Evaluation of Various Liquid and Dry Starter Fertilizer Formulations for Corn on High P-testing Soils
Conducted by: Greg Roth, Doug Beegle, Mark Antle, and Shaun Heinbaugh
Location: Centre County, PA
Collaborators: Brian Macafee, Farm Operations, Penn State
Research Objective: To evaluate the performance of a various liquid and dry starter fertilizer formulations for corn production on soils testing high for P.
Background: This study was a three year study to evaluate starter fertilizer alternatives on soils testing high for P. The treatments were designed to compare various dry blends of ammonium sulfate and P and K placed at 2×2, as well as several liquid pop-up fertilizer applied in the row with the seed.
Study Description: In 2001, a starter formulation trial was initiated in conjunction with the Farm Operations staff at Penn State. A field was selected that tested 56 ppm P and 142 ppm K, with a pH of 6.0. In 2002, another field was selected that tested 121 ppm P and 232 ppm K, with a pH of 6.2. In 2003, the experiment was conducted in a field that tested 66 ppm P and 165 ppm K, with a pH of 6.3. The previous crop was corn except in 2001, when it was wheat. Treatments included an untreated check, five dry starter fertilizers applied at 180 lb/A (10-30-10, 21-0-0-24, 16-8-8, 16-8-8-16, and16-8-0-16) and three liquid popup treatments (7-21-7, Nutra Flo 9-18-9, and Riser (7-17-3)). The Nutra Flo 9-18-9 and Riser fertilizers would be considered premium priced starter fertilizer products. The Riser also contained the micro nutrients Copper, Iron, Manganese and Zinc. Corn was planted no-till between May 1 and 6 in plots four rows wide and approximately 500–700 feet long. Plant tissue samples were collected for dry matter yield and nutrient uptake determinations at V6. Each treatment was replicated four times and harvested with a commercial combine in mid-November.
Results:
Early Growth
Differences in early growth measured at V6 were subtle and statistically different only in 2003. Growth responses were similar in 2002 and 2003 with the dry fertilizer treatments providing a 20–25% growth response. Growth responses were similar for most materials. The pop-up products resulted in a 0–10% growth response during those years. In 2001, performance of the products tended to be much different, with the pop-ups resulting in a 10–20% growth response and most of the dry materials except 10-30-10 resulted in no growth response. This was likely due to the dry spring in 2001, when May precipitation averaged 1.38 inches compared to 6.45 inches in 2002 and 3.65 inches in 2003. Thus when soil conditions are dry following planting, the response to dry starter fertilizers may be limited and pop-up performance may be superior. In normal or wet years, the reverse may be true.
Grain Yield
The grain yield response to the starter fertilizers varied among years with significant differences occurring in 2001 and 2003. Yields were limited by drought stress in 2001 and 2002. Grain yields of the check treatments averaged 106, 109, 160 bushels/acre in 2001, 2002, and 2003 respectively. In 2001, all of the 2×2 fertilizers tended to have lower yields than the check, similar to the early growth response patterns. We have observed this on several other occasions in other trials where the crop is impacted with a midsummer drought as occurred with this site. This yield depression did not occur with the pop-up fertilizers, however. In 2001, the pop-up treatments yielded significantly higher than the 2×2 treatments by about 10 bushels per acre and averaged about 4% higher yields than the check. Grain yield was similar among pop-up treatments in all years of the study. We also did not find any differences among the pop-ups in P or Zn uptake at V6 or notice any differences in emergence timing or plant populations during the study.
In 2002 and 2003, performance of the dry fertilizers was more positive than 2001, especially in 2003 when yields were considerably higher. Considering just the 2002 and 2003 data, the highest yielding and most consistent dry treatments were the 16-8-8-16 and the 10-30-10 treatments, with grain yield responses averaging between 5 and 10% higher than the check. The 16-8-8-16 treatment performed better than the 16-8-8 treatment which was formulated with ammonium nitrate rather than ammonium sulfate. It also performed better than the 16-8-0-16 and 21-0-0-24 treatments, which was surprising, especially in 2002 when soil test K levels were above optimum. We found a similar positive response to K in an earlier (1999) starter trial where a 6% yield increase was observed even though K levels in that field were 178 ppm. The 16-8-8-16 treatment is similarly priced to 10-30-10 and provides more N and less P on high P testing soils. Consequently, in this study, 16-8-8-8 appeared to be one of the most promising treatments as a replacement for conventional 10-30-10 starter fertilizers on high P soils.
Averaged over the three years, the numerical yield difference between the check and the 16-8-8-16 treatment was 4.6 bushels per acre. Of the dry fertilizers this was the highest and one of most economical. At a cost of $226/ton and 180 pound application rate, would cost $20.34/acre for the starter treatment. At a corn price of $3.00/bushel, the net return to the starter would be -$6.55/acre. If you assumed this program would supply 29 pounds of N that could be subtracted from the N fertility cost at $0.25/lb of N, then that would provide an additional benefit of $7.20/acre, which could offset the negative return to the starter. In summary, from an economic standpoint use of the 16-8-8-16 or any other starter would only be justified if it could serve to reduce some of the additional N that would be recommended on this field.
Using a similar analysis for the pop-up materials, the 7-21-7 material had the highest average yield and was also the lowest cost material. The average yield benefit was 3.8 bushels per acre and was fairly consistent each year (Figure 2). At a cost of $2/gallon and 3 gallon/acre application rate, would cost $6/acre for this starter treatment. At a corn price of $3.00/bushel, the net return to the starter would be $5.40/acre. In this case, there would be a slight economic yield advantage to the use of the 7-21-7 treatment.
| Treatment | Rate | Moisture % |
Yield bu/A |
% of check | V6 plant DM g/10 plants |
|---|---|---|---|---|---|
| check | 21.5 | 125.2 | 100.0 | 48.3 | |
| 10-30-10 | 180 lb/A | 21.4 | 129.0 | 103.0 | 57.2 |
| AS | 180 lb/A | 21.3 | 125.1 | 99.9 | 55.8 |
| 16-8-0-16 | 180 lb/A | 21.5 | 126.5 | 101.0 | 54.1 |
| 16-8-8 | 180 lb/A | 21.5 | 123.7 | 98.8 | 53.0 |
| 16-8-8-16 | 180 lb/A | 21.4 | 129.8 | 103.7 | 52.9 |
| 7-21-7 | 3 gal/A | 21.1 | 129.0 | 103.0 | 52.6 |
| 9-18-9 | 3 gal/A | 20.9 | 128.1 | 102.3 | 52.4 |
| Riser | 3 gal/A | 21.3 | 126.1 | 100.7 | 51.3 |
| Mean | 21.3 | 126.9 | 101.6 | 53.1 | |
| LSD(0.10 | NS | NS | NS |
Conclusions:
The results of this study demonstrated that on high P soils, there may be some alternatives to the typical 10-30-10 dry starter fertilizer that has been commonly used in Pennsylvania that could result in slight improvements in early growth and grain yields, and might be cost effective in some situations. The two most promising treatments were 180 pounds of a 16-8-8-16 blend in a 2×2 placement and 3 gal/acre of a 7-21-7 liquid fertilizer applied in the row with the seed. Yield responses to starters on these high P soils were generally small. Dry starter fertilizers may only be justified when assuming that the starter cost will offset some of the costs associated with the overall N fertility program. Yield responses to starter fertilizers measured in this study were likely impacted by the dry conditions in both 2001 and 2002 and may underestimate their potential in higher yielding environments. It should be noted that conventional starter fertilizers high in P are still recommended on corn for soils testing in the optimum range (30–50 ppm) for soil P.
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