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Research Plots In Iowa

By Randy Simonson, Ph.D.
Technical Services Manager

In our last newsletter, we showed some charts that graph the movement of phosphorus and potassium at our Catlin research farm. We are finding similar movements of phosphorus and potassium in test plots in Iowa. From 1995 to 1998, we had a nice set of research plots near Marv's Feed & Seed in Dunkerton, IA. Shown below are the phosphorus and potassium levels of the soil samples taken each of these four years, from four treatments that had six reps each. Both phosphorus and potassium move up substantially from the first to the second year of the plots. Potassium moves down the next two years, whereas phosphorus moves down and then back up.

This data backs up what we saw from the soil test levels at the Catlin Research Farm. In fact, if you look at the Catlin potassium chart from 1995 to 1998, you can see that the movement of potassium is very similar to the Iowa potassium chart.

Iowa Phosphorus Chart

Iowa Potassium Chart

Next we have tables showing the soil test levels, fertilizer applied, costs, yields and profits for the corn and soybeans at the Iowa plots. The university treatment recommended more phosphorus fertilizer for the corn than did any of the TSM treatments. The university recs for potassium were about the same as the TSM E in the corn. For the soybeans however, the TSM treatments recommended more P and K than the university. In both the corn and soybeans, the net profit after fertilizer costs are taken out, for TSM E and TSM I treatments were higher than the university. The TSM E in the corn produced almost a $20/acre increase in profit over the university and the TSM I did $15/acre better. The TSM I actually showed the highest profit in the soybean plots.

1995-1998 TSM Research Farm - Corn Means
Marv's Feed & Seed, Dunkerton, IA
Recommendations/ActionsTSM ATSM ETSM IUniversity
P1 soil levels (lbs/A)71676567
P2O5 applied (lbs/A)1412745
K soil levels (lbs/A)391396367386
K2O applied (lbs/A)63452847
Pre-Mix applied (lbs/A)463421-
TSM Blend (suspension)4.44.14.2-
Amount of Blend370275167-
Cost of Fertilizer ($/A)$40.19$29.99$18.53$17.32
pH6.76.86.86.8
Yield (bu/A)158163157150
Price ($/A)$ 2.51$2.51$ 2.51$ 2.51
Gross Profit ($/A)$396.58$409.13$394.07$376.50
Net Profit ($/A)$356.39$379.14$375.54$359.18

1995-1998 TSM Research Farm - Soybeans Means
Marv's Feed & Seed, Dunkerton, IA
Recommendations/ActionsTSM ATSM ETSM IUniversity
P1 soil levels (lbs/A)76707877
P2O5 applied (lbs/A)7520
K soil levels (lbs/A)371376363394
K2O applied (lbs/A)4326145
Pre-Mix applied (lbs/A)301910-
TSM Blend (suspension)4.94.84.9-
Amount of Blend24014976-
Cost of Fertilizer ($/A)$24.25$14.99$7.49$0.60
pH6.76.76.76.7
Yield (bu/A)56585755
Price ($/A)$6.36$6.36$6.36$6.36
Gross Profit ($/A)$356.16$368.88$362.52$349.80
Net Profit ($/A)$331.91$353.89$355.03$349.20

So, what can we deduct from this data. The soil test levels move from year to year and all fertilizer treatments move in a similar fashion. The crop yield and the amount of fertilizer applied have only minor influences on the soil test levels. However, the fertilizer treatments have a big influence on yield and net profit. In both locations, for both corn and soybeans the TSM E treatment has come out with the top yields. TSM E also produced the largest net profit with the exception of the soybeans at Iowa where the net profit for TSM I was slightly more.

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