Grid Sampling Results and Benefits  01/31/14 9:27:12 AM

Below is an example of the Marshall Silty Clay Loam soil association we have surrounding the plant at Plattsmouth. The Marshall association is generally deep in profile, well drained silty soil formed in loess (Loess is sediment formed by the accumulation of wind-blown silt, , twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate). We began grid sampling and fertilizing accordingly since 2010. We have a pH range from 5.4 to 6.7, organic matter range from 2.3 to 4.5, and a CEC range from 16.9 to 25.2 in the same 94 acre field. I selected 2-2.5 acre random grids within the field for comparison on nutrient levels and subsequent yield from 2010, 2011, 2012 and 2013.  So we have two years of data from corn and soybeans to consider.


Initial Grid Sampling



Grid A

Grid B

Field Ave





Organic Matter








P1 Phosphorus

12 ppm

161 ppm

31.3 ppm

P2 Phosphorus

20 ppm

162 ppm

42.20 oom


9 ppm

20 ppm

10.51 ppm


186 ppm

662 ppm

274.94 ppm


1.1 ppm

5.2 ppm

1.93 ppm

2010 Corn Yield

147 bu./acre

195 bu./acre

178.49 bu./acre

Applied 80 lbs of P--blanket treatment to whole field-Fall 2010




2011 Soybean Yield

32 bu./acre

66 bu./acre

62.52 bu./acre

Applied –Fall 2011

193.12 lbs of 11-52-0 MAP

121.71 lbs of 11-52-0 MAP

174.26 lbs of 11-52-0 MAP

2012 Corn Yield

116 bu./acre

145.6 bu/acre

126.45 bu./acre

Applied –Fall 2012

147.92 lbs of 11-52-0 MAP

90.89 lbs of 11-52-0 MAP

121.61 lbs of 11-52-0 MAP

2013 Soybean Yield

57.25 bu./acre

62.58 bu./acre

56.49 bu./acre

Applied 112 lbs of P--blanket treatment to whole field—Applied Fall 2013




Fall 2013

Prior to Fall application of P 







Organic Matter








P1 Phosphorus

40 ppm

159 ppm

64.41 ppm

P2 Phosphorus

56 ppm

148 ppm

100.06 ppm


12 ppm

19 ppm

13.14 ppm


235 ppm

401 ppm

228.47 ppm


1.5 ppm

7.7 ppm

2.79 ppm


Obviously the level of base-line fertility and nutrients subsequently applied varied widely between these two grids. The challenge was/is to maintain the high fertility levels and since we have identified the lower fertility leveled areas (Grid A)—we wanted to bring these levels up to increase production. The Grid Sampling Value is seen here as we don’t have to do too much fertility work in Grid B and we take those dollars and apply them for fertility in Grid A. Remember that the goal is to narrow the gap between your low and high producing areas of the field.

RESULTS—in 2010 we had a corn yield gap of 48 bushels/acre between grids A and B.  In 2012 the gap narrowed to 29.6 bushels/acre In 2011 we had a soybean yield gap of 34 bushels/acre between grids A and B.  In 2013 the gap narrowed to 5.33 bushels to the acre.  Consider the residual fertility numbers for (Grid A—Lower Fertility) in 2010 vs. 2013.  Through one blanket treatment of phosphorus (2010) and two prescribed treatments of 11-52-0 per grid,(2011 and 2012)  Phosphorus P1 levels have increased 28 ppm, P2 levels increased 26 ppm, Sulfur increased 3 ppm, Zinc increased 0.4 ppm—all within 4 years on Grid A.   Also, consider the overall field average—especially when the past 2 years have been fairly dry.  I would not have guessed the field average in the drought of 2012 to be 126 bu./acre or anywhere in that field have a yield of 145.6 bu./acre (Grid B)—especially when the field was wilting from moisture stress at V8—Hip high.  Who would have thought we could have had an average soybean yield of 56.49 bushels per acre in 2013 when we received only 1.40” of rain for the entire months of July and August.  The wet 2013 spring certainly played a role here.  Bottom Line--Balanced fertility levels aid in crop performance within dry growing conditions.  The grid sampling practice has narrowed our fertility extremes and decreased the yield gaps within the same field. 



John W. McNamara


Wiles Bros. Inc.

606 Wiles Road

Plattsmouth NE. 68048

(402) 298-8550--Office

(402) 499-3870--Cell

(402) 298-7174--Fax

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