily be lost to the atmosphere by ammonia volatilisation. To reduce losses:
- Manures can be rapidly incorporated into the soil
- Slurries can be applied using injection or band spreading methods
Nitrate leaching losses to water
Where there is sufficient rainfall following manure application to land, nitrate may be leached beyond crop rooting depth.
- Losses are potentially greatest from slurries and poultry manures, which contain larger amounts of readily available N than straw-based farmyard manures.
- The amount of N loss depends on:
-manure application rate
-rainfall volume after application
-soil type
Organic N release
The organic N content of manures is gradually released (mineralised)
and becomes slowly available to crops over a period of months to years.
The effect of each manure management factor on plant available nitrogen supply is displayed on screen, summarising information as shown in the following example:
