Optimization of Solid-state Fermentation Process for Sargassum Organic Fertilizer and Its Effect on Cold Resistance of Peppers

Abstract

【Objective】The study aims to explore the fermentation condition of Sargassum organic fertilizer and evaluate its quality and effect on cold resistance of pepper, with a view to providing a theoretical basis for the preparation process optimization of seaweed fertilizer and its application in agriculture.【Method】With Sargassum, chicken manure, coconut bran and tung seed cake as fermentation raw materials, solid-state fermentation technology was used to determine the carbon to nitrogen ratio, initial water content and fermentation inoculant addition amount of Sargassum organic fertilizer in the process of preparation. And the organic matter, total nitrogen, total phosphorus, total potassium, pH, moisture, heavy metals and fecal coliforms were detected. Seed germination tests were also conducted to determine its non-toxicity to plants. By taking a pot experiment, three treatments were set up: blank group (CK), commercial organic fertilizer group, and Sargassum organic fertilizer group, and preliminary exploration of the effect of Sargassum organic fertilizer on the cold resistance of peppers was conducted by comparing the chilling injury index, malondialdehyde content, soluble sugar content and proline mass fraction of leaves.【Result】The results showed that the optimal conditions for solid-state fermentation of Sargassum organic fertilizer were as follows: the carbon to nitrogen ratio was 25∶ 1, the initial water content was 50%, and fermentation inoculant addition amount was 2%. Under the condition, the maximum temperature of the fermentation stack reached 69 ℃, and the temperature of above 55 ℃ was kept for 6-7 days. The testing indexes met the national standard with organic matter content (dry basis) of 72.46%, total nutrients (dry basis) of 5.42%, water content of 28.96%, pH of 7.5, seed germination rate of 89%, and extremely low heavy metals and fecal coliform, etc. Compared with blank and commercial organic fertilizer treatment, the chilling injury index of pepper seedlings treated with Sargassum organic fertilizer decreased by 20.70% and 13.49%, respectively; the mass fraction of malondialdehyde decreased by 23.41% and 14.18%, respectively; the soluble sugar content increased by 27.96% and 21.94%, respectively; the mass fraction of proline increased by 15.49% and 9.01%. The above-mentioned results indicated that Sargassum organic fertilizer could effectively enhance the cold resistance of peppers.【Conclusion】The optimal process conditions of Sargassum organic fertilizer were fermentation carbon to nitrogen ratio of 25 ∶ 1, initial water content of 50%, fermentation inoculant content of 2%, and fertilizer quality reached the relevant national standards. It was non-toxic to plants and could effectively improve the cold resistance of peppers.

Keywords

• sargassum
• seaweed fertilizer
• pepper
• solid-state fermentation
• fermentation process optimization
• cold resistance
• fertilizer quality