Beth Metson Blog
August 2, 2013
Rotten NVZ business: a green light to compost users
The plant available nitrogen fraction in compost is more often than not low. Standard figures hover around the 3-5% mark. The majority of nitrogen within this product is in the organic form and so requires mineralising to plant available forms. This takes time and the right conditions. This has been recognised by the new NVZ regs that are now allowing growers who use compost to apply over the NVZ field limit (250kg Total N/ha) for organic fertiliser. This is good news for those of you looking to build soil organic matter especially after the damage done over the last few seasons.
NEW NVZ RULE
From 17 May 2013, subject to conditions, you may apply more than 250 kg N/ha in a rolling 12 month period if the only organic manure you apply to a field is compost. In this case, you may apply compost containing:
Up to 500 kg N/ha every two years; you can apply certified compost on any land as a mulch or work it into the soil.
Up to 1,000 kg N/ha every four years; the compost must only be applied as a mulch, and only in an orchard (growing fruit of the genera Malus, Prunus or Pyrus).
So this crudely means if you are farming in an NVZ designated area and apply compost you can now apply two years worth in one hit (4 years worth if you meet the orchard criteria).
This makes perfect sense when considering the slow release of nutrients from compost. This means savings on haulage and spreading costs which often up the price of this activity significantly.
NVZ closed periods don’t affect compost as it contains less than 30% readily available nitrogen, I haven’t come across any that are anywhere near this yet but always check with your supplier just in case. As with all organic manures it’s not an exact science and what has gone into it determines what is going to come out.
In order to make optimum use of the available nitrogen in any organic manure, it should be applied as close as possible to when maximum crop growth and nitrogen uptake occur. The nitrogen value of manures will generally be considerably reduced if applied in autumn or early winter due to losses of nitrogen by leaching (particularly on sandy or shallow soils) or denitrification (mainly on poorly drained soils).
Other important things to remember if you are applying compost:
- It comes in many forms; green and green/food compost – these differ in nutrient content and availability.
- Make sure if you are sourcing compost you are buying a product not a waste. Compost products are certified under BSI as PAS 100. If it is not certified it is a waste and therefore comes under a whole different set of rules and regulations.
- Compost suppliers are not responsible for your NVZ regulations, you are. Ensure if you are applying any form of organic manures you are adhering to the rules by keeping the right records, sticking to the limits and completed a field risk map.
- Compost does contain other nutrients such as Phosphate and Potassium. Phosphate in particular can be a limiting factor when considering where to apply compost. For most arable situations the P index target is 2, if you are applying compost to land with index 3 or above for Phosphate then the application rate should not be in excess of the Phosphate removed by the crop.
You can email Beth your comments and opinions via firstname.lastname@example.org.