Trailing two foliar fertilizer programs in soybeans to address nitrogen, sulfur and micronutrients

Michigan State University Extension, Michigan Soybean Promotion Committee, Agro100 and AgroLiquid partnered to trial two different foliar fertilizer programs in commercial soybeans.

Introduction

In 2017, Presque Isle County Michigan State University Extension trialed two foliar fertilizer programs in soybeans in an effort to ascertain if these products would increase soybean yield on a soil where nitrogen, sulfur and micronutrient deficiencies were likely, based on preliminary soil analysis. One product was SoyAgro (5N-0P-0K-3S-2Mn-1.50Zn-1.25Fe-0.25B, density = 10.68 pounds per gallon) from Agro100. The second treatment was a custom foliar fertilizer program from AgroLiquid, including FertiRain (12N-3P-3K-1.50S-0.05Mn-0.10Zn-0.10Fe, density = 9.91 pounds per gallon), plus additional foliar Mn (4 percent Mn).

Materials and methods

The trial was conducted in a cooperating grower’s commercial soybean field near Rogers City, Michigan, on Cheboygan loamy sand soil. A preliminary aggregate soil sample was collected May 3, 2017, and submitted to Midwest Labs for analysis. Results indicated a very low soil organic matter concentration (1 percemt soil organic matter), medium sulfur and zinc concentrations, and very low manganese and boron levels, requiring amendment with fertilizer inputs. Approximately 250 pounds per acre of 5-24-24 dry fertilizer was broadcast pre-plant. MG 0.4 soybeans were drilled at 176,000 seeds per acre in 7.5-inch rows May 15, 2017.

Plots 60 feet wide, corresponding to the grower’s spray boom width, and 250 feet long were established in the field running east-west. The two foliar fertilizer treatments and a control treatment were replicated five times in a completely randomized design.

SoyAgro was applied at a rate of 0.4 gallons per acre at both the six trifoliate (V6) stage July 10, 2017, and at 60-80 percent pod set (R4) Aug. 9, 2017, per manufacturer recommendations. The AgroLiquid custom fertilizer blend was applied only once at the V6 stage at a rate of 1.5 gallons per acre FertiRain, plus 0.50 gallons per acre Mn July 10, 2017.

Both treatments were diluted with water to achieve a final spray volume of 15 gallons per acre. Weather at the trial site was significantly wetter than normal, but growing degree-day (GDD) accumulation was near normal.

Soybean tissue nutrient status was evaluated immediately prior to the first foliar fertilizer application, and again about 20 days after each application. Soybean yield was measured Oct. 2, 2017, by harvesting samples of equal area from each plot with the cooperating grower’s combine, weighing with a weigh wagon and adjusting for grain moisture.

Results and discussion

No significant differences were observed in soybean yield across the three treatments (Table 1). This is not surprising, given that tissue nutrient levels of interest were sufficient all season long. No significant differences were observed between the treatments in macro or secondary tissue nutrient concentrations at any sample timing (Table 2).

However, significant differences were observed between SoyAgro and the other treatments in three tissue micronutrient concentrations, including zinc, manganese and boron, at the third sample timing Aug. 28, 2017 (Table 3). This suggests applications of SoyAgro increased tissue micronutrient concentrations, which may have increased soybean yield if those nutrients had been limiting.

Table 1. Average soybean yield by treatment and means separation at the 0.05 level.

Treatment

Yield (bu/a)

SoyAgro

29.73 a

AgroLiquid

32.93 a

Control

30.84 a

 

Table 2. Average macro and secondary tissue nutrient concentrations by treatment on Aug. 28, 2017, and means separation at the 0.05 level.

Treatment

N (%)

P (%)

K (%)

S (%)

SoyAgro

5.04 a

0.45 a

2.23 a

0.29 a

AgroLiquid

5.18 a

0.46 a

2.23 a

0.29 a

Control

5.18 a

0.46 a

2.23 a

0.30 a

 

Table 3. Average micronutrient concentrations by treatment on Aug. 28, 2017, and means separation at the 0.05 level.

Treatment

ZN (ppm)

MN (ppm)

FE (ppm)

B (ppm)

SoyAgro

69.25 a

175.50 a

105.50 a

44.75 a

AgroLiquid

53.20 b

150.20 ab

93.00 a

37.20 ab

Control

57.20 b

138.20 b

96.00 a

36.20 b

The authors wish to thank the Michigan Soybean Promotion Committee and the SMaRT program, Agro100 and AgroLiquid for supporting this research, and Robert Erke for his time and effort in conducting the trial.

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