Study On The Physiological Mechanism And Technology Of Synergistic And Efficient Fertilization In A Wheat-peanut Relay Intercropping System

The wheat–peanut relay intercropping rotation system is an important way to alleviate the conflict of land for grain and oil.Experiments were performed during 2015–2020 at the State Key Laboratory of Crop Biology and the experimental farm of Shandong Agricultural University,Tai’an,Shandong Province,China（36°09′N,117°09′E）.The winter wheat cultivar Jimai 22 and the peanut cultivar Shanhua101 were used as experimental materials.Two kinds of fertilizer,common compound fertilizer（CCF）and controlled-release compound fertilizer（CRF）at the same N-P₂O₅-K₂O proportion were used in our experiment.Nitrogen（300 kg/hm2）was applied the day before sowing and at the jointing stage or the flag leaf stage of winter wheat,and at the anthesis stage of peanut at the following ratios:50%–50%–0–0（JCF100）,35%–35%–0–30%（JCF70 and JCRF70）,50%–0–50%–0（FCF100）,and 35%–0–35%–30%（FCF70 and FCRF70）,with 0 kg/hm² as control（CK）.Nitrogen isotope-labeled urea was used to evaluate the effect of different N fertilizer management regimes on the photosynthetic characteristics,dry matter accumulation and distribution,nirtogen uptake and translocation,yield,quality and annual greenhouse-gas（GHG）emissions in the wheat–peanut rotation system.Our objective was to provide theoretical references for double high yield and high efficiency fertilization of wheat and peanut.1.Physiological characteristics and yield of peanut in a wheat-peanut rotation system under different fertilizer management regimesApplying N fertilizer to both crops in three splits（base and topdressing to wheat and topdressing to peanut）significantly increased the chlorophyll content,LAI,Pn,Ф_PSⅡand q_p.At all the corresponding growth stages,the effect of topdressing fertilizer in flag leaf stage was higher than that in jointing stage.Under the same application ratios of N–P₂O₅–K₂O and equal nutrient doses,treatment with CRF significantly increased the SOD,POD and APX contents at middle and later stage and simultaneously decreese the MDA content compared with those CCF treatment.The result indicate that the use of controlled-released compound fertilizer could increased the active oxygen scavenging capacity,and thus slower senescence of peanut.Applying N fertilizer in three splits significantly increased the wheat grain yield and peanut pod yield,and increased the total dry matter and N accumulation.In addition,treatment with CRF promoting N distribution in the pods,and ultimately improving the NHI.These results illustrate that applying N fertilizer in three splits and use CRF could prolong the functional period of peanut leaves and delay leaf senescence,thus increasing the pod yield of peanut.2.Effect of Controlled-Release Compound Fertilized on PhotosystemⅡPerformance and Quality of Intercropped Peanut with WheatThe probability of a trapped exciton moving an electron into the electron transport chain beyond Q_A（Ψ_o）and the performance index on absorption basis(PI_abs)were significantly increased under applying controlled-released compound fertilization,while the relative variable fluorescence intensity at the K-step（W_k）and at the J-step（V_j）was reduced.The comprehensive performance of electron transport chain in PSⅡreaction center and the electron transport capacity both in the donor side and the receptor side were increased obviously,and the performance of the receptor side was greater than that of the donor side.At the same fertilizer rate,there was no significant difference in the fat content between CCF and CRF.But significantly increased the soluble sugar and protein content,indicating that CRF was beneficial for protein accumulation in peanut kernels.Moreover,CRF treatment could increase oleinic acid content and decrease linoleic acid content in fatty acid in peanut and thus increase the ratio of oleinic acid to linoleic acid（O/L）ratio in peanut kernels,which was conducive to prolonging the shelf life of peanut products.3.Effect of different fertilizer management regimes on nitrogen utilization in a wheat-peanut relay intercropping rotation systemApplying N fertilizer in three splits and delaying the topdressing fertilization increased the N uptake of annual and peanut season.However,there were no significant differences on the N uptake of wheat season.Among all treatments in wheat,Ndff from topdressing¹⁵N-labeled fertilizer was higher than that from basal ¹⁵N-labeled fertilizer.In peanut,in the JCF70 and FCF70 treatments,N uptake from the topdressing N at anthesis stage was approximately twice that from the topdressing N at jointing or flag leaf stage.The topdressing N at flag leaf stage in FCF70 treatments was significantly higher than that of the topdressing N at jointing stage in JCF70 treatments,although the same ¹⁵N application rate was used at both stages.The ¹⁵NRE of topdressing N at jointing or flag leaf stage was significantly higher than that of basal N for all treatments in wheat.In peanut,under the same N rate,the ¹⁵NRE of topdressing N at flag leaf stage in FCF70 was higher than that of topdressing at jointing stage in JCF70.Topdressing N at anthesis stage was significantly higher than that of topdressing N at jointing stage in JCF70 and topdressing N at flag leaf stage in FCF70.The opposite trend was observed for apparent loss rates.The apparent loss rates in FCF70 were the lowest among all treatments,because of the high ¹⁵NRE and residual N in the soil.Thus,FCF70 was the optimal treatment for the wheat-peanut relay intercropping rotation system.4.Effect of different fertilizer management regimes on greenhouse gas emissions in a wheat-peanut relay intercropping rotation systemThe application of N fertiliser was found to significantly increase the N₂O emissions relative to CK,especially after irrigation and precipitation.In all the N fertilisation treatments,the mean N₂O emissions were larger in the growing season of peanut compared to the growing season of wheat due to the higher temperature and greater amount of rainfall in the former.Splitting N application into three applications was shown to significantly increase the cumulative N₂O emissions compared with two N applications.At the same fertiliser rate,the N₂O emissions were lower in treatment JCRF70 than in treatment JCF70for both the wheat and peanut growing seasons.The CO₂ emission fluxes exhibited the same trends as the N₂O emission in both the wheat growing season and the peanut growing season.The application of N fertiliser was found to significantly increase the annual net GWP.Under the same fertilizer rate,JCF70 significantly increased the net GWP by 7.2%relative to JCRF70.However,no significant difference in annual net GWP was observed between JCF100 and JCRF70.Compared with JCF100,JCF70 and JCRF70 significantly reduced the GHGI by 11.0%and 18.2%,respectively,mainly due to the increased grain yield due to the reasonable N fertiliser management.Additionally,the lowest annual GHGI was obtained in treatment JCRF70 due to a higher total grain yield.