Differential Watering and Organic Amendment Effects on the Yield, Quality and Metabolite Constituents of Pepper (Capsicum chinense Jacq.)
Akinbuwa Olumakinde *
Department of Plant Science and Biotechnology, Adekunle Ajasin University, Akungba-Akoko, Nigeria.
Agele Samuel
Department of Crop, Soil and Pest Management, Federal University of Technology, Akure, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Water deficit remains a major constraint to pepper production in tropical agro-ecosystems, necessitating sustainable soil and microbial management strategies. This study evaluated the effects of biochar and Trichoderma harzianum on the growth, yield, fruit quality, soil properties, and stress physiology of pepper (Capsicum chinense Jacq.) under varying watering regimes. A screenhouse experiment was conducted using a completely randomised design (CRD) with fourteen treatment combinations, including sole and combined applications of biochar and T. harzianum under 100, 60, and 40% field capacity, with each treatment replicated ten times. Growth, yield, physiological, and biochemical parameters, including antioxidant enzymes (SOD, CAT, POD, APX) and proline, were assessed alongside fruit quality and soil properties. The results showed that the combined application of biochar and T. harzianum under full irrigation (B+T+100% FC) produced the highest growth and yield, with plant height (90.27 cm), leaf area (166.69 cm²), and fruit yield (36.93 fruits plant⁻¹; 150.00 g fresh weight). The B+T+60% FC treatment also significantly enhanced growth and yield (35.23 fruits plant⁻¹), indicating improved tolerance to moderate water deficit, whereas 40% FC markedly reduced performance. Water stress significantly increased proline (60 µmol g⁻¹ DW), total phenolics (820 mg GAE/100 g DW), and antioxidant enzyme activities, while amendment treatments, particularly B+T, reduced these stress indicators (proline: 6–11 µmol g⁻¹). Chlorophyll content was highest under combined treatments at 60–100% FC (~73 mg g⁻¹ FW). Biochar improved ash (5.88%), crude fibre (38.11%), and protein (2.43%), whereas T. harzianum enhanced carbohydrate (65.44%) and vitamin content (155.22 mg/100 g). Mineral composition was highest under B+T+100% FC, notably K (224.19 mg/100 g), Ca (15.64 mg/100 g), and Mg (39.87 mg/100 g). Soil properties were also improved, with reduced bulk density (1.03 g cm⁻³) and increased water-holding capacity (34.10%) and organic matter (14.25%). Overall, the co-application of biochar and T. harzianum enhanced pepper productivity, stress tolerance, and soil quality under water-limited conditions.
Keywords: Biochar, Trichoderma harzianum, Capsicum chinense, water stress, Antioxidant enzymes