Preceding Crop Effect of Ley E17
Nykänen, A.1 ; Granstedt, A.1 & Salo, Y.2
Agricultural Research Centre of Finland, 1Research Station for Ecological Agriculture, Partala, FIN-51900 Juva, 2South-West Finland Research Station, Saarentie220, FIN-23120 Mietoinen
|In Ecological farming it is possible to make the
farming self-sufficient of nitrogen by cropping legume-rich leys. In Finland these leys
are most commmonly red clover-timothy leys. A preceding crop effect can be shown in the
form of increased net mineralisation of nitrogen and other organically bound plant
nutrients. The ploughing of the clover-rich ley can also cause a risk of nitrogen leaching
because the nitrogen fixed by the clover is then released. If there are no plants to take
up that nitrogen, it will be leached. Timing of the ley ploughing is avery important
factor considering nitrogen leaching.
The aim of the study is to find out, how to build up soil fertility, to minimize nitrogen leaching, and to get a better preceding crop effect of ley by having leys of different ages in crop rotation in organic farming. This will be done by observing the clover content, age and ploughing time of the ley, as well as the amount of biomass ploughed into the soil. Especially the clover content of the ley has an effect on the risk of nitrogen leaching affected by the ley.
The field trial is situated in two research stations in Finland and it includes six crop rotations. Continuous cereal cropping is included as a reference and the others consist of 1-, 2- and 3-year-old leys. Crop rotations have been started from different parts of the rotation. In the field experiment, the main plots consist of »ploughing time + subsequent crop« and the sub-plots of crop rotations.
Mineral nitrogen contents in the soil after ploughing the ley during the growing season of the subsequent cereal crop are measured for studying nitrogen release from organic material in the sopil. Botanical composition of the ley is determined fore stimation of the clover content. Total nitrogen and carbon contents of leys, cereals and the biomass ploughed into the soil are also analysed.
Based on the results of the first two experimental years, it seems that the clover content and the yields of 2-year-old leys have been higher than those of 3-years-old leys, mostly based on the results from ecological farms. The clover content and yield will be higher, if harvesting is done one or two weeks later compared to conventional farming.
The nitrate nitrogen content of the soil plough layer in spring on cereals was in the sequence Ley 1 Ley 2 Ley 3 (ley as a previous crop). In the soil layer of 60-90 cm the NO3-N content in the autumn was only 2-5 kg/ha in moraine soil, but in the fertile clay soil after »autumn ploughing« it was 15-20 kg/ha. Spring ploughing of the ley clearly diminished the risk of leaching compared to autumn ploughing.