不同灌溉和施肥模式对稻田磷形态转化和有效性的影响

Effects of various irrigation and fertilization schedules on the transformation and availability of phosphorus in paddy fields

为阐明不同灌溉和施肥模式对水稻磷吸收和利用效率、稻田土壤磷形态转化特征的影响及其对土壤磷素有效性的贡献,该研究以杂交籼稻中浙优1号为供试材料,设常规淹灌(Conventional Flooding,CF)、干湿交替(Alternate Wet and Dry irrigation,AWD)2种灌溉模式,以及不施肥(CK)、常规尿素(Ureal,100%PU)、常规尿素减氮20%(80%of Urea,80%PU)、缓控释复合肥减氮20%+生物炭(80%of Control-Released Fertilizer+Biochar,80%CRF+BC)和稳定性复合肥减氮20%+生物碳(80%of Stable Fertilizer+Biochar,80%SF+BC)5种施肥模式,对比分析了不同灌溉和施肥模式下水稻产量、磷吸收效率、稻田土壤磷有效性及土壤磷形态变化特征。结果表明:1)与CF相比,AWD灌溉模式下80%CRF+BC和80%SF+BC处理水稻产量显著高于100%PU和80%PU处理(P<0.05);2)AWD灌溉显著增加了成熟期80%SF+BC处理水稻穗部磷累积量,且80%CRF+BC与80%SF+BC处理水稻各器官磷累积量、磷吸收效率与磷肥偏生产力均显著高于80%PU处理;3)AWD灌溉显著提高80%CRF+BC和80%SF+BC处理土壤有效磷、无机磷、有机磷含量与磷活化系数,以及土壤各形态无机磷和0~15 cm土壤中活性有机磷(Moderately Labile Organic Phosphorus,MLOP)、活性有机磷(Labile Organic Phosphorus,LOP)含量,且其含量均显著高于两组尿素处理;4)相关分析表明,土壤中稳态有机磷(Moderately Resistant Organic Phosphorus,MROP)、LOP、MLOP和Al-P是土壤有效磷的主要决策因子,O-P(闭蓄态磷)和Ca-P是有效磷的主要限制因子。通过适宜的水肥管理提高MROP、LOP、MLOP含量可能是提高土壤有效磷的潜在有效途径。AWD灌溉模式下,生物炭配施稳定性复合肥/缓控释肥能通过调控土壤磷形态转化和磷素活化提高稻田磷有效性,进而提高水稻磷吸收累积和磷素利用效率。研究结果可为通过不同水肥管理模式提高水稻磷利用效率提供理论依据。

Phosphorus has been one of the most limiting factors to food security in modern agriculture,due to the nonrenewable natural resource.This study aims to investigate the effects of irrigation and fertilization schedules on the phosphorus absorption,transformation,and use efficiency in paddy fields.A systematic evaluation was made on the contribution to the phosphorus availability of rice in the paddy soil.Taking the hybrid indica rice Zhongzheyou 1 as the experimental material,two irrigation schedules were set,including the conventional flooding and alternate wet/dry(AWD)irrigation.Five types of nitrogen application were the zero fertilizer(CK),traditional nitrogen level(100%PU),80%of traditional nitrogen level(80%PU),80%of control-released nitrogen fertilizer plus biochar(control released fertilizer,80%CRF+BC),and 80%of stable compound nitrogen fertilizer plus biochar(stable fertilizer,80%SF+BC).An analysis was performed on the rice yield and phosphorus absorption efficiency,as well as the contents of soil available phosphorus,and the composition of the various phosphorus forms.The results showed that:1)The AWD irrigation under various treatments significantly increased the rice yield(P<0.05),compared with the CF schedule.The maximum yields of 9656.2 and 10032.4 kg/hm2 were achieved in the 80%CRF+BC and 80%SF+BC treatments,respectively.All yields here were also significantly higher than those in the 100%PU and 80%PU treatments.2)The AWD also significantly improved the content of phosphorus that accumulated in the panicle at the maturity stage of rice in the 80%SF+BC treatment.The phosphorus accumulation in the different organs of rice,the absorption efficiency,and partial factor productivity were all significantly higher in the 80%CRF+BC and 80%SF+BC treatments than those in the 80%PU one;3)There were the higher contents of soil available phosphorus,inorganic/organic phosphorus,and soil phosphorus activated coefficient at the depth of 0-15 cm and>15-30 cm in the 80%CRF+BC and 80%SF+BC treatments,including the moderately labile organic phosphorus(MLOP),and labile organic phosphorus(LOP)at the depth of 0-15 cm,compared with the 100%PU and 80%PU treatments;4)A correlation analysis showed that there was the largest direct path coefficient of available phosphorus with the moderately resistant organic phosphorus(MROP,0.599).The direct path coefficient with the LOP and MLOP,Ca-,Al-and O-Phosphate were 0.248,0.177,-0.169,0.126,and-0.079,respectively.It indicated that the MROP,LOPs,MLOP,and Al-Phosphate were the main decision-making factors for the soil available phosphorus,whereas,the Ca-and O-phosphate were the limiting factors for the available phosphorus.Correspondingly,an effective way can be expected to increase the content of MROP,LOP,and MLOP under the appropriate water and fertilizer management,further to increase the soil available phosphorus.Furthermore,the phosphorus uptake and use efficiency of rice can be achieved for the better transformation and activity of soil phosphorus at the mature stage of rice under the suitable AWD irrigation,control-released nitrogen fertilizers,or stable compound nitrogen fertilizer plus biochar in paddy fields.