Reisanbausysteme im Wandel - Wechselwirkungen zwischen Pflanze und Boden: Stoffbilanzen und Ertragsanalyse
Zusammenfassung der Projektergebnisse
Throughout most of South East Asia, emerging water shortages entail shifts in rice-based production systems, replacing the irrigated dry season rice by a less water-demanding upland crop. Subproject 4-A (Nutrient cycling, balances and yield gaps in changing rice cropping systems) assessed the effects of seasonal changes in soil aeration status on soil N supply and on N uptake and grain yield by wet season rice. The study compared rice-rice with maize-rice rotations over two years in 64 farmer fields in the provinces of Tarlac and Pangasinan and researcher-managed plots on the IRRI research farm in Laguna. Across sites and years, the inclusion of an aerobic soil phase (maize cultivation) was associated with a reduced soil C content and N supplying capacity, and in changed kinetics of soil N mineralization. Thus, in the double rice system, soil Nmin peaked about 2 weeks after the harvest of the dry season rice at around 35 mg N/kg soil (IRRI), while after maize, the peak was less pronounced (20 mg kg^-1) and occurred only after 6-7 weeks. Rice grain yields and crop N uptake differed between sites. Highest mean yields (4.2 t ha^-1) and crop N uptake (84 kg/ha) were obtained on the Mollison on the IRRI farm. Yields were considerably lower and more variable on the Fluvisol in farmers’ fields in Pangasinan (3.3 t ha^-1) and Tarlac (2.5 t ha^-1). The inclusion of an aerobic soil phase (pre crop of maize) significantly reduced wet season rice yields in Tarlac and Pangasinan, but not in Laguna. We conclude that an aerobic soil phase in the emerging rice-upland crop rotations will negatively affect soil N supply, and increase the already large gap between attainable and actual rice yields. Particularly on soils with inherently low C and N stocks, the emerging water-saving systems will require increased organic amendments and higher N fertilizer applications, if current yield levels are to be maintained.
Projektbezogene Publikationen (Auswahl)
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(2016) Seasonal soil N dynamics in emerging rice-based cropping systems of the Philippines. Jahrestagung der Deutschen Gesellschaft für Pflanzenernährung, 22. April 2015, Göttingen
Liese, B, Angulo, C, Becker, M.
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(2017) Yield and yield variability of rice in merging cropping systems of the Philippines. Tropentag 2017, 20-22 September 2017, Bonn
Liese, B., Becker, M.
