E. David Dickens, Bryan C. McElvany, David J. Moorhead, Bob Boland, and Kris M. Irwin 1

Transcription

1 Publication Number 3R-8 December 8 Water Quality Effects based on Soil Solution Nitrate-Nitrogen after Poultry Litter and Diammonium Phosphate plus Urea Applications in a Slash Pine Plantation in Brantley County Georgia E. David Dickens, Bryan C. McElvany, David J. Moorhead, Bob Boland, and Kris M. Irwin 1 INTRODUCTION Poultry litter is commonly used as a fertilizer for pastures, hay fields, and cropland in Georgia. The repeated application of litter has led to elevated nutrient and bacteria levels in area streams. Application of litter to forestland is a promising alternative as there are over 24 million acres of forestland in Georgia. Many forest soils are low in available nitrogen (N) and phosphorus (P), and to a lesser extent, potassium (K). Southern pine tree and stand growth response to poultry litter applications can be significant and produce positive financial returns. A study funded by the Georgia Environmental Protection Division (GA-EPD) was initiated to investigate the effects of poultry litter application to forestland on water quality. The focus of this paper was to quantify nitrate-n in soil solution by fertilizer treatment over a 3½ year study period. METHODOLOGY This study was initiated in 1 to investigate water quality effects of Annual (poultry) litter (695 lb/ac on 3 January 2; 718 lb/ac on 18 February 3; and 754 lb/ac on 24 February 4) with an overall mean total-n of 1.8 percent on an as sampled basis; One-time litter (2554 lb/ac on 3 January 2 with a mean 1.8 percent total-n on an as sampled basis; and DAP + urea, diammonium phosphate ((NH 4 ) 2 HPO 4 ; 213 lb/ac P 2 O lb/ac N) + urea (CO(NH 2 ) 2 ; 123 lb/ac N) application in a 1994 planted slash pine (Pinus elliottii) stand in Brantley County, Georgia (Table 1). The soil series of the study site was verified by a Natural Resource Conversation Service (NRCS) as primarily Hurricane (somewhat poorly drained, sandy, siliceous, thermic Oxyaquic Alorthods), and to a lesser extent, Chipley (somewhat poorly drained, sandy, thermic, coated Aquic Quartzipssamments). Pretreatment topsoil ph (-6 inch) ranged from 5.4 to 6. in the Annual and One-time litter plots, 5.3 to 5.6 in the Control plots, and 5.2 to 5.5 in the DAP + urea plots. The study area design was randomized complete block with three replications per treatment. Gross treatment plot size was.25 acres with 4 feet of untreated buffer between each plot. Porous cup suction lysimeters (two per plot) were installed to a depth of 3.3 feet in each plot (24 suction lysimeters in total). Groundwater wells were installed to the saturated water zone up-gradient of the study area, one plot for each treatment, and down-gradient of the study area in a line transect for a total of 6 wells to an average well depth of 18 feet. Background soil solution samples were taken prior to treatments (29 January 2). Post-application soil solution and groundwater samples were collected every 3 months from March 2 through July 5.

2 A rainfall data recorder was installed on-site. However, electrical, rodent, and litterfall problems resulted in unreliable rainfall data collection. Therefore, rainfall data from a weather station located approximately 12 miles east of the site (Figure 1) were used during the study period to discern any rainfall pattern to nitrate-n concentration correlations. Table 1. Application levels and nitrogen analysis for the fertilizer treatments used in the 1994 planted slash pine stand in Brantley County, Georgia. Treatment Time of Application Material Amount Total-N NH 4 -N Organic-N Total-N (lb/ac) (%) (%) (%) (lb/ac) Control na DAP + urea Jan-2 59 (18) (46) -- One-time litter Jan Annual litter Jan Feb Feb Nitrate-N in the layer poultry litter was negligible ranging from. to.34 mg/l. Litter N values expressed on an as sampled basis. Litter solids averaged 3% (-4% range). Rainfall (inches) January February March April May June July Month August September October November December yr ave Figure 1. Rainfall amounts by month during the water quality study period and the 25-year running average from a weather station 12 miles east of the 1994 planted slash pine stand in Brantley County, Georgia. RESULTS The characteristics of the layer litter applied to individual plots during the study period were variable with percent solids ranging from to 4 percent, total-n ranging from 1.2 to 3.46 percent, ammonium-

3 N ranging from.6 to 1.2 percent, and nitrate-n ranging from. to.32 mg/l (Table 1). These variable characteristics created a non-uniform distribution of the litter in the One-time and Annual litter plots. The lbs/ac application level differences ranged from 15 to 25 percent of the mean within individual plots. The United States Environmental Protection Agency (EPA) drinking water standard for nitrate-n of mg/l was used as a threshold value for both the suction lysimeters and well soil solution samples in this study. Soil solution nitrate-n means from the Annual litter applications were above the EPA drinking water threshold during all quarterly collection periods starting 12 months after the first application (January 3), and remained above the threshold through July 4, and then dropped to below mg/l 33 months after the first application and 9 months after the third and final application in October 4 (Figure 2). Soil solution nitrate-n from the One-time litter application had one sample above the threshold at 15 mg/l 12 months after application (January 3), which then declined to < 3 mg/l during the next collection period (April 3). Soil solution nitrate-n levels from the DAP + urea application were above the threshold after application, 32 and 78 mg/l, 9 months (October 2) and 12 months (January 3), respectively. Then, 15 months after application, these numbers fell below the threshold (Figure 2). Study period mean lysimeter soil solution nitrate-n levels were 1.1 mg/l for the Control, 8. mg/l for the DAP + urea, 2.5 mg/l for the One-time litter, and 18.5 mg/l for the Annual litter (Table 2). Two well soil solution nitrate-n values were above mg/l. The Control plot well had a soil solution nitrate-n value of 42 mg/l on the July 3 sampling date (Figure 3). This was likely due to the landowner spreading the leftover litter that was piled adjacent to the control plot in March 2 and the continuation of the annual fertilizer regime on this adjacent field. None of the lysimeters in the same plot had soil solution values greater than 4.2 mg/l during the study period. The Annual litter well maximum soil solution nitrate-n value was 16 mg/l on the July 4 sampling date, 6 months after the third and final annual application (Figure 3). The Up-gradient, DAP + urea, One-time litter, and Down-gradient wells did not produce soil solution nitrate-n values above mg/l during the study period. Study period mean soil solution nitrate-n levels were.44 mg/l for the Up-gradient well, 4.7 mg/l for the Control,.8 mg/l for the One-time litter application,.17 mg/l for the DAP + urea, 3.2 mg/l for the Annual litter, and 1.1 mg/l for the Down-gradient well (Table 2). Table 2. Soil Solution nitrate-n means and ranges from the lysimeters (@ 3.3 feet) and wells (@ 18 feet) by treatment/location in a 1994 planted slash pine stand in Brantley County, Georgia. Treatment/Location Lysimeter Lysimeter Well Well (Mean) (Range) (Mean) (Range) NO 3 -N soil solution concentration (mg/l) Control DAP + urea One-time litter Annual litter Up-gradient Down-gradient

4 SUMMARY AND DISCUSSION In this study, the One-time litter application of 2554 lb/ac (226 lb/ac NH 4 -N and 55 lb/ac organic-n) had the least adverse effect on soil nitrate-n solution levels. All fertilization treatments had no major adverse effect on Down-gradient groundwater quality based on nitrate-n concentrations over the study period. No correlations were detected between rainfall and soil solution peak nitrate-n patterns using monthly rainfall data from the nearest weather station. Nitrate-N concentrations were above mg/l in the onetime DAP + urea application lysimeters in October 2 after a 4.1 inch rainfall month (44 inches for January through October 2) and in January 3 after a. inch rainfall month (53 inches rainfall January 2 through January 3). Lysimeter nitrate-n concentrations were above mg/l in the Onetime litter application in January 3 after a.5 cm rainfall month (53 inches rainfall January 2 through January 3). Lysimeter nitrate-n concentrations were much above mg/l in the Annual litter in April 3 after a 3.7 inch rainfall month (58 inches for May 2 through April 3), July 3 after a 12.8 cm rainfall month (59 inches for August 2 through July 3), and in April 4 after a 5 inches rainfall month (49 inches for May 3 through April 4). The DAP + urea and One-time litter application maximum nitrate-n concentration lysimeter values occurred 12 months after application, declining to values much below the mg/l threshold starting 15 months after application. The Annual litter application had the most adverse water quality effect (based on nitrate-n concentrations in the suction lysimeters) of the three fertilization treatments used in this study. The Annual litter nitrate-n concentration increased at a slightly slower rate than the DAP + urea and One-time litter application (Figure 2), having a first major peak (6 mg/l) 18 months after the first application (5 months after the second application), and a second and final major peak (8 mg/l) 26 months after the initial application (14 months after the second application and 2 months after the third application). The Annual litter lysimeters nitrate-n concentration fell below the mg/l threshold in October 4, 33 months after the initial application ( months after the second application and 8 months after the third and final application (Figure 2). 9 Nitrate-N (mg/l) Jan-2 Apr-2 Jul-2 Oct-2 Jan-3 Apr-3 Jul-3 Oct-3 Jan-4 Apr-4 Jul-4 Oct-4 Jan-5 Apr-5 Jul-5 Litter Applications: January 3, 2 February 18, 3 February 24, 4 Annual Control DAP+Urea One Time Date Sampled Figure 2. Porous cup suction lysimeters (@ 3.3 feet depth) nitrate-n means by treatment during the study period from the 1994 planted slash pine stand in Brantley County, Georgia.

5 Litter Applications: January 3, 2 February 18, 3 February 24, 4 Upgradient Annual Control One Time Nitrate-N (mg/l) DAP+U Downgradient 5 Jan-2 Apr-2 Jul-2 Oct-2 Jan-3 Apr-3 Jul-3 Oct-3 Jan-4 Apr-4 Jul-4 Oct-4 Jan-5 Apr-5 Jul-5 Figure 3. Groundwater monitoring well (@ 18 feet depth) nitrate-n concentrations by treatment during the study period from the 1994 planted slash pine stand in Brantley County, Georgia. ABOUT THE AUTHORS 1 Associate Professor, Warnell School of Forestry & Natural Resources; Treutlen County Extension Coordinator, College of Agricultural and Environmental Sciences; Professor, Warnell School of Forestry & Natural Resources; Brantley County Extension Coordinator, College of Agricultural and Environmental Sciences; and Public Service Associate, Warnell School of Forestry & Natural Resources, respectively. CITATION Dickens, E.D., B.C. McElvany, D.J. Moorhead, B. Boland, and K.M. Irwin. 8. Water quality effects based on soil solution nitrate-nitrogen after poultry litter and diammonium phosphate plus urea applications in a Slash pine plantation in Brantley County Georgia. Georgia Forest Productivity Series No. 3R p. Athens, Georgia Phone: fax: An Equal Opportunity/Affirmative Action Institution In compliance with federal law, including the provisions of Title IX of the Education Amendments of 1972, Title VI of the Civil Rights Act of 1964, Sections 53 and 54 of the Rehabilitation Act of 1973, and the Americans with Disabilities Act of 199, the University of Georgia does not discriminate on the basis of race, sex, religion, color, national or ethnic origin, age, disability, or military service in its administration of educational policies, programs, or activities; its admissions policies; scholarship and loan programs; athletic or other University-administered programs; or employment. In addition, the University does not discriminate on the basis of sexual orientation consistent with the University non-discrimination policy. Inquiries or complaints should be directed to the director of the Equal Opportunity Office, Peabody Hall, 29 South Jackson Street, University of Georgia, Athens, GA 362 Telephone (V/TDD).Fax