Reducing Environmental Risk by Improving N Management in Intensive Chinese Agricultural Systems

Key Laboratory of Plant and Soil Interactions, Ministry of Education, China, and College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 03/2009; 106(9):3041-6. DOI: 10.1073/pnas.0813417106
Source: PubMed


Excessive N fertilization in intensive agricultural areas of China has resulted in serious environmental problems because of atmospheric, soil, and water enrichment with reactive N of agricultural origin. This study examines grain yields and N loss pathways using a synthetic approach in 2 of the most intensive double-cropping systems in China: waterlogged rice/upland wheat in the Taihu region of east China versus irrigated wheat/rainfed maize on the North China Plain. When compared with knowledge-based optimum N fertilization with 30-60% N savings, we found that current agricultural N practices with 550-600 kg of N per hectare fertilizer annually do not significantly increase crop yields but do lead to about 2 times larger N losses to the environment. The higher N loss rates and lower N retention rates indicate little utilization of residual N by the succeeding crop in rice/wheat systems in comparison with wheat/maize systems. Periodic waterlogging of upland systems caused large N losses by denitrification in the Taihu region. Calcareous soils and concentrated summer rainfall resulted in ammonia volatilization (19% for wheat and 24% for maize) and nitrate leaching being the main N loss pathways in wheat/maize systems. More than 2-fold increases in atmospheric deposition and irrigation water N reflect heavy air and water pollution and these have become important N sources to agricultural ecosystems. A better N balance can be achieved without sacrificing crop yields but significantly reducing environmental risk by adopting optimum N fertilization techniques, controlling the primary N loss pathways, and improving the performance of the agricultural Extension Service.

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Available from: Peter Christie, Jun 18, 2015
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    • "Agriculture practices are constantly contributing to this kind of contamination. Excessive fertilization in intensive agricultural areas has caused some serious environmental problems because of water and soil enrichment with NO 3 − of agricultural origin (Ju et al., 2009). Recently nitrate pollution has also been correlated with urban areas. "
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    ABSTRACT: Nitrate (NO3(-)) water pollution is one of the most prevailing and relevant ecological issues. For instance, the wide presence of this pollutant in the environment is dramatically altering the quality of superficial and underground waters. Therefore, we set up a floating bed vegetated with a terrestrial herbaceous species (Italian ryegrass) with the aim to remediate hydroponic solutions polluted with NO3(-). The floating bed allowed the plants to grow and achieve an adequate development. Ryegrass was not affected by the treatments. On the contrary, plant biomass production and total nitrogen content (N-K) increased proportionally to the amount of NO3(-) applied. Regarding to the water cleaning experiments, the vegetated floating beds permitted to remove almost completely all the NO3(-) added from the hydroponic solutions with an initial concentration of 50, 100 and 150mgL(-1). Furthermore, the calculation of the bioconcentration factor (BCF) indicated this species as successfully applicable for the remediation of solutions polluted by NO3(-). In conclusion, the results highlight that the combination of ryegrass and the floating bed system resulted to be effective in the remediation of aqueous solutions polluted by NO3(-).
    Science of The Total Environment 11/2015; 542(Pt A). DOI:10.1016/j.scitotenv.2015.10.156 · 4.10 Impact Factor
    • "Chen et al., 2006b; Cui et al., 2008; Ma et al., 2008); e.g. Ju et al. (2009) reported a huge discrepancy between farmers' current N application rate (588 kg N ha À1 ) and actually required N rate under good agricultural practice (286 kg N ha À1 ). "
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    ABSTRACT: Overuse of nitrogen (N) fertilizer constitutes the major issue of current crop production in China, exerting a substantial effect on global warming through massive emission of greenhouse gas (GHG). Despite the ongoing effort, which includes the promotion of technologically sophisticated N management schemes, farmers' N rates maintain at excessive rates. Therefore the current study tests three simple and easily to apply N fertilizer recommendation strategies, which could be implemented on large scale through the existing agricultural advisory system of China, at comparatively low cost. Building on a detailed crop production dataset of 65 winter wheat (WW) and summer maize (SM) producing farm households of the North China Plain, scenario analysis is applied. The effects of the three N strategies under constant and changing yield levels on product carbon footprint (PCF) and gross margin (GM) are determined for the production condition of every individual farm household. The N fixed rate strategy realized the highest improvement potential in PCF and GM in WW; while the N coefficient strategy performed best in SM. The analysis furthermore revealed that improved N management has a significant positive effect on PCF, but only a marginal and insignificant effect on GM. On the other side, a potential 10% yield loss would have only a marginal effect on PCF, but a detrimental effect on farmers' income. With farmers currently applying excessive N rates as "cheap insurance" against potential N limitation, it will be of vital importance to avoid any yield reductions (caused by N limitation) and respective severe financial losses, when promoting and implementing advanced fertilization strategies. To achieve this, it is furthermore recommended to increase the price of fertilizer, improve the agricultural extensions system, and recognize farmers' fertilizer related decision-making processes as key research areas. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of Environmental Management 11/2015; 163:146-154. DOI:10.1016/j.jenvman.2015.08.014 · 2.72 Impact Factor
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    • "In China, wheat is the second largest staple crop and provides more than 20% of the total grains (National Bureau of Statistics of China). In order to increase grain yield, excessive nitrogen (N) fertilizer has often been applied [3e5], which have caused a series of problems related to production costs and environment such as eutrophication of groundwater and soil acidification [6] [7]. "
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    ABSTRACT: The temporal dynamics of nematode abundance and community composition were monitored in a nitrogen (N) fertilization experiment during the main growth stages of winter wheat in Northern China Plain. A randomized complete block design was used with four levels of N fertilization (50, 100, 150 and 300 kg N ha-1 y-1 denoted as N1, N2, N3 and N4, respectively). The results showed that winter wheat aboveground biomass increased but soil pH decreased with elevating N fertilization. Total nematode abundance reached the highest values at the shooting stage of wheat, and was significantly increased by the N fertilization. On the contrary, nematode generic richness declined with increasing N fertilization. The relative abundance of bacterivores showed minor changes among different fertilization treatments whereas that of fungivores was suppressed by the N4 treatment. Plant parasites were the most abundant under the N2 treatment. The relative abundance of omnivores-predators declined with increasing N fertilization. The results indicate that trophic groups have distinctive responses to different levels of N fertilization, and N fertilization may induce an abundant but simple nematode community in the winter wheat field of North China Plain. Our findings also highlight the potential of adequate N application to reduce plant parasites and to control agriculture pests.
    European Journal of Soil Biology 11/2015; 71:13-20. DOI:10.1016/j.ejsobi.2015.09.002 · 1.72 Impact Factor
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