Net Nitrogen Mineralisation in Maize-Cover Crop Rotations in Mediterranean Central Chile

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.

Nitrogen Fertilizer Recovery and Partitioning Related to Soybean Yield

“…1d)). Salazar et al (2020), in study with a longer incubation period, recorded that mineralization becomes positive when there are adequate conditions for decomposition, otherwise the fresh organic matter added to soil in a first time induce the immobilization. Therefore, probably a strong immobilization of N at the beginning of the development of soybean and the application of the fertilizer at increasing N rates led to more N percentage remaining in the soil in the Trop environment (Fig.…”

Microbial regulation of net N mineralisation is driven by C, N, P content and stoichiometry

“…However, the application of plant residues with mineral N largely decreased soil TP and Olsen‐P content relative to the initial value. Plant residues are known to cause nitrogen immobilisation due to the presence of more C and a higher N decomposition rate, resulting in a suppressed N content (Marzi et al, 2019; Salazar et al, 2020). Microbes store surplus C as biomass or shift microbial community to adjust soil element stoichiometry as the C:N or C:P imbalance increases, indicating N or P constraint for microorganisms (Huang et al, 2021).…”

Assessment of Mineralized Nitrogen During Maize Growth Succeeding Different Winter Cover Crops in the Mediterranean Environment

“…To assess mineralized N, under field conditions, without any profound alteration of the soil and climatic conditions, in situ evaluations are used. In situ field experiments are more labour intensive but provide more realistic estimates of soil N mineralization under environmental conditions and take into account the effects of soil architecture [6,7]. In this method, mineralized N is estimated by increasing mineral N values in soil samples, incubated under field conditions [8].…”

“…Several techniques have been proposed to quantify N mineralization and/or immobilization through in situ incubations [8,9] such as core sampling, resin-core sampling and buried bags [7]. All these techniques have the disadvantage of underestimating the total mineralized N, as they lack to consider plant presence.…”