Md Rasel Parvej, Foster, Matthew, Dodla, Syam
Rasel Parvej, Syam Dodla, and Matthew Foster
Starter fertilizer is also called “pop-up” fertilizer and usually applied in the seed furrow or in 2 by 2 band i.e., 2 inches side and 2 inches below the seed depth. Louisiana corn producers mostly use ammonium polyphosphate such as 10-34-0 or 11-37-0 as starter fertilizer and apply it in the seed furrow with their planter. These starter fertilizers mostly contain small amounts (10 or 11%) of nitrogen (N) and high amounts (34 or 37%) of phosphorus (P2O5). Some starter fertilizers may also contain small amounts of potassium (K2O), sulfur (S), and some micronutrients such as zinc (Zn), manganese (Mn), etc. Starter fertilizer is usually applied at a lower rate (5 gallons per acre) for in-furrow application due to the chance of salt injury from ammonium-nitrogen but can be applied at a higher rate (up to 10 gallons per acre) for 2 by 2 banding. Although adequate soil moisture at planting can reduce the likelihood of salt injury, high rates of nitrogen fertilizer is still not recommended for in-furrow application.
The main purpose of applying starter fertilizer is to help the germinating corn seedling to boost up early-season growth by easily accessible nutrients placed near the seeds, resulting in increased yield potential. However, corn grain yield response to starter fertilizer is very inconsistent with no yield response being common across mid-South and Midwest. Therefore, each year Louisiana producers often ask the same question whether they should apply starter fertilizer at corn planting. The most common extension answer is “it depends”. Mascagni et al. (2007) conducted 15 site-years research trials from 1991 to 2005 on starter fertilizer (10-34-0 or 11-37-0) for corn production in northeast Louisiana and found that starter fertilizer increased corn yield by 8 to 25 bushels per acre in only 5 out of 15 trials (Figure 1). They reported that the positive yield response to starter fertilizer came only from phosphorus but not from nitrogen. This was because 5 gallons of in-furrow starter fertilizer (10-34-0) contains 19.8 pounds phosphorus (P2O5) but only 5.8 pounds nitrogen (N) per acre, which is a very small amount to make any yield difference by nitrogen at planting. Note that corn requires 30 to 45 pounds nitrogen from planting to V6 stage (6 visible collar leaves and plant is about 12-18 inches tall); therefore, corn nitrogen requirement during the early season can only be fulfilled by applying N as broadcast (Urea; 46-0-0) followed by incorporation before planting or as sidedress (UAN; 32-0-0) at planting. The most important point that Mascagni et al. (2007) reported was that starter fertilizer increased corn yield only in coarse-textured soils such as sandy loam soils. They also reported that sandy loam soils were cold-natured soils with low organic matter content and nutrient holding capacity, where phosphorus deficiency symptoms were common during early corn growing season (mid-March to mid-April). However, they mentioned some benefits of starter fertilizer regardless of soil type and yield response such as improved early-season plant growth and 3 to 4 day earlier mid-silk stage along with earlier maturity. Therefore, based on the research conducted in Louisiana and other corn producing states, the following points need to be considered before making decision in using starter fertilizers.
Overall, starter fertilizer may only benefit corn yield in a very specific situation. If corn price is low and input cost is high, corn producers may not need to spend their money on using starter fertilizer in most fields. However, with high corn prices this year, starter fertilizer, if not too expensive, can be a cheap insurance for early corn planting in coarse-textured soils against the detrimental cold and wet weather conditions often experienced by Louisiana corn producers in March.
Figure 1. Corn yield response to starter fertilizer in research trials conducted by Mascagni et al. (2007) on Mississippi River alluvial sandy loam/silt soils at the Northeast Research Station in St. Joseph, Louisiana. [NS, not significant at the 0.05 probability level; Source: Mascagni (Rick), H.J., D. Boquet, and B. Bell. 2007. Influence of starter fertilizer on corn yield and plant development on Mississippi River alluvial soils. Better Crops. Vol. 91(2)]