Corn Response to Fertilizer Placement Treatments in an Irrigated No-Till System

Corn (Zea mays L.) plants express unexpected K-deficiency symptoms when grown under certain conservation tillage production systems on high-K-testing soils. This field study was conducted to determine if K fertilizer treatments interact with P and N planting-time fertilizer placement treatments to affect crop growth, nutrient composition, and yield in an irrigated no-till corn production system on high-K-testing soil. The 3-yr study was conducted on Lowry silt loam soils (coarse-silty, mixed, superactive, mesic Typic Haplustolls) near Pierre, SD. Fertilizer placement (main plot) treatments consisted of P and N fertilizers that were applied with the corn planter to (i) the soil surface, (ii) the seed furrow, or (iii) a band 5 cm to the side of the seed furrow and 5 cm deep. Fertilizer products containing K, also applied at planting time, provided a with-K subplot comparison with subplots that received no added K fertilizer. Corn plants were sampled for root pull resistance, shoot dry weight, and shoot mineral nutrient composition at the tassel stage of development and grain yield. Data combined over the 3 yr of the study revealed that added K fertilizer had no effect on grain yield and did not interact with P and N fertilizer placement treatments to affect grain yield. When P fertilizer was placed with the seed and N fertilizer was placed in a 5- by 5-cm band, corn plants had 185 kg root⁻¹ pull resistance, 0.26 g shoot⁻¹ P accumulation, and 10.5 Mg ha⁻¹ grain yield. However, when P and N fertilizers were applied to the soil surface, corn plants had significantly less root pull resistance (151 kg root⁻¹), P accumulation (0.22 g P shoot⁻¹) and grain yield (10.1 Mg ha⁻¹). Added K fertilizer decreased shoot dry weight (added K = 97 g shoot⁻¹, no K = 103 g), decreased P accumulation (added K = 0.22 g P plant⁻¹, no K = 0.25 g), increased shoot N concentration (added K = 19.3 mg N g⁻¹, no K = 19.0 mg), and had no significant effect on K concentration or accumulation. We conclude that, although planting-time fertilizer placement was important for optimum corn growth and yield production in irrigated no-till systems, added K fertilizer did not interact with fertilizer placement to improve yield on the high-K-testing soils used in this study.