Corn starter fertilizers have been used successfully to increase early plant growth, nutrient uptake, and yields in research trials and on the farm. They also promote earlier maturity, improve southern corn billbug control, and help suppress weeds through earlier shading. Use of starter fertilizers is increasing in North Carolina and the southeastern United States.
Why Use a Starter Fertilizer?
Cool air and soil slow corn plant and root growth in the spring. When root growth is restricted, corn plants often turn purple. Early season purpling varies with variety, but most often it is a symptom of an induced phosphorus (P) deficiency. The deficiency is described as induced because it may occur on soils that test high for phosphorus. It occurs because phosphorus moves slowly in the soil. If roots do not grow enough to reach soil phosphorus reserves, the plant begins to starve for that nutrient.
In most cases, phosphorus deficiencies are temporary, and symptoms disappear as soon as soil temperatures rise to a point where root growth is stimulated and the plant can reach more phosphorus. Grain yields are not reduced every year by root stunting, but yield losses can be significant in years when temperatures are low. Additional factors that limit root growth can also induce phosphorus deficiencies. Some common causes include soil compaction, herbicide injury and insect or nematode damage to the root system.
Starter fertilizers may be used to overcome slow root growth and the potential for reduced nutrient uptake. Starter and “pop-up” fertilizers involve at-planting placement of a small supply of nutrients near the seed (for starter fertilizer) or in the seed furrow (for pop-up types) so seedling roots can rapidly reach the nutrient source. These fertilizers are not intended to supply all nutrients needed by the crop. Their primary purpose is to provide an accessible nutrient source for root and plant growth when adverse conditions occur soon after planting.