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Productivity and spatial variation in unpuddled rice-based systems
Dissertation Abstract:
Traditional production of irrigated rice on puddled soil requires considerable irrigation water. Dry seedling rice on unpuddled soil with overhead sprinkler irrigation was examined as a water saving alternative in two cropping systems (dry season rice-mungbean and maize-wet season rice) in the Philippines. Rice yield at 24–27 sampling locations across 2.4 ha fields averaged 5.3 Mg ha-1 (CV = 16.4%) in the dry season and 5 Mg ha-1 (CV = 21.8%) in the wet season. Rice yield as fraction of theoretical climatic yield potential averaged 56 percent for the dry season and 70 percent for the wet season. System productivity expressed as rice equivalent yield was 11.2 Mg ha-1 for maize-rice and 6.4 Mg ha-1 for rice-mungbean. Rice yield was negatively correlated with electrical conductivity (ECa) to 0.5-m depth in the dry season. It was negatively correlated with penetration resistance in the top 0.15 m and ECa to 0.5-m depth in the wet season. Examination of the cropping systems in small replicated plots failed to capture spatial variations encountered in the large fields. Variations in soil physical properties associated with previous rice production on pulled soils might affect spatial variation in productivity of unpuddled rice-based systems.