Corn Responses to In‐Furrow Phosphorus and Potassium Starter Fertilizer Applications

Starter N–P or N–P–K fertilizers often are applied to corn ( Zea mays L.), but questions arise concerning the usefulness of starter K. This study assessed responses of corn grain yield, early growth, and early P and K concentration and uptake to in‐furrow fluid P–K and K starter fertilizers. Six replicated small‐plot trials evaluated a control receiving no P or K, 3–8–15 (N–P–K) starter at 5 to 7 kg P ha −1 and 10 to 14 kg K ha −1 , 0–0–25 (N–P–K) starter at 10 to 14 kg K ha −1 ; broadcast fertilizer at 49 to 66 kg P ha −1 and 112 to 140 kg K ha −1 ; and broadcast‐starter combinations. More N (191–224 kg ha −1 ) was applied uniformly. Eight replicated field‐length strip‐trials evaluated 0–0–25 starter at 10 to 14 kg K ha −1 , broadcast fertilizer at 112 kg K ha −1 , and broadcast plus starter. More N (168–224 kg ha −1 ) and P (49–66 kg ha −1 ) were applied uniformly. The fields encompassed various tillage systems, hybrids, soils, and soil‐test levels. Starter P‐K applied in addition to broadcast P‐K increased growth and P and K uptake compared with broadcast P–K at two trials, but did not increase yield. Starter K applied in addition to broadcast P–K at the small‐plot trials or broadcast K at the strip‐trials did not increase growth compared with broadcast fertilization, decreased K uptake at 2 of the 14 trials, and did not affect yield. Potassium seldom had a starter effect on corn. Starter K may not increase corn early growth or yield unless the soil is deficient in K and broadcast K is not applied.