Nitrogen use efficiency indices as influenced by planting time and schedule of N application in rice ( Oryza sativa L.)

A field experiment was conducted at Rice Research Station, Kaul (Kaithal), India during kharif season of 2017 and 2018 to study the effect of transplanting time as well as of dose and time of fertilizer nitrogen (N) in rice crop on nitrogen use efficiency (NUE) indices viz. agronomical efficiency (AE), physiological efficiency (PE), agro physiological efficiency (APE), apparent recovery efficiency (ARE), utilization efficiency (UE), partial production efficiency (PPE), nutrient increment efficiency (NIE), partial nutrient balance (PNB), nutrient harvest index (NHI) and nutrient efficiency ratio (NER). The experimental treatments consisted of three transplanting schedules (P1: 3rd week of June, P2: 1st week of July, P3: 3rd week of July), four levels of N fertilizer (N1: 90, N2: 120, N3: 150, N4: 180 kg/ha) and four schedules of N fertilizer application (T1: ½ at transplanting + ½ at 21 DAT, T2: ½ at 21 DAT + ½ at 42 DAT, T3: 1/3 at transplanting + 1/3 at 21 DAT + 1/3 at 42 DAT and T4: LCC based). The nitrogen use efficiencies viz. AE, PE, APE, UE, PPE, NIE and NER were higher with late planting (3rd week of July). Application of N at 120 kg/ha was found most suitable as it resulted into maximum increase in most of the efficiency indices over 90 kg/ha and also exhibited the highest AE, APE, and PPE. Most of the efficiencies were higher when N fertilizer was applied in two equal splits at 0 and 21days after transplanting (DAT).