2 results
Soil mineral N and N net mineralization during autumn and winter under an oilseed rape – winter wheat – winter barley rotation in different crop management systems
- K. SIELING, O. GÜNTHER-BORSTEL, T. TEEBKEN, H. HANUS
-
- Journal:
- The Journal of Agricultural Science / Volume 132 / Issue 2 / March 1999
- Published online by Cambridge University Press:
- 01 March 1999, pp. 127-137
-
- Article
- Export citation
-
Soil sampling in autumn gives important information on the soil N dynamic. In the growing seasons 1991/92 to 1995/96, the effects of different crop management systems on soil mineral N (NO3-N plus NH4-N:Nmin) were investigated in a factorial field experiment at Hohenschulen Experimental Station near Kiel in NW Germany. The crop rotation was oilseed rape – winter wheat – winter barley, and soil tillage (conservation tillage without ploughing, conventional tillage), application of pig slurry (none, autumn, autumn+spring), mineral N fertilization (0, 120 and 240 kg N ha−1) and fungicide application (none, three applications) were all varied. Each year, the treatments occurred in all three crops of the rotation and were located on the same plots. Nmin was determined on four dates (‘After drilling’, ‘End of autumn growth’ before winter, ‘Beginning of spring growth’ before N fertilizer application, and ‘After harvest’) to 90 cm in 30 cm horizons.
Under all crops, Nmin showed a large year to year variation. Highest values of 132 kg N ha−1 were observed ‘After drilling’, which decreased until ‘End of growth’. The increase of autumn Nmin (‘After drilling’, ‘End of autumn growth’) was mainly due to autumn slurry, whereas mineral N fertilizer mainly affected Nmin ‘After harvest’. Soil tillage and fungicide application only slightly modified Nmin at all dates.
The relationship between N leaching and Nmin measured either ‘After drilling’ or at the ‘End of autumn growth’ in 1991/92–1994/95 remained too poor to be used to estimate N leaching. N net mineralization during autumn and winter varied with crops, as estimated by the Nmin changes between ‘After drilling’ minus ‘Start of spring growth’ plus N uptake by the crop at ‘Start of spring growth’ plus N leaching during winter. On average over the years, 39 kg N ha−1 were mineralized under oilseed rape and 42 kg N ha−1 under wheat compared with 31 kg N ha−1 under barley. However, a large year-to-year variation occurred. In addition, the ranking of the years differed with the crops. Slurry application led to different amounts of mineralized N. Under barley only 25 kg N ha−1 were calculated for the autumn slurry, but 42 kg N ha−1 for the autumn plus spring slurry treatment. In contrast, under oilseed rape the highest value of 41 kg N ha−1 occurred in the autumn slurry plots. Under wheat, slurry application only slightly affected N mineralization. Increased mineral N fertilization decreased N release under oilseed rape, but significantly increased it under cereals. Application of fungicides did not affect N mineralization during winter.
Effect of slurry application and mineral nitrogen fertilization on N leaching in different crop combinations
- K. SIELING, O. GÜNTHER-BORSTEL, H. HANUS
-
- Journal:
- The Journal of Agricultural Science / Volume 128 / Issue 1 / February 1997
- Published online by Cambridge University Press:
- 01 February 1997, pp. 79-86
-
- Article
- Export citation
-
Nitrogen (N) fertilizer not used by the crop can increase the risk of nitrate leaching into the groundwater. In two growing seasons, 1990/91 and 1991/92, the relationships between N fertilization and yield, N uptake by the grain and the N leaching in the subsequent percolation period were investigated in a multifactorial field experiment at Hohenschulen Experimental Station near Kiel in NW Germany. The crop rotation was oilseed rape – winter wheat – winter barley, and effects of soil tillage (minimum tillage without ploughing, conventional tillage), application of pig slurry (none, application in autumn, application in autumn and in spring), mineral N fertilization (none, 80 or 200 kg N ha−1 to oilseed rape and 120 or 240 kg N ha−1 to cereals) and application of fungicides (none, intensive) were all tested. In each year, the rotation and the treatments were located on the same plots. Mineral N fertilization and fungicide application increased yield and N uptake by grain or seed in all crops. In contrast, the application of slurry, especially in autumn, had only small effects on yield and N uptake. Nitrogen losses by leaching (measured using porous ceramic cups) were affected mainly by the year and the crop. In 1992/93, averaged over all factors, 80 kg N ha−1 was leached compared with 28 kg N ha−1 the previous year. Oilseed rape reduced N losses, whereas under winter wheat up to 160 kg N ha−1 was leached. Due to a lower N-use efficiency, autumn applications of slurry increased N leaching, and mineral N fertilization of the preceding crop also led to higher N losses.
Since the amount of leached N depends both on the nitrogen left by the preceding crop (unused fertilizer N as well as N in residues) and on N uptake by the subsequent crop, it is not possible to apportion the N losses to any particular crop in the rotation. The cropping sequence, together with its previous and subsequent crops, must also be considered.
To minimize leaching, N fertilization must meet the needs of the growing crop. In order to improve the efficiency further, investigations must be conducted in order to understand the dynamics of N in the plant–soil system in conjunction with the weather and crop management practices.