Assessing different methodologies for irrigation scheduling in protected environment: a case study of green bell pepper

This research aimed at assessing four different methodologies to estimate daily irrigation depth, based on the monitoring of soil water status (soil water content sensors, SWS, and tensiometers, TS) and atmospheric evaporative demand (weighing lysimeter, WL, and Piché evaporimeter, PE), of green bell pepper Capsicum annum L.) cultivated in a greenhouse. Furthermore, two different strategies to apply the daily irrigation depths, i.e., single watering (at 8:00 a.m.) or split into two equal applications (at 8:00 a.m. and at 4:30 p.m.), were also investigated. The experiment was conducted in a completely randomized design and according to a 4 × 2 factorial scheme with eight replications. The statistical analysis showed that total water volume (TWV), commercial yield, and crop water use efficiency (WUE) were influenced by the method used to estimate crop water requirement and the irrigation strategies. The TWV applied during the whole crop cycle was 562.7 mm, 731.2 mm, 769.4 mm, and 843.1 mm for treatments with WL, PE, SWS, and TS, respectively. The highest commercial yield was obtained in treatments in which the highest irrigation depth was applied (SWS, 11.55 t ha-1, and TS, 10.09 t ha-1). On the other hand, relatively higher WUE was achieved in treatments managed with SWS (1.63 kg m-3) and WL (1.55 kg m-3). Splitting the estimated daily irrigation depth into two applications promoted the commercial productivity and WUE (9.24 t ha-1 m-3) ha-1 and 1.60 kg compared to the single application (7.06 t and 1.22 kg m-3). Splitting the daily irrigation depth is, therefore, a promising strategy to increase WUE for green bell pepper crops in protected environments