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Materials and methods

Experiment description The experiment was conducted in the wet season of 2001 at the research farm of the Indian Agricultural Research Institute (IARI), New Delhi, India (28o36′ N, 77o12′ E). The soil was classified as a Typic Ustochrept with average sand, silt, and clay contents in the 0–20-cm topsoil of 52%, 36%, and 12%, respectively. The available N content was low (129 kg ha–1), whereas available P (12 kg ha–1) and K (146 kg ha–1) contents in the 0–20-cm layers were in the medium range. The average saturated hydraulic conductivity down to a depth of 60 cm was 0.51 cm h–1. The water held by the soil at–10 kPa (pF 2) and at–1,500 kPa (pF 4.2) matrix potential was 28% and 6% by weight, respectively (0–20-cm depth). The groundwater table was more than 3 m below the soil surface throughout the crop season. The experiment consisted of two puddled treatments and five nonpuddled treatments. To avoid lateral water flow from the flooded, puddled plots to the aerobic nonpuddled plots, the puddled plots were grouped together and separated from the nonpuddled plots by a bare strip 2 m wide. The puddled and nonpuddled treatments were laid out in a randomized block design with four replicates in bunded plots of 10× 7 m. The treatments were q TPR: transplanted puddled rice (hill spacing 20× 20 cm). q WSR: wet-seeded puddled rice (row spacing 20 cm). q DSR: dry-seeded rice (row spacing 20 cm). q FB: dry-seeded rice on “flat beds”(using row spacing as in the raised beds: 2 rows spaced 20 cm apart, then 47 cm till the next 2 rows). q RB00: dry-seeded rice on raised beds (raised bed width 37 cm …