Impact of long-term N fertilisation on CO2 evolution from old and young SOM pools measured during the maize cropping season.
Sci Total Environ
; 658: 1539-1548, 2019 Mar 25.
Article
em En
| MEDLINE
| ID: mdl-30678012
ABSTRACT
The relationship between carbon (C) inputs and nitrogen (N) fertilisation is a key element of soil organic matter (SOM) dynamics, which remains poorly resolved. In temperate climates, it is critical to investigate the interactive effect of C and N inputs on SOM stabilisation under low or high substrate availability. We measured SOM content and in situ soil respiration in a long-term field experiment in Sweden, which started in 1956. In 2000, the previous C3 crops were replaced with C4 maize, making it possible to trace old- (C3-derived) and young-C (C4-derived) sources in CO2 and SOM under bare fallow, maize cropped with or without N-fertilisation (root C-inputs). Soil respiration and its isotopic composition were measured in the field prior to sowing, every second week during crop growth and once after harvest. During 1956-1999, the bare fallow lost 38% of its SOM, following an exponential decay trend. Despite root C inputs, total SOM content under C3 crops declined from 1.5% in 1956 to 1.4% and 1.2% C in fertilised and unfertilised treatments, respectively, in 1999. After the crop change in 2000, estimated C input increased by 5% (under fertilisation), but SOM content continued to decline (as before 2000), to 1.25% (fertilised) and 1.03% (unfertilised) in 2017. Analysis of δ13C revealed that 9 and 11% of young-C was retained in unfertilised and fertilised SOM, respectively. However, up to 70% of soil respiration derived from young-C. Comparing the contributions of old- and young-C to CO2 and SOM showed that, irrespective to the time of measurement, young-C was always more available for microbial decomposition than old-C, particularly under fertilisation. We conclude that the amount of C entering the soil through root inputs was insufficient to counterbalance SOM losses over time. Moreover, soil nutrient status and recent root-C availability appear to be important for CO2 release, and must be considered in further recommendations on maintaining/improving SOM stocks.
Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Compostos Orgânicos
/
Solo
/
Carbono
/
Zea mays
/
Produção Agrícola
/
Nitrogênio
Tipo de estudo:
Guideline
País/Região como assunto:
Europa
Idioma:
En
Revista:
Sci Total Environ
Ano de publicação:
2019
Tipo de documento:
Article