| Summary: | 碩士 === 國立中興大學 === 農藝學研究所 === 82 ===
Pot experiments were conducted in the second crop of 1992 to investigate the effects of soil moisture management on uptake of phosphorus and growth of two rice cultivars, Taichung 189 and Taichung sen 10. Two soils,latosol and alluvials, were used to compare the effects of soil moisture, tension and placements of phosphate fertilizer on availability of phosphorus. phosphate fertilizer with hill-placement at 10 cm depth was practiced, while the control group was broadcasted and mixed with soil. The soil moisture tension were practiced by soil-drying to reach 0.02 and -0.04 MPa before next irrigation, while the control (0.00MPa) group was submerged continuously. A field experiment was also conducted in the first crop of 1993 for comparison.
Experimental results showed that root activity of rice was improved by hill-placement of phosphate fertilizer or soil-drying. Root activity of Taichung 189 with phosphate fertilizer hill-placement was 261% higher than that of the control plot under the treatment of 0.04MPa soil moisture tension. The asne result also found in Taichung sen 10 Soil-drying showed a great benefit for improving root activity of rice at deep soil layer. Root activity at 15 cm depth of Taichung 189 was enhanced from 1.33 to 3.15 A/g dry weight root after soildrying, while Taichung Sen 10 increased from 1.77 to 3.87A/g dry weight root.
Total accumulation of phosphorus in rice plant with phosphate fertilizer hill-placement were higher than that of the control plot by 60,64 and 322% respectively, under 0.00, 0.02 and 0.04 MPa soil moisture tension treatments. A better grain filling was responsible for a greater phosphorus uptake, which due to hill-placement of phosphave fertilizer. In the case of Taichung Sen 10, 1000-kernels weight were increased about 4.6-43.1%, and grain yield ahout 44-141%.
Grain yield of Taichung 189 decreased by 63-73% in 0.02 and 0.04 MPa trdatments than that in the control, while that of Taichung Sen 10 decreased by 32-54%. High soil moisture tension might restricr performance of tillering and sink capacity (kermels per panicle), and hence the yield of rice. Hill-placement of phosphate fertillizer could eliminate the adverse effects of soil drying, and thus improve yield of rice. Field experiment showed that grain yield of rice was 13.7-15.3% higher in the band-placement of phosphate fertilizer than that from broadcasting after soil-drying. phosphate concentration qradient was increased and phosphate use efficiency was improved ahout 90-134% by band and hill-placement of phosphate fertilizer. The results suggest that phosphate use efficiency, which is affected by soil moisture condition, can be improved by management of phosphate fertilizer.
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