Optimum Castor Meal Application in the Cultivation of Pak Choi (<i>Brassica chinensis</i> L.) with Toxicity Survey for Earthworms (<i>Eisenia andrei</i>)

Abstract

In Taiwan, castor meal (CM) is often used by farmers as an organic fertilizer for the supplement of plant nutrition. It can rapidly increase nitrogen availability for crops. However, the excessive application of CM will affect the ecosystem. This study was conducted to evaluate the optimum concentration of CM that can be used as a fertilizer for balancing crop production and soil ecosystem health (by considering earthworms). Pak choi was selected for the experiment. A randomized block design with three replications was used, with treatments consisting of five concentrations of CM (namely 25, 50, 100, 150, and 200 kg/0.1 ha) and fermented livestock compost 800 kg/0.1 ha, represented as CM25, CM50, CM100, CM150, CM200, and LC800, respectively. The results revealed that soil properties, leaf nutrient concentration, and plant traits, namely plant diameter, plant height, and fresh and dry root and shoot matter, improved with the increasing concentrations of CM, and CM100–CM200, and led to the highest production of pak choi which was equivalent to that with LC800. However, the weight of earthworms decreased as CM concentrations increased. The weight of earthworms was similar between CM25, CM50, CM100, and LC800. In conclusion, given the characteristics of high nitrogen as a fertilizer, the optimal dose of CM was 100–150 kg/0.1 ha for obtaining a balance between crop production and ecosystem safety.

Keywords

• castor meal
• biological production
• ecosystem
• earthworm
• toxicity