Effect Of P Level On Rice With Different P-Efficiency To Arsenic-Stress

With excess As was released into environment by intensive industrial and agricultural activities, As contamination in soils has been of great concern all over the world. One practical and feasible method is to take appropriate agronomic abatement measures (nutrition management, varieties, et al) to control the transformation of pollutants from soil to plants, by minimizing the accumulation of contaminants in the edible parts of plants. Rice is a dominant staple crop around the world and more vulnerable to arsenic contamination. By contaminating rice artificially with different levels of P and As, pot experiments at the seedling and maturation stage of rice with different P efficiency were conducted to analysis the effect of P level on rice to As-stress, and the relationship between rice to As-stress and the characteristics of P nutrition of rice.The analysis provides a theoretical foundation for the establishment of agronomic abatement technology system (nutrition management, varieties) of moderate or slightly arsenic contaminated paddies in south China. The main works of this paper are as follows:(1) Seedling soil culture experiment showed that the shoot height, number of tillers, shoot and root dry matter weight of the rice decreased with the increase of As concentration. In contrast, As concentration in shoot and root of the rice increased along with increasing of As supply. The growth of the rice and its roots As absorption were promoted significantly with the addition of P. When As concentration in soil was25mg/kg and50mg/kg, the30mg/kg P treatment inhibited the translocation of As in rice plants, while150mg/kg P treatment promoted the translocation of As. The rice with different P-efficiency showed the same tendency. At the same treatment, the dry weight of shoot and root of P-efficient rice99011was significantly higher than P-inefficient rice99056. When As was added in soils, the As translocation factor of P-inefficient rice99056was lowest at30mg/kg P supply, when the As translocation factor of P-inefficient rice99056was lower than P-efficient rice99011. Whether rice seedlings were planted or not, pH, available P and As in soil all increased with increasing of As and P supply. At the same treatment, pH and available P in soils decreased after planting rice, and soil pH of P-efficient rice99011declined to a lager extent. When P-in-soil supply was less than or equal to30mg/kg and As-in-soil concentration was less than or equal to50mg/kg, the soil available P of P-efficient rice99011was lower than P-inefficient rice99056, while the condition was opposite at other treatments. The soil available As of P-efficient rice99011was higher than P-inefficient rice99056at the same treatment (except for P supply of150mg/kg and As supply of100mg/kg treatment and P supply of150mg/kg and As supply of200mg/kg treatment). The binding forms of As in the soil were mainly Fe-As and O-As, While little for Al-As and Ca-As. At low P level, Fe-As in the rhizosphere of P-efficient rice99011was lower than P-inefficient rice99056; and O-As in the rhizosphere of P-efficient rice99011was higher than P-inefficient rice99056. The condition was opposite at high P level.(2) Maturation soil culture experiment showed that the grain yield of per plant decreased with increasing of As concentration in the soil. When As concentration in soil was50mg/kg, the grain yield of per plant increased with increasing of P supply. When As concentration in soil was150mg/kg, the grain yield of per plant was highest at30mg/kg P treatment and there was no yield at150mg/kg P treatment. The rice with different P-efficiency showed the same tendency. At the same treatment, the grain yield of P-efficient rice99011was markedly higher than P-inefficient rice99056(except for the150mg/kg P and50mg/kg As treatment of P-inefficient rice99056). When As concentration in soil was50mg/kg, the dry weight of stem and leaf increased with growing process, that is, maturity stage> booting stage> tillering stage, which could also be applied to As concentration in stem and leaf. On the contrary, P concentration in stem and leaf decreased with extension of growth stage, that is, tillering stage> booting stage>maturity stage. The rice with different P-efficiency showed the same tendency.(3) When As concentration in soil was50mg/kg, the results of P and As distribution in different parts of rice at maturation stage was as follows. For P-efficient rice99011, number of iron plaque on root surface, P concentration in iron plaque and P concentration in root was decreased with increasing P supply. The concentration of As in root was lowest at150mg/kg P treatment. The concentration of As in stem and leaf, husk were lowest at30mg/kg P treatment. The concentration of As in brown rice had no significant difference between different P treatments. For P-inefficient rice99056, number of iron plaque on root surface and P concentration in root was highest at150mg/kg P treatment and lowest at30mg/kg P treatment. P concentration in the iron plaque was highest at150mg/kg P treatment. The concentration of As in root was lowest at150mg/kg P treatment. The concentration of As in husk increased with increasing P supply. The concentration of As in stem and leaf and brown rice had no significant difference between different P treatments.(4) At the same treatment, number of iron plaque on root surface and P concentration in iron plaque of P-efficient rice99011were higher than P-inefficient rice99056(except for the150mg/kg P treatment). Otherwise, As concentration in iron plaque, root, stem and leaf, concentration of As and P in husk, P concentration in brown rice of P-efficient rice99011were lower than P-inefficient rice99056; As concentration in brown rice had no significant difference between the two rice with different P-efficiency.Taking yield and food security into comprehensively consideration, P-efficient rice99011is more suitable in moderate or slightly As contaminated soils, and yield can be increased with appropriate P supply.