Mung Bean Nutrient Uptake and Root Response to Phosphorus and Potassium Placement Strategies

A pot experiment was conducted to examine the effect of co-application of phosphorus (P) and/or potassium (K) fertilizer to a soil layer on Mung bean (Vigna radiata R. Wilczek) grown in a Yellow Chromosol soil. We hypothesized that adding K to a P- enriched soil layer would increase recovery of K due to increased root proliferation. Layers enriched with P, K or a combination of P and K were placed at either 5 or 20 cm depth in 50 cm deep pots, and a uniform PK application treatment included for comparison. Mung bean was grown for 45 days and key growth and nutrient uptake attributes were assessed. Phosphorus application increased shoot and root dry matter yield and shoot yield was 40% higher in the shallow P treatment and 77% higher in the shallow PK than in the uniform PK treatment. Shallow co-application of P and K increased shoot P and K content compared with shallow P alone. Apparent P fertilizer recovery (%PAFR) followed the same pattern, and there was an 8 to 12-fold increase in %KAFR. There was no evidence of an increase in either the proportion or mass density of roots in the enriched soil layers in any treatment. P and K fertilizer use efficiency was maximized by co-application in an enriched soil layer. When multiple nutrient deficiencies occur co-application of nutrients in a soil layer accessible to roots maximizes fertilizer use efficiency.