Fruit quality, antioxidant capacity and texture of bell pepper (Capsicum annuum) fruit as a function of maturity stage, irrigation and nitrogen levels

Introduction Capsicum production is mostly done under polyhouse conditions for quality and longer seasonal availability. With increasing importance of precision in input application, fruit quality and need of robotic harvesting, a comprehensive information on changing quality dynamics, texture and yield is required. The precision in irrigation and nitrogen fertilizer application levels to optimize yield and harvest quality will be useful to lower usage of input fertilizers thus enhancing sustainability. Methods This study investigated the effects of three levels each of irrigation (I 1 -I 3 ), sensor based irrigation at 18, 20 & 22% soil moisture level and nitrogen (N 1 N 3 ) 100, 150 and 200 kg N/ha fertilizer dose during two consecutive years on total soluble solids, ascorbic acid, antioxidant capacity, bioactive compounds, textural attributes and peduncle stalk firmness of the fruit from 30 days after anthesis (DAA) to 70 days DAA. Results In comparison to other treatments and harvest days, the fruits harvested at 60 DAA and I3N3 treatment showed higher fruit quality. The treatments showed significantly higher vitamin C (138.2 and 133.7 mg/100 g FW, respectively) content in I3N2 and I3N3 over control (102.6 mg/100 g FW) at 60 days of harvest. Antioxidant capacity was significantly higher in all treatments (78.9–83.1%) on 60th day over control (66.8%). Total phenolics content was significantly higher in I2N3 (178.5 mg GAE/100gFW) treated fruit on 60th day over control (115.6 mg GAE/100 gFW). On the 60th DAA, fruit texture showed significant difference over control (1.37 N) in all treatments (1.71–2.27 N) while the peduncle texture did not vary significantly among treatments but the hardness force showed huge rise in overall mean from 30th to 60th day of anthesis (8.7 and 34.4 N, respectively). Conclusions These findings can be useful for application of precise irrigation and nutrition doses, optimized harvest days for significantly higher fruit quality, predict the force required to harvest capsicum fruit by cutting peduncle and use as input data for algorithm development and machine learning to co-relate textural data for development of mechanical robotic harvesters for capsicum fruit.