Another proof of the yield decline in the continous aerobic rice system
2005
Visperas, R.M. | Shaobing, Peng | Bouman, B. | Castaneda, A. (International Rice Research Inst., DAPO 7777, Metro Manila (Philippines))
The aerobic rice system means growing rice under nonflooded conditions in nonpuddled soil. Experiments showed that growing rice under aerobic conditions saves water, but with a corresponding yield penalty. In 2001, a long-term experiment started to compare aerobic and flood-irrigated rice in both the dry (DS) and wet seasons (WS). Aerobic rice was irrigated up to field capacity when tensiometer readings at 15-cm depth reached -30 kPa, while 5-10 cm of water was maintained in flooded rice. In all six seasons, flooded rice yielded significantly more than aerobic rice. The differences in grain yield between flooded and aerobic rice increased from 15% in the first season to 70% in the sixth season, suggesting a yield decline in the continuous aerobic rice. During the 2004 DS, Apo was grown under aerobic conditions in plots where flooded and aerobic rice had been grown continuously during the previous seasons so that we can compare the first and seventh season aerobic rice under the same climatic conditions. The yield of the 1st season aerobic rice was 50% higher than that of the 7th season aerobic rice. Total biomass, panicles/sq. m spikelets/sq m, and 1000- grain weight of 1st season. Aerobic rice were also significantly higher than those of the 7th season aerobic rice, but harvest index and grain-filling percentage were similar. Total N content of the aboveground biomass was significantly higher in the 1st aerobic rice than in the 7th season aerobic rice at all stages, indicating that differences in N uptake or availability may be a reason for the lower yield of the 7th season aerobic rice.
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