Corn Starter and Phosphorus Enhancing Product

INSIGHTS

• Phosphorus (P) is an essential nutrient important for many plant functions but can be tied up in the soil.

• Starter fertilizer responses were observed at five of eight trial sites in 2023.

• AVAIL^® T5 further increased yield at 3 of the 8 trial sites, and only when added to lower rates of 10-34-0.

• Use of phosphorus enhancing products like AVAIL T5 has the potential to increase P uptake in some soils, possibly leading to yield increases.

Introduction

Phosphorus is essential for plant growth and development. Adequate phosphorus levels aid in many different functions in the plant, from root development, photosynthesis, and reproductive processes. Much of the phosphorus in the soil solution is unavailable for plant uptake due to being bonded to positively charged soil ions. Due to this, soil applications of manure or fertilizers containing phosphorus may not be immediately available for the same reasons.

Because phosphorus is an essential plant nutrient that is relatively tied up in the soil solution, there is interest in practices to make it more available. AVAIL T5 is a phosphorus enhancing product that reacts with positively charged soil nutrients like calcium, aluminum, and magnesium to prevent phosphorus from becoming tied up. AVAIL T5 is added to fertilizer to sequester surrounding antagonistic metals in the soil, therefore increasing phosphate solubility and making it more available to the plant. Previous research has found that AVAIL T5 has potential to increase yield with lower amounts of phosphorus fertilizer in certain soil conditions, possibly allowing reduced fertilizer rates.1 Since phosphorus availability in the soil is also negatively influenced by high or low soil pH levels, it is possible that AVAIL T5 may provide more value under these conditions. With more available phosphorus in the soil solution there’s a better chance for root interception and plant uptake.

Agronomy in Action Trial

The Agronomy in Action Research team evaluated the effect of two rates of phosphorus fertilizer in combination with AVAIL T5 phosphorus enhancer in 2023. The two rates of starter fertilizer were used to ensure that AVAIL T5 responses were not masked by the availability of phosphorous at the higher rate. The trial compared an untreated check to 2.5 gal/acre (GPA) and 5 gal/acre rates of 10-34-0 (ammonium polyphosphate) fertilizer applied in-furrow at planting, both with and without AVAIL T5. Early maturity locations planted G06A27-D brand and later maturity locations planted G15J91-V brand corn hybrids. Trials were harvested with a research combine, taking yield and moisture measurements at harvest.

Trial Results

Table 1. Phosphorous trial site pH and phosphorous levels.

Of the eight trial locations, five had a positive yield response to 10-34-0 starter fertilizer applications at planting. Four of the five responsive sites responded to both 2.5 and 5 GPA rates (Graph 3). The fifth location, Waterloo, NE, only responded to the 5 GPA rate. There was no yield response to starter fertilizer at either rate or AVAIL T5 with the 3 remaining locations (Graph 2). University trials have also found varied responses to starter fertilizer, often contributing it to differences in tillage, pH, soil texture, soil drainage and soil P and potassium (K) levels.^2,3,4 Soil test phosphorus results at the 2023 trial sites ranged from high to very high at all locations (Table 1), likely limiting potential for response to applied phosphorus or AVAIL T5. Previous trials have shown yield responses from starter fertilizer to decline with increasing soil test P and K levels, yet yield increases still occurred in trials with soils having high P and K levels.⁵

Graph 1. Yield Response to 10-34-0 and AVAIL T5 additive averaged across responsive sites.

Graph 2. Yield Response to 10-34-0 and AVAIL T5 additive averaged across NON-responsive sites.

When averaging across the four sites responsive to both starter fertilizer rates, adding AVAIL T5 to the low rate (2.5 GPA) increased yields. At the same sites, there was no response to AVAIL T5 when added to the 5 GPA starter rate. AVAIL T5 also did not further increase yield when added to either starter rate at the Waterloo, NE site even though increasing starter fertilizer rate to 5 GPA did increase yield. This suggests that the 5 GPA starter rate provided enough plant available P on its own, eliminating the need for AVAIL T5. When looking within the five individual starter fertilizer responsive sites, only three had yield increases resulting from adding AVAIL T5 (Graph 3). Yield responses resulting from adding AVAIL T5 at those three sites (Bridgewater, SD; Blue Earth, MN; and Clay Center, NE), which all had high or very high soil P levels, may have been attributed to two of three sites having lower soil pH values (<5.5) that reduced P solubility (Table 1). Findings from this study agree with previously published research that AVAIL T5 can increase yield potential in some conditions, but not predictably and not consistently.1 Before broadly adopting fertilizer additives into an operation, growers should conduct side-by-side comparisons with their current practices to determine the suitability of any product.

Graph 3. Yield contributions of 10-34-0 starter fertilizer and AVAIL T5 phosphorus enhancer at sites with a starter response, 2023.

Phosphorus Management

Like other nutrients, phosphorus availability is affected by soil acidity, so monitor soil pH levels and apply lime accordingly. Phosphorus placement is another consideration, and using directed placement of starter fertilizers can sometimes aid in root interception of phosphorus in the soil. Care should be taken to limit phosphorus applications and keep soil test levels out of the excessively high category. There is concern of losing phosphorus from fields too, and care should be taken to not apply manure or fertilizer to frozen ground. Heavy rain can result in large losses of phosphorus from soil and sediment runoff.

Reference

¹ Hopkins, B.G. et al. (2018) Avail phosphorus fertilizer enhancer: Meta‐analysis of 503 field evaluations, Agronomy Journal, 110(1), pp. 389–398.

² Mallarino, A.P., J.M. Bordoli, and R. Borges. 1999. Phosphorus and potassium placement effects on early growth and nutrient uptake of no-till corn and relationships with grain yield. Agron. J. 91:37-45.

³ Randall, G.W., and R.G. Hoeft. 1988. Placement methods for improved efficiency of P and K fertilizers: A review. J. Prod. Agric. 1:70-79.

⁴ Wolkowski, R.P. 2000. Row-placed fertilizer for maize grown with an in-row crop residue management system in southern Wisconsin. Soil Tillage Res. 54:55-62.

⁵ Quinn, D.J., C.D. Lee, H.J. Poffenbarger. 2020. Corn yield response to sub-surface banded starter fertilizer in the U.S: A meta-analysis. Fields Crops research, https://doi.org/10.1016/j.fcr.2020.107834