Response Of Phosphorus Absorption And Transportation In Rice And Phosphorus Forms Transformation In Paddy Field To Water And Fertilizer Regulation

The important factors affected the growth of rice is water and phosphorus.Previous studies have shown that water stress and low phosphorus have great influence on the physiological function and the yield of rice,but there are still few studies on the response characteristics of different rice varieties under water stress and low phosphorus,the availability of phosphorus in paddy fields,the transformation characteristics of phosphorus forms and their relationship with phosphorus utilization efficiency of rice under different irrigation regimes.In order to clarify the physiological regulation characteristics of rice under water stress and low phosphorus,and the relationship between the transformation characteristics of phosphorus forms in paddy fields and the absorption and utilization of phosphorus in rice under different irrigation and fertilization modes.In this paper,Nipponbare（Nip）,Kasalath（Kas）,upland rice（U502）and zhongzheyou No.1 were as the experimental materials,the effects of different phosphorus levels and water stress on the growth,phosphorus absorption,root oxidative damage and antioxidant enzyme activities of different rice varieties and their adaptability were studied,and the role of root no signal molecule in alleviating oxidative damage of rice under water stress and low phosphorus was discussed through hydroponics culture.Furthermore,the effects of different irrigation modes and phosphorus application levels on phosphorus absorption and transportation in rice,phosphorus form transformation in paddy fields and their relationship with rice yield formation were studied through soil culture.Finally,the effects of different fertilization and irrigation regimes on phosphorus absorption and utilization efficiency of rice,the characteristics of soil phosphorus form transformation and the key limiting factors of phosphorus availability were discussed through the long-term field experiment,and the optimal management mode of water and fertilization suitable for the areas of single-cropping rice in Zhejiang Province was indicated.The results are as follows:1.Physiological regulation characteristics of different rice varieties adapted to water stress and low phosphorusCompared with the normal phosphorus level（phosphorus concentration 0.32 m M）,the biomass and phosphorus absorption accumulation of different rice varieties（Nip,Kas,and U502）were significantly decreased under low phosphorus stress（phosphorus concentration 0.016 m M）,the oxidative damage level of rice roots and leaves were increased,at the same time,the activity of acid phosphatase in roots and leaves,the activities of osmotic regulators（such as proline and anthocyanin）and antioxidant enzymes（such as（Superoxide dismutase,Peroxidase,POD,CAT））of Nip,Kas,and U502rice were significantly increased.The growth and phosphorus absorption of Nip and Kas rice was further inhibited on low phosphorus and water stress.However,there was no significant effect on the biomass of U502 rice.The results indicate that the different rice varieties can improve their adaptability to low phosphorus and water stress by increasing the uptake of nutrients or the redistribution strategy after nutrient absorption,as well as the activities of osmotic regulators and antioxidant enzyme,and there are significant differences among different rice varieties.2.Physiological regulation of NO in rice root adaptation to water and low phosphorus stressCompared with the control,the NO content in the roots of Nip,Kas,and U502 was significantly increased by exogenous addition of SNP（Sodium Nitroprusside）under the water stress and low phosphorus.And the proline content in the roots of Nip and U502,the activities of SOD and POD in the roots of Kas,the activities of POD and CAT in the roots of Nip and the activities of CAT in the roots of U502 were significantly increased by exogenous addition of SNP under water stress.As well as,the content of proline in the roots of Kas and U502,the activities of SOD,CAT and POD in the roots of Kas and the activities of POD in the roots of Nip and U502 were significantly increased by exogenous addition of SNP under low phosphorus.But the content of MDA in the roots of Nip,Kas and U502 were significantly reduced by exogenous addition of SNP.The results indicate that NO in roots can be acted as a signal factor to synergistically regulate the content of proline and increase the activity of antioxidant enzyme,and then reduce the content of MDA in roots under water and low phosphorus stress.3.Effects of different irrigation patterns and phosphorus application levels on the phosphorus absorption and transportation in rice and the transformation of phosphorus forms in paddy fields.With the increasing of phosphorus application,the yield of rice,seed setting percentage,phosphorus accumulation in panicle,phosphorus transport capacity,phosphorus transport efficiency and phosphorus contribution rate were increased under the conventional flooding（CF）and the alternate wet-dry irrigation（AWD）.The highest yield of rice was 54.3 g/pot under AWD irrigation with P₉₀ treatment.The partial phosphorus productivity,phosphorus agronomic efficiency,the phosphorus harvest index and the phosphorus accumulation in the panicle of rice were significantly increased under AWD irrigation,and the highest phosphorus accumulation in all parts of rice was under AWD irrigation with P₉₀ treatment.At the same time,the content of total phosphorus,available phosphorus,inorganic phosphorus,Al-phosphate（Al-P）,Ca-phosphate（Ca-P）,labile organic phosphorus（LOP）and highly resistant organic phosphorus（HROP）were significantly increased,and the content of the occluded phosphorus（O-P）and moderately labile organic phosphorus（MLOP）were significantly decreased in paddy fields.These results illustrate that the content of available phosphorus can be increased by activating the O-P,increasing the content of the Al-P,Ca-P,LOP and HROP in paddy soil,thereby the phosphorus in the panicle of rice can be accumulated and the yield of rice can be increased under AWD irrigation with P₉₀ treatment.4.Effects of different irrigation and fertilization regimes on the transformation and availability of phosphorus forms in paddy fieldsCompared with the conventional flooding regime（CF）,the yield of rice with different fertilization regimes was significantly improved under the AWD irrigation regime（P<0.05）,and the highest values were 9656.2 kg·hm^-2 and 10032.4 kg·hm^-2 with the 80%CRF+BC and 80%SF+BC treatments,respectively.Under AWD irrigation with80%CRF+BC and 80%SF+BC,the phosphorus accumulation in the different organ of rice,the phosphorus uptake efficiency and the partial phosphorus productivity were improved significantly,and the phosphorus activation coefficient,the content of the available phosphorus,the inorganic phosphorus,the organic phosphorus,various forms of inorganic phosphorus,MLOP and LOP at the depth of 0-15 cm the paddy soil also were higher than those of other treatments.Correlation analysis showed that the main decision-making factors were the moderately resistant organic phosphorus（MROP）,LOP,MLOP and Al-P,and the main limited factor were Ca-P and O-P for the available phosphorus.The increasing of MROP,LOP and MLOP by the appropriate water and fertilizer management may be a potentially effective way to improve the available phosphorus.These results illustrates that the control-released nitrogen fertilizers or stable compound nitrogen fertilizer with biochar under AWD irrigation regime can increase the phosphorus availability in paddy fields via regulating the transformation of the different soil phosphorus forms and activating soil phosphorus,thereby increasing rice phosphorus uptake and phosphorus utilized efficiency.