Nano Urea Fertilization in Sweet Corn Using Leaf Colour Chart and Its Effect on Nitrogen Use Efficiency

Broad based blanket recommendations of fertilizer nitrogen (N) in field may end up with lower N use efficiency because of large field-to field variability of soil N. At the identical time, crop should not suffer from the deficiency of N. Nitrogen fertilizer must be applied only when necessary and must be based on the crop’s nitrogen status. So, keeping in view the significance of N on productivity, a field experiment was conducted during summer seasons of 2022 and 2023 on medium black calcareous soil at Junagadh (Gujarat) to study nano urea fertilization in sweet corn using leaf colour chart (LCC) and its effect on nitrogen use efficiency. Ten treatments comprising 40 kg N as basal (through DAP and urea) + 40 kg N through urea at 25-30 DAS (days after sowing) + 40 kg N through urea at 40-45 DAS (T1), 40 kg N as basal + 40 kg N through urea at 25-30 DAS + two foliar spray of nano urea 0.4% (4 ml/l water) when LCC ≤ 4 (T2), 40 kg N as basal + 30 kg N through urea at 25-30 DAS + three foliar spray of nano urea 0.4% when LCC ≤ 4 (T3), 40 kg N as basal + 20 kg N through urea at 25-30 DAS + four foliar spray of nano urea 0.4% when LCC ≤ 4 (T4), 40 kg N as basal + 20 kg N through urea at 25-30 DAS + three foliar spray of nano urea 0.4% when LCC ≤ 4 (T5), 40 kg N as basal + 10 kg N through urea at 25-30 DAS + four foliar spray of nano urea 0.4% when LCC ≤ 4 (T6), 40 kg N as basal + 10 kg N through urea at 25-30 DAS + three foliar spray of nano urea 0.4% when LCC ≤ 4 (T7), 40 kg N as basal + four foliar spray of nano urea 0.4% when LCC ≤ 4 (T8), 40 kg N as basal + three foliar spray of nano urea 0.4% when LCC ≤ 4 (T9) and control (without N application) (T10) in Randomized Block Design with three replications. Recommended dose of 60 kg P2O5 and 60 kg K2O/ha were applied uniformly to all the plots as basal application. The experimental results revealed that 40 kg N as basal + 40 kg N through urea at 25-30 DAS + two foliar spray of nano urea 0.4% when LCC ≤ 4 recorded significantly the highest nitrogen, phosphorus and potassium uptake by cob and fodder and their total uptake by sweet corn, which remained at par with T3 and T1. Significantly maximum available nitrogen in soil after harvest of sweet corn was noted with T1, which remained at par with T2, T3 and T4. It can be concluded that nano urea fertilization in sweet corn using leaf colour chart ultimately resulted in improved nitrogen use efficiency, which also sustained the fertility of medium black calcareous soil.