Approaches to calculating P balance at the field‐scale in Europe

Policies for mitigating phosphorus (P) loss from agriculture are being developed in a number of European countries and calculation of P balance at farm‐gate or field‐scale is likely to be a part of such policies. The aim of the paper was to study P balance at the field‐scale in 18 countries that participated in the European Union's (EU) European Co‐operation in the Field of Scientific and Technical Research (COST) action on “Quantifying the Agricultural Contribution to Eutrophication (COST 832)”. A questionnaire related to P balance at the field‐scale was sent to representatives in the 18 countries and all replied. The field as a unit is defined differently in the various European agricultural systems. The identification of the inputs and outputs differ among the countries. For example, P losses may or may not be taken into account in balances. Phosphorus balance at the field‐scale is used in all countries in the context of soil analysis and P recommendations for crops and advisory and research purposes, while only a few countries use it for policy purposes (agri‐environmental). There is wide variation in P balances between countries in relation to soil fertility and vulnerability of water to eutrophication from nutrients from agricultural sources. In several eastern European countries, Hungary for example, fertilizer P use has dropped to about one tenth of the levels used in the 1980's. Many of these countries now have a negative P balance. In western European countries, by contrast, although fertilizer P use has decreased in recent years, the average input is higher than the average off take, and soil test phosphorus (STP) values remains high and continue to increase in some areas. Twelve different soil extractants for STP are used in Europe, and their interpretation can hinder direct comparisons. Calculating P balance at the field‐scale involves approximations in estimating inputs and outputs and spatial variations in fertility in individual fields. Accuracy of data and standardization of methods for calculating balances with inputs and outputs will be a challenge for the future development of a sustainable agriculture in Europe.     

水资源供需平衡评价系统软件UML建模

针对实例引入基于面向对象的 UML标准建模语言进行水资源供需平衡评价系统分析和系统设计 ;用 Rational Rose进行系统 UML软件模型的建模 ;抽象出一些实例对象的 C 类 ,用 Visual C 开发了32位中文版 Windows平台上的水资源供需平衡评价软件等一系列工作。     

黄土丘陵区不同类型农地的养分循环平衡特征

该文以黄土丘陵沟壑区的安塞试验站长期肥料定位试验的实测资料为研究对象，定量研究川地、坡地、梯田不同类型农地养分循环特征。研究结果表明：川地、坡地、梯田与农民习惯施肥水平相类似的处理，年养分盈亏量分别是：川地每年每hm²氮素盈余10.2 kg，P₂O₅盈余56.6 kg；坡地每年每hm²氮素亏损7.0 kg，P₂O₅亏损14.7 kg；梯田每年每km²氮素盈余104.9 kg，P₂O₅盈余107.3 kg。退耕还林和实施“坡改梯”工程是黄土丘陵沟壑区农地养分循环不断朝良性方向发展的关键措施。     

基于模型的温室加温控制目标优化系统研究

温室加温控制目标的设定合理与否，直接影响温室作物生长及温室环境调控的能耗。本研究以温室作物生长模拟模型和温室加温能耗预测模型为基础，建立了基于模型的温室加温控制目标计算机优化系统。系统包括一个数据库(温室、作物以及气象资料)和三个模型(作物生长模拟模型、温室加温能耗预测模型以及加温控制目标优化模型)。系统的输入主要为温室类型、温室结构、覆盖材料、作物信息以及室外气象资料，系统输出主要为作物干物质生产量、温室加温能耗量以及干物质生产能耗量利用效率最高和生物量最高的温室白天和夜间的加温控制目标(温度设置点)。以2003年1月20日～2月20日上海孙桥现代农业开发区Venlo型自控玻璃温室水果型黄瓜生产为实例进行分析，结果表明，在上海地区冬季进行温室水果型黄瓜生产时，在开花至果实采收初期将白天和夜间加温控制目标分别设为23℃和17℃时可以获得最高的干物质生产量；将白天和夜间的温室加温的温度分别设为20℃和15℃能够使黄瓜干物质生产的能耗量利用效率达最大，并能够使黄瓜干物质产量也处于较高的水平。本研究建立的基于模型的温室加温控制目标优化系统为中国温室气候控制中温度的优化调控提供了理论依据和决策支持。     

Water balance simulation of a dryland soil during fallow under conventional and conservation tillage in semiarid Aragon, Northeast Spain

In Central Aragon, winter cereal is sown in the autumn (November–December), commonly after a 16–18 months fallow period aimed at conserving soil water. This paper uses the Simple Soil–Plant–Atmosphere Transfer (SiSPAT) model, in conjunction with field data, to study the effect of long fallowing on the soil water balance under three tillage management systems (conventional tillage, CT; reduced tillage, RT; and no-tillage, NT). This was on the assumption that soil properties would remain unchanged during the entire fallow season. Once the model was validated with data obtained before primary tillage implementation, the differences between simulated and observed soil water losses for the CT and RT treatments could be interpreted as the direct effect of the soil tillage system. The model was calibrated and validated in a long-term tillage experiment using data from three contrasting long-fallow seasons over the period 1999–2002, where special attention was paid to predicting soil hydraulic properties in the pre-tillage conditions. The capacity of the model to simulate the soil water balance and its components over long fallowing was demonstrated. Both the fallow rainfall pattern and the tillage management system affected the soil water budget and components predicted by the model. The model predicted that about 81% of fallow seasonal rainfall is lost by evaporation in long-fallow periods with both a dry autumn in the first year of fallow and a rainfall above normal in spring. Whereas, when the fallow season is characterised by a wet autumn during the first year of fallow the model predicted a decrease in soil water evaporation and an increase in water storage and deep drainage components. In this case, the predicted water lost by evaporation was higher under NT (64%) than under RT (56%) and CT (44%). The comparison between measured and simulated soil water loss showed that the practice of tillage decreased soil water conservation in the short term. The long-term analysis of the soil water balance showed that, in fallow periods with a wet autumn during the first year of fallow, the soil water loss measured under CT and RT was moderately greater than that predicted by the model.     

县域耕地后备资源与规划期内数量质量并重的占补平衡分析

耕地后备资源是耕地的重要补充来源,在耕地占补平衡中具有重要作用,但在补充耕地能力上长期存在偏主观、重数量等情况。利用国土部新一轮耕地后备资源调查评价试点县成果,在新增耕地系数和等级折算系数的基础上提出了耕地数量与耕地数量质量并重的平衡测算方法,分析县域规划期内实现耕地占补平衡的能力。以湖南省沅江市为例,测算至2020年实现数量平衡和数量质量平衡需开发的耕地后备资源面积。结果显示,满足耕地数量平衡需开发耕地后备资源面积为1 083.37 hm2;满足数量质量并重平衡,最低需开发耕地后备资源面积1 083.37 hm2,最高需开发1 351.65 hm2。通过测算,沅江市耕地后备资源开发可满足县域耕地占补数量、质量平衡的需要,但存在较大压力,尤以数量质量并重平衡为甚。因此,明晰县域耕地后备资源补充耕地的能力有利于合理安排新增建设项目,确保实现土地利用总体规划保护耕地的目标。     

Glacier mass balance and its impacts on streamflow in a typical inland river basin in the Tianshan Mountains,northwestern China

Glaciers are known as natural 'solid reservoirs', and they play a dual role between the composition of water resources and the river runoff regulation in arid and semi-arid areas of China. In this study, we used in situ observation data from Urumqi Glacier No. 1, Xinjiang Uygur Autonomous Region, in combination with meteorological data from stations and a digital elevation model, to develop a distributed degree-day model for glaciers in the Urumqi River Basin to simulate glacier mass balance processes and quantify their effect on streamflow during 1980-2020. The results indicate that the mass loss and the equilibrium line altitude (ELA) of glaciers in the last 41 years had an increasing trend, with the average mass balance and ELA being -0.85 (±0.32) m w.e./a (meter water-equivalent per year) and 4188 m a.s.l., respectively. The glacier mass loss has increased significantly during 1999-2020, mostly due to the increase in temperature and the extension of ablation season. During 1980-2011, the average annual glacier meltwater runoff in the Urumqi River Basin was 0.48×10⁸ m³, accounting for 18.56% of the total streamflow. We found that the annual streamflow in different catchments in the Urumqi River Basin had a strong response to the changes in glacier mass balance, especially from July to August, and the glacier meltwater runoff increased significantly. In summary, it is quite possible that the results of this research can provide a reference for the study of glacier water resources in glacier-recharged basins in arid and semi-arid areas.     

环境因子对两种纳米金属氧化物在水体中稳定性的影响

以纳米二氧化铈(Nano-Ce O2)及纳米二氧化钛(Nano-Ti O2)为主要实验材料,研究腐植酸(HA)、离子强度(IS)与p H对其在水体中稳定性的影响。结果表明:HA浓度升高(0~5 mg·L-1),两种纳米颗粒在水体中的稳定性均增强,其原因是吸附在纳米颗粒表面的HA使颗粒间产生巨大的空间位阻斥力与静电斥力,从而减弱了颗粒的凝聚;IS增加(1~50 mmol·L-1Na Cl),两种纳米材料稳定性均降低,颗粒凝聚后粒径变大,且HA的存在(5 mg·L-1)能显著减弱IS对其稳定性的影响,其原因是吸附在纳米颗粒表面的HA使颗粒间产生空间位阻斥力及静电斥力且这两种斥力占主导作用。实验p H范围内(6.01~10.02),随着p H的增加,纳米颗粒的稳定性增强,但当本体溶液中存在HA(5 mg·L-1),p H变化对纳米颗粒稳定性几乎不产生影响。此外,计算并运用XDLVO(extended Derjaguin-Landau-Verwey-Overbeek)理论进行预测分析的结果表明,XDLVO理论的预测与实验结果非常吻合。该研究结果有助于深入了解Nano-Ce O2及Nano-Ti O2在水体中的环境行为,并为进一步预测两者的生态环境风险提供理论依据。     

茭白-鸭共作系统中氮平衡及经济效益分析

分析了单作茭白(CK)、茭白田放养鸭20只·667 m^-2(D20)、25只·667 m^-2(D25)、30只·667 m^-2(D30)等不同共作系统中氮素输入、输出与盈余(盈余=输入-输出),以及经济效益情况。结果表明:茭白-鸭共作系统中茭白平均产量为1 332.41 kg·667 m^-2,比单作茭白增产26.31%。单作茭白总氮输入为22.27 kg N·667 m^-2,其中化肥氮输入占到89.10%,产品氮输出为5.00 kg N·667 m^-2,占总氮输入的22.45%,氮盈余为17.27 kg N·667 m^-2,占总氮输入的77.55%,土壤氮残留为7.11 kg N·667 m^-2,损失为10.16 kg N·667 m^-2;茭白-鸭共作系统总氮输入平均为23.72 kg N·667 m^-2,其中化肥氮输入占65.13%,产品氮输出平均为7.65 kg N·667 m^-2,占总氮输入的32.24%,氮盈余平均为16.07 kg N·667 m^-2,占总氮输入的67.76%,土壤氮残留为7.18 kg N·667 m^-2,损失为8.89 kg N·667 m^-2。茭白-鸭共作系统投入成本平均为3 114 元·667 m^-2,比单作茭白高84.59%,主要是鸭饲料、围网、鸭舍等成本增加。茭白-鸭共作系统产品产值平均为6 568 元·667 m^-2,比单作茭白高55.64%。D25处理经济效益(经济效益=产品产值-投入成本)最高为3 589 元·667 m^-2,比CK处理高41.69%。综合考虑氮平衡和经济效益,本试验条件下,茭白田放养鸭25只·667 m^-2的共作系统的经济效益较高,并且氮素盈余和损失较少,可降低对环境的污染风险。