Bio-Organic Fertilizer: A Green Technology to Reduce Synthetic N and P Fertilizer for Rice Production

Abstract

Decomposed organic materials, in combination with plant growth-promoting bacteria (PGPB), are environmentally friendly and reduce synthetic fertilizer use in rice production. A bio-organic fertilizer (BoF) was prepared using kitchen waste (79%), chita-dhan (unfilled rice grain) biochar (15%), rock phosphate (5%), and a consortium of 10 PGPB (1%) to supplement 30% nitrogen and to replace triple superphosphate (TSP) fertilizer in rice production with an improvement of soil health. PGPB were local isolates and identified using 16S ribosomal RNA partial gene sequences as Bacillus mycoides, Proteus sp., Bacillus cereus, Bacillus subtilis, Bacillus pumilus, Paenibacillus polymyxa, and Paenibacillus spp. Isolates could fix N₂ by 0.7-1.4 g kg^-1, solubilize 0.1-1.2 g kg^-1 phosphate, and produce 0.1-40 g kg^-1 indoleacetic acid. The performance of BoF was evaluated by 16 field experiments and 18 farmers' field demonstration trials during the year 2017-2020 in different parts of Bangladesh. Performances of BoF were evaluated based on control (T₁), full synthetic fertilizer dose of N, P, and K (T₂), BoF (2 t ha^-1) + 70% N as urea + 100% K as muriate of potash (T₃), 70% N as urea + 100% P as TSP + 100% K as muriate of potash (T₄), and 2 t ha^-1 BoF (T₅) treatments. At the research station, average grain yield improved by 10-13% in T₃ compared with T₂ treatment. Depending on seasons, higher agronomic N use efficiency (19-30%), physiological N use efficiency (8-18%), partial factor productivity (PFP)_N (114-150%), recovery efficiency (RE)_N (3-31%), N harvest index (HI_N) (14-24%), agronomic P use efficiency (22-25%), partial factor productivity of P (9-12%), ARE_P (15-23%), and HI_P (3-6%) were obtained in T₃ compared with T₂ treatment. Research results were reflected in farmers' field, and significant (P < 0.05) higher plant height, tiller, panicle, grain yield, partial factor productivity of N and P were obtained in the same treatment. Application of BoF improved soil organic carbon by 6-13%, along with an increased number of PGPB as compared with full synthetic fertilizer dose. In conclusion, tested BoF can be considered as a green technology to reduce 30% synthetic N and 100% TSP requirements in rice production with improved soil health.

Keywords: biochar; free-living N2 fixing bacteria; indoleacetic acid; kitchen waste; nitrogen use efficiency; phosphate solubilizing bacteria; phosphorus use efficiency.

FIGURE 1

Bangladesh Map showing different locations of PGPB collections, field experiments, and farmers’ field trials.

FIGURE 2

Effect of fertilizer management practices on grain yield of rice. Grain yield data obtained from field experiments conducted at BRRI research stations (eight experiments in each season) during years 2017–2020. (A) T. Aman wet seasons, (B) Boro irrigated seasons. Line that divides box represents median of data. End of box shows upper and lower quartiles (n = 24 for each season). T₁ = control, T₂ = FSFD: full synthetic fertilizer dose of N, P, and K at 80–20–50 and 140–20–80 kg ha^–1 as urea, triple super phosphate (TSP), and muriate of potash (MoP) in T. Aman wet and Boro irrigated seasons, respectively; T₃ = BoF (2 t ha^–1) + 70% N as urea + 100% K as MoP, T₄ = 70% N as urea + 100% P as TSP + 100% K as MoP; T₅ = sole BoF at 2 t ha^–1. BoF was added as dry weight basis.

FIGURE 3

Effect of fertilizer management practices on agronomic efficiency of N (AE_N), physiological efficiency of N (PE_N), partial factor productivity of N (PFP_N), recovery efficiency of N (RE_N), and N harvest index (HI_N). Data generated from field experiments conducted at BRRI research stations (eight experiments in each season) during years 2017–2020. (A) T. Aman wet seasons, (B) Boro irrigated seasons. Error bar indicates standard error (n = 24). FSFD, full synthetic fertilizer dose of N, P, and K at 80–20–50 and 140–20–80 kg ha^–1 as urea, triple superphosphate (TSP), and muriate of potash (MoP) in T. Aman wet and Boro irrigated seasons, respectively. BoF (2 t ha^–1) + 70% N as urea + 100% K as MoP; 70% N as urea + 100% P as TSP + 100% K as MoP. Sole BoF at 2 t ha^–1. BoF was added as dry weight basis.

FIGURE 4

Effect of fertilizer management practices on agronomy use efficiency of P (AE_P), partial factor productivity of P (PFP_P), recovery efficiency of P (RE_P), and P harvest index (HI_P). Data generated from field experiments conducted at BRRI research stations (eight experiments in each season) during years 2017–2020. (A) T. Aman wet seasons, (B) Boro irrigated seasons. Error bar indicates standard error (n = 24). FSFD, full synthetic fertilizer dose of N, P, and K at 80–20–50 and 140–20–80 kg ha^–1 as urea, triple superphosphate (TSP), and muriate of potash (MoP) in T. Aman wet and Boro irrigated seasons, respectively. BoF (2 t ha^–1) + 70% N as urea + 100% K as MoP; 70% N as urea + 100% P as TSP + 100% K as MoP. Sole BoF at 2 t ha^–1. BoF was added as dry weight basis.