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

Starter N-P or N-P-K fertilizers oft en 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.