Broadcast and Deep‐Band Placement of Phosphorus and Potassium for Soybean Managed with Ridge Tillage

The efficiency of broadcast and band P and K placement methods for ridge tilled soybean [ Glycine Max (L.) Merr.] has not been extensively researched. This study evaluated grain yield, early plant growth, and nutrient uptake (V5–V6 stages), and soil‐test responses to broadcast and deep‐band (15–20 cm below the ridge surface) placements in 14 trials. Fertilizer rates were 0, 14, and 56 kg P ha −1 and 0, 33, and 132 kg K ha −1 A randomized complete‐block design was used. Soil‐test P (STP) was 7 to 61 mg kg −1 (Bray‐P 1 test, 15‐cm depth) and soil‐test K (STK) was 100 to 197 mg kg −1 (ammonium acetate test). Phosphorus increased yield ( P ≤ 0.1) at four sites. Band P was better at one site (30 kg ha −1 ) and broadcast P was better (40 kg ha −1 ) at another site. Both P placements increased dry weight (DW) at two sites. Yield and DW responses to P were observed when STP was <19 mg kg −1 Phosphorus increased plant P uptake at eight sites, and band P was better than broadcast P at three sites. Potassium increased yield at two sites, and only band K increased yield at one of these sites. Potassium increased DW at four sites, and increases were always larger for band K. Band K increased K uptake at 10 sites and broadcast K increased K uptake only at two sites. Soil‐test P in ridges predicted P sufficiency better than mean STP from ridges and valleys at two sites. Although K fertilization seldom increased yield in this study, increased plant K uptake with banding compared with broadcasting suggests that banding may be more efficient for grain production in other conditions.