Estimating soil N mineralization is important for determining the amount of N fertilizer needed to obtain optimum yields at minimal environmental and economic costs. The aim of this work was to determine the most appropriate laboratory method for the estimation of N mineralization during a winter wheat-growing season in calcareous soils under a humid Mediterranean climate. Laboratory methods were developed involving three chemical extractants, CaCl2, KCl, and NaHCO3, and several soil-drying and extraction temperatures. Soil N indexes calculated based on extractions were compared with potentially mineralizable N (No). Moreover, soil mineralization indexes estimated from both chemical extractions and aerobic incubation were related to apparent N mineralization and wheat N uptake in a pot experiment. The mineralization index estimated from an extraction with KCl boiled at 100°C (HotKCl) was the index that best correlated with No and the apparent mineralization under greenhouse conditions. The combination of preplant soil mineral N and the HotKCl N mineralization index was more strongly correlated with wheat N uptake than soil mineral N data alone. Consequently, estimation of N mineralization using HotKCl extraction is the most appropriate methodology for establishing N fertilizer use recommendations for wheat cultivation in calcareous soils under Mediterranean conditions.
1NEIKER-Basque Institute for Agricultural Research and Development, Berreaga, Derio, Bizkaia, Spain.
2Department of Plant Biology and Ecology, University of the Basque Country, Bilbao, Spain.
3Department of Chemical and Environmental Engineering, College of Technical Mining and Civil Engineering, University of the Basque Country, Bilbao, Spain.
Address for correspondence: Dr. Ana Aizpurua, NEIKER-Basque Institute for Agricultural Research and Development, Berreaga, 1. E-48160 Derio, Bizkaia, Spain. E-mail: email@example.com
Financial Disclosures/Conflicts of Interest: This study was funded by the National Institute of Agricultural and Food Research and Technology (RTA2009-00028) and by the Department for Environment Planning, Agriculture and Fisheries of the Basque Government. The authors thank the Department of Education, Language Policy and Culture of the Basque Government that granted the first author a doctoral scholarship.
Received February 6, 2014.
Accepted for publication April 14, 2014.