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20171
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Subject: Soil Science × Author: Amandeep Singh × End date: 2017 × Start date: 2017 × Thesis Type: M.Sc ×
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    Refinement of leaf colour chart based fertilizer nitrogen management technology using PAU-LCC in transplanted rice
    (Punjab Agricultural University, Ludhiana, 2017) Amandeep Singh; Varinderpal Singh
    Large field to field variability in inherent soil nitrogen (N) supply restricts efficient fertilizer N use when soil test based fertilizer N recommendations are used in transplanted rice. A field experiment was conducted at PAU, Ludhiana to study spectral properties of transplanted rice to guide need-based fertilizer N application and to study need of basal N application in new rice varieties i.e. PR 121, PR 122, PR123 and PR 124. The spectral properties of rice leaves at different growth stages measured using PAU-LCC (PAU-Leaf colour chart), SPAD (chlorophyll) meter and GreenSeeker optical sensor correlated well with leaf N concentration except at 10 days after transplanting (DAT). The PAU-LCC and SPAD meter readings were poorly correlated with leaf dry weight at early growth stages but correlation improved as growth progressed. The NDVI values integrate intensity of leaf colour greenness and biomass and are thus well correlated with leaf dry weight at different growth stages. Close linear relationship (R2=0.732, n= 504) between PAU-LCC score and SPAD meter readings suggested that PAU-LCC can be used as economical substitute to SPAD for making need based fertilizer N topdressings in transplanted rice. The PAU-LCC 4 guided N applications produced grain yield equivalent to soil test based N applications with saving of 60 kg N ha-1, and thus led to maximum agronomic (46.7 kg kg-1 N) and recovery efficiency (82.5 per cent) of applied fertilizer N. Whereas, PAU-LCC 4.5 guided N management improved grain yield production by 8.47 percent with the use of fertilizer N equivalent to soil test based N management in new rice varieties (PR 121, PR 122, PR123 and PR 124). The basal N dose can be delayed till 10 DAT while using threshold leaf greenness of PAU-LCC 4.5.