Substrate composition and urban–rural location determine yield and quality of lettuce and radish

Urban horticulture offers opportunities for sustainable local vegetable production, but the effects of reducing peat substrates on crop yield and quality in both urban and rural settings in the Baltic climate remain poorly understood. This study investigated the growth of lettuce (Lactuca sativa L.) and radish (Raphanus sativus L.) in open-air container systems with partial peat replacements across urban and rural sites. Substrate treatments included peat: perlite (4: 1), peat: coconut coir (1: 1), peat: hempseed sheaves (1.5: 1, in 2023), and peat: leaf compost (4: 1, in 2024). Results showed that substrate composition significantly affected both crop yield and plant morphology, while the urban versus rural location had a smaller, year-dependent impact. Lettuce produced the highest yields in peat: leaf compost and peat: coconut coir substrates. Radish yields were highest in peat: perlite and peat: leaf compost substrates. Peat: hempseed sheaves did not support adequate growth. Substrate type also influenced plant nutrient content, with nitrogen, phosphorus, and potassium levels varying between substrates and years, while calcium, magnesium, and sulfur remained relatively constant. The study demonstrates that reducing peat content by 20% is feasible using alternative materials without compromising crop yield or quality.