Working group recommendations for nutrient management

By Matt Reese

The Directors’ Agricultural Nutrients and Water Quality Working Group met earlier this week at the Ohio Department of Agriculture to finalize their extensive findings on how agriculture is contributing to water quality problems and how this can be controlled. The group was assembled to aggregate all of the available information on the problem, organize it and present it to the directors of the Ohio Department of Agriculture, the Department of Natural Resources and the Environmental Protection Agency, who will then make recommendations to the governor.

“The 4Rs are a good starting point for messaging and provide a great resource for farmers to turn to,” said Karen Chapman, who represented the Environmental Defense Fund (EDF) in the Working Group. “EDF believes that adaptive management programs are key to putting the 4Rs into action. These are programs where farmers and their advisors gather data using tools like cornstalk nitrogen tests, strip trials for N and P, aerial imagery, management data and yield data to figure out what is going on for a given season with the crop and the crop’s estimated nutrient uptake. With a couple seasons of this type of data, farmers begin to see that they can make adjustments for greater efficiency and better economic results. Our recommendations to the Directors will be to support implementing the 4Rs through Adaptive Management programs, with partnerships among a variety of state and federal agencies, certified crop advisors, the fertilizer industry, and local staff.”

Chapman also said that EDF is recommending the need for trapping nutrients when they do leave farm fields.

“Combined with adaptive management for nutrient use efficiency, we also have to trap and treat the nutrients coming off the fields — in both surface and subsurface flows, because farmers can only do so much to control what leaves,” she said. “So, we need to put practices on the landscape — and provide the right incentives for doing so — that will most effectively trap those nutrients without taking too much land out of production. This is a big task, but one that we think could have long-lasting results.”

The Ohio AgriBusiness Association is also pushing for the 4R approach to nutrient management. The Ohio Farm Bureau is submitting a 36-page document of recommendations. Greg LaBarge, who represented Ohio State University Extension in the Working Group, compiled the following recommendations for the three directors.

Soil Sampling

1)    The basis of fertilizer application should be a representative soil sample from the target application site. Soil sampling should be used to monitor changes in soil test levels with a target of soil test Bray 1 Phosphorous levels in the 15 to 30 parts per million range. If wheat or alfalfa is in the rotation then target ranges are 25-40 parts per million. Specialty crops and other commercial crops may have differing soil test level needs that need to be considered.

2)    Soil sample trends are as or more important than the single year test to validate fertility management programs. Soil management, zones which can be based off soil type, topography or yield response maps provide a sound basis to develop a representative sample area. Collect 15 random cores at 8 inches deep from representative areas of the field. Area should be no larger than 25 acres unless a yield response criterion is used to determine the sample area. Bulk the collected cores in a suitable container, mix well then pull the appropriate size sample (usually 1 pint) for analysis. Submit the soil sample to a reputable lab for analysis. The better a sample represents the sample area the greater the confidence that appropriate fertilizer recommendations can be made. Grid Sampling is an alternative where point soil samples are collected at predetermined distances then through statistical process estimates of nutrients concentrations between the points are made.

3)    Samples should be taken a minimum of every 4-5 years or once per rotation. More frequent sampling will be suggested where the soil test level of a nutrient is near the critical level. A 150-bushel corn crop removes 56 pounds of P. Phosphorous chemistry in the soil buffers the crop removal so that for each 15-20 lbs of P2O5 removal phosphorous levels in the soil are lowered 1 part per million. So our 150-bushel crop will lower the soil test at most 3 parts per million.

Fertilizer rate recommendations

1)    The purpose for a soil sample should be to generate a fertilizer recommendation. The Tri-State Fertilizer recommendations were generated using calibration studies with a Bray P1 soil test result. Fertilizer recommendations for corn (Table 1), soybeans (Table 2) and wheat (Table 3) are listed below. The tables are updated to reflect the higher yield potentials utilizing the equations from the Tri State Fertilizer Recommendations publication can be found at: http://ohioline.osu.edu/e2567/index.html. The philosophy of these recommendations can be found in the original publication.

Table 1. Fertilizer P Recommendations for Corn. (adapted from Tri-state Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa)

 

Realistic Yield Goal (bu/acre)

Soil Test Level

120

145

170

200

225

250

275

PPM (lb/acre)

lbs P2O5/acre recommended

5 (10)

95

105

115

125

135

145

155

10 (20)

70

80

90

100

110

120

125

15-30 (30-60)

45

55

65

75

85

95

100

35 (70)

20

25

30

40

45

50

50

40 (80)

0

0

0

0

0

0

0

 

 

 

 

 

 

 

 

 

 

 

 

Table 2. Fertilizer P Recommendations for Soybean. (adapted from Tri-state Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa)

 

Realistic Yield Goal (bu/acre)

 

Soil Test Level

30

40

50

60

70

80

90

PPM (lb/acre)

lbs P2O5/acre recommended

5 (10)

75

80

90

100

105

115

125

10 (20)

50

55

65

75

80

90

100

15-30 (30-60)

25

30

40

50

55

65

70

35 (70)

10

15

25

25

30

35

35

40 (80)

0

0

0

0

0

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3. Fertilizer P Recommendations for Wheat. (adapted from Tri-state Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa)

 

Realistic Yield Goal (bu/acre)

Soil Test Level

50

65

80

95

110

125

PPM (lb/acre)

lbs P2O5/acre recommended

15 (30)

80

90

100

110

120

130

20 (40)

55

65

75

85

95

105

25-40 (50-80)

30

40

50

60

70

80

45 (90)

15

20

25

30

35

40

50 (100)

0

0

0

0

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In all, more than 25 organizations, government agencies, and private companies are submitting their recommendations to the three directors, who will present the findings to the governor in the coming weeks. From there, additional steps will be taken to address the challenging problems associated with agriculture and water quality.

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