中国农业生态系统氮磷钾平衡时空变异研究

Nitrogen, phosphorus, and potassium balances for agroecosystems in China from 1993 to 2001 were calculated at national and provincial levels using statistical data and related parameters, and their spatial and temporal variabilities were analyzed with GIS to estimate the potential impacts of nutrient N, P and K surpluses or deficits to soil, water and air. At the national scale, the N and P balances from 1993 to 2001 showed a surplus, with the nitrogen surplus remaining relatively stable from 1997-2001. Although during this period the P surplus pattern was similar to N, it had smaller values and kept increasing as the use of phosphate fertilizer increased year by year. However, K was deficient from 1993 to 2001 even though from 1999 to 2001 the K deficit decreased. The spatial analysis revealed higher N surpluses in the more developed southeastern provinces and lowest in the western and northern provinces where there was less chemical fertilizer input. The serious K deficit mainly occurred in Shanghai and Beijing municipalities, Jiangsu, Zhejiang and Hubei provinces, and Xinjiang autonomous regions. For the years 1992, 1996 and 2001, N surpluses and K deficits had significant positive spatial correlations with per capita gross domestic product (GDP), per capita gross industrial output value, and per capita net income of rural households. This showed that the level of economic development played an important role on nutrient balances in the agroecosystems.     

中国坡耕地分布特征与退耕还林草政策影响分析

The Grain-for-Green Policy in China could not only improve China's ecological quality, but also influence grain supplies for a short term. Based on data from the detailed nationwide land use survey in 1996 and the steep cultivated land survey update in 2000, a regression model for the driving forces affecting steep cultivated lands was developed, and cluster analysis was used to identify seven steep cultivated land types in order to analyze the grain availability impact of the project with land usage estimates for 2010 and 2030. The results suggested that consecutive days with minimum daily temperature over 10 ℃ and the dominant slope in a county constrained the spatial distribution of steep cultivated lands. In terms of socioeconomic factors, steep cultivated land was a complex interaction of population size, gross domestic production level, and the richness and quality of cultivated lands having slopes less than 15°. The trends for steep cultivated land in 2010 and 2030 were forecast using a driving forces model and China's grain security criteria and showed that the Grain-for-Green Policy at the national level would not cause a grain shortage or threaten food security criteria. However, if steep sloped lands were to be retired from production, some regions would need grain supplements as early as 2010. Also, assuming that only 60% of the cultivated land at the national level was needed, population and economic development pressures in 2030 would require some steep cultivated lands to be used for grain production.     

中国南方大棚蔬菜地氮平衡与损失

High rates of fertilizer nitrogen (N) are applied in greenhouse vegetable fields in southeastern China to maximize production;however,the N budgets of such intensive vegetable production remain to be explored.The goal of this study was to determine the annual N balance and loss in a greenhouse vegetable system of annual rotation of tomato,cucumber,and celery at five N (urea) application rates (0,348,522,696,and 870 kg N ha-1 year-1).Total N input to the 0-50 cm soil layer ranged from 531 to 1 053 kg ha-1,and N fertilizer was the main N source,accounting for 66%-83% of the total annual N input.In comparison,irrigation water,wet deposition,and seeds in total accounted for less than 1% of the total N input.The fertilizer N use efficiency was only 18% under the conventional application rate of 870 kg N ha-1 and decreased as the application rate increased from 522 to 870 kg N ha-1.Apparent N losses were 196-201 kg N ha-1,of which 71%-86% was lost by leaching at the application rates of 522-870 kg N ha-1.Thus,leaching was the primary N loss pathway at high N application rates and the amount of N leached was proportional to the N applied during the cucumber season.Moreover,dissolved organic N accounted for 10% of the leached N,whereas NH3 volatilization only contributed 0.1%-0.6% of the apparent N losses under the five N application rates in this greenhouse vegetable system.     

太湖地区水稻最适宜施氮量研究

To determine the optimal amount of nitrogen(N) fertilizer for achieving a sustainable rice production at the Taihu Lake region of China,two-year on-farm field experiments were performed at four sites using various N application rates.The results showed that 22%-30% of the applied N was recovered in crop and 7%-31% in soils at the rates of 100-350 kg N ha 1.Nitrogen losses increased with N application rates,from 44% of the applied fertilizer N at the rate of 100 kg N ha 1 to 69% of the N applied at 350 kg N ha 1.Ammonia volatilization and apparent denitrification were the main pathways of N losses.The N application rate of 300 kg N ha 1,which is commonly used by local farmers in the study region,was found to lead to a significant reduction in economic and environmental efficiency.Considering the cost for mitigating environmental pollution and the maximum net economic income,an application rate of 100-150 kg N ha 1 would be recommended.This recommended N application rate could greatly reduce N loss from 199 kg N ha 1 occurring at the N application rate of 300 kg N ha 1 to 80-110 kg N ha 1,with the rice grain yield still reaching 7 300-8 300 kg DW ha 1 in the meantime.     

氮施用水平和方式对高粱作物产量和质量的影响

A field study was conducted for two years at the Arid Zone Research Institute, Dera Ismail Khan, Pakistan, to determine the optimum level of nitrogen and efficient application method in the production of sorghum （Sorghum bicolor L.）. Using four levels of nitrogen, i.e., 0, 60, 90, and 120 kg ha^-1, and two different application methods （soil application and foliar spray）, the experiment was laid out in a split-plot design, where the main plots were used to determine the effective method of application and the subplots were used to detect the influence of N levels on the grain yield. The average data obtained after two years of study indicated an increase in the grain yields with an increase in N levels irrespective of the method used of N application. The grain yield increased from 2.92 to 5.61 t ha^-1 in the plots that were treated with 90 kg N ha^-1 compared with the control plots. Quadratic regression analysis showed that the increase in the yield was higher at the lower levels of N compared with the succeeding higher levels. The soil application method, producing an average grain yield of 4.79 t ha^-1, was found to be superior to the foliar spray method with an average grain yield of 4.56 t ha^-1. The protein content of the grain showed a linear increase with N application, attaining the maximum at 120 kg N ha^-1 in both the methods of N application. In addition, compared with the method of soil application, higher crude protein contents were observed using the method of foliar spray at all N levels.     

不同的水稻品种产量及生理氮素利用效率的差异

Efficient use of N in agricultural practice can increase yield, decrease production costs and reduce the risk of environmental pollution. Effects of N fertilizer application rates on grain yield and physiological N use efficiency (PE) in relation to the accumulation and redistribution of biomass and N in rice (Oryza sativa L.) cultivars were studied at two experimental farms of Nanjing Agricultural University, Nanjing, China in 2004. Three high N use efficiency (NUE) rice cultivars (Wuyunjing 7, Nanguang and 4007) and one low NUE rice cultivar (Elio) with similar growth patterns were studied under seven N rates (0, 60, 120, 180, 240, 300 and 360 kg ha^-1). Grain yield increased with the N application rate and attained plateau at 180 kg N ha^-1 for rice cultivars at each site. Increasing N rate decreased PE for biomass and grain yield. Grain yield and PE of Elio were about 20% and 18% lower than those of high NUE cultivars. Differences in biomass, N accumulation and N redistribution were observed at the post-heading stage among rice cultivars with differing NUEs. The less reproductive tillers of Elio resulted in less demand for C and N during grain filling, thus leading to lower PE of Elio compared with the high NUE rice cultivars.     

中国水稻不同产量、品种和种植制度下氮需求量变异状况

Better understanding of the factors that influence crop nitrogen(N) requirement plays an important role in improving regional N recommendations for rice(Oryza sativa L.) production. We collected data from 1 280 plot-level measurements in different reaches of the Yangtze River, China to determine which factors contributed to variability in N requirement in rice. Yield, variety, and cropping system were significantly related to N requirement. The N requirement remained consistent at about 18.6 kg N Mg~(-1)grain as grain yield increased from 7 to 9 Mg ha~(-1), then decreased to 18.1, 16.9, and 15.9 kg N Mg~(-1)grain as yield increased to 9–10, 10–11, and 11 Mg ha~(-1), respectively. The decreased requirement for N with increasing yield was attributable to declining N concentrations in grain and straw and increased harvest index. Super rice variety had lower N requirement(17.7 kg N Mg~(-1)grain) than ordinary inbred and hybrid varieties(18.5 and 18.3 kg N Mg~(-1)grain, respectively), which was a result of lower grain and straw N concentrations of super rice. The N requirements were 19.2, 17.8, and 17.5 kg N Mg~(-1)grain for early, middle, and late rice cropping systems, respectively. In conclusion, the rice N requirement was affected by multiple factors, including yield, variety, and cropping system, all of which should be considered when planning for optimal N management.     

Application of controlled-release urea increases maize N uptake, environmental benefits and economic returns via optimizing temporal and spatial distributions of soil mineral N

The creation of controlled-release urea (CRU) is a potent substitute for conventional fertilizers in order to preserve the availability of nitrogen (N) in soil, prevent environmental pollution, and move toward green agriculture. The main objectives of this study were to assess the impacts of CRU''s full application on maize production and to clarify the connection between the nutrient release pattern of CRU and maize nutrient uptake. In order to learn more about the effects of CRU application on maize yields, N uptake, mineral N (N_min) dynamics, N balance in soil-crop systems, and economic returns, a series of field experiments were carried out in 2018–2020 in Dalian City, Liaoning Province, China. There were 4 different treatments in the experiments: no N fertilizer input (control, CK); application of common urea at 210 kg ha^-1 (U), the ideal fertilization management level for the study site; application of polyurethane-coated urea at the same N input rate as U (PCU); and application of PCU at a 20% reduction in N input rate (0.8PCU). Our findings showed that using CRU (i.e., PCU and 0.8PCU) may considerably increase maize N absorption, maintain maize yields, and increase N use efficiency (NUE) compared to U. The grain yield showed considerable positive correlations with total N uptake in leaf in U and 0.8PCU, but negative correlations with that in PCU, indicating that PCU caused excessive maize absorption while 0.8PCU could achieve a better yield response to N supply. Besides, PCU was able to maintain N fertilizer in the soil profile 0–20 cm away from the fertilization point, and higher N_min content was observed in the 0–20 cm soil layer at various growth stages, particularly at the middle and late growing stages, optimizing the temporal and spatial distributions of N_min. Additionally, compared to that in U, the apparent N loss rate in PCU was reduced by 36.2%, and applying CRU (PCU and 0.8PCU) increased net profit by 8.5% to 15.2% with less labor and fertilization frequency. It was concluded that using CRU could be an effective N fertilizer management strategy to sustain maize production, improve NUE, and increase economic returns while minimizing environmental risks.     

华北平原夏玉米临界氮稀释曲线的验证

The concept of critical N concentration （Nc） has been widely used in agronomy as the basis for diagnosis of crop N status, and allows discrimination between field situations of sub-optimal and supra-optimal N supply. A critical N dilution curve of Nc= 34.0W-0.37, where W is the aboveground biomass （Mg DM ha-1） and Nc the critical N concentration in aboveground dry matter （g kg-1 DM）, was developed for spring maize in Europe. Our objectives were to validate whether this European critical N dilution curve was appropriate for summer maize production in the North China Plain （NCP） and to develop a critical N dilution curve especially for summer maize production in this region. In total 231 data points from 16 experiments were used to test the European critical N dilution curve. These observations showed that the European critical N dilution curve was unsuitable for summer maize in the NCP, especially at the early growth stage. From the data obtained, a critical N dilution curve for summer maize in the NCP was described by the equation of Nc = 27.2W-0.27, when aboveground biomass was between 0.64 and 11.17 Mg DM ha-1. Based on this curve, more than 90% of the data for the N deficiency supply treatments had an N nutrition index （NNI） 〈 1 and 92% of the data for the N excess supply treatments had an NNI 〉 1.     

Simulating soil erodibility in southeastern China using a sequential Gaussian algorithm

Soil erodibility(K) is a key factor of soil erosion, and its appropriate quantification and interpolation are vitally important for soil and water conservation.The traditional point-represent-polygon approaches and common kriging method for the estimation of K, however, do not sufficiently represent the original data. The objectives of this study were to simulate the spatial distribution of K using a sequential Gaussian algorithm and analyze the uncertainty in evaluating the risk of soil erodibility in southeastern China. We determined 101 sampling points in the area and collected disturbed soil samples from the 0–20 cm layer at each point. Soil properties were determined, and K was calculated using five common models: the EPIC(Erosion/Productivity Impact Calculator),approximate nomograph, Torri, Shirazi, and Wang models. Among the chosen models, the EPIC model performed the best at estimating K(KEPIC), which ranged from 0.019 to 0.060 t ha h(ha MJ mm)~(-1), with a mean of 0.043 t ha h(ha MJ mm)~(-1). The KEPICwas moderately spatially variable and had a limited spatial structure, increasing from south to north in our study area, and all spatial simulations using the cooperative kriging(CK) interpolation and the sequential Gaussian simulation(SGS) with 10, 25, 50, 100, 200, and 500 realizations had acceptable accuracies. The CK interpolation narrowed the range,and the SGS maintained the original characteristics of the calculated data. The proportions of the risk area were 38.0% and 10.1%, when the risk probability for K was 60% and 80%, respectively, and high risk areas were mostly located in the north. The results provide scientific guidance for managing the risk of soil erodibility in southeastern China.     

中国区域粮食生产优势度的演变及分析

该文采用地区粮食优势度指数，实证了1994至2005年间中国粮食生产区域格局的演变情况。结果显示，近10年来中国粮食优势省区有集中的趋势，经济最为发达的北京、上海、天津和浙江等省（市）的粮食生产优势度下降最为严重，辽宁和吉林两省上升最大；东部地区的粮食生产优势正在逐步减弱，粮食生产重心正向中部和东北地区转移。粮食生产优势的区域变动可以从种粮收益、经营规模、农业劳动力机会成本等方面进行解释，东部地区虽然粮食收益较高，但是较小的规模、较高的劳力成本、以及经济作物的相对高收益都对粮食生产产生了负面影响。由此可见，东部地区粮食生产的逐步退出是历史必然。     

中国耕地生态保护补偿的省级差序分区及补偿标准

耕地生态保护补偿概念的引入为中国耕地保护提供了全新视角，然而国家层面尚未形成系统的制度架构与方法。科学划定补偿分区、量化补偿标准是这一制度设计的关键。该研究以省域为研究单元，辨析耕地生态承载力的空间转移与生态公平的理论关系，依据耕地生态承载力盈亏和耕地保有量目标是否完成构建"四象限"差序分区，运用机会成本法测算补偿标准，并进一步优化支付/获偿总额。结果表明：1）2019年中国耕地生态承载力呈"北盈南亏"、耕地保有量呈"西盈东亏"的空间分异；2）补偿差序分区呈东北-西南方向"条带状穿插"的空间形态：全额获偿区以耕地大省为主（8个省级行政区），减额获偿区主要位于中部平原和丘陵区（6个省级行政区）；全额支付区大多地处东部沿海发达地区（5个省级行政区），减额支付区集中在黄土高原、四川盆地、青藏高原（12个省级行政区）；3）从全额支付区到全额获偿区，补偿标准均值呈"阶梯式"递减，中国耕地生态保护补偿标准为6.13万元/hm2；4）经计算，黑龙江省获偿最多为1 683亿元，浙江省支付最多为2 151亿元。引入洛伦兹曲线验证，得到耕地生态保护补偿使省域间财政收入差距缩小了0.06。因此，该研究提出了耕地生态保护补偿差序分区和标准量化方法，为提高耕地保护主体动力、建立国家耕地生态保护补偿制度提供了科学参考。     

Soil nitrogen balance and nitrogen utilization of winter wheat affected by straw management and nitrogen application in the Yangtze river basin of China

Straw incorporation is a useful management practice in sustainable agricultural systems to improve soil fertility and to reduce air pollution from straw burning. A three-year field experiment was conducted under two rice straw managements and four nitrogen (N) application rates in Rugao, China during 2010–2013, to examine whether straw management practices integrated with fertilizer N applications affect crop yield, N balance and N use efficiency in the wheat season of rice-wheat cropping systems. The results showed that straw incorporation had positive effects on plant N uptake and grain yield. This may be attributed to the greater soil water content and lower amount of seasonal rainfall. However, straw incorporation resulted in lower soil inorganic N and more N surplus at the early growth stage. Grain yield had a significant relation with wheat N uptake from sowing to jointing and from jointing to anthesis with straw incorporation. Therefore, our results suggest that in adjusting the ratio of basal and topdressing N fertilizer, it is important for the supply of optimum N to the crop and to maintain grain production with straw incorporation.     

中国农田生态系统氮素平衡模型的建立及其应用

借助物质流分析中"输入=输出+盈余"的物质守恒原理,以氮素养分为介质建立中国农田生态系统氮素平衡模型,然后用2004年中国农业统计资料和文献查询获取的参数,估算中国不同地区的氮养分输入输出以及养分盈余并分析养分产生的环境效应。模型计算结果表明,2004年农田生态系统通过挥发、反硝化、植株蒸腾、淋溶径流和侵蚀等途径损失的氮为1132.8万t,盈余在农田生态系统土壤中的氮为1301.2万t;通过损失途径进入环境中的氮养分和盈余在农田生态系统中的单位面积耕地氮养分负荷高风险地区均集中在中国的东南沿海和部分中部地区。优化化学氮肥用量,有机氮肥与化学氮肥配合施用是降低农田生态系统氮养分污染潜势的最基本措施,针对中国不同地区因地制宜地制定合理种植结构和推广农田精准化施肥也是十分必要的。     

白洋淀流域种植结构及氮盈余的时空变化特征

针对种植业氮素过量投入造成的流域农业面源污染问题,该研究以白洋淀流域核心区域粮食作物和经济作物为研究对象,以粮经比为种植结构评价指标,从氮素平衡角度考虑,探究白洋淀流域种植结构变化对区域水环境的影响。研究结果显示：1)白洋淀流域种植结构时空变化明显,时间上,研究期内白洋淀流域粮经比总体呈小幅度上升趋势(4.47～5.72);空间上,距白洋淀淀区距离越大,区域内粮经比越小,临白洋淀区粮经比(15.11～19.23)明显高于白洋淀上游粮经比(2.44～2.64);2)白洋淀流域种植业氮盈余量时空分异特征明显,时间上,研究期内白洋淀流域种植业氮盈余量总体呈下降趋势((26.29～18.49)×10⁴ t);空间上,各区域种植业氮盈余量表现为：白洋淀中游((10.39～14.48)×10⁴ t)、白洋淀下游((4.35～7.09)×10⁴ t)、临白洋淀((2.24～2.64)×10⁴ t)、白洋淀上游((1.51～2.58)×10⁴ t);3)白洋淀流域种植业氮盈余强度与粮经比呈显著...