Abstract:

: As a major measure to handle livestock manure, digestate is the by-product during biogas production in anaerobic fermentation. Digestate can be returned to cropland as a replacement for chemical fertilizer regarding its cost-effectiveness and rich nutrient content. However, the optimal rates of digestate to substitute chemical fertilizer have not been validated academically. A field study on nine treatments of no fertilizer, chemical fertilizer, and digestate at different rates was conducted to investigate the effects of substituting chemical fertilizer with digestate. The results revealed that replacing chemical fertilizer with liquid digestate did not significantly affect the rice growth regarding the maximum number of seedlings, plant height, tiller numbers, spikelets numbers, ear length, the number of grains per spike, and grain yields. However, improvements were found in the maximum number of seedlings, plant height, tiller number spikelet numbers, the area of the second and third backward leaves, grain yields, and quality when liquid and solid digestate were combined. Furthermore, taking the nutrient inputs, rice growth, grain yield, and quality into consideration, applying liquid digestate of 150 t ha −1 and 75 t ha −1 of liquid combined with 15 t ha −1 solid digestate was suggested for rice production at the study venue.

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