Rationale behind the integrated use of irrigation and fertilization in optimizing citrus production on Indian Inceptisol

Introduction Nutrients and water-like inputs are the two pillars of production outcomes in citriculture. However, an effective premise of optimizing irrigation requirement (IR) and recommended doses of fertilizers (RDF) together is still not clearly understood. Methods A 4-year field experiment was carried out in 4-year-old Nagpur mandarin ( Citrus reticulata Blanco as scion budded on Citrus jumbhiri Lush as rough lemon rootstock) orchard raised on Typic Ustochrept. Three management zones (MZs), viz., low production management zone (LPMZ), medium production management zone (MPMZ), and high production management zone (HPMZ), were delineated through tree canopy-based spatial variogram and fixed treatments as T 1 (HPMZ, 60% RDF + 80% IR), T 2 (MPMZ, 80% RDF + 90% IR), and T3 (LPMZ, 100% RDF + 100% IR). Discussion The tree canopy volume following the four annual cycles of treatments was observed as 8.08, 6.28, and 5.88 m3 with corresponding fruit yields (kg tree -1 ) of 35.53 (4.39 kg m −3 canopy), 28.15 (4.08 kg m −3 canopy), and 24.26 (4.12 kg m −3 canopy) under HPMZ, MPMZ, and LPMZ, respectively, with coefficients of variation (CVs) of 12.6%–15.5% and 11.8%–13.1%, respectively. Water use efficiency (WUE) and nutrient use efficiency (NUE) within HPMZ (T 1 , 80% IR × 60% RDF) were observed to be 1.83-fold and 2.44-fold higher over LPMZ (T 3 , 100% IR × 100% RDF), providing useful insights into avoiding over-optimization of IR and RDF to develop MZs as a manageable spatial grid, independent of spatial dependence of soil variables for precision crop management. These responses corroborated with response on fruit quality parameters and plant available nutrients in soil, with corresponding CVs of 10.2%–14.3% and 10.0%– 17.1%. Pearson correlation analysis further showed that plant available nutrients within HPMZ were highly correlated with fruit yield compared to relationships, either within MPMZ or within LPMZ. Tailoring MZs-based input use exploiting spatial variability in soil properties hence provided a more rationalized input use efficiency (IUE) than non-variable rate application.