| Traditional rice cultivation employs soil puddling prior to rice transplanting. Puddling degrades soil aggregates and generates compaction, thereby lowering hydraulic conductivity and reducing the water required to maintain flooding. Although considered beneficial for rice, these physical modifications may constrain the growth of subsequent dry-season crops and limit total system productivity. For traditional and novel rice cultural practices, we evaluated crop growth and water dynamics in the rice-wheat rotation on two hydrologically-distinct landscape settings (upland & lowland) in Kathmandu, Nepal. Agronomic strategies evaluated in this factorial experiment were rice tillage regime (surface, subsoiler, and subsoiler + moldboard plow) and establishment method (puddling w/transplanting (TPR) & nopuddle w/direct seeding (DSR)).; Within the rice season, soil puddling increased bulk density ( from 10–15 cm) and diminished saturated conductivity by two-thirds. Seepage and percolation (SP) rates, however, were primarily controlled by landscape placement with average water losses more than doubling in the upland environment. Tillage had no impact on SP and neither tillage nor establishment influenced drought probability. Low SP and consistent flooding in the 1st year benefited productivity, with highest yields in the TPR lowland plots (TPR-lowland 6.4, DSR-lowland 5.2, TPR-upland 5.7, DSR-upland 4.7 t ha−1). Fertilizer N was increased in the 2nd year and results suggest that rice productivity is roughly equivalent irrespective of landscape and establishment practice with non-limiting N (TPR-lowland 6.9, DSR-lowland 6.5, TPR-upland 7.0, DSR-upland 6.5 t ha−1).; Rice cultural practices did not affect wheat yield or soil water acquisition. DSR improved wheat establishment (10–15% greater early leaf area), but did not confer a productivity advantage. Wheat season bulk densities suggest that management-induced soil physical changes did not persist on the vertic (2:1 clays) soils at our site. Rather than soil physical properties, irrigation timing appears to be a more tractable productivity constraint to wheat and contributed to superior rooting (11 vs. 3% total root activity beyond 54 cm), harvest index (41 vs. 27%), and yield (4.4 vs. 3.0 mt ha −1) in the 2nd year.; Non-traditional rice cultural practices are not a promising avenue for improving the performance of the rice-wheat rotation in the Kathmandu Valley, but DSR yields can approach those from traditional practices with non-limiting nitrogen fertility. |
