Does it make sense to introduce herbal graas in the crop rotation?

Introducing multifunctional grass mixtures in the crop rotation can contribute to solve some of the great challenges in organic farming as regards the fertility of the soil, the load of weed, biodiversity and sustainable feed protein. But what about the financial perspective?

2019.04.25 | Gårdejer og konsulent, Niels Tvedegaard

From experiments with the grass mixtures. Photo: Helene Uller-Kristensen

Organic plant growers need more solid crop rotations and are at the same time short of alternative fertiliser sources to replace conventional slurry. In areas with a low livestock intensity the problem is particularly relevant. 

In the Organic RDD project 'MultiPlant' there has been conducted a series of experiments with different mixtures, adjusted to different user purposes; 

  1. a protein mixture, where the grass is used for production of grass protein and biogas; 
  2. an engergy mixture, where the grass exclusively is used for biogas; 
  3. a pollination mixture, where the purpose is to favour bees and other insect needs, but where the output also can be used for biogas.

Every mixture contains different levels of a series of different herbs, including lucerne, chicory, plantain, caraway, birdsfoot trefoil, burnet, yarrow, Knautia arvensis, normal brown elle and cow parsley.

The seeding price per hectare of respectively protein- and the energy mixture is about twice as much as the price of a normal mixture of clover grass. The pollination mixture is very expensive with an estimated price of approx DKK 5.600 per hectare. 

The calculation presupposes 20 percent clover grass with herbs, which substitutes alternative cultivation of grain.

Before: Spring corn-winter corn-spring corn-winter corn-pulses

After: Spring corn-herb grass-spring corn-winter corn-pulses 

Based on the present fertiliser rules (import of 50 kg. conventional slurry per hectare) a sales price of approx DKK 1,20 per kg. solid of respectively protein- and the energy mixture is required. Due to the high seeding price there is a need for a sales price of approx DKK 1,60 per kg. solid for the pollination mixture. These prices presuppose, that the farmer defray the expenses of harvest and transportation of approx 15 km.

In a scenario without access to conventional slurry or other fertiliser sources the picture looks different; one price for herbal graas of approx DKK 0,50 per kg. solid inproves the finances, if the alternative is grain without fertiliser supply. 

When gas and energy from the raw material is extracted at the biogas facility, there is a fertiliser product left: bio-slurry. The financial perspective as regards collecting and deliver bio-slurry is highly dependent on, which the access the farmer has to conventional slurry. 

Our calculations shows that, if the farmer has close access to conventional slurry, then it is not beneficial to collect the bio-slurry. Not even, if the bio-slurry can be collected free of charge from the biogas facility. 

In the elucidated crop rotation the conventional slurry covers the need. It looks different though in the scenario without access to conventional slurry. If the bio-slurry can be delivered within a transportation range of 15 km, the access to the bio-slurry would improve the economy in the crop rotation with approx DKK 700. per hectare.

The project "Multiplant" is a part of the Organic RDD 2-programme, which is coordinated by ICROFS (International Centre for Research in Organic Food Systems)The funding support comes from the Green Development and Demonstration Programme (GUDP) under the Ministry of Environment and Food of Denmark.


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Agriculture and food
Tags: Biodiversitet, økologi, græsmarksblandinger, urtegræs, planteavl, foderprotein