Biochar from sewage sludge on soil and plant characteristics of Arugula (Eruca sativa)

Swine sewage sludge is challenging to manage due to the large volumes produced and its high pathogen content. Recently, thermal treatments such as pyrolysis have gained interest as a means to convert dried swine sewage sludge into biochar, which is increasingly applied to soils to enhance plant growth. This study evaluated the effects of biochar produced from dried swine sewage sludge on the growth of Arugula (Eruca sativa) in a greenhouse. Biochar was created through fast pyrolysis at 500°C. This was applied to the test plants with a Completely Randomized Design (CRD) involving six treatments (T0: Dried Swine Sewage Sludge 100g; T1: biochar 20g; T2: biochar 40g; T3: biochar 60g; T4: biochar 80g; T5: biochar 100g) in four replications. Results indicated that biochar is high in nitrogen (2.52%) and phosphorus (9.85%), while Dried Swine Sewage Sludge is rich in potassium (0.7057%). Increasing biochar to certain levels improved nutrient availability in the soil, leading to significant gains in chlorophyll content (0.1144 µg/mL), total soluble solids (4.50 °Brix), leaf count (7.6 number of leaves per plant at 4th week), and plant height (37.75mm during the 2nd week). Biochar application above 40g had a negative impact on horticultural characteristics, specifically the plant height, plant mass (fresh weight) and number of leaves, suggesting that excessive biochar may inhibit development. Despite this, higher biochar levels still enriched soil nutrients (N, 2.52%; Cu, 0.1448%; Fe, 5.44895%; Mn, 0.61375%; Ca, 0.69275%; P2O5, 7.964%; K2O, 2.303%), highlighting the importance of balancing biochar rates for optimal plant performance.