Net Nitrogen Mineralisation in Maize-Cover Crop Rotations in Mediterranean Central Chile
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ORIGINAL PAPER
Net Nitrogen Mineralisation in Maize-Cover Crop Rotations in Mediterranean Central Chile Osvaldo Salazar 1
&
Manuel Casanova 1 & Francisco Nájera 1 & Américo Contreras 2 & Yasna Tapia 1
Received: 22 October 2019 / Accepted: 29 January 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract The main aim of this study was to evaluate the effects of the maize-cover crop rotation (Zm-cc) in the soil net nitrogen mineralisation (NNM) by measuring in situ NNM incubation in the upper soil (0–25 cm) during spring-summer (October– March) and autumn-winter (April–September) seasons and compared with other rotation in Mediterranean Central Chile. The study was carried out at 5 experimental fields (only irrigated in spring-summer period), where four common soil use or maizebased rotations were evaluated: permanent fallow (F-F); maize-fallow (Zm-F); maize-cover crop (Zm-cc); and permanent cover crops (cc-cc). In these fields were carried out NNM in situ determinations in F-F (n = 18), Zm-F (n = 31), Zm-cc (n = 43), and cccc (n = 51) combinations (totalise n = 143), which were collected during spring-summer and autumn-winter in different periods between 2011 and 2018. During the spring-summer period, it was found that the NNM was highest in the Zm-cc rotations with a mean value of 36 kg N ha−1, whereas the lowest NNM values were in F-F soil use with and mean of 6 kg N ha−1. In contrast, during autumn-winter season, the NNM was highest in the F-F soil use with a mean of 34 kg N ha−1, while the lowest NNM values were found in Zm-cc rotation with a mean of − 38 kg N ha−1. During the spring-summer period, the Zm-cc rotation had the highest NNM values because cc increased the soil organic matter (SOM) content for microbial activity, whereas in autumnwinter, the Zm-cc rotation had the lowest NNM values because the cc added fresh SOM that increased N immobilisation process. Keywords Climate change . Nitrogen dynamics . N immobilisation . Soil temperature
1 Introduction Net nitrogen mineralisation (NNM) from soil organic matter is normally defined as an outcome of two concurrent and oppositely directional processes (gross N mineralisation and gross N immobilisation turnover), but in the field includes processes such gaseous losses, leaching, atmospheric deposition, and ammonium dynamics (fixation/release) (Luxhøi et al. 2006). Recently, Clivot et al. (2017) highlighted that improved assessment and prediction of NNM rates under field conditions are essential for a better management of N in arable cropping systems and improve fertiliser recommendations to farmers, because actual availability of inorganic N depends on the rate of NNM and its * Osvaldo Salazar [email protected] 1
Departamento de Ingeniería y Suelos, Facultad de Ciencias Agronómicas, Universidad de Chile, Casilla, 1004 Santiago, Chile
2
Escuela de Pregrado, Facultad de Ciencias Agronómicas, Universidad de Chile, Casilla, 1004 Santiago, Chile
transport through the soil. Fernández et al. (2017) noted that some of the reasons for the focus on N f
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