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S. Kuo

Acidifying soil to prevent annual bluegrass (Poa annua L.) from infesting creeping bentgrass (Agrostis palustris Hud.) reduces soil P and Ca availability. This study examined Ca and P effects on the growth of these two grasses in four moderately acidic soils using CaSO4 as a Ca source. Each soil received four P rates (0, 10, 40, or 80 mg·kg-1) and three Ca (as CaSO4) rates (0, 400, or 800 mg·kg-1). Neither Ca nor P treatments substantially changed pH or exchangeable soil Al. Clipping yields, tissue P concentration, and P uptake of both grasses were affected by soil NaHCO3-P levels. Compared to bentgrass, annual bluegrass had higher clipping yields and P uptake at high P rates or high NaHCO3-P levels; this result indicates that annual bluegrass was as acid-tolerant as the bentgrass, provided that available P in the soil is adequate. Adding CaSO4 to the Papac soil, which contained the least amount of exchangeable Ca among the four soils, markedly enhanced the clipping tissue P concentration and P uptake of creeping bentgrass but not those of annual bluegrass; this result indicates that a differential response to Ca existed between the two grasses. Maintaining an adequate soil Ca availability was necessary to improve bentgrass growth, particularly for the acid soil containing low available Ca initially.

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Jongtae Lee, Jinseong Moon, Heedae Kim, Injong Ha, and Sangdae Lee

, decreases in exchangeable calcium and magnesium, and reduction of cation exchange capacity associated with the N fertilization rates. Hence, higher N fertilization rates eventually led to lower N fertilizer efficiency ( Barak et al., 1997 ). In particular

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James E. Altland, M. Gabriela Buamscha, and Donald A. Horneck

, S.M. 2006 Gypsum amendment and exchangeable calcium and magnesium affecting phosphorus and nitrogen in runoff Soil Sci. Soc. Amer. J. 70 1788 1796 Fisher, P. Huang, J. Argo, W. 2006 Modeling

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Mingxia Wen, Peng Wang, Weiqin Gao, Shaohui Wu, and Bei Huang

) served as the experimental material. The soil fertility of the test site was as follows: pH 5.14; organic matter, 40.6 g/kg; hydrolytic nitrogen, 302.4 mg/kg; available phosphorus, 495 mg/kg; available potassium, 270 mg/kg; exchangeable calcium, 2.07 cmol

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Xiaoli Ma, Xuefeng Liu, Pingwei Xiang, Shichun Qiu, Xiangcheng Yuan, and Mei Yang

phosphorus 23.75 mg/kg, available potassium 99.51 mg/kg, exchangeable calcium 1270.0 mg/kg, exchangeable magnesium 205.0 mg/kg, available zinc 1.61 mg/kg, available iron 7.77 mg/kg, available manganese 8.37 mg/kg, available copper 0.81 mg/kg, and available

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Anna L. Testen, Delphina P. Mamiro, Hosea D. Mtui, Jackson Nahson, Ernest R. Mbega, David M. Francis, and Sally A. Miller

nitrogen: modified Kjeldahl method ( Wilke, 2005 ), phosphorus: Bray 1 method ( Bray and Kurtz, 1945 ), exchangeable potassium, exchangeable calcium, exchangeable magnesium, and exchangeable sodium: 1 m ammonium acetate extractant (pH 7.0) with