University of Georgia; SQM Tifton, GA USA

Transcription

1 Evaluation Of Growth, Yield, Grade And Chloride Content Of Flue-Cured Tobacco Fertilized With Various Rates Of KCl And K-Mag As Potassium Sources MOORE, J.M.; BAFALLUY, R.; LAHUE, S.S.; TROXELL, C.E. University of Georgia; SQM Tifton, GA USA

2 Introduction In 2008, as fertilizer prices increased rapidly, farmers asked why not supplement their fertilizer program with a cheaper source of potassium in order to reduce their overall fertilizer costs. My response was that the cheaper potassium (muriate of potash, MOP) contained high levels of Chloride and tobacco fertilizers were limited in the amount of Cl.

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4 $ ST Source: Green Markets Potash Prices Potash Prices Blend Grade fob U.S. Midwest Warehouse

5 Introduction 746 kg ha-1 of provides 22.4 kg Cl ha -1 Additional Cl is applied using Telone II soil fumigant (Active Ingredient: 1,3- Dichloropropene) Resulting cured tobacco contained acceptable Cl content. None of the tobacco purchasers expressed any concern with current Cl levels.

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7 (b) Field Crop Tobacco Fertilizers: 1. For field crop tobacco fertilizers having total nitrogen guarantees up to and including 4% - maximum chlorine 2%. 2. For field crop tobacco fertilizers having total nitrogen guarantees above 4% - maximum chlorine not more than one half of the total nitrogen guaranteed.

8 Introduction What might be the results of applying greater amounts of Cl containing fertilizer materials under Georgia growing conditions?

9 Chloride and Flue-Cured Tobacco Fertilization 22 to 33 kg Cl ha -1 maximum are recommended for flue-cured tobacco Soil fumigants add 39 kg Cl ha -1 (in-row application), 67 kg Cl ha -1 (broadcast application). KCl cheaper source of potassium, but heavy application will increase Cl application beyond 22 to 33 kg Cl ha -1

10 abnormally green thickened brittle cupped leaf margins smooth, sleek appearance poor fire holding Excessive Cl

11 Chlorine Toxicity (Cl) There is evidence that kg ha -1 of Cl may improve tobacco yield. Higher rates may reduce growth and cause leaves to become abnormally green, thickened, and brittle, with cupped leaf margins. Leaves may have a distinctive smooth, sleek appearance.

12 Chlorine Toxicity (Cl) Toxicity symptoms are more common when ammonium rather that nitrate nitrogen is used. Soil ph about reduces Cl uptake. Cured leaves have dingy, uneven colors and may tend to absorb excess moisture.

13 Materials and Methods Research Trials conducted in 2010 & 2011 University of Georgia Coastal Plain Experiment Station, Tifton, Georgia Soil Series Ocilla loamy coarse sand 1 row plots (1.12 m x 17.8 m) 6 replications (2010); 4 replications (2011) Mechanically transplanted 55 cm in the drill Hand harvested in 4 harvests Cured in bulk curing barns Cured leaf weighed and graded by USDA graders.

14 Materials and Methods Treatments 14, 29, 44, 60, 75, 91, 106, 137 kg Cl ha -1 provided from KCl 10 days following transplanting. 45 kg N ha -1 applied after transplanting using (NH 4 NO 3 ) Remaining K 2 O applied as to provide 202 kg ha -1. An additional 45 kg N ha -1 applied as

15 Potassium Sources Used

16 Chloride Application Rates and Sources (kg/ha) KMag 180 KCl 160 Total K 2 O applied (202 kg ha -1 ) (kg ha -1 )

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20 Data Collected Yield Grade Index Price Index Cl in cured leaf

21 Data Collected Yield NS Grade Index NS Price Index NS Cl in cured leaf **

22 Yield (kg ha -1 ) Yield (Kg/Ha) of Flue-Cured Tobacco Fertilized with Various Rates of KCl 2010 & 2011, Tifton, Georgia Treatments: (kg Cl ha -1)

23 Grade Index (1-99) Grade Index of Flue-Cured Tobacco Fertilized with Various Rates of KCl 2010 & 2011, Tifton, Georgia 74,0 73,3 72,7 72,4 71,8 71,9 72,0 70,9 71,1 71,2 72,4 72,4 72,0 70,0 69,5 68,8 69,9 68,4 68, ,0 65, ,0 62,0 60, Treatments: kg Cl ha -1

24 % Cl Chloride Content of Cured Leaf by Harvest of Flue-Cured Tobacco Fertilized with Various Rates of KCl 2010, Tifton, Georgia 1,60 1,40 1,20 1,00 0,80 Harvest 1 Harvest 2 Harvest 3 Harvest ab 0.75bc 0.81bc 1.28a 0,60 0,40 0,20 0, cd 0.46cd 0.21d 0.30d Treatments: (kg Cl ha -1)

25 % Cl Chloride Content by Harvest of Flue-Cured Tobacco Fertilized with Various Rates of KCl 2011, Tifton, Georgia 4,00 3,50 3,00 2,50 2,00 1,50 1,00 0,50 0,00 Harvest a Harvest 2 Harvest 3 Harvest b 2.57b 1.89c 1.46c 0.96d 0.59de 0.24e Treatments: (kg Cl ha -1)

26 Results and Discussion 2010 & 2011 lowest leaves had the highest concentration of Chloride in the cured leaf. Generally Cl concentration was reduced as leaves were removed from the stalk and cured for analysis.

27 Results and Discussion In 2010 only the first harvest of the highest rate was determined to exceed the 1% threshold. In 2011 the 60 kg ha -1 rate showed greater than 1% in the first harvest. The first and second harvests beginning with the 75 kg ha -1 rate up through 137 kg ha -1 yielded leaf that exceeded the 1% threshold.

28 Results and Discussion General Extension recommendations from limiting Cl application to a maximum of 22 to 33 kg Cl ha -1 appear to accurate, if conservative in the absence of soil fumigant application.

29 Mitigating Factors in Georgia Sandy sandy loam soils used for production. Soils are subject to leaching. Plentiful rainfall / irrigation available for tobacco production. Application of soil fumigants occurs two to three weeks prior to transplanting.

30 Mitigating Factors in Georgia Broadcast application of KCl prior to soil preparation, fumigation and transplanting results in dilution of Cl in the soil and potential for leaching. N-P-K fertilizers are often delayed 10 days after transplanting.

31 Thank You!!!