Potash for Organic Growers

Principles of manuring

The principles of manuring are the same whatever the production system. Organic and non-organic farming have many common objectives and are working with the same basic resources. It is unfortunate that promotion and advocacy of the different systems emphasises differences and encourages conflict.

The objectives of organic production as stated by the Soil Association for example are:- the operation of a sustainable relationship between the health of soil, plants, animals, people and the biosphere to produce healthy food whilst protecting and enhancing the environment.

With regard to plant nutrition the organic aims are:

to work within natural systems and cycles;

to maintain or increase long term fertility;

as far as possible to use renewable resources in preference to non-renewable resources;

to use other specific materials when extreme need arises.

In practice this means:

Optimising nutrient recycling by using manures to best effect;

Balancing nutrients within the rotation;

Feeding the soil rather than the plant.

For phosphate and potash these also represent the aims of non-organic farmers. Nutrients from manures are taken into account when deciding fertiliser use; phosphate and potash are applied to replace the nutrients removed in the crop in order to maintain soil fertility and nutrient status.

The main difference between an organic and non-organic approach is seen with nitrogen which, although taken up by the plant principally as nitrate in both systems, has different emphasis on sourcing. Organic systems rely on soil, manure and legume N, rather than supplementing these with purchased fertiliser N.

All systems need to pay careful attention to minimising nutrient losses for both financial and environmental reasons. With organic systems, emphasis is also placed on maximising root and biological activity in the soil but the importance of such principles is also recognised by non-organic farmers - for example even the most intensive potato growers prepare deep beds of well structured soil to maximise rooting and soil exploration. Organic standards favour the use of natural, untreated products, which limits the available range of nutrient sources. Non-organic farmers may normally be influenced more by the cost of materials but this often reflects the degree of processing, energy inputs, transport and convenience.