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Production Papers

Starter Fertilizers for Corn on Soils Testing High in Phosphorus in the Northeastern USA

Dep. of Crop and Soil Sciences, Pennsylvania State Univ., University Park, PA 16802

^* Corresponding author (gwr{at}psu.edu)

Received for publication July 27, 2005.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Starter fertilizers with a high P analysis are commonly used in the northeastern USA for corn (Zea mays L.) production, despite many soils testing above optimum (>50 mg P kg^–1). The objective of this study was to evaluate responses to high P starter fertilizers in a band 5 cm from the row compared to alternatives such as banded higher N or conventional and low-salt in-furrow fertilizers. Two studies were conducted during 2000 through 2003 in Pennsylvania. The first study was a 3-yr on-farm study conducted to evaluate an untreated check, (NH₄)₂SO₄ (AS), and 10–13–8.3 (N–P–K) as starters at 41 locations across Pennsylvania on high P testing soils. Early growth increased by 17% using 10–13–8.3 and 15% using AS compared to the check. Grain yields were 3.3% higher than the check for the AS treatment. Yields from the 10–13–8.3 were not different than the check but averaged 2.0% higher. A second 3-yr study consisted of an untreated check, five banded granular starter fertilizer blends (10–13–8.3, 21–0-0–24, 16–3.5–6.7–16, 16–3.5–6.7, and 16–0-6.7–16) applied at 202 kg ha^–1, and three liquid in-furrow treatments applied at 35 kg ha^–1 (7–9.1–5.8, 7–7.4–2.5 and 7–7.8–7.5). Early growth and grain yield were significantly increased in 1 of 3 yr with some higher N starters. Eliminating starters, using higher N or in-furrow starters on high P soils all appear to be possible management alternatives to high P starters.

Abbreviations: AN, ammonium nitrate • AS, (NH₄)₂SO₄ or ammonium sulfate • RM, relative maturity • UAN, urea ammonium nitrate solution

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
INCREASING P soil test levels, the impending use of P-indexing as a nutrient management tool and the need to reduce costs while maintaining high yields have resulted in a need to evaluate alternatives to the typical high P starter fertilizers used for corn production in the U.S. Northeast. According to the Agricultural Analytical Services Laboratory at Penn State, 51% of the soils tested for agronomic crop production in Pennsylvania have P soil test levels in the above optimum range (above 50 mg kg^–1 Mehlich-3 P) (AASL, 2004). Despite these high soil tests, high P analysis starter fertilizers are commonly used for corn production on these soils. In the 2001 crop year, for example, the National Agricultural Statistics Service (2002) estimated that 79% of the 607 000 ha of corn fields received P fertilizer applications that averaged 23 kg P ha^–1.

Several researchers have reported early growth or yield responses to starter fertilizer on soils with high P soil test levels (Touchton, 1988; Jokela, 1992; Bundy and Andraski, 1999), which may explain some of the use of starters on these high P soils. Bundy and Andraski (1999), in Wisconsin found an average corn yield response of 0.25 Mg ha^–1 to starter fertilizer and found that profitable starter fertilizer responses were most closely linked to soils with lower K soils test levels, later maturing hybrids, and later planting dates.

In other regions of the USA starter fertilizers that contained only N or high N/P ratios have resulted in similar benefits of early season corn growth and yield responses compared to more traditional high P starter fertilizers in Virginia (Alley et al., 1997), Indiana (Mengel, 1992), Missouri (Scharf, 1999), and Alabama (Touchton, 1988). Vetsch and Randall (2000) reported that the response of corn grain yields to starter fertilizer on high P soils was reduced from 0.5 to 0.2 Mg ha^–1 when a N fertilizer was injected near the row, and suggested that the starter effect on high P soils may be due to N rather than P.

Under no-till conditions on high P soils in Pennsylvania, liquid starter fertilizers containing various ratios of N, P, and K resulted in little benefit to corn from P but there were occasional benefits from formulations containing higher N levels or K (Roth et al., 2003). In one trial in this study, yields were significantly increased by 8% when some of the N in an N/P starter blend was AS compared to the standard N/P starter blend composed of urea-ammonium nitrate solution (UAN) and ammonium polyphosphate solution. It was not evident why corn at this site responded to the AS in this study but indicated that there may be potential for AS or AS blends as high N starter fertilizers for corn in this region. Mitchell (1982) also found that AS was an effective starter fertilizer for corn in Delaware. This material also provided an acidifying effect that increased micronutrient availability on their sandy soils. Vetsch and Randall (2000) in Minnesota also concluded that the starter effect in no-till corn production on fields testing high in P may be due to N rather than P. In Iowa, Bermudez and Mallarino (2002) reported that large starter responses in no-till corn are most likely where soil test P is low or where preplant or sidedress N applications are deficient.

Another possibility for reducing P inputs on high P soils would be the use of low rate, in-furrow starter fertilizers, which have become popular with some corn producers. Advantages of these fertilizers are reduced handling costs, less down time during planting, potential for lower input costs, and low rates of applied P. Bates (1971) reported that in-furrow fertilizers resulted in a 36% increase in corn growth over 22 trials in Ontario and a 2.9% increase in yield. Randall and Hoeft (1988) reviewed in-furrow starter responses on corn and cited studies where there were stand reductions on sandy soils or where rates were excessive (>8–17 kg ha^–1 N + K). In another study, early planted no-till corn growth responses to in-furrow starter fertilizers were less consistent than treatments banded 5 cm beside the row (Ritchie et al., 1996).

This study was designed to investigate some alternatives to the traditional starter fertilizer that could minimize further P additions to these soils, focusing their effects on early season growth, nutrient uptake, and yield. Specifically, the objectives of the study were to evaluate the early growth, yield, and nutrient uptake of (i) AS and conventional high P banded granular starter fertilizers on soils testing high in P across a range of environments, (ii) with AS or ammonium nitrate (AN) blends as alternative banded granular starter fertilizers, and (iii) several low rate liquid fertilizers applied in-furrow as an alternative to conventional higher P banded starter fertilizers.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
On-Farm Study
Field experiments were conducted in 2000, 2001, and 2002 at a total of 41 locations in major corn-producing regions of Pennsylvania in conjunction with extension agents, crop consultants, and farm operators to assess the potential of AS compared to a high P starter fertilizer traditionally used in corn production in the region. Field sites were selected where soil test levels (Mehlich 3 (Wolf and Beegle, 1995) using inductively coupled plasma spectrometer [ICP] determinations) were in excess of 50 mg kg^–1 P and ranged from 52 to 886 mg kg^–1 P. All were above the 30 to 50 mg kg^–1 optimum range for P recommended in Pennsylvania (Beegle, 2004). Most of the soils had a silt loam to silty clay loam surface texture and would be classified as Typic Hapludalfs and Typic Dystrudepts common in this region. Three starter fertilizer treatments, an untreated check, AS, and 10–13–8.3 (N–P–K) were evaluated in each trial. Both fertilizers were dry, blended, granular products.

At each location, each treatment was replicated three times in a randomized, complete block design with large plots in an effort to reduce experimental variation. Individual plots consisted of four to six rows, spaced 76 cm apart and were generally 150 to 300 m long. Plots were planted with cooperators equipment. The same fertilizer setting was used for the 10–13–8.3 and the AS. The target rate was 190 kg ha^–1 10–13–8.3. Starter fertilizer placement was generally 5 cm to the side of the row, with the depth varying depending on soil conditions and equipment. Weed control and other fertilizer applications were managed by the cooperators. At approximately V6–V7, in 2001 and 2002, 10 whole plant samples were clipped at the soil level from each plot, dried, and weighed to determine early season dry matter accumulation. Samples were then ground and analyzed for nutrient content. Plant analyses were conducted by the Agricultural Analytical Services Laboratory at Penn State. Nitrogen was determined using the combustion procedure (Horneck and Miller, 1998); P, K, and Zn were analyzed using the dry ash method (Miller, 1998a); S was determined by the microwave digestion method (Miller, 1998b). At harvest grain yields were obtained from each site using weigh wagons or farm scales and the moisture content was measured from each plot at harvest. Yields were adjusted to a standard moisture content of 155 g kg^–1.

An analysis of variance using SAS (SAS Institute, 2001) PROC GLM was performed for yield on each individual site–year. A combined analysis of variance was performed for each year using PROC MIXED with sites and replications as random variables and treatments as fixed variables. Another combined analysis was performed across all environments using PROC MIXED with environment and replications as random variables. Means for all measurements were separated by Fishers Protected LSD (P = 0.05).

Starter Formulation Study
This study consisted of three replicated strip trials conducted in different fields in 2001, 2002, and 2003 near State College, PA, on Hagerstown silt loam soils (fine, mixed, mesic Typic Hapludalfs). Planting date, previous crop and soil test information is shown in Table 1. The trials consisted of nine treatments and four replications at each site in a randomized complete block design. Individual plot sizes were four 76-cm rows wide and 180 to 305 m long. Each site was no-till planted using row cleaners and the hybrid ‘NK Brand 58D1’ (107 d relative maturity, RM) in 2001 and ‘Pioneer Brand 34K77’ (107 d RM) in 2002 and 2003. Nitrogen fertilizer totaling 180 kg N ha^–1 was applied in a split application with 60 kg N ha^–1 applied before planting as broadcast UAN and 120 kg N ha^–1 applied at a dribbled sidedress application of UAN at V7. No additional fertilizer was added at any of the sites. The starter fertilizer treatments consisted of an untreated check, five dry, granular starter fertilizer blends (10–13–8.3, 21–0-0–24, 16–3.5–0–16, 16–3.5–6.7–16, and 16–3.5–6.7) applied at 202 kg ha^–1 as a band 5 cm to the side of the row, and three liquid in-furrow treatments applied at 35 kg ha^–1 in the row (7–9.1–5.8, 7–7.4–2.5, and 7–7.8–7.5). The granular fertilizer blends were composed of AS, monoammonium phosphate, and muriate of potash, except for the 16–3.5–6.7 blend which was made with AN instead of AS. The liquid 7–9.1–5.8 was a commodity grade blend of ammonium polyphosphate solution and soluble potash. The 7–7.4–2.5 product is marketed as RiseR (UAP Northeast, Avon, NY) and contains UAN solution, ammonium poly phosphate solution, potassium hydroxide, copper EDTA, iron HDTA, manganese EDTA, and zinc EDTA. The 7–7.8–7.5 was a clear liquid 100% orthophosphate marketed as a "Diamond Grade" product (Nutra-Flo, Sioux City, IA).

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
On-Farm Study
During the 3-yr study period, conditions for corn growth and yield were good in 2000, mixed in 2001, with some sites experiencing drought stress, and marginal in 2002 with more widespread drought stress. Corn grain yields in the check treatments, across all sites, averaged 10.7, 7.8, and 5.9 Mg ha^–1 during 2000, 2001, and 2002, respectively. Occasional drought is typical in these environments, however, and needs to be considered in developing fertilizer recommendations.

Early season growth responses to starter fertilizers were common (9 of 33 sites in 2001 and 2002). Pearson correlation coefficients between soil test P and relative early growth were –0.16 for the high P starter and –0.11 for the AS starter. Consequently responses were not highly related to the soil test level, confirming that even on these high testing soils, early season effects from starter fertilizers are possible (Table 2). Compared to no starter, relative early season growth differences from the P based and AS treatments averaged 123 and 118%, respectively in 2001 and 118 and 113%, respectively in 2002. Averaged over both years, early season growth responses to the AS were similar to those observed with the P-based starter fertilizer. At individual sites however, there was often some differences in the effect of the two starters on early season growth. At one site (12), AS resulted in the largest growth, while at three sites (19, 32, and 35) the P starter provided the largest growth response. At four sites (14, 23, 28, and 33), both starter fertilizers resulted in more growth than the check. Early season growth responses to starter fertilizers have been observed on high P testing soils in other studies (Bundy and Andraski, 1999; Bermudez and Mallarino, 2002). Bermudez and Mallarino (2002) also suggested that early season growth response to starter fertilizers was independent of soil test P level and a result of either increased P concentrations near the seed or due to other nutrients in the starter. Both of these possibilities are consistent with the early growth responses to both P based and AS starters on high P-testing soils.

Starter Formulation Study
Weather conditions in this study were similar to those encountered in the on-farm study. Lower than average July precipitation caused some drought stress that impacted yields in both 2001 and 2002 (Table 4). In 2003, more favorable late season precipitation resulted in above average yields for this field. Precipitation in May, during the month following planting, was considerably lower in 2001, when May precipitation averaged 35 mm compared to 164 mm in 2002 and 93 mm in 2003.

In 2001, three of the banded fertilizers had lower yields than any of the in-furrow fertilizer treatments, similar to the early season growth response patterns. There was also a trend for lower yields than the check with the granular fertilizers but was significantly different only for the 16–3.5–6.7. This negative effect of granular starter fertilizers on yield was also observed in two trials in the on-farm study. This effect may have been due to some salt injury associated with starter fertilizer, even though the rates of N + K were well within the guidelines suggested for this region. This lack of yield reduction with the in-furrow fertilizers may have been due to the lower rates of material applied. In 2001, on average, the in-furrow treatments yielded about 0.7 Mg ha^–1 higher than the dry starter treatments.

The banded or in-furrow starter fertilizers had no significant effects on yield in 2002, but several treatments resulted in significantly higher yields than the check in 2003. Yields of the 10–13–8.3, 21–0–0–24, 16–3.5–6.7, and 16–3.5–6.7–16 were significantly higher yielding than the check treatment in this year. The variation in response over years in this study is similar to the variation in response observed in the on-farm study. In this study, the best response to granular fertilizers was in the wettest year, in 2003, and the poorest performance was associated with the dry spring conditions in 2001.

Of the granular blends, there was a trend for higher yields with the 16–3.5–6.7–16 compared to the 16–3.5–6.7 treatment which was formulated with AN rather than AS. It performed better than the 16–3.5–0–16 and 21–0-0–24 treatments in 2003, even though soil test K levels were in the optimum range of 100 to 150 mg kg^–1 for this soil. A similar positive response to K was found in an earlier starter trial (Roth et al., 2003) where a 6% yield increase was observed even though soil test K levels in that field were 178 mg kg^–1. The 16–3.5–6.7–16 treatment is similarly priced to 10–13–8.3 and provides more N and less P on high P-testing soils. Consequently, based on this study, 16–3.5–6.7–16 might warrant additional evaluation as a possible alternative to the traditional 10–13–8.3 starter fertilizer on high P soils.

Averaged over the 3 yr, the numerical yield difference between the check and the 16–3.5–6.7–16 treatment was 0.29 Mg ha^–1. Of the granular fertilizers, this was the highest yielding and one of most economical treatments. At a cost of $0.25 kg^–1 and 202 kg ha^–1 application rate, this starter treatment would cost $50.50 ha^–1. At a corn price of $0.12 kg^–1, the net return to the starter would be negative: –$15.70 ha^–1. If the 32 kg N ha^–1in this treatment could be subtracted from the N fertility cost at $0.55 kg^–1 N, then that would provide an additional benefit of $17.80 ha^–1, which could offset the negative return to the starter calculated without accounting for the value of the N in the starter. In summary, from an economic standpoint use of the 16–3.5–6.7–16 might only be justified if it could serve to reduce some of the additional N that would be recommended on this field.

Among the in-furrow treatments, grain yields were similar in all years of the study. Averaged over all years the yield differences between the in-furrow treatments and the checks were not significant. The numerical yield advantage of the 7–9.1–5.8 treatment over the check was 0.23 Mg ha^–1 or 2.5% and this difference was relatively consistent each year. This is similar to the 2.9% yield response to in-furrow fertilizer measured by Bates (1971) and the responses of 1.3 and 2.3% reported by Richards et al. (1985). Mascagni and Boquet (1996) reported slightly greater responses with 9.4, 1.2, and 5.4% higher corn yields in 3 yr from an in-furrow application of ammonium polyphosphate than a control on a high P-testing soil in Louisiana.

From an economic perspective, there was a trend for the highest average yield with the 7–9.1–5.8 treatment compared to the other in-furrow treatments and this was also the lowest cost material. The average yield benefit compared to the check was 0.23 Mg ha^–1. Assuming the cost of the material was $0.416 kg^–1 and 35 kg ha^–1 application rate, this starter treatment would cost $14.56 ha^–1. At a corn price of $0.12 kg^–1, the value of the increased yield would be $27.60 ha^–1 and the net return to the starter would be $13.04 ha^–1. In this scenario, there could be a slight economic yield advantage to the use of the 7–9.1–5.8 treatment provided that the yield differences of this magnitude could be confirmed in future studies. The cost of the other in-furrow fertilizers was more than double the cost of the 7–9.1–5.8 with slightly lower numerical yields, so based on this data the economic returns to these treatments would be negative.

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
In this region, early corn growth responses to starter fertilizers are somewhat unpredictable but can occur on soils with Mehlich-3 P soil test levels above the optimum range of 30 to 50 mg P kg^–1. Averaged over all starter fertilizers, early season growth response was 16% in one study and 11% in another study. Yield responses were less frequent and smaller in magnitude than early growth responses, averaging 2 to 3% in both studies. These responses are consistent with observations in other regions.

Responses to granular starter fertilizers on soils with above optimum P soil test levels in this region were small and economically, their use is not justified unless they can be used as part of the N fertilizer budget for the crop. If so, alternatives to the P-based starter fertilizers such as the AS or AS-based blended granular fertilizers could result in similar yields and economic returns while significantly reducing P inputs on soils used for corn production in our region. In some situations, where some response to K might be anticipated due to spatial variability or other factors, a blend of AS, P, and K, such as the 16–3.5–6.7–16 used in the formulation study might increase yield response, while significantly reducing P inputs compared to the traditional approach.

In-furrow fertilizers could also be an alternative that might provide some early season growth responses and occasional small yield increases and economic returns, with minimal P inputs. While there was no significant yield response to the in-furrow treatments, there was a small but consistent numerical yield response to the 7–9.1–5.8 that is similar to results in other published studies. Also there appeared to be no difference in yield response to the low salt formulations or to the formulation containing micronutrients and a growth regulator applied in furrow. The most economical and profitable alternative in-furrow treatment appeared to be the 7–9.1–5.8 or perhaps ammonium polyphosphate (10–15–0), as reported in other work.

In summary, based on this study and others, corn producers in our region have three management alternatives for starter fertilizer management on these high P soils that could reduce P inputs compared to the traditional high P starters. Starter fertilizer can be eliminated and the savings in fertilizer cost will offset any small increase in yield. Higher N starter fertilizers such as AS or AS blends can be used as part of the N fertilizer program and these may provide some improvement in early growth and small yield benefits. Finally, producers could choose low cost in-furrow fertilizers, as used in this study, that may provide some early growth and small yield improvements.

	ACKNOWLEDGMENTS

 
This research was supported in part by agricultural research funds administered by the Pennsylvania Department of Agriculture.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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This Article Abstract Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Roth, G. W. Articles by Antle, M. E. Search for Related Content PubMed Articles by Roth, G. W. Articles by Antle, M. E. Agricola Articles by Roth, G. W. Articles by Antle, M. E. Related Collections Phosphorus Maize Soil Fertility and Productivity