1. Using Plants for Nitrogen Wilbur Frye Professor Emeritus U.K. Executive Director K.D.A.

2. INTRODUCTION Throughout history of agriculture, N harvested was replaced by legumes, if at all N in animal wastes traced to legumes Value of green manures found in writings of Xenophon (434 to 355 B.C.) Colonial America knew value of green manure, but little practiced on farms ─Used long-term pasture rotations ─Applied animal manure for grain crops ─Moved to virgin soil

3. INTRODUCTION, cont’d World War I was dawn of synthetic N ─Haber/Bosch process for synthetic ammonia N 2 + H 2 →→ NH 3 air nat. gas ammonia World War II NH 3 used to make explosives Ushered in era of cheap synthetic N fertilizers NH 3 → amm. nitrate, amm. sulfate, MAP, DAP, urea, UAN

4. Farmers quit using: Green manure crops Animal manures Crop rotations with legumes Natural N salts—e.g., sodium nitrate

5. ERA OF EXPENSIVE FERTILIZERS Are we there yet? How much farther? What can we do to ease the pain?

6. USING PLANTS FOR NITROGEN Three questions to answer: ● Is it practical? ● What are the benefits? ● Is it economical?

8. Winter Legume Cover Crops Well adapted to Kentucky & southern Indiana ▪ Hairy vetch best Cropping systems ▪ Continuous no-till corn ▪ Corn—wheat—soybean rotation (2-year) ▪ Corn—wheat rotation (2-year) (farther north)

9. Is It Practical? Tillage—No-till, conventional tillage, reduced tillage Planting—Overseed late Aug.–early Sept. before harvest —Drill after harvest Hope for snow during extreme cold Plant corn by mid-May directly into live cover Spray—Burn-down + weed control Cutter-roller—Burn-down + weed control Possibilities of Roundup-Ready corn

14. Above-ground Dry Matter Yield in Southeast (tons/acre) Ky.Ala.La.N.C.Ga. Crimson cl.1.12.02.22.43.0 Hairy vetch1.92.21.7 1.9 Bigflower v.1.0---- Sub. Clover---- 1.72.71.8 Winter pea---- 2.5----

15. Above-ground N Accumulation in Cover Crops N, lb./acre% fixation KentuckyHairy vetch15384 C. clover5636 Bigflo. Vetch7558 Rye25--- AlabamaHairy vetch11979 C. clover11979 Rye25--- GeorgiaHairy vetch13775 C. clover15278 Rye34---

17. Corn Yield--Lexington

20. Liabilities of Legume Cover Crops Cost of seed and seeding Loss of economic production (left for mulch instead of harvested) Depleted soil water in dry spring weather ▪ May decrease stand ▪ Increase water stress in early season Cooler, wetter, no-till soil in normal spring ▪ More N loss, less N mineralization Volunteers in winter wheat—from hard seeds

21. Effect of Planting Method Dry mat. N content CoverInterseedDrillInterseedDrill tons/ac. lb./ac. Hairy vetch 1.68 1.37 121 93 Bigflower vetch 1.22 1.06 88 76 Crimson clover 1.96 0.59 119 39

22. Effect of Planting Date on % Corn Yield

23. Effect of Kill Date (Waggner, 1987) Dry matter, lb./acre N content, lb./acre Cover crop Early kill Late kill Early kill Late kill Hairy vetch 3,000 5,205 120 171 Crimson clover 3,402 4,804 101 124

24. Soil Water at Corn Planting Depth, inches %

25. Returns Above Direct Expenses Based on 1981 and 1982 Prices $/ac. N fertilizer, lb/ac.

26. Re-establishing Legume and Grass Hay and Pasture Legume hay—Corn—Legume hay Alfalfa, red clover, etc. Grass-legume hay—Corn—Hay Grass-legume pasture—Corn—Pasture

27. First year responses of corn to fertilizer N after 5 years of alfalfa Check 141 Spring N (75 lb/acre) 143 1997 Corn yield (bu./acre) 1998 Corn yield (bu./acre) Second year responses of corn to fertilizer N after 5 years of alfalfa Check 126 Spring N (150 lb/acre) 139 Lexington, KY, W.O. Thom

28. % of N Recovered from Labeled Alfalfa and Urea N added In tops 1 st crop In soil > 1 st crop Lost > 1 st crop In tops 2 nd crop Sourcelb./acre % % % % Alfalfa 86 16 67 17 5 Alfalfa 35 18 67 15 4 Urea 45 46 33 21 3

31. Biological Nitrogen Fixation in Forage Crop Communities N fixed (lb./ac./yr.) Alfalfa Lexington KY 189 Red clover Lexington KY 138 White clover Lexington KY 114 White clover New Zealand 603* Birdsfoot trefoil Minnesota 52-103 Soybean Corn belt USA 13-136 Heichel (1985)* On B horizon with minimal soil N

32. Economics of Renovating Pastures with Clover Increased revenues ▪ Weaning wt. ▲40 lb. ▪ Conception ▲10% 81 more lb/cow = $81 Decreased expenses ▪ None considered=$0 Positive effect: $81 Decreased revenues ▪ None considered=$0 Increased expenses ▪ Renovation-$25/ac./yr. ▪ 2 ac./cow-calf unit Neg. effect: 2 x $25=$50 Net effect: $31/cow-calf/yr

33. Benefits of Legume Cover Crops Biologically fixed N 2 from air More efficient use of water ▪ Less runoff & more infiltration ▪ Lower evaporation & higher transpiration More effective erosion control Better weed control Increased soil organic N and C Increased soil productivity (rotation effect) Less overall leaching of N (released slowly)

34. Potential Problems Low germination of cover crop in very dry fall—drilling may help Winter kill—extreme cold w/o snow cover Decreased stand of summer crop—dry weather before and after crop planting Hard seeds that last a year or more interfere with wheat in rotation—may need wheat herbicides

35. USING PLANTS FOR NITROGEN ● Is it practical? ● What are the benefits? ● Is it economical?