All cropping systems require fertilizer inputs in order to maintain crop yields. Farmers continue to search for ways to increase soybean yields, such as applying micronutrients and using foliar applications of fertilizer. Although micronutrients are just as essential to plant growth as macronutrients, past research has indicated most Iowa soils can supply the micronutrient needs of soybeans

Fawcett, Jim

Mallarino, Antonio

Miller, Lance

Schnabel, Matt

Sievers, Josh

Smidt, Micah

English

All cropping systems require fertilizer inputs in order to maintain crop yields. Farmers continue to search for ways to increase soybean yields, such as applying micronutrients and using foliar applications of fertilizer. Although micronutrients are just as essential to plant growth as macronutrients, past research has indicated most Iowa soils can supply the micronutrient needs of soybeans.</p

Digital Repository @ Iowa State University (ISU)

Iowa State University, Northern Research and Demonstration Farm ISRF14-22   32 On-Farm Soybean Fertilizer Trials  RFR-A1448  Jim Fawcett, extension field agronomist (retired) Antonio Mallarino, professor Department of Agronomy Josh Sievers, Northwest Farm, superintendent Micah Smidt, Northern Farm, superintendent Matt Schnabel, Northern Farm, ag specialist Lance Miller, Southeast Farm, ag specialist  Introduction All cropping systems require fertilizer inputs in order to maintain crop yields. Farmers continue to search for ways to increase soybean yields, such as applying micronutrients and using foliar applications of fertilizer. Although micronutrients are just as essential to plant growth as macronutrients, past research has indicated most Iowa soils can supply the micronutrient needs of soybeans.  Materials and Methods In 2014, five trials utilizing various methods of fertilizing soybeans were investigated (Table 1). All trials were conducted on-farm by farmer cooperators using the farmers’ equipment. Strips were arranged in a randomized complete block design with at least three replications per treatment. Strip length and width varied from field to field depending on equipment size and size of field. All strips were machine harvested for grain yield.  In Trial 1, a foliar application of fertilizer containing sulfur (S), boron (B), manganese (Mn), and zinc (Zn) to soybeans at the R1 growth stage was compared with untreated soybeans. Soil samples were collected to a 6-in. depth before spraying on the day of the foliar application and analyzed for nutrients. All analyses were made on dried soil. In Trial 2, a foliar application of fertilizer containing nitrogen (N), S, B, Mn, and Zn to soybeans at the V6 stage was compared with untreated soybeans. In Trials 3 and 4, a foliar application of fertilizer containing 30 lb/acre N and 4 lb/acre S was compared with untreated soybeans. In Trial 5, soybeans planted with two application rates of starter fertilizer (five and eight gallons/acre of 3-18-18) were compared with soybeans planted without starter. The starter was applied 3 in. to the side and 0.75 in. below the seed. Prior to planting, the soil in this field tested high in phosphorus (25 ppm) and low in potassium (150 ppm).  Results and Discussion No increase in soybean yields was seen with the foliar application of micronutrients in either Trial 1 or 2 (Table 2). This agrees with past research that has shown yield increases are not common with micronutrient applications to soybeans on most of Iowa’s soils. In 2013, in on-farm trials investigating foliar applications of micronutrients to soybeans, there was a yield increase in only one of 10 trials. The percent organic matter in the soil in Trial 1 was 8.4 percent (Table 3), which would likely be more than sufficient to supply the micronutrient needs of the crop.  With the soil test in Trial 1, no yield increase from zinc and manganese were expected because soil levels were high according to interpretations in Iowa (only for zinc) and the north-central region. There are no interpretations for boron in Iowa, and we should have seen a yield increase in this trial according to interpretations in Illinois, but no increase according to interpretations in South Dakota. Results will be used with other ongoing research to establish interpretations.  There was no effect of the foliar application of N and S to soybeans in Trials 3 and 4. Neither application rate of the starter fertilizer in Trial 5 had any effect on soybean yield.   Iowa State University, Northern Research and Demonstration Farm ISRF14-22   33   Table 1. Variety, row spacing, planting date, planting population, previous crop, and tillage practices in on-farm soybean fertilizer trials in 2014. Exp. no. Trial County Variety Row spacing (in.) Planting date Planting population (seeds/A) Previous crop Tillage 140402 1 Cerro Gordo Croplan R2T2240 30 5/24/14 160,000  Corn No-till 140163 2 Lyon Pioneer 92Y22 30 5/15/14 140,000 Corn Strip till 140715 3 Louisa Asgrow 3832 30 5/3/14 150,000 Corn Conventional 140717 4 Des Moines Asgrow 3832 30 5/4/14 150,000 Corn Conventional 140405 5 Worth  AgVenture 22E1  30  5/18/14  148,000  Corn Conventional   Table 2. Yield from on-farm soybean fertilizer trials in 2014.     Yield (bu/A)  Exp. no. Trial Treatment Treatment Control Response P-valuex 140402  1  Micro Mix [1 qt/A Winfield Max-in ZMB® (S, B, Mn, Zn) + 1 pt/A Max-in Boron] @ R1 55 55 0 0.77 140163  2  1 qt/A Brandt Smart Trio® (4% N, 3% S, 0.25% B, 3% Mn, 3% Zn) @ V6 55 54 1 0.49 140715 3 75 lb/A of 40-0-0-5.5 (30 lb/A N & 4 lb/A S)  @ R3 76 78 -2 0.49 140717 4 75 lb/A of 40-0-0-5.5 (30 lb/A N & 4 lb/A S)  @ R3 62 64 -2 0.18 xP-Value = the calculated probability that the difference in yields can be attributed to the treatments and not other factors. For example, if a trial has a P-Value of 0.10, then we are 90 percent confident the yield differences are in response to treatments. For P = 0.05, we would be 95 percent confident.  Table 2. Yield from on-farm soybean fertilizer trials in 2014, continued. Exp. no. Trial Treatment Yield (bu/A)x P-valuey 140405 5 8 gal/A Starter 48 a 0.25   5 gal/A Starter 46 a    Control 46 a  xValues denoted with the same letter are not significantly different at the  significance level 0.05. yP-Value = the calculated probability that the difference in yields can be attributed to the treatments and not other factors. For example, if a trial has a P-Value of 0.10, then we are 90 percent confident the yield differences are in response to treatments. For P = 0.05, we would be 95 percent confident.  Table 3. Soil analysis from one on-farm soybean micronutrient trial in 2014. Exp. no. Trial Phosphorus (ppm)x Potassium (ppm)x pH Organic matter (%) Boron (ppm)y Zinc (ppm)c Man-ganese (ppm)z 140402 1 47 248 6.7 8.4 1.3 1.5 8.9 xMehlich- 3 method yHot-water method zDTPA method 

On-Farm Soybean Fertilizer Trials

Iowa State University, Northwest Research Farm and Allee Demonstration Farm ISRF14-29, 31   50 On-Farm Soybean Fertilizer Trials  RFR-A1448  Jim Fawcett, extension field agronomist (retired) Antonio Mallarino, professor Department of Agronomy Josh Sievers, Northwest Farm, superintendent Micah Smidt, Northern Farm, superintendent Matt Schnabel, Northern Farm, ag specialist Lance Miller, Southeast Farm, ag specialist  Introduction All cropping systems require fertilizer inputs in order to maintain crop yields. Farmers continue to search for ways to increase soybean yields, such as applying micronutrients and using foliar applications of fertilizer. Although micronutrients are just as essential to plant growth as macronutrients, past research has indicated most Iowa soils can supply the micronutrient needs of soybeans.  Materials and Methods In 2014, five trials utilizing various methods of fertilizing soybeans were investigated (Table 1). All trials were conducted on-farm by farmer cooperators using the farmers’ equipment. Strips were arranged in a randomized complete block design with at least three replications per treatment. Strip length and width varied from field to field depending on equipment size and size of field. All strips were machine harvested for grain yield.  In Trial 1, a foliar application of fertilizer containing sulfur (S), boron (B), manganese (Mn), and zinc (Zn) to soybeans at the R1 growth stage was compared with untreated soybeans. Soil samples were collected to a 6-in. depth before spraying on the day of the foliar application and analyzed for nutrients. All analyses were made on dried soil. In Trial 2, a foliar application of fertilizer containing nitrogen (N), S, B, Mn, and Zn to soybeans at the V6 stage was compared with untreated soybeans. In Trials 3 and 4, a foliar application of fertilizer containing 30 lb/acre N and 4 lb/acre S was compared with untreated soybeans. In Trial 5, soybeans planted with two application rates of starter fertilizer (five and eight gallons/acre of 3-18-18) were compared with soybeans planted without starter. The starter was applied 3 in. to the side and 0.75 in. below the seed. Prior to planting, the soil in this field tested high in phosphorus (25 ppm) and low in potassium (150 ppm).  Results and Discussion No increase in soybean yields was seen with the foliar application of micronutrients in either Trial 1 or 2 (Table 2). This agrees with past research that has shown yield increases are not common with micronutrient applications to soybeans on most of Iowa’s soils. In 2013, in on-farm trials investigating foliar applications of micronutrients to soybeans, there was a yield increase in only one of 10 trials. The percent organic matter in the soil in Trial 1 was 8.4 percent (Table 3), which would likely be more than sufficient to supply the micronutrient needs of the crop.  With the soil test in Trial 1, no yield increase from zinc and manganese were expected because soil levels were high according to interpretations in Iowa (only for zinc) and the north-central region. There are no interpretations for boron in Iowa, and we should have seen a yield increase in this trial according to interpretations in Illinois, but no increase according to interpretations in South Dakota. Results will be used with other ongoing research to establish interpretations.  There was no effect of the foliar application of N and S to soybeans in Trials 3 and 4. Neither application rate of the starter fertilizer in Trial 5 had any effect on soybean yield.   Iowa State University, Northwest Research Farm and Allee Demonstration Farm ISRF14-29, 31   51   Table 1. Variety, row spacing, planting date, planting population, previous crop, and tillage practices in on-farm soybean fertilizer trials in 2014. Exp. no. Trial County Variety Row spacing (in.) Planting date Planting population (seeds/A) Previous crop Tillage 140402 1 Cerro Gordo Croplan R2T2240 30 5/24/14 160,000  Corn No-till 140163 2 Lyon Pioneer 92Y22 30 5/15/14 140,000 Corn Strip till 140715 3 Louisa Asgrow 3832 30 5/3/14 150,000 Corn Conventional 140717 4 Des Moines Asgrow 3832 30 5/4/14 150,000 Corn Conventional 140405 5 Worth  AgVenture 22E1  30  5/18/14  148,000  Corn Conventional   Table 2. Yield from on-farm soybean fertilizer trials in 2014.     Yield (bu/A)  Exp. no. Trial Treatment Treatment Control Response P-valuex 140402  1  Micro Mix [1 qt/A Winfield Max-in ZMB® (S, B, Mn, Zn) + 1 pt/A Max-in Boron] @ R1 55 55 0 0.77 140163  2  1 qt/A Brandt Smart Trio® (4% N, 3% S, 0.25% B, 3% Mn, 3% Zn) @ V6 55 54 1 0.49 140715 3 75 lb/A of 40-0-0-5.5 (30 lb/A N & 4 lb/A S)  @ R3 76 78 -2 0.49 140717 4 75 lb/A of 40-0-0-5.5 (30 lb/A N & 4 lb/A S)  @ R3 62 64 -2 0.18 xP-Value = the calculated probability that the difference in yields can be attributed to the treatments and not other factors. For example, if a trial has a P-Value of 0.10, then we are 90 percent confident the yield differences are in response to treatments. For P = 0.05, we would be 95 percent confident.  Table 2. Yield from on-farm soybean fertilizer trials in 2014, continued. Exp. no. Trial Treatment Yield (bu/A)x P-valuey 140405 5 8 gal/A Starter 48 a 0.25   5 gal/A Starter 46 a    Control 46 a  xValues denoted with the same letter are not significantly different at the  significance level 0.05. yP-Value = the calculated probability that the difference in yields can be attributed to the treatments and not other factors. For example, if a trial has a P-Value of 0.10, then we are 90 percent confident the yield differences are in response to treatments. For P = 0.05, we would be 95 percent confident.  Table 3. Soil analysis from one on-farm soybean micronutrient trial in 2014. Exp. no. Trial Phosphorus (ppm)x Potassium (ppm)x pH Organic matter (%) Boron (ppm)y Zinc (ppm)c Man-ganese (ppm)z 140402 1 47 248 6.7 8.4 1.3 1.5 8.9 xMehlich- 3 method yHot-water method zDTPA method 

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On-Farm Soybean Fertilizer Trials

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Digital Repository @ Iowa State University (ISU)

Digital Repository @ Iowa State University (ISU)

Digital Repository @ Iowa State University (ISU)