Article

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: 9.81). 03/2009; 106(9):3041-6. DOI: 10.1073/pnas.0813417106
Source: PubMed

ABSTRACT 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.

5 Followers
 · 
197 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Understanding plant traits that are associated with high grain yield and high nitrogen use efficiency (NUE) is very important in breeding program to develop N-efficient varieties. However, such traits are yet to be identified in rice. We investigated this issue using rice varieties differing in response to N rates. Four japonica rice varieties, Huaidao 5 (HD-5), Lianjing 7 (LJ-7), Ninjing 1 (NJ-1) and Yangjing 4038 (YJ-4) were grown in the field, and four N rates, 0, 100, 200 and 300 kg ha−1, were applied during the growing season. Results show that both HD-5 and LJ-7 produced higher grain yield, took up higher amount of N from the soil, and exhibited higher NUE than NJ-7 or YJ-4 at lower N rates (0, 100 or 200 kg ha−1). Grain yield and NUE were comparable among the four varieties at the N rate of 300 kg ha−1. When compared with NJ-1 or YJ-4, both HD-5 and LJ-7 had greater root and shoot biomass, deeper root distribution, longer root length, greater root length density, root oxidation activity and crop growth rate, higher photosynthetic NUE, and more remobilization of nonstructural carbohydrate from stems during grain filling at lower N rates. Our results suggest that HD-5 and LJ-7 can maintain grain yield at lower N rates as N-efficient varieties. The shoot and root traits, especially the deeper roots, greater root oxidation activity and higher photosynthetic NUE at lower N rates, could be used in selection for N-efficient rice varieties.
    Field Crops Research 04/2015; 175. DOI:10.1016/j.fcr.2015.02.007 · 2.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Complex and inter-related factors explain the excessive use of fertilizer observed in many intensive farming systems in China, and hence act as barriers to development of a comprehensive policy and intervention framework for mitigation of diffuse water pollution from agriculture (DWPA). This review provides an original and contemporary synthesis of these factors that is broader, deeper and more inter-related than existing assessments. The analysis confirms that DWPA cannot be addressed by single regulatory or policy measures. There is a need to develop a mitigation framework that encompasses central policy directives, reform in governance at local level, an enabling regulatory environment, horizontal and vertical coordination in food supply chains, unbiased incentives for efficient fertilizer use and protection of water resources, enhanced agricultural, food safety and environmental education for farmers and consumers, and engagement of multiple actors beyond government.
    Agriculture Ecosystems & Environment 04/2015; 1. DOI:10.1016/j.agee.2015.02.016 · 3.20 Impact Factor
  • Source
    Agronomy journal 01/2015; 107(1):305. DOI:10.2134/agronj13.0567 · 1.54 Impact Factor

Preview

Download
11 Downloads
Available from