Enhancing slurry N content cuts fertiliser costs and reduces greenhouse gases

Slurry additive R&D findings

Livestock farmers can enhance the nitrogen value in slurry by threefold if they treat their tanks this season with the inoculant SlurryBugs + Booster, according to the latest research findings from the Lancaster University’s Environmental Centre.

That three-fold improvement in nitrogen is worth £1.40 per 1,000 litres of slurry, a figure that translates to more than £3,400 worth of nitrogen retained for an average 150 cow herd in 200 days of slurry produced over the winter housing period. In addition, the inoculant helped to reduce significantly CO2 and methane emissions.           

The slurry which was taken from a commercial herd with an average 26kg DMI per cow per day and stored in an outdoor tank, was treated with the inoculant over a five week period. Slurry from the same herd stored in an adjacent lagoon remained untreated and acted as the control. After five weeks, samples from the tank and lagoon were analysed at the Lancaster Environment Centre for total nitrogen, as well as organic nitrogen and ammonium nitrogen.

The Lancaster Environment Centre’s Dr Maria-Fernanda Aller who carried out the analysis on behalf of EnviroSystems comments: “The SlurryBugs + Booster treated slurry resulted in a threefold improvement in total N value and an increase in the proportion of organic nitrogen relative to ammonium nitrogen.
"The proportion of organic N in the treated samples was 57% and in the untreated samples this value was 43%, therefore slurry nutrient value improved following treatment.” See Table 1.

Table 1: Inoculant treated slurry v control and impact on N value

 

Five weeks 

Nitrogen (kg/m3 fresh weight slurry) 

Control

Inoculant treated 

Organic N 

0.71

3.15

Ammonium- N 

0.94

2.40

Total N 

1.7

5.6

Source: Lancaster Environmental Centre

“The larger amount of N found in the treated slurry reduces ammonia emissions and has a positive effect when applied to soils as the extra organic N takes longer to break down in the soil. This increase in organic N also lowers the risk of N loss by leaching, an important aspect in Nitrate Vulnerable Zones.”

In addition, SlurryBugs + Booster demonstrated an ability to reduce greenhouse gas emissions from slurry over the five week period. CO2 emissions from treated samples were reduced threefold and methane emissions reduced by over half when compared to the untreated samples. See table 2.

Table 2. Inoculant treated slurry v control and impact on greenhouse gas emissions

 

Slurry

Type 

CO2 

CH4 

Total
 

Inoculant treated

354.6

33.6

388.2
 

Control

1052.9

81.4

1134.3
         

Source: Lancaster Environmental Centre

CO2, CH4 and total gas emissions from slurry samples measured in mg CO2 g-1 h-1 of dry weight slurry

EnviroSystems Liz Russell adds: “These findings have confirmed that treating slurry with SlurryBugs + Booster improves the value of slurry, both in terms of its nutritional and organic content, therefore bringing significant savings to the fertiliser bill next spring. After the five week evaluation period, the untreated slurry contained 1.7kg/ m3 N, while the nitrogen content in the treated slurry increased to 5.6kg/m3 N, a threefold improvement accompanied by an increased nitrogen value of £23 per cow or £3,450 for a 150 cow herd.

“Furthermore, increasing organic nitrogen by more than three times helps to retain soil nutrients and prevent their leaching, thereby enabling farmers to further reduce unit input costs and exploit the potential of their land. The inoculant also proved to be of value in reducing the levels of harmful greenhouse gases emitted through retention of the carbon in the treated slurry.”

 Written by Liz Snaith

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