Scheduling irrigation for improving water productivity and fruit quality in citrus (cv. Nagpur mandarin) under a dry tropical climate

Abstract

Water scarcity is a major constraint to citrus production in tropical regions. Proper irrigation scheduling using efficient irrigation methods such as micro irrigation systems is a key to sustainable citriculture. In recent years, plant-based measurements have emerged as potential methods for irrigation management in crops. Infrared thermometry (IT) is one of the modern tools to monitor plant water stress. Crop water stress index (CWSI) computed using plant foliage temperature measured by IT has been considered as a potential index for irrigation scheduling. The present study was conducted to evaluate the effects of CWSI-based drip irrigation scheduling on water use, plant water status, fruit yield and quality and water productivity of citrus in central India. Differential irrigation was scheduled at CWSI of 0.6, 0.4 and 0.2 in combination with 40% crop evapotranspiration ( ETc), 60% ETc and 80% ETc, respectively, and compared with alternate day full irrigation (FI, 100% ET) using drip irrigation system. The fruit yield in irrigation at CWSI 0.4 + 60% ETc was at par with that at CWSI 0.2 + 80% ETc and FI. However, 40% water saving resulted in 74% higher water productivity in irrigation at CWSI 0.4 + 60% ETc compared with FI. The fruits under CWSI 0.4 + 60% ETc had superior qualities (high fruit weight, total soluble solids and lower acidity) than FI fruits. Plant canopy volume (PCV) was highly correlated (R2 = 0.89) with crop water use. Overall, the study reveals that irrigation at CWSI 0.4 + 60% ETc could improve the water productivity and fruit quality with substantial water saving in citrus production in water scarce region.