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Nitrate leaching from organic arable crop rotations is mostly determined by autumn field management
M. Askegaard1,4*, J. E. Olesen1, I. A. Rasmussen2,5 and K. Kristensen3
Abstract
Two main challenges facing organic arable farming are the supply of nitrogen (N) to the crop and the control of perennial weeds.
Nitrate leaching from different organic arable crop rotations was investigated over three consecutive four-year crop rotations in a field experiment at three locations in Denmark (12 years in total). The experimental treatments were: (i) crop rotation, (ii) catch crop and (iii) animal manure. Nitrate leaching was estimated from measured soil nitrate concentration in ceramic suction cells and modelled drainage.
There were significant effects on annual N leaching of location (coarse sand > loamy sand > sandy loam) and catch crops (without > with). Including a grass-clover green manure on 25% of the area did not increase N leaching compared with crop rotations without green manure. Also the application of animal manure did not influence N leaching, probably because even in the manured treatments the application rate was lower than crop demand.
The results identify management of crop and soil during autumn as the main determinant of N leaching. Nitrate leaching was lowest for a catch crop soil cover during autumn and winter (avg. 20 kg N ha−1), a soil cover of weeds/volunteers had on avg. 30 kg N ha−1, and the largest N leaching losses were found after stubble cultivation (avg. 55 kg N ha−1). The N leaching losses increased with increasing number of autumn soil cultivations.
Source
Agriculture, Ecosystems & Environment (2011) 142: 149-160
DOI: 10.1016/j.agee.2011.04.014
Author Locations and Affiliations
(1) Department of Agroecology and Environment, Aarhus University, Blichers Allé 20, P.O. Box 50, DK-8830 Tjele, Denmark
(2) Department of Integrated Pest Management, Aarhus University, Forsøgsvej 1, DK-4200 Slagelse, Denmark
(3) Department of Genetics and Biotechnology, Aarhus University, P.O. Box 50, DK-8830 Tjele, Denmark
(4) The Knowledge Centre for Agriculture, Agro Food Park 15, DK 8200 Århus N, Denmark
(5) International Centre for Research in Organic Food Systems (ICROFS), P.O. Box 50, DK-8830 Tjele, Denmark
* Corresponding author, E-mail mga@vfl.dk
Posted September 2011