1. Summary of the Nitrogen and Carbon Cycle on Georgia’s Pasture-Based Dairies N.S. Hill, Professor Dept. Crop and Soil Sci., UGA, Athens

2. Outline Nitrogen: The most mobile of plant nutrients Why are we concerned with N? What research are we conducting? Interpretation of results. Carbon: Can pasture-based dairies sequester carbon? Are there practical benefits beyond removing Ghg from atmosphere?

3. WHAT ARE THE SOIL CHEMICAL PROPERTIES THAT MAKE NITRATE LEACHING OF SUCH CONCERN? _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ CONSIDER SURFACE CHARGES ON SOIL PARTICLES

4. WHAT ARE THE SOIL CHEMICAL PROPERTIES THAT MAKE NITRATE LEACHING OF SUCH CONCERN? _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ K+K+

5. _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ K+K+ NO 3 - Groundwater NO 3 levels considered safe: 10 ppm (= 10 mg NO 3 L -1 )

6. NH 3

8. Soil water-NO 3 -N (ppm) from cropped land to which dairy effluent was applied. Application strategy changed in 1998 to accommodate nutrient demand by forage crops. (ASAE 2001:1-9.)

9. WHAT HAPPENS TO N WHEN LAND IS MANAGED USING HIGH INTENSITY GRAZING SYSTEMS?

10. Research Effort Conduct a farm-gate N budget – pollution potential? 2 locations (farms)

13. Farm Fertilizer Applied Ammonia Volatilized Nitrate Leached ----------kg N ha -1 ----------- Wrens Farm 605*1961.7 Quitman Farm 320 # 740.4 Total fertilizer N applied and N losses associated with the sampling period at Wrens (1 Jun 2008-31 Aug 2009) and Quitman (1 Aug 2008-31 Aug 2009). (Eason, unpublished) * Applied as dry urea # Applied as UAN via irrigation

14. Nitrate concentrations (a) and water flux (b) from the Orangeburg soil on the Wrens farm. (c) Shows VWC for three depths in the soil profile. (Eason, unpublished)

15. Nitrate concentrations (a) and water flux (b) from the Stilson soil on the Quitman farm. (c) Shows VWC for three depths in the soil profile. (Eason, unpublished)

16. Nitrate concentrations (a) and water flux (b) from the Tifton soil on the Quitman farm. (c) Shows VWC for three depths in the soil profile. (Eason, unpublished)

17. Farm-gate Balance: Nitrogen Inputs and Outputs in Pasture-Based Dairies Farm Records Experimental * Experimental * *

18. Source--------- kg N yr -1 ---------% of Total N input N inputMineral Fertilizer603943380678.940.7 Grain Feed119594367915.652.6 Maize Silage122401.60 Hay301155873.96.7 Total7658983074100 N outputMilk120661421715.815.3 N 2 O emmision2032? (~4000)2.7N/A NH 3 volatilization2310374630.2.90 NO 3 Leached2044363.317.1 Total37407193274833.3 N in forage/soil39182607465166.7 N use efficiency67%89% Farm-gate N balance for Wrens and Quitman farms. (Eason, unpublished)

19. PaddockInitial1 year2 years3 years ------ % Soil Organic Carbon ------ P40.6250.6700.725 1.277 P80.5850.6800.925 1.268 P140.6630.9501.083 1.163 Mean0.6240.7670.911 1.236 Accumulation of soil organic carbon in 3 paddocks located in a pasture-based dairy in Wrens, GA. (2007-2009) For each 0.1% increase in organic carbon = 2000 lbs sequestered C. 3 years after grazing system started, averaging 3200 lbs sequestered C per year

20. ------- Dry years -------Wet year Accumulation of Organic Carbon in 3 Paddocks as a Function of Time After Conversion into Dairy Pasture, (Wrens, GA)

21. Implications of Fixed Carbon: Greater soil water-holding capacity Greater water infiltration rate in soil Greater soil nutrient retention capacity Nutrient “banking” Al and Desiree Wehner : “We are not getting the same fertilizer response on our farm we started in 1993 as the ones we started in the last 3 years”. “How long can we ‘mine’ the nutrients in the soil during periods of low milk prices?”

22. Aromatic a.a. (yellow) Aliphatic (orange) Carboxyl (red) Phenolic (blue) Spatial complexity of soil organic matter forms at nanometre scales. Lehman et al., 2008. Nature Geoscience 1:238-242. Soil particles are purple

23. Lots of Challenges and Life Can Get Serious…. …. So Enjoy the Intangibles!!!