Post-Layby Nitrogen Application to Fine Textured Soils of the North Carolina Piedmont

Transcription

1 Post-Layby Nitrogen Application to Fine Textured Soils of the North Carolina Piedmont J. Hunter Mason Department of Crop Science North Carolina State University

2 Outline Introduction Project Background Locations Experimental Outline Results Conclusions Questions

3 Introduction Nitrogen (N) has the largest impact on the yield and quality of flue-cured tobacco. Excess N delays ripening and can increase curing difficulties. Insufficient N produces pale leaves that often require harvesting before fully ripened. Both factors impact smoke flavor and aroma. Water is essential for N uptake. Limiting factor in North Carolina production 20% of the crop is irrigated

4 Introduction Current practices for N application are in the form of two separate timings days after transplanting and at layby Can result in too much N applied in dry season or too little N applied in wet season. Late season N application to coarse soil texture is acceptable (Drake, 2014; Drake, 2015). Reduced rates of liquid N are acceptable in fine textures soils (Vann, 2015). Average N application rate in the Piedmont is 80 lbs./a

5 Introduction Extension survey results indicate that N application rates to fine textured soil are greater than recommended. 10 to 15 lbs. N/acre too much In addition, current practices may result in reduced leaf quality and yield on fine textured soils. Reduced leaching potential of nitrogen Little information is available regarding post-layby N application.

6 Purpose To determine most appropriate timings of nitrogen applications based on growing conditions Evaluate as many as three nitrogen applications: After transplanting, layby, and two weeks after layby Reduce input cost and environmental impact Avoid applying excess nitrogen How might 3 application timings impact leaf yield and quality?

7 2015 Locations Yadkin County Boonville, NC Hobson Farms Ext. Agent: James Boggs Stokes County Lawsonville, NC Merrit Farms Ext. Agent: Tim Hambrick

8 Experimental Design Randomized Complete Block Design 4 row plots 16 x 40 plot size Targeted plant population of 6,000 plants/acre CO 2 pressurized backpack used for liquid N application 28% UAN, applied in a sidedress application Applied to the soil surface after layby, not incorporated

9 Experimental Design Nitrogen Applications: 7-10 Days After Transplanting (AT) ½ rate of liquid N 75 lbs./acre of Potassium from Layby and Two Weeks after Layby (2WAL) Remaining N rates applied in one or both of these intervals Rates dependent upon treatment

10 Treatments Three targeted nitrogen rates: 50, 70, and 90 lbs. N/acre Each rate applied at 75, 100, and 125% of the targeted rate with various combinations of application timings Six treatments consisted of three separate application timings. AT, Layby, and 2 WAL Six treatments followed current application practices. One application after transplanting and one application at layby

11 Treatments Treatment # Nitrogen Application Timing Total Nitrogen AT Layby 2WAL lbs./acre

12 Data Collection 5 leaf tissue samples collected at layby, after topping, and after curing. Used to quantify total N content and uptake SPAD measurements collected 2 WAL and after topping. Correlation between N uptake and leaf color Harvested by individual stalk position. 85% moisture loss assumed for final yield Subsample of harvested leaf collected for Quality sample. Subsample cured on-farm in plastic mesh bag Each plot assigned USDA grade for each stalk position Crop value determined through combination of yield and quality. Composite cured leaf samples collected for leaf chemistry quantification (currently unavailable). Results analyzed in SAS ver. 9.4.

13 Rainfall Totals Month Stokes 2015 Stokes Avg. Yadkin 2015 Yadkin Avg Inches Apr May June July Aug Sept Oct Total *Included Rainfall: Stokes (April 30 - Sept. 18) Yadkin (May 7 - Oct. 23)

14 May 5 th Aug. 3 rd Total Rainfall Estimates

15 2015 Results: Yield, Quality, and Value Timing Total N Yield Quality Value AT + Layby + 2WAL lbs./acre lbs./acre $/acre ,513 a 76 a 2,365 a ,362 a 61 a 1,728 a ,614 a 76 a 2,525 a ,686 a 75 a 2,659 a ,660 a 71 a 2,436 a ,783 a 76 a 2,831 a ,688 a 74 a 2,572 a ,598 a 75 a 2,444 a ,919 a 78 a 3,054 a ,734 a 74 a 2,626 a ,666 a 67 a 2,312 a ,804 a 70 a 2,615 a

16 SPAD Measurements & Nitrogen Content Timing Total N SPAD % Nitrogen Content AT + Layby + 2WAL lbs./acre 2WAL Topping Layby Topping a 48.7 a 4.67 a 4.26 a a 49.9 a 4.47 a 4.76 a a 50.6 a 4.81 a 4.37 a a 48.4 a 4.67 a 4.32 a a 49.1 a 4.87 a 4.21 a a 50.2 a 5.01 a 4.46 a a 49.4 a 4.64 a 4.09 a a 49.4 a 4.96 a 4.38 a a 48.3 a 4.84 a 4.65 a a 49.5 a 4.69 a 4.47 a a 52.4 a 4.78 a 4.41 a a 50.1 a 4.98 a 4.79 a

17 Preliminary Conclusions Year one of multi-year study Dry seasons, like 2015, leads to reduced N uptake No water = no way for plant to obtain N from soil Lower N rates were very comparable to higher N rates No statistical difference with N available in tissue samples Save growers money and time in a dry year

18 Preliminary Conclusions Consider applying 50% at transplant and 25% at layby. 25% after layby, if needed due to rainfall. Yield and Quality were exceptionally low. Due to poor growing conditions In a dry season, reduced N is preferable Timely ripening Cost Management

19 References Drake, M.P., M.C. Vann, and L.R. Fisher Nitrogen Application Rate Influence on Yield, Quality, and Chemical Constituents of Flue-cured Tobacco, Part I: Application Timing. Tobacco Science. p Drake, M.P., M.C. Vann, and L.R. Fisher Influence of Nitrogen Application Rate on the Yield, Quality, and Chemical Components of Flue-cured Tobacco, Part II: Application Method. Tobacco Science. p Vann, M.C Effects of Soil Tillage on Flue-cured Tobacco Growth, Weed Control, and Soil Physical Properties. Raleigh, NC: North Carolina State University. Dissertation.

20 Dr. Matthew Vann Matthew Inman Scott Whitley Joseph Cheek Camden Finch Will Norris Tim Hambrick James Boggs Acknowledgements

21 Questions??