Distribution Of Se In Soil-rice Systems In West Part Of Hainan Island

Low soil selenium and selenium deficiency soil areas approximately account for72%of the total land area in China, and even the average selenium content in rice is below the critical value selenium in some provinces and cities. About80%of selenium concentrations uptake by the human body are from rice consumption, so improving the level of selenium in rice is of great importance to ensure selenium intake human body required for. In Hainan Island, selenium-rich soil areas with concentrating distribution, are up to about9500km2, accounting for27%of the total island area. Besides, the climate condition is also very suitable to develop selenium-enriched rice in Hainan. To date the researches on the selenium-rich rice variety breeding and Se-enriched way have gained some advances. However, little is known regarding Se accumulation and distribution in soil-rice systems in the selenium-rich area. Therefore, accumulation and distribution of Se in soil and rice was studied in a wide range of western Hainan as the research area. Main results are as follows:1. In different nitrogen and phosphorus levels, selenium content in rice plants varied significantly, and the rising phosphorus levels can effectively improve the selenium content of rice roots. Whereas, selenium content in the polished rice weren’t significantly varied from nitrogen and phosphorus levels. In the low-pH soil, selenium was mainly accumulated in the polished rice from N2P2(urea1.02g pot-1; superphosphate2.92g pot-1) treatment. For high-pH soil, it was in the in N2P1(urea1.02g pot-1; superphosphate2.33g pot-1) treatment that selenium was mainly accumulated in the polished rice.2. Selenium content was relatively rich up to0.40mg kg-1on average in the top layer soil of the study area. However, its spatial variation was very large, varying from0.23to1.58mg kg-1. Distribution of soil parent material also represented a spatial variation, and soil selenium content distribution followed right-skewed normal distribution model.3. In this study, polished rice and rice straw selenium content were0.070and0.138mg kg-1, respectively, and selenium content in rice straw was significantly higher than that in polished rice (Sig.<0.01). Se concentrations in rice plants cultivated in selenium-rich soil were significantly higher than rice plants cultivated in the selenium-low soil.4. Se concentrations in rice plants (polished rice and straw) were increased with the addition of soil Se levels, while and selenium bio-concentration factor (BCF) were decreased. Selenium-BCF variability of the rice straw was gradually increased. Selenium-BCF of polished rice was significantly. lower than the rice straw rice (Sig.<0.01), the range of which was wider than related with soil organic matter, pH and CEC. When the selenium content in the rice straw was less than0.3mg kg-1, the selenium content in the polished rice was significantly positively correlated with the increasing of selenium levels in the rice straw. Whereas, the trend was gradually no significant when the straw selenium content out of0.3mg kg-1.6. The bio-concentration factors (BCF) of the polished rice and the straw were declined with the increasing of soil selenium content. And there was a significant linear correlation between BCF of the polished rice and BCF of the straw (P<0.01).