Foliar nutrient diagnosis norms for litchi (Litchi chinensis Sonn. cv. Feizixiao) in South China

Foliar nutrient diagnosis is a potent tool for nutrient management in crops. Litchi (Litchi chinensis Sonn.) plantation in China dominates the worldwide litchi cultivation, and Feizixiao is the most widely cultivated species in China. Herein, 538 leaf samples were collected at fruit swelling stage and the terminal shoot maturing stage during 2016–2017, and the fruit yields of all the sampled trees were recorded. The suitability of four nutrient diagnosis methods including critical value approach (CVA), sufficiency range approach (SRA), modified diagnosis and recommendation integrated system (M-DRIS), and compositional nutrient diagnosis (CND) in Feizixiao were compared. Only a few of foliar nutrients could be diagnosed by CVA. Similar evaluations were achieved by both M-DRIS and CND, but the diagnosis accuracy highly varied with the severity of nutrient deficiency or abundance and the diagnosis year. Finally, SRA was accepted to establish the diagnosis norms due to its stable assessments for all nutrients. The optimal foliar nutrient range for Feizixiao is recommended as N 16.7–19.2, P 1.06–1.25, K 5.1–6.7, Ca 7.7–11.0, Mg 2.5–3.7 and S 1.51–1.81 g kg−1, and Zn 19.6–32.6 and B 11.5–19.2 mg kg−1 at the fruit swelling stage , and N 19.7–22.0, P 1.69–1.95, K 10.8–12.7, Ca 3.0–4.1, Mg 2.5–2.9 and S 1.38–1.57 g kg−1, and Zn 15.0–18.9 and B 10.8–16.8 mg kg−1 at the terminal shoot maturing stage.