Crops notes April 2009

On a recent visit to a potato grower, the nutrient value of organic manures for potatoes was considered. Potato growers have been using organic manures such as poultry litter to replace ‘bagged’ fertiliser for several years. Litter can be applied at up to 14.5 tonnes per hectare and should be incorporated maximum benefit to the crop.

The fertiliser value of organic manures has always been worth a lot of money, but this value has increased dramatically due to the recent large increases in fertiliser prices.

The table below shows the potential value of organic manures in terms of inorganic fertiliser prices. Decisions on the amount of organic manure to apply should always be based around a soil analysis. For example, were a soil has a P index of 3 and a K index of 2 minus based on this analysis this field can receive 12.5 tonnes of broiler litter per hectare and at that level no further P or K will be required.

(£values based on CAN@£270/t; Triple Superphosphate@£370/t; Muriate of Potash@£300/t)

(* Based on spring application and incorporation within 24hours.)

Organic manures being applied to potato ground in the Hillsborough area.

When agreeing on the application and NPK value of individual manure applications make sure that manures are applied to fields that have a need for NPK avoiding waste and that manures are applied as accurately as possible.

Chemical (bagged) fertiliser applications

Arable farmers are reminded that fertilisers containing nitrogen (N) and phosphorous (P) must not be applied unless there is a crop requirement, taking account of soil fertility status and the supply of N and P from the application of organic manures.

Where growers wish to apply ‘bagged’ fertiliser containing P, the fertility status of the field must first be established through a soil test. This will indicate the P index of the soil on which the type and rate of P fertiliser to be used can be determined.

Growers are expected to provide evidence of soil nutrient status if ‘bagged’ N or P fertiliser has been applied. Growers who continue as in the past to apply the same ‘bagged’ fertiliser programme to their cereals or potatoes, ignoring soil analysis, may well be in breach of the Nitrates Directive and they are putting their Single Farm Payment at risk.

Equipment with directions for use is available at your local DARD office. Fields need to be sampled every four years and the size of the area for one sample must not be more than four hectares. Samples can be left back to the DARD office where a charge of £9.50 including VAT will be collected.

Winter cereals have had a challenging start to the season, due to poor ground conditions or late sowing. As soon as ground conditions allow, all winter cereals, especially winter barley, should receive 35kg/ha of nitrogen (for example two and a half, 50kg bags /ha of CAN). This will encourage tillering in wheat and ensure tiller survival in winter barley crops.