Effect of Soil Compaction on the Grain Yield of Rice(Oryza sativa L.)under Water-Deficit Stress during the Reproductive Stage

Abstract

The effects of soil compaction under water deficit conditions during the reproductive stage on the grain yield of rice were examined with various cultivars. In a field experiment, three rice cultivars were grown in compacted and non-compacted upland conditions and irrigation was terminated at the early reproductive stage. The grain yield and total dry weight(DW) at maturity was similarly reduced by soil compaction regardless of the rank of the cultivars in drought resistance. However, the yield was superior in the cultivars that showed higher yield and DW under non-compacted conditions. In greenhouse experiments, six rice cultivars were grown in the pot of 1.0 meter in depth containing soil at three levels of soil bulk density(SBD), and water supply was reduced by lowering the water table during the reproductive stage. The effects of SBD on DW and grain yield were similar among six cultivars. In both field and pot experiments the yield reduction was predominantly caused by a smaller number of spikelets, with greater reduction of DW than the reduction of harvest index. We concluded that soil compaction reduced rice grain yield by decreasing the number of fertile spikelet that was mainly caused by the suppression of DW and partly by sterility due to water deficit regardless of cultivar. There was no clear difference among the cultivars in the yield response to soil compaction, but the local drought-resistant cultivars, which showed a relatively superior yield and DW under the non-compacted upland condition, showed a higher yield even on compacted soil.