Nutritional phosphorus recommendation for garlic cultivars grown in subtropical climate

ABSTRACT

The study aimed to propose critical levels (CL) and sufficiency ranges of phosphorus (P) in leaves and soil, and rates of maximum technical (MTE) and economic (MEE) efficiency, to maximize marketable bulb yield in garlic (Allium sativum) cultivars grown in a subtropical climate. Field experiments were conducted for two seasons on clay soils in southern Brazil. The cultivars ‘Chonan’, ‘Ito’, and ‘Roxo Caxiense’ were subjected to the application of P rates (0, 50, 100, 250, and 500 kg P₂O₅·ha^-1·yr^-1). Garlic yield, soil P concentrations (Mehlich-1), and total P in leaves were determined. The CL in relation to total yield garlic yield were 3.5, 4.5, and 3.4 g P·kg^-1 in leaves and 18, 28, and 14 mg P·dm^-3 in soil, for ‘Chonan’, ‘Ito’, and ‘Roxo Caxiense’, respectively. The CL in relation to marketable garlic yield were 4.0, 3.5, and 3.6 g P·kg^-1 in leaves and 22, 26, and 13 mg P·dm^-3 in soil, for the respective cultivars. The MTE rates were 397 and 336 kg P₂O₅·ha^-1, and the MEE rates were 353 and 297 kg P₂O₅·ha^-1, for total and marketable garlic bulb yield. Based on our results, we recommend that garlic growers use when possible the individual nutritional reference values for specific garlic cultivars.

Key words
P fertilization; leaf analysis; nutritional diagnosis methods; P efficiency use; machine learning