Effects Of Different Fertilization Modes On Nitrogen Use Efficiency Of Rice

In order to study the effect of different fertilization on nitrogen uptake efficiency and physiological characteristics of rice,two different experiments were designed.The effects of different fertilization methods(mechanical deepfertilization and manual fertilization)on the nitrogen uptake efficiency and physiological characteristics of direct-seeded and transplanted rice were studied.The secondexperiment was different fertilization depths(0,4,8,12 and 16 cm).The tested materials were hybrid rice Tianyou 998 and conventional rice Yuxiangyouzhan.The main resultswere as follows:1.There were significant effects on the nitrogenase assimilation activity of rice leaves.among different fertilization methods The effect of deep fertilization on nitrate reductase activity and glutamine synthetase activity during heading stage of transplanted rice and direct seeded rice were significantly increased.Correlation analysis showed that the nitrate reductase activity of rice leaves was positively correlated with effective panicle number and seed setting rate.The same trend happened between glutamine synthetase activity and seed setting rate at maturity.The results showed that reasonable fertilization depth(8cm deep the soil)could improve the nitrogenase assimilation activity of rice leaves in thekey periods(jointing stage and heading stage),and could improve effective panicle number and seed setting rate of rice.2.Deep fertilization could significantly increase the activities of peroxidase and catalase in the transplanted rice and direct-seeded rice during the whole growth period.The lowest enzyme activity in the leafwas found in no fertilization.treatmentat the same time,deep fertilization could reduce the content of malondialdehyde in leaves,especially at tillering stage and mature stage.In theexperiment of different fertilization depthsthe depth of 8 cm in the soil significantly increased the activity of peroxidase and catalase in the leaves of direct-seeded rice,but remarkably decreased the content of malondialdehyde(MDA)in the leaves.The correlation analysis also showed that the activity of peroxidase and the activity of catalase were significantly positively correlated with the effective panicle and seed setting rate at the heading stage.There was also significant negative correlation among the content of malondialdehyde(MDA)and effective paniclenumber,grain number per panicle,andseed setting rate.The results indicated that a reasonable fertilization method(deep fertilization 8cm)could improve the leaf antioxidant enzyme activity,reduce the degree of membrane lipid peroxidation.3.Different fertilization methods affected the absorption of nitrogen in rice.Deep fertilization significantly increased the content of nitrogen in stem and leaf in direct seeded rice at jointing stage.The effects of deep fertilization and manual fertilization on the nitrogen content inthe leaf and stem in rice were not significant,but the nitrogen content was significantly increased.There was significant difference in total nitrogen content in the water among different fertilization depths in direct-seeded rice.The shallowerfertilization depth led to higher total nitrogen content in the early stage and lower total nitrogen content in the late stage in the water.However,the deeperfertilization led to the opposite results.Thereasonable fertilization depths(8cmdeep in the soil)could remained reseanable total nitrogen content in the water.The highest accumulation of nitrogen attillering stage was found in direct-seeded rice.Based on the results of twoabove experiments,it could be fould that mechanical deep fertilization could improve the nitrogen use efficiency of rice under the treatment of nitrogen fertilization depth in 8cmsoil.4.Different fertilization methods couldaffect the uptake of phosphorus and potassium in rice plants.In addition to tillering stage,phosphorus and potassium contentsin leaves stem and sheath were the highest in the treatment ofdeep fertilization,especially at jointing stage and heading stage.The phosphoruscontent in thegrain was not very different,but deep fertilization could promote the transfer of potassium to grain.And deep fertilization could also significantly improve the efficiency of phosphorus and potassium use(absorption and utilization efficiency,agronomic efficiency,physiological utilization efficiency)in rice.Correlation analysis showed that there was a significant positive correlation between phosphorus and potassium contentsin leaf and grain number per panicle at jointing stage.Therefore,the reasonable fertilization deep(8cm deep in the soil)could not only improve the efficiency of fertilizer use but also improve the phosphorus and potassium contents of leaves during jointing stage,but also significantly increase the grain number per panicle and increase the yield of rice.Insummary,different fertilization methods had significant effects on nitrogen uptake efficiency and physiological characteristics of direct-seeded and transplanted rice.The reasonable fertilization depth(8cmdeep in the soil)could significantly improve the activity of enzyme activity of rice leaves and enhance the efficiency of rice uptake and utilization,and finally increase the effective panicle and seed setting rate of rice and improve the yield of direct seeded rice.