Eco-friendly Cellulose Hydrogel as Controlled Release of Fertilizer for a Sustainable Production of Upland Rice in Sarawak

Dayang Fazirah, Abg Ahmad (2024) Eco-friendly Cellulose Hydrogel as Controlled Release of Fertilizer for a Sustainable Production of Upland Rice in Sarawak. PhD thesis, University Malaysia Sarawak (UNIMAS).

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Abstract

Fertilizers and irrigation are the primary components for upland rice cultivation to increase the quality and yield of the rice crops. Most farmers apply conventional fertilizers, however, low efficiency of plant uptake (<50%) is often reported due to nutrient losses through heavy leaching, surface run-off, undesirable reaction with organic compound in the soils, and vaporization and volatilization processes. A promising agricultural alternative to address these challenges is the encapsulation of fertilizers in superabsorbent hydrogels as controlled-release fertilizers to minimize fertilizer losses, extend nutrient supply for a longer period and enhance nutrient uptake efficiency. Therefore, this study fabricates an eco-friendly cellulose-based hydrogel as a controlled-release fertilizer (CRF) derives from waste papers, with a focus on evaluating the effect of the fabricated cellulose hydrogel CRF on the growth performance and production of upland rice, as well as nitrogen uptake and nitrogen use efficiency of the rice plants. To perform the study, a series of cellulose-based cellulose hydrogels were synthesized by crosslinking cellulose fibers extracted from waste papers and carboxymethylcellulose (CMC) with epichlorohydrin (ECH). Fourier transform infrared (FTIR) characterization at 400–500 cm-1 wavenumber using attenuated total reflectance (ATR) technique showed that cellulose fibers and CMC were successfully crosslinked with ECH to form hydrogel. Field emission scanning electron microscopy (FESEM) micrograph of 1000x-magnification displayed highly porous structures. Maximum swelling ratio of >2000% was obtained in C3 cellulose hydrogel (3% (w/v) cellulose, 1.75% (w/v) CMC, 5 mL ECH). Soil moisture retention increased in the presence of C3 cellulose hydrogel (36.5% in topsoil, 30.1% in wet clayey soil, 23.4% in sandy soil) after 7 days, relative to soil without C3 cellulose hydrogel. Urea as a model fertilizer was loaded onto the cellulose hydrogels with maximum loading capacity recorded at 0.51 g g-1. The urea release profile of C3 cellulose hydrogel demonstrated gradual release in soils within 42 days (74.71% in topsoil, 73.37% in wet clayey soil, 71.84% in sandy soil) relative to conventional urea within 7 days (97.32% in topsoil, 95.09% in wet clayey soil, 98.47% in sandy soil). The effects of cellulose hydrogel as CRF in upland rice cultivation were evaluated using Maswangi (MRQ74) Mardi rice variety. The study was conducted at Pusat Penyelidikan Tumbuhan (PPT), University Malaysia Sarawak (UNIMAS), Kota Samarahan, Sarawak (12809.3N, 1102541.3E). The application of cellulose hydrogels CRF at an optimum rate of nitrogen (N) fertilizer, T4H (790 kg N ha-1 = 75%) resulted in maximum grain yield, increasing by 71% relative to control. Maximum nutrient uptake of 0.25 g kg-1 was also observed in the rice plants treated with T4H CRF. Further analysis revealed that T4H CRF recorded the highest harvest index, HI (45.5%); nitrogen harvest index, NHI (67.9%); nutrient use efficiency, NUE (52.6%) and nutrient agronomic efficiency, NAE (12.8 kg kg-1), respectively. Observations show that CRF with only 75% N applied (T4H) in soil improved grain yield when compared to CRF with 100% N and 100% recommended dose of fertilizer (RDF) in farmers’ conventional split application. This suggested that CRF with a moderate N application might produce the highest potential yield and improved N efficiencies while enhancing crop production and further increase in N supply did not increase yield and N efficiencies. The results suggest that the application of T4H CRF for upland rice would enhance HI, N efficiencies and improve the yield of upland rice. Also, all growth parameters and yield were positively influenced by the application of CRF as a basal dose compared to split application of conventional urea fertilizers.

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