| Abstract: | Abstract When in‐row subsoilers are used to plant crops in no‐tillage systems, starter fertilizers are often applied in the in‐row subsoil track. Although rates applied are small, the actual concentration within the rooting zone can be excessive, and injury to germinating seed and young plants can be severe. The purpose of this greenhouse study was to determine the effect of starter fertilizer placement, rate, and source on germination, growth, and nutrient uptake ef corn (Zea mays L.) seedlings. Fertilizers were surface applied, mixed with the upper 7.5‐cm, 7.5‐ to 15‐cm and the 0‐ to 15‐cm soil depths. Fertilizer rates were equivalent to 15 and 30 kg/ha of field applied P. Sources were diammonium phosphate (DAP, 18–46–0) and ammonium polyphosphate (APP, 10–34–0). Treatments did not affect germination, but the surface application resulted in severe crust formation which had to be mechanically broken. Plant heights and weights and root weights were increased by fertilizer. Nitrogen was primarily responsible for increased plant growth 2 weeks after emergence, but P appeared to have the greatest effect at 4 and 6 weeks. Although seedling death or severe damage to plants did not result from any source, rate, or application zone, some damage did occur. Optimum treatments varied with sampling dates, but after 6 weeks, optimum treatments in terms of greatest root and shoot weights and plant heights were the low rate of APP mixed with the 0‐ to 7.5‐ or the 0‐ to 15‐cm soil depths. |
