Co-applied Nitrogen and Auxin via Nano-clay-Polymer Composites Enhances Yield and Nitrogen Use Efficiency

Simultaneous application of nitrate (NO3--N) and synthetic auxin in nano-clay-polymer composites (NCPC) is hypothesized to increase rice yield and nitrogen (N) use efficiency. A pot experiment was conducted in 2019 at ICAR-National Rice Research Institute (NRRI), Cuttack, Odisha, India, during Rabi season with rice variety Sahbhagi dhan with eight treatments, viz. control, auxin 1-naphthaleneacetic acid (NAA), sodium nitrate (NaNO3), NAA + NaNO3, NCPC, NCPC + NAA, NCPC + NaNO3 and NCPC + NAA + NaNO3, in four replicates using a basal addition of 1/ 3 1/ 3 of the recommended dose, i.e. 35.71 mg N kg(-1). Except for the control, urea was applied to all the treatments at maximum tillering and panicle initiation stages using one-third of the recommended N dose at each stage without further addition of NAA or NCPC. Phosphorus and potassium were added at the rate of 17.86 mg kg(-1) in all pots (including control). Plant yield increased more in NCPC-loaded NaNO3 fertilizer treatments than the NaNO3 fertilizers alone. Combined application of NaNO3 and NAA loaded in NCPC resulted in the highest yield, which was 71%, 43% and 28% higher than the control, sole application of NAA and sole application of NaNO3, respectively. Combined application of NCPC, NaNO3 and NAA was found to have 7.6% higher total N content in grain than the NaNO3 alone. Although the pH and electrical conductivity remained unchanged among all treatments, it was found that soil available N (175 mg kg(-1)) and N uptake in straw and grain were highest in the NCPC + NAA + NaNO3 treatment. Hence, we conclude that smart delivery of NO3--N and synthetic auxin through NCPC offers significant benefits in terms of yield, N content and N use efficiencies in rice.

Automated summary

Simultaneous application of nitrate and synthetic auxin in nano-clay-polymer composites (NCPC) can increase rice yield and nitrogen use efficiency. The NCPC-loaded NaNO3 fertilizer treatments showed higher plant yield, and the combined application of NaNO3 and NAA loaded in NCPC resulted in the highest yield. The combined application of NCPC, NaNO3, and NAA also increased the total nitrogen content in grain.