Keep down costs by producing more fertiliser on your farm

Monday 25 March 2013
Keep down costs by producing more fertiliser on your farm

This was the take-home message from Lancashire’s most recent slurry demonstration event which focussed on appreciating and increasing the value of your slurry.

The fine dry weather on the day meant that most farmers were out actually spreading their slurry while they could get on the land, but for the farmers that attended the event they saw and heard first-hand how slurry can be improved and potentially how money can be saved.

Slurry event, Lancs March 2013 - Liz Russell from EnvirosystemsThe event was organised by Myerscough College in conjunction with EnviroSystems and also included advice from independent agronomist Joe Winstanley.

The day started at Moons Farm, Catterall courtesy of Stuart Shepherd who has been using EnviroSystems SlurryBugs for the past 10 years. SlurryBugs is a combination of bacteria and enzymes (biological treatment) which are added to slurry to increase the microbial activity in the slurry and are designed to retain nutrients during storage, hence leaving a more nutrient-rich product for spreading. See the SlurryBugs website for more information (

Stuart started using the product to alleviate problems that he was having with the slurry crusting in his underground storage tanks which was difficult to pump out. Since using the Bugs he has noticed that the consistency of the slurry has improved and is nor more uniform through the tank, with the resultant liquid now easier to pump and spread.

The slurry which we saw in the outside pit was frothy with no crust at all on the surface. Stuart just agitates the slurry for about 30 minutes prior to spreading, a huge saving in both time and fuel in comparison to those of us that have their tractors and slurry mixers running for hours or even days to break down the thick crust which often forms. Stuart also commented on the reduction in odour during spreading which is quite important given the location of the farm very close to a residential area.

EnviroSystems' Liz Russell spoke about how Stuart’s slurry analysed, with the key points being the pH, DM and total nitrogen. The pH of the treated slurry was 7.6 and the total solids 12.3%. Although the slurry was of a higher DM content than ‘typical’ cattle slurry at 6% Stuart commented that he had no problems in pumping it for spreading.

Slurry event, Lancs March 2013 - Joe WinstanleyThe group then moved on to Myerscough College’s Lodge Farm at Bilsborrow where SlurryBugs have also been used. The farm has also been involved in some trial work which farm manager Roger Leach gave a brief summary of.

After lunch Joe Winstanley spoke to the group about nutrient planning on their own farms and the value of testing both soil and slurry to determine the nutritive value.  By doing this you can work out what you need to apply and where, with the potential to save money by using slurry to greater effect by targeting it to areas where the nutrient indices need building up.


Fertiliser needed = crop requirement – nutrients from other sources

Joe took the group through the basic process involved in developing a nutrient plan.


1)  Create a base line

Soil samples must be taken so that you know what nutrients are actually there already as these are the main form of nutrient supply to the crop. If you don’t know this basic information then you will only be guessing what the soil needs. Soil testing is best done in the winter, ideally 6 months after any applications of slurry or fertiliser. A soil basic test will provide you with information on pH, P, K and Mg.

Most farmers tend to think in terms of nitrogen application when they are talking crop growth, but it is vital not to forget phosphate and potash. If these levels aren’t correct then the crop will never reach its potential regardless of how much nitrogen you apply. Target indices of 2 for P and 2- for K should be aimed for in grassland. pH is also very important as it will affect the availability of various nutrients to the plant, with the ideal being 6.5 - 7.

Over-application of potash is common on many grassland farms and is most likely due to the fact that many farmers have historically used a standard blend such as 20:10:10 to help build their indices up and still continue to use them despite the target soil potash levels being met. However on silage ground potash may be low as there is a much greater off-take with the crop which needs to be replaced.

Soil texture is also important, especially to determine nitrogen supply in the soil. The most accurate way of doing this is to send a soil sample in for textural analysis - this only ever needs to be done once per field as it will not alter over time.

Soil nitrogen cannot be measured using standard soil tests – it is more typically calculated using the soil nitrogen supply (SNS) field assessment method. This involves using standard tables in RB209 (Fertiliser Manual) and factoring in variables such as soil type, cropping history and rainfall.


2) Crop Requirement

Once you know the soil nutrient indices then the requirements of the crop are easy to determine based on the standard recommendations in RB209. Computer programs such as PLANET, Gatekeeper or Muddy Boots can be utilised to make this process simpler, or you can take advice from a FACTS qualified advisor. Joe cautioned against taking such advice from a fertiliser salesman as the likelihood is that their interests will lie in selling you fertiliser!


3) Manure Planning

When planning manure applications, particularly in NVZ’s, regulations including closed periods and field limits must always be adhered to. 

Nutrient content of manures will vary according to species and also the farming system eg. livestock fed on high concentrate diets will produce manure with a much higher nutrient content than stock fed solely on forage. Standard manure nutrient values from RB209 can be used, but if your farming system is not typical then testing would be recommended and as the results from Moons Farm show there can be huge variation in nutrient content if your slurry is treated in any way.

The Dry Matter (DM) content of the manure is a good indicator of the phosphate content and can be determined on-farm using a simple hydrometer. The method of slurry application will also affect nitrogen availability eg. 35% of the N in slurry applied to the surface using a splash plate will be available to the plant compared to over 45% if the slurry is applied using shallow injection. Basically the greater the surface area of slurry which comes into contact with the air, the lower the nitrogen availability as more will be lost through volatilisation.

Joe then looked at the fertiliser value of various manures based on their nutrient content and availability eg. 6% DM slurry applied at a rate of 7400 gallons/acre would be worth over £300. Ideally manure should be targeted towards the fields with the lowest P & K indices as it is cheaper to build up the indices using manure as opposed to artificial fertiliser.


4)  Calculating fertiliser requirements

To calculate the fertiliser requirements for your farm you need to subtract the nutritive value of other sources (such as manure) from the total crop requirements.

The farmers attending the event were invited to bring along samples of their own farm slurry for testing in the labs at Myerscough. A follow-up evening meeting has been arranged for Thursday 11th April to discuss these results in more detail and advise how they can be used to develop nutrient management plans for your individual farm.


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