Derivatization and Cross-Linking of Papyrus Reed for Use as Super Absorbent Mulch Substrate
Mwihaki, Josephine E.
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Water is vital for the life and survival of plants. It is essential for transportation of plant nutrients from the soil; it maintains the plant posture and serves as a raw material for various chemical processes like photosynthesis, transpiration, as well as buffer the plant against wide temperature fluctuations. Lack of enough water to crops may lead to wilting and eventually death, some farmers have resulted to irrigation and mulching with plant remains and inorganic materials which lose water quickly. The study of application of hydrogel in agriculture is an area which has not been adequately empirically examined particularly in the African agricultural setup. Even though papyrus reeds have been found to have the ability to absorb and retain substantial amount of water, the study explores whether the papyrus reeds could retain more water when modified. The study, therefore, sought to enhance water retention of papyrus reed fibers through appropriate derivatization with ethylene diamine and phosphoric acid which was then cross-linked by the use of citric acid and urea respectively and it was then used as a mulching agent. The derivatized mulch was characterized by the use of Fourier Transform Infra-Red spectroscopy (FTIR) and Scanning Electron Microscopy (SEM); the swelling ratio was also calculated from the data collected from the laboratory. The modified mulch was applied in the field to evaluate the growth and yield parameters for growing kales and spinach. The FTIR peaks were observed for P-H at 2318 cm-1stretching vibration mode, P-OH at 788.90 cm-1stretching vibration mode of the phosphoric group, N-H at 3246.25 cm-1 bending vibration of primary amines, C-N at 1382 cm-1 stretching vibration mode, C-O at 875 cm-1 stretching and C=O at 1735 cm-1 stretching was attributed to a carboxyl group. The SEM images showed increase in the number of crevices and pores on the surface of the derivatized and cross-linked papyrus reed. The phosphate derivative absorbed 12 times its original weight while the ethylene diamine derivative absorbed 6.6 times its weight. The phosphate mulch with urea crosslink was the most optimal hence used for the field experiments. The cross-linked mulch had significantly higher yields of kales and spinach in terms of weight, where spinach had a mean of 2 kg, a mean length of 27.8 cm, mean width of 9.96 cm and a mean of 4 leaves. Kales grown with cross-linked mulch had a mean weight of 1.9 kg, a mean length of 24 cm, a mean width of 10.7 cm and a mean of 4 leaves. The study results conclude that modified papyrus mulch preserves more water; it is biodegradable, leads to high yield and helps to save labor and water by reducing frequency of irrigation. Based on the results of this study, it is recommended that the modified mulch be used in arid and semi-arid areas after the cost benefit analysis is done.