"Supporting nitrogen" delays the senescence of peanut in sandy loam soil
Traditional basal application causes insufficient nutrition supply of leguminous crops in sandy loam soil,which leads to cause nitrogen deficiency and premature senescence in late growth stage.To improve peanut yield,effect of nitrogen topdressing at late growth stage on leaf senescence and yield was studied by field experi-ments using varieties of HY22(large kernel)and HY39(small kernel)from 2020 to 2023.Nitrogen fertilizer was ap-plied at the beginning of nodule senescence(90 d after sowing).5 nitrogen levels of N0,N20(20 kg/hm2),N40(40 kg/hm2),N60(60 kg/hm2)and N80(80 kg/hm2)were set.Results showed that topdressing"supporting nitrogen"could significantly increase yield.Among the treatments,N40,N60 and N80 led to significantly higher yields in both varieties.Compared with N0,during the 3-year experiment,pod yield of HY22 increased by 8.43%-12.81%(N40),7.65%-10.82%(N60),and 6.85%-9.52%(N80)respectively,while HY39 increased by 5.28%-17.28%,5.18%-17.21%,3.37%-14.19%,respectively.Compared with no fertilization,SPAD and net photosynthetic rate of the 2 varieties under N40 were significantly increased by 10.91%-12.3%and 44.88%-83.58%respectively.Activi-ties of superoxide dismutase,peroxidase and catalase in leaves at late growth stage were also increased by 36.75%and 40.06%,4.87%and 8.86%,19.03%and 58.33%,respectively.Accumulation of malondialdehyde in leaves was reduced,accumulation of dry matter in pods was significantly increased,weight of 100 pods was increased,and thus the yield was increased.In summary,under the condition of basal application of 60 kg/hm2 nitrogen fertilizer,with 120 kg/hm2 phosphorus fertilizer(P2O5)and 120 kg/hm2 potassium fertilizer(K2O),the topdressing of 40 kg/hm2 ni-trogen fertilizer could significantly increase leaf antioxidant enzyme activity,delay leaf senescence,improve leaf photosynthetic capacity,and thus increase the yield.
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