Nutrient balances on organic pig farms

In organic pig production it is very important to preserve nutrients as far as possible, partly to minimise losses to the surrounding environment and partly to counter deficiencies in rotations associated with generally low levels of nutrients. This project examines the removal and loss of nutrients from out-door sow herds with a view to establishing the possibilities of retaining nutrients to benefit subsequent crops. Information obtained in this project and other relevant DARCOF projects is being synthesised and used partly to calculate nutrient balances for actual and model farms and partly for the development of an optimising model for nutrient utilisation on organic pig farms. The investigations are divided into two main parts:

Farm balances of nutrients

In 1997, part of the project was started at four organic pig farms, which also hosted the project "Organic pig meat, DS, and pig production systems", conducted by the Danish Institute of Agricultural Science. As the basis for analysing nutrient balances at the field, herd and farm levels, a systematic study is being carried out which involves mapping of the fold systems, feed utilisation and feed production for the individual categories of ani-mals, their location on pastures, descriptions of the folds, the transfer of animals between fields, as well as gene-ral production conditions, such as manuring strategy, yields etc. which are registered for all farm fields.

Utilisation and loss of nutrients by out-door sow herds

The distribution of nutrients is being examined for two farrowing folds located next to each other (with a total area of about 8,000 m2) using 312 assessment points 5 metres apart in a co-ordinate grid. The grid also includes points outside the folds as control references. At these points, soil samples are taken in the spring (before the sows come out), in October and in the following spring. Using geostatistical methods the deposition of nutrients in the field is analysed, and the correlation to yield and nutrient uptake in the following crops assessed.

As a supplement to these distribution studies, on two other farms a determination of the nitrogen concentration at 1 metre's depth is made in the spring, autumn and winter in four types of field (pregnancy folds, farrowing folds, fields with sows as manure producers, and under-sown fields as reference). Furthermore, suction cells are placed in an under-sown field on the fourth of the organic pig production farms to determine nutrient con-centrations in water washed out of the root zone. In 1998, this field was used as a farrowing fold.

Summary
Publications

Project title
V.2 Nutrient balances in organic pig production, focusing on the optimal utilisation of nutrients deposited by out-door pigs

Project leader
Jørgen Eriksen, Danish Institute of Agricultural Science, Department of Plant Growth and Soil Science, Research Centre Foulum, P.O. Box 50, DK 8830 TjeleTel: +45 8999 1900. Fax: +45 8999 1719.
E-mail: Joergen.Eriksen@agrsci.dk

Project participants
Sven G. Sommer and Søren O. Petersen, Danish Institute of Agricultural Science, Department of Plant Growth and Soil Science
Ib Sillebak Kristensen and Vivi Aarestrup Larsen, Danish Institute of Agricultural Science, Department of Land Use