Elsevier

European Journal of Agronomy

Volume 45, February 2013, Pages 20-26
European Journal of Agronomy

Effects of long-term repeated mineral and organic fertilizer applications on soil organic carbon and total nitrogen in a semi-arid cropland

https://doi.org/10.1016/j.eja.2012.11.002Get rights and content

Abstract

To meet and the ever increasing need for food and mitigation of global climate changes, plenty of fertilizers have been used to increase crop yield in China, especially in semi-arid regions. In this study, we investigated the impacts of long-term fertilization on wheat yields, soil organic carbon (SOC) and soil nitrogen (N) in the semi-arid Loess Plateau, China. One fallow and eight winter wheat-wheat (Triticum aestivum L.) rotation cropping plots were selected for the field experiment from 1984 to 2010 in the semi-arid Loess Plateau, China. In total we conducted eight fertilization treatments including no fertilizer, mineral nitrogen fertilizer (N), mineral phosphate (P), cattle manure (M), N + P, N + M, P + M and N + P + M. In 2010, we collected three replicate soil samples from each plot to the depth of 100 cm from soil surface. Meanwhile, soil bulk density, SOC, total N, and mineral N (ammonium and nitrate), wheat grain and aboveground biomass yields in each plot were measured. We found that mineral fertilizers, especially those applied together with cattle manure, increased winter wheat grain and aboveground biomass yields dramatically. Moreover, wheat biomass was found to have significant correlation with SOC and soil total N in the 0–20 cm soil layer. We also found that SOC and soil N were highest in the topsoil layers (0–30 cm) than other layers and declined to the depth of 50 cm with insignificant changes from 50 to 100 cm in all treatments. Compared to the data in 1984, fertilizer application increased surface soil SOC content, especially for the N + P + M treatment after 26 years cropping and fertilization. However, changes in soil total N and mineral N differed from SOC with decreasing N in mineral-fertilized and fallow plots but increasing N in the M-fertilized plots.

Highlights

SOC, total N and crop yield were measured with long term fertilizer application. ► Fertilizer application significant increased winter wheat grain and biomass yield. ► SOC was positive correlated to crop yield. ► The SOC pool generally increased with fertilizers application. ► Total N decreased in mineral-fertilized, but increased in manure-fertilized plots.

Introduction

Since the beginning of the last century, average global temperatures have risen significantly, causing drier summers, warmer winters, and extreme precipitation events (Lal, 2004). Climate change is generally ascribed to human activities which are intensifying emissions of greenhouse gases such as CO2, CH4 and N2O, of which CO2 is having the greatest effect (Ramaswamy, 2001). Because atmospheric CO2 is connected to many carbon pools (oceanic, geological and biotic), reducing carbon (C) emission and increasing C sinks are of great importance for global warming mitigation.

Croplands cover more than 11% of the world's land area and store about 1500 GT of C, of which more than 70% is stored in the upper 100 cm of soils (Eswarran et al., 1993). Cropland soils can function as either sources or sinks for atmospheric CO2 (White et al., 2000, Follett et al., 2001, Leifeld and Fuhrer, 2009, Wang et al., 2009, Yu et al., 2012, Zhang et al., 2012) and play important roles in the global C cycle and balance. Carbon dynamics in cropland ecosystems are strongly influenced by various processes such as photosynthesis and decomposition which are affected by cultivation practices (Ganjegunte et al., 2005, Triberti et al., 2008, Zhang et al., 2012).

Several studies have demonstrated that conversion cropland to forest or grassland increases soil organic carbon (SOC) storage (Leifeld and Fuhrer, 2009, Wang et al., 2009). However, since food demand is increasing, especially in developing countries which have over 850 million food-insecure people (Borlaug, 2007), little cropland can be converted to forest or grassland. Therefore, changes in cultivation practices will play a critical role in future management of soil carbon storage.

Changes in cultivation practices also affect soil nitrogen (N), and it has been well documented that over 90% of N in most surface soil occurs in organic forms coupled with SOC (Nieder and Benbi, 2008). Soil N is often limited in semi-arid areas, and an understanding of the long-term SOC dynamics can contribute to N management in these areas (Vitousek et al., 1997, Wang et al., 2009).

Growing interest in the potential of soils to sequester atmospheric CO2 has stimulated considerable efforts to monitor changes of soil organic carbon in cropland ecosystems globally (Triberti et al., 2008, Yu et al., 2012, Wiesmeier et al., 2012). The changes of soil carbon concentration or content in winter wheat-maize cropping system under long term fertilizer applications were widely reported in China (Cai and Qin, 2006, Gong et al., 2009, Hai et al., 2010, Zhang et al., 2009). However, changes in SOC and N concentrations and storage in continuous wheat-wheat cropping land, especially in the semi-arid area of Chinese Loess Plateau, have rarely been reported in long-term studies of effects of mineral and manure fertilizers (Gao et al., 2009). Data from such studies will be important for developing strategies for sustainable cropland management in the semi-arid area. Therefore, the objective of this study was to determine the effects of long-term mineral and manure fertilizers on SOC and soil N content in continuous wheat-wheat cropping land in the Chinese Loess Plateau.

Section snippets

Study area

The field experiment was established in 1984 at the Changwu State Key Agro-ecological Experimental Station (Changwu County, Shaanxi Province, China). The site (107°40′E, 35°12′N, 1220 m a.s.l.) has typical characteristics of the Loess Plateau region, north-west China, including a semi-arid climate with warm summers and very cold winters. The 50-year mean annual temperatures is 9.1 °C and mean annual precipitation is 580 mm, about 70% falling between June and September. The driest months are May

Winter wheat grain and aboveground biomass yields

Compared with unfertilized treatment, wheat grain and aboveground biomass were markedly increased in all fertilized treatments except for the P only treatment (Fig. 1). As expected, the N + P + M treatment showed the highest wheat grain and aboveground biomass yields, increasing them by 69% and 62% relative to the CK treatment, respectively. However, the lowest wheat grain and aboveground biomass yields were observed in the P only treatment (Fig. 1).

Higher increasing of wheat grain and aboveground

Discussion

Our results clearly support the hypothesis that long-term mineral and manure fertilizers application has great positive impact on SOC and soil N content in continuous wheat-wheat cropping land in the Chinese Loess Plateau. In this study, mineral fertilizer treatments significantly increased the grain and biomass yields of winter wheat, especially in conjunction with cattle manure applications, and that both grain and biomass yields correlated with SOC and total N concentrations (Fig. 1, Fig. 3

Conclusions

The fertilizer treatments, especially cattle manure applications, significantly increased winter wheat yields (grain and aboveground biomass) and both SOC and total N contents in the examined loess plateau soil. In addition, SOC stocks were significantly correlated with crop biomass yield. Thus, cropping and fertilizer treatment could promote C sequestration in soils of the semi-arid region of north-west China, which supports a population of approximately 80 million, and contains ca. 1.3

Acknowledgements

This work was supported by the fundamental Research Funds for the Central University (GK201103003), the Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China (131025) and the Natural Science Foundation of Shaanxi (2011JQ5005).

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