Effect of Graded Molybdenum Application on Soil Molybdenum Pools, Critical Threshold and Cauliflower Productivity in an Acid Alfisols
摘要
Molybdenum (Mo) deficiency limits crop productivity in acid soils because low pH reduces Mo availability. However, information on soil Mo fractionation and critical soil Mo thresholds for cauliflower production remains limited. This study aimed to quantify changes in soil Mo fractions under graded Mo application and to evaluate the yield response of cauliflower grown in an acid Alfisols of the north-western Himalaya. A field experiment was conducted over two consecutive growing seasons using a randomized block design (RBD) with three replications. The experiment comprised of ten treatments: a control, a general recommended dose (GRD), and the remaining eight treatments with graded levels of soil-applied Mo along with GRD. Soil samples (0–15 cm) collected after the second growing season were analyzed for available Mo and operationally defined Mo fractions. Plant physiological attributes and curd yield were recorded following standard procedures. Graded Mo application significantly increased soil available Mo, improved plant physiological attributes including plant height, curd initiation and maturity, thereby enhancing curd development, quality, and cauliflower yield. Residual Mo dominated the total soil Mo pool (38–49%), followed by oxide-bound (27–32%), organic-bound (17–21%), and exchangeable Mo (6–9%), with all fractions increasing progressively with Mo dose. Curd yield increased significantly up to 5 kg Mo ha− 1 (233.90 q ha− 1), beyond which a progressive decline was recorded. The quadratic-plateau model identified the agronomically optimum dose, while the quadratic model figured out the critical soil Mo level. Graded Mo application differentially enriched soil Mo fractions in a dose-dependent manner, with labile pools responding more readily than the residual fraction. An optimum Mo dose of 3.28 kg ha− 1 and a critical soil Mo threshold of 0.2634 mg kg− 1 were established for cauliflower in acid Alfisols, providing a quantitative basis for precision Mo fertilization recommendations.