Combined Effects of CaCO 3 and the Proportion of N-NH 4 + Among the Total Applied Inorganic N on the Growth and Mineral
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ORIGINAL PAPER
Combined Effects of CaCO3 and the Proportion of N-NH4+ Among the Total Applied Inorganic N on the Growth and Mineral Uptake of Rabbiteye Blueberry Guy Tamir 1
&
Shmuel Zilkah 2 & Nir Dai 2 & Raneen Shawahna 3 & Shiran Cohen 3 & Asher Bar-Tal 3
Received: 1 May 2020 / Accepted: 7 September 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract Blueberry production is limited to acidic soils (pH < 5.5) for reasons that are not thoroughly understood. The objective of this study was to examine the effects of proportion of N-NH4+ among the total applied inorganic N {N-NH4+/(N-NH4++N-NO3¯)} (RNH4+) on rabbiteye blueberry plant growth and mineral uptake under different CaCO3 soil levels. Rabbiteye blueberry (Vaccinium virgatum Ait., cv. TitanTM) plants were grown in sandy soil mixed with four levels of applied CaCO3 [0 (control, without any added CaCO3), 1%, 5%, or 10% (w/w)] in full factorial combination with three levels of RNH4+ (33%, 66%, or 100%), which were applied through a fertigation system. Leachate pH, biomass accumulation, the concentration of chlorophyll in the leaves, and the concentrations of minerals in leaves and stems were measured. Increased rates of RNH4+ induced acidification of the leachate solution, which was diminished by the increasing rates of applied CaCO3 in the soil. Biomass production decreased linearly as the leachate pH rose above 5.5. Biomass production was positively associated with increased Mn concentrations in the leaves and with decreased Ca concentrations in the stems. The current study demonstrates that the application of high levels of RNH4+ can reduce the pH of neutral and alkaline soils with moderate level of CaCO3 below the threshold (5.5), and enables the production of rabbiteye blueberry in unsuitable soils. Keywords Biomass production . Leachate pH . Ammonium . Nitrate . Calcium concentration . Manganese concentration
1 Introduction Blueberry production has expanded rapidly in recent decades (Brazelton et al. 2019; Osorio et al. 2020) and is spreading to areas with suboptimal soils. The optimal soil conditions for blueberry growth are pH < 5.5, high organic content (Darnell and Hiss 2006; Korcak 1989), and very good drainage (Finn et al. 1993). Blueberry is a calcifuge (i.e., mainly established on silicate soils; Haynes and Swift 1985; Korcak 1988). This means that calcareous soils, which cover > 47% of Earth’s
* Guy Tamir [email protected] 1
Agricultural Research and Development, Central Mountain Region, Tekoa, Israel
2
Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
3
Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
land area (Lal 2009), are not suitable for blueberry production. CaCO3 is the soil component with the greatest capacity to buffer pH reduction; therefore, the pH levels of calcareous soils are mostly above 7.0 (Bloom et al. 2005). Haynes and Swift (1985) showed that the optimal pH for the
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