Although available iron is usually abundant for the growth of rice cultivated in waterlogged condition, the rice crop may suffer from its deficiency when cultivated in aerobic soil since the soil properties are totall...Although available iron is usually abundant for the growth of rice cultivated in waterlogged condition, the rice crop may suffer from its deficiency when cultivated in aerobic soil since the soil properties are totally different from waterlogged. Solubility of iron is very low in soils with high Eh and/or high pH. A field experiment with five different depth (10, 20, 30, 40 and 50 cm) of groundwater, and a pot experiment with five treatments of ammonium nitrate ratio (100/0, 75/25, 50/50, 25/75 and 0/100) were conducted to study the characteristics of iron nutrition of rice in non full irrigation condition. Moreover, the contents of iron extracted by 1 mol L 1 HCl of rice plant samples of 8 cultivars from both aerobic and waterlogged cultivation were analyzed to study the effect of water regimes on iron content of rice plants. The results were as follows: (1) The average content of available Fe (2.70 mg kg 1 ) of 5 layers of the soil treated with 10 cm depth of groundwater was significantly higher than that (0.83 mg kg 1 ) with 50 cm depth of groundwater, and the iron concentration of rice plant of the former was much higher than that of the later. (2) Iron deficiency of rice became much severe when high ratio of nitrate (more than 75 percent) in nitrogen fertilizer applied at different intervals in aerobic cultivation. (3) The iron concentrations of 3 cultivars, Wuyujing3 (99 mg kg 1 ), Yangdao4 (87 mg kg 1 ) and 9520 (95 mg kg 1 ), of rice plants cultivated in aerobic condition were significantly less than those(195, 197 and 175 mg kg 1 ) respectively in waterlogged condition at tillering stage. And even much significant differences existed in the iron concentrations of different cultivars growing in the aerobic and waterlogged condition at maturity.展开更多
Yang's (1996) sediment transport theory based on unit stream power is one ofthe most accurate theories, but in his equations the use of product of slope and critical velocityinstead for critical unit stream power ...Yang's (1996) sediment transport theory based on unit stream power is one ofthe most accurate theories, but in his equations the use of product of slope and critical velocityinstead for critical unit stream power is not suitable. Dimensionless critical unit stream powerrequired at incipient motion can be derived from the principle of conservation of power as afunction of dimensionless particle diameter and relative roughness. Based on a lot of data sets,this new criterion was developed. By use of this new criteria, Yang's (1973) sand transport formulaand his 1984 gravel transport formula could be improved when sediment concentration is less thanabout 100 ppm by weight.展开更多
文摘Although available iron is usually abundant for the growth of rice cultivated in waterlogged condition, the rice crop may suffer from its deficiency when cultivated in aerobic soil since the soil properties are totally different from waterlogged. Solubility of iron is very low in soils with high Eh and/or high pH. A field experiment with five different depth (10, 20, 30, 40 and 50 cm) of groundwater, and a pot experiment with five treatments of ammonium nitrate ratio (100/0, 75/25, 50/50, 25/75 and 0/100) were conducted to study the characteristics of iron nutrition of rice in non full irrigation condition. Moreover, the contents of iron extracted by 1 mol L 1 HCl of rice plant samples of 8 cultivars from both aerobic and waterlogged cultivation were analyzed to study the effect of water regimes on iron content of rice plants. The results were as follows: (1) The average content of available Fe (2.70 mg kg 1 ) of 5 layers of the soil treated with 10 cm depth of groundwater was significantly higher than that (0.83 mg kg 1 ) with 50 cm depth of groundwater, and the iron concentration of rice plant of the former was much higher than that of the later. (2) Iron deficiency of rice became much severe when high ratio of nitrate (more than 75 percent) in nitrogen fertilizer applied at different intervals in aerobic cultivation. (3) The iron concentrations of 3 cultivars, Wuyujing3 (99 mg kg 1 ), Yangdao4 (87 mg kg 1 ) and 9520 (95 mg kg 1 ), of rice plants cultivated in aerobic condition were significantly less than those(195, 197 and 175 mg kg 1 ) respectively in waterlogged condition at tillering stage. And even much significant differences existed in the iron concentrations of different cultivars growing in the aerobic and waterlogged condition at maturity.
文摘Yang's (1996) sediment transport theory based on unit stream power is one ofthe most accurate theories, but in his equations the use of product of slope and critical velocityinstead for critical unit stream power is not suitable. Dimensionless critical unit stream powerrequired at incipient motion can be derived from the principle of conservation of power as afunction of dimensionless particle diameter and relative roughness. Based on a lot of data sets,this new criterion was developed. By use of this new criteria, Yang's (1973) sand transport formulaand his 1984 gravel transport formula could be improved when sediment concentration is less thanabout 100 ppm by weight.
