Who Will Feed China in the 21st Century? Income Growth and Food Demand and Supply in China

This study uses resource‐based measures to explore the evolution of China's demand and supply for food. China's dietary shift from plant to animal‐based foods, induced by its income growth, is likely to impose considerable pressure on agricultural resources. China's demand for food on this measure appears consistent with global trends, while China is an out‐performer on the supply side, producing much more food than its income level and land endowment would predict. China's current per capita income is in a range where consumption growth is high and in excess of production growth, but the gap between supply and demand is likely to diminish as population and per capita consumption growth decelerate. Continuing agricultural productivity growth and sustainable resource management will be important influences on the growth of China's future net import demand for food.     

Modeling skewness with the linear stochastic plateau model to determine optimal nitrogen rates

Accurate modeling of skewness is needed to increase the actuarial fairness of crop insurance. We test Day's conjecture that crop yield skewness becomes negative as nitrogen rates increase and determine how well a linear response stochastic plateau (LRSP) production function matches the pattern of observed skewness using four long‐term nitrogen experiments. Stillwater wheat is consistent with Day's conjecture, but the skewness for Lahoma and Altus wheat yields as well as Altus cotton yields are not. The LRSP assumes normal random effects and can explain only a small part of observed skewness, so a new LRSP with skew‐normal random effects is introduced, which comes closer to explaining the observed skewness and should increase the accuracy of nitrogen rate recommendations. Negative skewness reduced optimal nitrogen rates and positive skewness increased optimal nitrogen rates.     

Towards the implementation of the European Water Framework Directive?: Lessons learned from water quality simulations in an agricultural watershed

The main objective of the European Water Framework Directive (WFD) is the achievement of a good ecological and chemical status of the water environment (water bodies). This status corresponds to the limit value of Germany's Working Group of the Federal States on Water Problems Issues (LAWA) for water quality class II (3 mg/l total nitrogen). The rivers in the intensively cropped Upper Ems River basin (northwestern Germany) show total nitrogen concentrations in excess of 5–10 mg/l. Hence, the objective of our study was to find a land use and land management scenario that would reduce the total nitrogen concentration to meet the WFD requirements for good ecological and chemical status. We developed consecutive land use and management scenarios on the basis of policy instruments such as the support of agro-environmental measures by Common Agricultural Policy and regional landscape development programs. The model simulations were done by using the Soil and Water Assessment Tool (SWAT). Results of SWAT scenario calculations showed that drastic measures, which are unrealistic from a socio-economic point of view, would be needed to achieve the water quality target in the basin (reduction of arable land from 77.2% to 46% [13% organic farming], increase of pasture from 4% to 15%, afforestation from 10% to 21%, increase of protected wetlands from 0% to 9%, etc.). The example shows additionally that the achievement of the WFD targets is only possible with a consideration of regional landscape and land use distinctions. A related problem yet to be addressed is the general lack of measured water quality data with which to calibrate and validate water quality models such as SWAT. This adds considerable uncertainty to already complicated and uncertainty situations. Thus, improved strategies for water quality monitoring, and data accessibility must be established.     

A Note on the Profitability of Wheat-ethanol-feedlot Production in Alberta

A risk analysis of the economics of alternative wheat supplies to a small ethanol-beef feedlot facility was conducted, based on historical data from an 18-year period (1978–96). Alternatives simulated were Black, Dark Brown and Brown soil zone locations in Alberta growing either Hard Red Spring (HRS) wheat, Canadian Prairie Spring (CPS) wheat or irrigated Soft White (SWW) wheat to supply a 10 ML per year ethanol plant. The plant would use the coproduct of wet distillers grains in the finishing of approximately 14,000 steer calves per year. Three valuation scenarios were considered: selling ethanol at its market price, inclusion of current Alberta tax incentive levels for ethanol sale, and sale of wheat to the Canadian Wheat Board as opposed to sale to an ethanol plant. Ethanol facility and total net revenues were highest for the CPS-Dark Brown soil scenario due to its relatively high ethanol yields per tonne of feedstock, and high grain yields per hectare. An integrated feedstock-ethanol-livestock operation selling ethanol at current subsidy (tax incentives) levels will lose money approximately half to two-thirds of the time over the long run. Without subsidies, an integrated facility would lose money two-thirds to three-quarters of the time. Nous avons réalisé, à partir de données recueillies durant une période de 18 ans (1978 à 1996), une analyse de risque des aspects économiques de diverses provenances de blé pour une petite exploitation éthanol-parc d'engraissement. Les options simulées consistaient en emplacements situés dans les zones de sols noirs, brunfoncé et bruns de I'Alberta, produisant soil du blé roux vitreux deprintemps (BRVP), du blé de printemps des Prairies canadiennes (BPPC) ou du blé blanc tendre (BBT) sous irrigation pour alimenter un atelier d'éthanol d'un volume de fabrication de 10 millions de litres par année. L'atelier hypothétique utiliserait le co-produit des drêches de distillerie humides pour engraisser quelque 14 OOOjeunes bouvillons par année. Trois scénarios de valorisation étaient envisagés: vente de I'éthanol au prix de marché, inclusion des incitatifs fiscaux actuels de I'Alberta pour la vente de I'éthanol et vente du bléà la Commission canadienne du blé par opposition à la vente à un atelier de production d'éthanol. Les revenus nets tirés de I'atelieret les revenus nets totaux les plus élevés de l'exploitation étaient obtenus dans le scénario BPPC-sol brunfoncé en raison des rendements d'éthanol relativement élevés par tonne de blé et des bons rendements grainiers par hectare obtenus dans cette combinaison. Selon les résultats obtenus, un atelier intégré blé-éthanol-parc d'engraissement écoulant son éthanol au niveau de subvention actuel (incitatifs fiscaux), perdrait de I'argen d'environ la moitié aux deux tiers du temps. Sans ces subventions, il ne rentrerait dans ses dépenses qu'unefois sur trois ou unefois sur quatre seulement.     

The Current State of the Russian Agricultural Sector

Russia's agriculture produces around 3.7 per cent of the country's GDP, employs 9.2 per cent of the national workforce and contributes around 6 per cent of the country's exports. The sector has shown remarkable resilience in the face of wider economic turbulence. Self‐sufficiency rates for the main agricultural commodities are relatively high. Agricultural exports have grown very significantly since 2000 especially for wheat and meslin (wheat and rye mixture). Meat production has been growing steadily, particularly in the poultry and pork sectors. Whilst the agri‐food sector has great potential to play an even more prominent role in Russia's economy, it suffers from relatively low productivity and an outdated technological base. The main drive for efficiency has come mainly from the relatively large‐scale agricultural firms, who generated more than half of the total value of agricultural output in 2016. Foreign policy instability, including economic sanctions, the devaluation of the national currency and declining economic growth have weakened the sector and caused an increase in the prices of imported goods and equipment. At the same time Russian products have replaced high value‐added imports and Russia's agricultural producers are expanding into new markets.     

Hedonic Price Functions for Wheat in the World Market: Implications for Canadian Wheat Export Strategy

This study derives econometric estimates of the marginal implicit values of major characteristics of wheat in world markets for two recent time periods using pooled time-series and cross-sectional data. The results indicate that a one percentage point increase in protein content was associated with an average 0.3% price premium from 1976–77 to 1979–80. This price response had increased to an average 0.5% premium from 1980–81 to 1983–84, when there was an average world market protein premium of about U.S. $6.00 for a one percentage point increase in protein per tonne of wheat. During the latter time period, there was a premium for white wheat of nearly U.S. $16 per tonne. Wheat exported from the United States and Canada appeared to be discounted in price relative to wheat from Australia. Given the general order of the inverse relationship between yield and protein content that applies in wheat breeding, it is apparent that total revenue from Canadian wheat exports could be considerably increased by more emphasis on the development of higher-yielding wheats that are adapted to the higher-moisture regions of the Prairies. More emphasis on development of white wheats that are suited to Prairie growing conditions is also merited. La présente étude vise à obtenir des estimations économétriques à partir de valeurs marginales implicites des caractéristiques principales du blé sur les marchés mondiaux pour deux périodes de temps récentes, à l'aide de séries chronologiques regroupées et de données transversales. Les résultats obtenus montrent qu'une augmentation de un pour cent de la teneur en protéines correspond en moyenne à une bonification de 0,3% de 1976–1977 à 1979–1980. Cette réaction des prix a atteint en moyenne 0,5% de 1980–1981 a 1983–1984, alors qu'une augmentation de un pour cent de la teneur en protéines par tonne de blé donnait lieu à une bonification moyenne, sur les marchés mondiaux, d'environ 6 $ US. Pendant la dernière période, le blé blanc faisait l'objet d'une bonification de près de 16 $ US par tonne. Le blé exporté des États-Unis et du Canada semble avoir été vendu à rabais, comparativement au blé venant d'Australie. Compte tenu du rapport inverse généralement observé entre le rendement et la teneur en protéines dans un contexte de sélection végétale, il semble que le total des revenus tirés des exportations canadiennes de blé pourrait s'accroître considérablement si l'on mettait davantage l'accent sur la production de variétés à rendement plus élevé, adaptées aux régions à haut taux d'humidité des Prairies. II serait également justifié de consacrer davantage d'énergie à la production de blés blancs mieux adaptés aux conditions de croissance des Prairies.     

The Market Structure and Price Competition in China's Wheat Import Market:

This paper reveals that wheat exporters to China compete in an imperfectly competitive market. U.S. wheat exports face strong price competition from Argentina, Australia, Canada, and the European Community, but has a highly elastic demand in China. By adopting an aggressive promotion policy, the U.S. could reduce the market shares of Argentina and Canada. China would shift to wheat from Argentina, Australia, and Canada if U.S. wheat exports were interrupted because of high prices or non-price trade frictions. An expansion in China's wheat imports would accrue to wheat from Argentina and the U.S.     

Impact of farm management diversity on the environmental and economic performance of the wheat–maize cropping system in the North China Plain

To assess the attainable greenhouse gas (GHG) mitigation potential from crop production in China's most important grain production region, the North China Plain (NCP), single farm environmental and economic performances of 65 winter wheat–summer maize (WW–SM) producing households were determined. The results revealed a huge heterogeneity among farms, with up to five times higher environmental impact of worst compared to best performing farms. Astonishingly no trade-off between productivity and sustainability could be identified in the region, with high-yield farms emitting no different amounts of GHGs per hectare compared to low-yield farms. Building on cluster analysis, with farms grouped according to their economic and environmental performance into ‘poor’, ‘fair' and ‘good’ producers, the regional GHG mitigation potential was estimated. Under the scenario assumption that all grain in the NCP is produced under ‘good’ production conditions, 21% and 7% of GHG could be mitigated in wheat and maize production, respectively. The study shows that in the NCP, exemplary for China's rapidly developing agricultural sector, the crop management skills of a substantial share of farmers could obviously not keep pace with the massive input intensification. Among others, farmer–farmer trainings are recommended to close the gap in crop production performance among producers.     

Impact of the US–EC price war on major wheat exporters' shares of the Chinese market

China is both the world's largest producer and consumer of wheat. In an attempt to gain a larger slice of the important Chinese market, both the European Community and the United States have offered China subsidised wheat. In addition, other exporters have offered attractive credit arrangements to China. The objective of this paper is to measure the overall impact of these policies on each exporter's share of the Chinese market. To that end, an improved version of the constant market shares model is applied to data on Chinese wheat imports in the 1980's. The results indicate that the United States has been outperforming the other exporters since subsidised US wheat sales were authorised for China in 1987. The implications of the analysis for the smaller exporters and international wheat trade are discussed.     

Optimal Protein Segregation Strategies for Wheat Growers

A technology that can measure wheat grain protein concentration and then segregate grain based on measurements during harvesting is on the horizon. This new technology provides wheat growers with opportunities to segregate grain that can be directed to premium markets. In this article, we identify an individual grower's optimal segregation and blending strategies under non‐uniformly curved price schedules. When price schedules are three‐step shaped, we show that the optimal segregation and blending strategies can be obtained by solving a specified non‐linear programming problem. Based on cash price and protein distribution data for wheat in the U.S. Pacific Northwest region over 1991–2011, an application of our theoretical model shows that on average a Hard Red Winter (respectively, Hard Red Spring) wheat grower should be willing to pay about 17.7 (respectively, 30.8) cents for segregating one bushel of wheat. We also study how growers’ net returns would be affected were the technology to be adopted.     

Designing a forest-energy policy to reduce forest fires in Galicia (Spain): A contingent valuation application

Recent issues of this journal have presented an interesting debate regarding forest fires in Galicia, Spain. This article proposes a forest-energy programme that will contribute to reducing the risk of forest fires in this Atlantic Region of Southern Europe. We apply the contingent valuation method to assess a programme whereby 10% of the electricity produced from coal, fuel oil and gas would be replaced by electricity generated in biomass power plants. The programme would begin implementation in 2005 and it would take 6 years (up to 2010) before we reach the 10% goal. The results show that Galician households are willing to pay a mean of 38 Euros per year. In addition, we have introduced an innovative procedure to detect protest responses related to the payment vehicle in a contingent valuation. Heckman's sample-selection procedure is used to analyse the WTP function.     

水资源安全视角下我国粮油虚拟水贸易实证研究

[目的]通过测算我国粮油虚拟水进出口量,估算粮油虚拟水贸易对农业用水的贡献率,以期为我国实施农产品虚拟水贸易战略缓解农业用水短缺问题提供有益借鉴。[方法]文章利用标准彭曼公式估算2001—2017年我国粮油单位质量虚拟水含量,进而计算出2001—2017年我国粮油虚拟水进出口量,进一步计算我国粮油虚拟水贸易对农业用水的贡献率。[结果](1)我国粮油单位质量虚拟水平均含量由高到低依次为棉籽、大豆、油菜籽、花生、大米、小麦和玉米;(2) 2001—2017年我国粮油虚拟水贸易一直处于净进口状态,并且净进口量整体呈增长趋势,2001—2017年我国粮油虚拟水净进口量累计达2.216万亿m3,相当于节约了同等数量粮油生产用水量;(3)我国油料虚拟水净进口量远远高于粮食虚拟水净进口量,大豆和油菜籽是虚拟水净进口最多的油料,并且其进口市场集中度很高;(4) 2001—2017年我国粮油虚拟水贸易对农业用水的贡献率不断提高,由8%增至40%。[结论]虚拟水贸易大大节约了我国农业用水量,在一定程度上缓解了我国农业用水短缺问题,为我国节约水资源和实施水资源可持续发展战略提供了新的发展思路。     

The genetic and economic impact of the CIMMYT wheat breeding program on local producers in the Yaqui Valley,Sonora Mexico

This article quantifies the productivity gain from CIMMYT‐released semidwarf bread wheat (Triticum aestivum) cultivars over time, using test plot data from Mexico's Yaqui Valley. Previous studies have shown a deceleration in irrigated wheat yield growth since the 1980s, which could be due to slowing increase in genetic potential. Our results suggest that CIMMYT cultivars contributed a 0.46% annual increase (about 38 kg/ha annually) to wheat yields in the Yaqui Valley, which raised local wheat producers’ revenue by an average of $4 million annually for the period 1990 to 2002, and by approximately $9 million in 2002.     

Economywide effects of climate‐smart agriculture in Ethiopia

Climate‐smart agriculture (CSA) is an approach for transforming and reorienting agricultural systems to support food security under climate change. Few studies, however, quantify at the national scale CSA's economic effects or compare CSA to input‐intensive technologies, like fertilizer or irrigation. Such quantification may help with priority setting among competing agricultural investment options. Our study uses an integrated biophysical and economic modeling approach to quantify and contrast the economywide effects of CSA (integrated soil fertility management in our study) and input‐intensive technologies in Ethiopia's cereal systems. We simulate impacts for 20‐year sequences of variable weather, with and without climate change. Results indicate that adopting CSA on 25% of Ethiopia's maize and wheat land increases annual gross domestic product (GDP) by an average 0.18% (US$49.8 million) and reduces the national poverty rate by 0.15 percentage points (112,100 people). CSA is more effective than doubling fertilizer use on the same area, which increases GDP by US$33.0 million and assists 75,300 people out of poverty. CSA and fertilizer have some substitutability, but CSA and irrigation appear complementary. Although not a panacea for food security concerns, greater adoption of CSA in Ethiopia could deliver economic gains but would need substantial tailoring to farmer‐specific contexts.     

Price Discrimination in Russian Wheat Exports: Evidence from Firm‐level Data

Russia emerged as an important wheat exporter in recent years raising the question of how this will affect international wheat markets. In particular developing countries – the main destination of Russian wheat exports – could be harmed by aggressive pricing behaviour. This article analyses the exertion of price discrimination by Russian wheat exporting firms based on Krugman's pricing‐to‐market hypothesis. We apply Knetter's panel model to a firm‐level dataset and find evidence for price‐discriminating behaviour by Russian firms in 25 out of 61 destination countries over the period 2002–2011.     

龙头企业、专利投入与农业产业高质量发展研究

[目的]中共十九大报告提出实施乡村振兴战略,对中国粮食产业高质量发展和农业供给侧结构性改革有了进一步要求。小麦作为中国主要粮食作物之一,小麦产业是中国农业产业的代表性产业之一,其发展对中国粮食安全具有重要意义。以小麦产业为例,探究农业科技创新中龙头企业、专利投入与中国小麦产业发展的关系。[方法]文章基于2015—2018年的短面板数据,利用耦合协调度模型测算中国31省(市、自治区)的小麦产质量耦合协调度,解析中国小麦产业耦合协调发展的实际情况,并运用工具变量Tobit方法实证分析中国小麦产质量耦合协调度的影响因素。[结果]中国小麦产质量耦合协调度总体偏低。龙头企业数量、农业基础设施对小麦产质量耦合协调度产生显著的正向影响,地区小麦专利数量在龙头企业对小麦产业的影响中具有正向调节作用。[结论](1)中国小麦产质量耦合协调度总体上还处于较低水平;(2)在小麦产质量耦合协调度回归模型中,粮食播种面积是一个有效的工具变量,它在很大程度上决定了龙头企业选址;(3)小麦专利数量对小麦产质量耦合协调具有直接促进作用,但是这种作用不显著;(4)地区小麦专利的调节效应增强了龙头企业与小麦产质量耦合协调度的影响。     

Evaluating the U.S. Wheat Protein Complex

This paper models the economic linkages between a commodity (wheat gluten) and a commodity characteristic (wheat protein). The purpose of this research is to address several issues in the wheat protein complex including the impact of the U.S. gluten import quota on producer protein premiums. Four important conclusions are found. First, the hard red winter (HRW) protein market strongly influences wheat gluten market but the wheat gluten market has its greatest influence on the hard red spring (HRS) protein market. Second, the demand for intrinsic protein is estimated to be very elastic. Thus, the returns to breeding or biotechnology programs designed to raise protein levels of wheat are likely to remain stable in response to small increases in wheat protein content. Third, the U.S. import quota on wheat gluten is estimated to provide a 14% increase in the price of wheat gluten in the first year. By the third year, prices are only 5% above the prequota price. U.S. gluten supplies increase about 15% in the first year and remain at about that level for the next two years. Although these are small estimated impacts, they are not far from what the USITC had anticipated. Finally, the three‐year quota increases protein premiums and provides about $500 ($1000) in additional revenue for an average 1000‐acre farm producing HRW (HRS) wheat. Les auteurs ont modélisé les liens économiques entre un produit (le gluten de blé) et une de ses caractéristiques (les protéines). L'objectif était de répondre à plusieurs questions associées au complexe des protéines du blé, notamment l'incidence du contingentement des importations de gluten par les États‐Unis sur les primes consenties aux producteurs en fonction de la valeur protéique du blé. De leur étude, les auteurs tirent quatre grandes conclusions. La premiére est que le marché des protéines du blé roux vitreux d'hiver (BRVH) exerce une forte influence sur le marché du gluten qui, lui, influe principalement sur le marché des protéines du blé roux vitreux de printemps (BRVP). Deuxiémement, on estime que la demande de protéines intrinséques est trés élastique. De petites hausses de la teneur en protéines du blé devraient donc se traduire par un rendement stable des programmes d'hybridation ou de biotechnologie destinés à augmenter la concentration de protéines dans le blé. En troisième lieu, on estime que le contingentement des importations de gluten par les États‐Unis a entraîné une majoration de 14 % du prix de ce produit la premiére année. Deux ans plus tard, les cours s'étaient stabilisés à 5 % au‐dessus du prix en vigueur avant le contingentement. L'offre américaine de gluten augmentera d'environ 15 % la premiére année et se maintiendra à peu prés au même niveau les deux années suivantes. Même si elles ne sont guère importantes, pareilles retombées se rapprochent de celles anticipées par l'USITC. Enfln, les trois années de contingentement ont donné lieu à un relèvement des primes versées pour la concentration en protéines et débouché sur une hausse moyenne de 500 $ (1 000 $) du revenu des exploitations de 1 000 acres qui produisent du BRVH (BRVP).     

胆固醇认知对城镇居民鸡蛋食用量的影响

目的 鸡蛋胆固醇与身体健康问题是人们关注的焦点,直接关系到人们的鸡蛋食用量。方法 文章基于消费者视角,根据实地调研数据,采用分位数回归方法实证分析了胆固醇认知对城镇居民鸡蛋食用量的影响。结果 （1）城镇居民基本上实现了每人每日食用一枚鸡蛋,与鸡蛋实际食用量相比,调研到的样本目前还未达到认为合理的食用量。超过2/3的样本认为食用鸡蛋会导致胆固醇摄入量增加,从而会影响人体健康。（2）经模型验证,胆固醇认知对城镇居民鸡蛋食用量具有显著的负向影响,说明城镇居民为了身体健康以及减少胆固醇摄入量,会有意减少鸡蛋食用量,而且城镇居民鸡蛋胆固醇的负面认知更容易促使其鸡蛋食用量控制在自认为合理的范围以内。结论 基于此,该文结合胆固醇认知等对城镇居民鸡蛋食用量具有显著影响的变量,提出了引导消费者科学购买及食用鸡蛋的对策建议。     

Effects of food consumption patterns on paddy field use in Taiwan

Societal metabolism and land use are significant and interrelated issues, and play a role in sustainable development. How a society's metabolism relates to local land use is typically affected by the particular context of the society under study, which is usually shaped by many factors, including economic, ecological, cultural, technological, and political factors. This study examines the effects of changes in food consumption patterns – decreasing per capita consumption of rice and increasing per capita consumption of wheat flour and meat – on the use of paddy fields in Taiwan. Although rice is grown domestically, wheat, which is a substitute for rice, is mainly imported. Moreover, the domestic livestock industry depends heavily on imported crops for low-cost feed. Accordingly, dietary changes have significantly decreased the demand for local paddy fields to grow crops. Additionally, the diversion of paddy fields to grow forage crops, which has been promoted by the Taiwanese government by guaranteeing prices for feed maize for 14 years, was discouraged when Taiwan joined the World Trade Organization in 2002, as Taiwan was required at that time to reduce by 20% its aggregate measure of support. The presented Taiwan case provides an empirical example of how a change in input characteristics (supply sources in a spatial dimension) of societal metabolism can, together with other factors, significantly affect local paddy fields, and discusses the underlying implications for sustainable development.     

氮肥减量及秸秆替代过量氮肥下冬小麦/夏玉米轮作体系氮素淋失风险研究

针对过量施用氮肥和地下水硝酸盐超标的现状,探索减量施氮、秸秆替代过量氮肥下土壤氮素的淋失风险,以期为降低氮素淋失风险提供科学依据。通过在河北省徐水县进行连续4年的冬小麦—夏玉米轮作体系田间定位试验,分析耕作(少耕和常规耕作)、施氮量(无机氮0、200和300 kg/hm~2)和秸秆(还田、不还田)等措施对作物收获后土壤无机氮累积、土壤—作物体系氮平衡状况以及冬小麦和夏玉米产量的影响。结果表明,小麦收获后,过量施氮处理0~100 cm土壤硝态氮累积量显著高于其它处理,高达221 kg/hm~2,过高的土壤残留硝态氮增加玉米高温多雨季氮素淋洗风险。3年氮平衡累积量比较显示,过量施氮、少耕/常规耕作减量施氮秸秆还田3处理的氮平衡值无显著性差异,以少耕减量施氮秸秆还田最低,为236 kg/hm~2,过量施氮处理最高,为281 kg/hm~2,三者均显著高于少耕/常规耕作减量施氮秸秆不还田处理。冬小麦—夏玉米轮作体系氮平衡值与0~100 cm土层的土壤无机氮、土壤硝态氮累积量呈显著正相关,说明氮素大量盈余会导致0~100 cm土壤剖面无机氮大量累积,尤其是硝态氮大量累积。少耕和常规耕作减量施氮秸秆还田处理的冬小麦、夏玉米产量与过量施氮无显著差异。综合考虑土壤无机氮累积量、氮平衡值和作物产量,少耕或者常规耕作下,可以利用秸秆氮替代过量无机氮,降低氮素淋洗风险。