Recent soybean fertility studies. R. Jay Goos and Hannah Ohm Department of Soil Science North Dakota State University

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1 Recent soybean fertility studies R. Jay Goos and Hannah Ohm Department of Soil Science North Dakota State University

2 Two recent soybean fertility studies Calibration of the ureide tissue test under field conditions Evaluation of four iron fertilizers for control of iron deficiency chlorosis (IDC) in soybeans

3 What the heck are "ureides"?

4 Nitrogen flows from soybean roots to the tops, almost entirely in two forms: Nitrate from the soil solution "Ureides" from the nodules NO 3 - Ureides

5 The rhizobia in the nodule take apart N 2, creating ammonia, NH 3,which instantly forms ammonium (NH 4+ ) Plants aren't very good at transporting ammonium Root cells convert the ammonium from N- fixation into ureides for transport to the tops Dry beans are ureide exporters, too Peas, lentils, alfalfa are not

6 Inside of the nodule, N 2 is made into NH Ureides flow to tops Plant cells convert NH 4 + into ureides. So...what are these "ureides?"

7 Meet the ureides. Essentially, two urea molecules connected together. Allantoin Allantoic Acid

8 The ureide test for N fixation has been known for about 30 years, so what is new? We developed a much simpler method for determining ureides. Our objective...calibrate the ureide tissue test with field data

9 Inoculation studies... Carrington, 2007*, 2015**, 2016** Minot, 2015*, 2016* * No history of soybeans **No recent history of soybeans (5+ years) My collaborators are Dr. Jasper Teboh, Carrington, Dr. Shana Forster, Minot, Dr. Shiny Mathews, NDSU Soil Testing Lab

10 Numbers of Bradyrhizobium japonicum per gram of soil at planting: Carrington, , 12 Carrington, Carrington, Minot, Minot,

11 5-12 B. japonicum per gram of soil

12 5-12 B. japonicum per gram of soil

13 Carrington, B. japoncium per gram of soil > 3000 ppm ureide-n in all samples at flowering, with or without inoculation No response to inoculation

14 243 B. japonicum per gram of soil

15 5 B. japonicum per gram of soil

16 5 B. japonicum per gram of soil

17 No B. japonicum detected in the soil

18 No B. japonicum detected in the soil

19 Ureide test is simple. Cut off plant, remove leaf blades, dry. Critical level at flowering is somewhere in the range of ppm of ureide-n Useful tool for diagnosing poor color, settling disputes over inoculum performance, determining if inoculants are needed at all Big response to inoculation with < 12 B. japonicum per gram of soil, no response when counts were >153 per gram

20 Evaluation of four iron fertilizers for control of iron deficiency chlorosis (IDC) in soybeans

21 The most widely-accepted iron fertilizer is FeEDDHA The product 'Soygreen' is a high-quality FeEDDHA product, with about 80% of the iron chelated in the desirable ortho-ortho form New products are entering the market, what is their quality? Objective, to compare four commercial samples of iron fertilizers as to their ability to correct IDC in soybeans

22 Four fertilizers Two "higher quality" materials FeEDDHA-1, 6% Fe, about 80% "soil stable" FeHBED, 9% Fe, about 77% "soil stable" Two "lower quality" materials FeEDDHA-2, 6% Fe, about 47% "soil stable" FeEDDHSA liquid, 1.8% Fe, about 42% "soil stable"

23 "Soil Stability Test" React calcareous soil with 12 ppm of Fe for a week See how much remains in solution Higher quality Lower quality Higher quality FeEDDHA FeEDDHA FeEDDHA

24 Two greenhouse crops grown to 4th trifoliolate stage 0, 0.5, 1, 1.5 mg Fe/pot Chlorophyll measured with Minolta SPAD meter Growth and Fe uptake measured

25 Results for the first crop

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30 Conclusions, crop 1 Quality of the iron fertilizer didn't seem to matter much, all four sources gave a large response Perhaps a slight advantage to the higherquality FeEDDHA-1

31 So, the soil in each pot was mixed, the nitrate levels in the soil equalized, and the pots replanted

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39 Conclusions from the second crop Quality did, indeed matter The higher-quality FeEDDHA-1 and FeHBED gave the best response The lower-quality FeEDDHSA and FeEDDHA-2 gave the least response Conclusion, a higher-quality Fe fertilizer should give you a longer response

40 These studies supported by: The North Dakota Soybean Council The Russell and Anna Duncan Foundation