Groundwater Corn And Cattle

Author : Niranga M. Wickramarathne
Publisher :
ISBN 13 :
Total Pages : 150 pages
Book Rating : 4.:/5 (19 download)

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Download or read book Groundwater Nitrogen and Phosphorus Dynamics Under Cattle Grazing and Row Crop Management in Two Contrasting Soils in Missouri written by Niranga M. Wickramarathne and published by . This book was released on 2017 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nutrient pollution of water resources has been a major environmental problem for decades. Excessive use of chemical fertilizer and livestock management results in agricultural non-point source pollution. The regional characterization of nutrient contamination in groundwater is important for the identification of the groundwater zones receiving heavy nutrient loads from the surface. The objectives of this study were, (1) To quantify landscape and buffer effects on NO[subscript 3]-N and TN in groundwater under rotational cattle grazing, (2) To quantify landscape and buffer effects on PO[subscript 4]-P and TP transport in groundwater under rotational cattle grazing, and (3) To access the spatial and temporal variations of NO[subscript 3]-N, TN, PO[subscript 4]-P and TP concentrations in groundwater under row crop management. The experiment was conducted in two different watersheds. (1) Horticulture and Agroforestry Research Center (HARC) near New Franklin, Missouri and (2) The Romine experimental watershed within the Good Water Creek Experimenatl Watershed (GCEW) near Centralia, Missouri. The experimental design at HARC consisted of two rotationally grazed watersheds with a grass buffer (GB) and an agroforestry buffer (AB). The predominant soil within the treatment watersheds is Menfro silt loam. The grazed portion of both watersheds had common forage species; tall fescue [Schedonorus phoenix (Scop.) Holub], red clover (Trifolium pratense L.), and lespedeza (Lespedeza Michx)., and the AB treatment had four rows of poplar trees (Populus tremula L.) at the footslope. A transect of three wells was installed at summit, backslope, and footslope positions in both watersheds. Wells were identified by the buffer type and landscape position as AB summit, AB backslope, AB footslslope, GB summit, GB backslope and GB footslope. The Romine experimental watershed consisted of crop rotation (corn, wheat, soybeans, and sorghum), grassland and woodland. The watershed is under conservation tillage. The soils within the watershed comprise naturally formed argillic horizon located between 0.15 and 0.3 m below the soil surface. Three groundwater monitoring wells were installed in strategic locations around the resurgent flow area and named as Romine north (RN), Romine south (RS) and Romine west (RW). A series of shallow piezometers were also installed across a catena sequence from summit to the footslope and numbers were given 1-7. Out of all the piezometers four piezometers had no water during the study period. The productive piezometers were identified as PZ 4, PZ 6 and PZ 7. Weekly groundwater samples were collected from both study sites and analyzed for NO[subscript 3]-N, TN, PO[subscript 4]-P and TP concentrations from December 2014 to December 2016. At HARC both NO[subscript 3] --N and TN concentrations were significantly lower at the footslope than at the summit and backslope (p0.001). The median concentrations of NO[subscript 3]-N and TN were 0 mg L[superscript -1] and 0.24 mg L[superscript -1] at the footslope, compared to the median concentrations 1.4 mg L[superscript -1] at the summit and backslope. In addition, the NO[subscript 3]ˉ--N/Clˉ ratio was significantly lower at the footslope than at the summit and backslope, suggesting that denitrification was the main process for the very low NO[subscript 3]-N concentrations at the footslope. Seasonal differences in TN and NO[subscript 3]-N were most apparent in the footslope wells, and the seasonal pattern in concentrations was different between the two watershed treatments. Overall, the results showed that landscape position most affected TN and NO[subscript 3]-N concentrations in groundwater and denitrification was the major cause of the very low NO[subscript 3]-N concentrations at the footslope. The presence of trees in the AB treatment further reduced NO[subscript 3]-N concentrations at the footslope. In the same study site, median 2015 AB (0.14 mg L[superscript -1]) and GB (0.2 mg L[superscript -1]) footslope TP were also significantly greater (p0.001) than the concentrations in 2016 (AB 0.04 mg L[superscript -1] and GB 0.08 mg L[superscript -1]). Median PO[subscript 4]-P and TP at the footslope were significantly lower (p0.001) than the concentrations of 0.1 mg L[superscript -1] PO[subscript 4]-P and