农业建筑与环境工程专业现存问题及其对策的探讨

农业建筑与环境工程专业现存的主要问题是:专业的发展方向、地位、业务归口单位应该进一步明确;专业需要得到全社会的承认和支持;对专业的边缘性和综合性的特点应该有充分的认识,要在工程技术和生物技术的结合方面作深入的研究工作;专业跨多门传统学科的特点与课程安排之间的矛盾要很好地解决;专业本身要主动适应大农业经济建设的需要,进一步加快和深化改革。     

西北农业高校图书馆信息化建设

本文从信息资源建设、信息化人力资源建设、信息资源共享体系等几个方面，探讨西北农业高校图书馆信息化建设。     

Control of Rainfall-Induced Soil Erosion with Various Types of Polyacrylamide (8 pp)

Background   Several types of organic polymers with various molecular weights and surface charges are produced for various industrial and agricultural purposes, and recent studies have shown that high molecular weight anionic polymers are the most effective in reducing runoff and soil loss. However, anionic polyacrylamide (PAM) is marketed under various commercial names with variable molecular weight and length according to its chemistry (Barvenik 1994). Consequently, its interactions with soil and efficiency in reducing soil erosion are expected to vary. Moreover, types of PAM other than those recommended for erosion control may also be effective in reducing soil erosion. Objectives   The objective of this research is to test the influence of 9 types of polyacrylamide (PAM) on water infiltration and soil loss of an arid silt loam soil under simulated rainfall conditions. Method  logy. Nine types of organic polymers varied in surface charge, ranging from +20 to –75, and molecular weight ranging from very low to very high were used in this study. Soil plots with dimensions of 60 cm by 120 cm having moderate slope of3 to 5% were constructed in the field and equipped with runoff collection installations. A specific type of PAM was spread on soil plots at a rate of 10 kg/ha. Rainfall was supplied from a drip type rainfall simulator at constant intensity and duration of 80 mm/h and 50 min, respectively. Runoff, infiltration and soil loss were measured for each plot subjected to a specific type of PAM and compared to control plots. Results and Conclusions   Land application of PAMs significantly increased infiltration prior to runoff but had insignificant effect on total infiltration volume and final infiltration rate under the present experimental conditions. Experimental results confirmed that anionic polymers were more effective in reducing soil loss than that of non-ionic or cationic polymers. In fact the cationic, low molecular weight and low surface charge non-ionic PAMs had insignificant effect on soil loss. High molecular weight anionic PAM with 30% surface charge (A-130) was more effective(46% reduction) than those having a high molecular weight and a lower surface charge of 20% (A-110 and A-120) with an aver-age soil loss reduction of 24%. The PAM A-836, described assoil erosion polymer with 20% surface charge and high molecular weight, reduced soil erosion by 41%. Unexpectedly, the anionic PAM with low molecular weight but very high surface charge was also effective in reducing soil loss (47% reduction). Recommendations and Outlook   Land application of PAM improves water infiltration and highly reduces soil erosion thus improving agricultural production. Application of PAM could be the only viable way to improve arid land farming. It seemed that various types of PAMs, other than those specifically produced for erosion protection can be used to combat soil erosion. This means that farmers in poor countries can use any type of PAM that is available to them to improve agricultural production.     

Soil conservation policy measures to control wind erosion in northwestern Europe

Wind erosion is not as significant or a widespread problem in Europe as in dryer parts of the world, but it can cause major damage in small areas. The hazard is greatest in the lowlands of northwestern Europe with more than 3 million ha at high-potential wind erosion risk. Crop damage and off-site damage have prompted farmers and policymakers to pay more attention to wind erosion control. A great variety of measures have been developed in the last decades. Most farmers, however, only use measures to protect their high value crops. In existing policies, little attention is paid to the off-site effects and long-term effects of wind erosion. There are no direct policy measures at a European level to control soil erosion, and few measures exist in individual Member States. Agricultural or environmental EC policies offer different policy tools to approach the wind erosion problems related to agricultural practices. Tools like subsidies for the re-afforestation of arable land can help regional policy makers with the implementation of wind erosion control measures. A case study concerning the ‘Code of Good Agricultural Practice’ shows that regional differences result in different control measures that fits best given the physical, social and economic context. The formulation of the practical details of such code should therefore remain a task of the local or regional government. The main objectives of a Code of Good Agricultural Practice could be formulated at national or European level.     

航空遥感技术在林改宗地勘界中的研究与应用

指出了在集体林权制度改革中,林地宗地勾绘是核心内容,分析了采用高分辨率大比例尺航空正射影像图与电子矢量化地形图叠加进行林改宗地勘界,研究表明：其技术比传统地形图上勾绘宗地方法更能提高工作效率及勾绘精度。     

普通小麦品种小偃54中α/β-醇溶蛋白编码基因的克隆与序列分析

醇溶蛋白是小麦籽粒贮藏蛋白的重要组分,其组成与含量对小麦加工品质具有重要影响。本研究建立了利用PCR从普通小麦基因组BAC文库中筛选含有α/β-醇溶蛋白基因序列BAC克隆的方法,并获得9个不同的含有α/β-醇溶蛋白基因的BAC克隆。从其中鉴定出17个α/β-醇溶蛋白基因,其编码区序列长度为852~957 bp。12个序列在编码区内存在提前终止密码子,推测为假基因。其他5个成员(Gli-Xy54-1、Gli-Xy54-2、Gli-Xy54-3、Gli-Xy54-7和Gli-Xy54-13)分别编码291、310、311、287和317个氨基酸残基,都具有α/β-醇溶蛋白一级结构的典型特征。根据推导的氨基酸序列中乳糜泻病诱发因子的分布情况及多聚谷氨酰胺重复区的长度差异,推测Gli-Xy54-7可能定位于6A染色体,Gli-Xy54-2、Gli-Xy54-3和Gli-Xy54-13可能定位于6B染色体,Gli-Xy54-1可能定位于6D染色体。基因聚类分析支持了上述推论。这是第一次从普通小麦中筛选到包含α/β-醇溶蛋白基因的BAC克隆,并从中得到目标基因全长,对进一步研究普通小麦基因组中α/β-醇溶蛋白编码基因的组成、表达与功能有较好的参考价值。     

Impacts of population growth, economic development, and technical change on global food production and consumption

Over the next decades mankind will demand more food from fewer land and water resources. This study quantifies the food production impacts of four alternative development scenarios from the Millennium Ecosystem Assessment and the Special Report on Emission Scenarios. Partially and jointly considered are land and water supply impacts from population growth, and technical change, as well as forest and agricultural commodity demand shifts from population growth and economic development. The income impacts on food demand are computed with dynamic elasticities. Simulations with a global, partial equilibrium model of the agricultural and forest sectors show that per capita food levels increase in all examined development scenarios with minor impacts on food prices. Global agricultural land increases by up to 14% between 2010 and 2030. Deforestation restrictions strongly impact the price of land and water resources but have little consequences for the global level of food production and food prices. While projected income changes have the highest partial impact on per capita food consumption levels, population growth leads to the highest increase in total food production. The impact of technical change is amplified or mitigated by adaptations of land management intensities.     

Sensitivity to information upscaling of agro-ecological assessments: Application to soil organic carbon management

Upscaling of agro-ecological indicators applied in regional analyses is sensitive to scale issues of the input data. This study develops a methodology to quantify this sensitivity for an indicator of soil organic carbon (SOC) dynamics at the farming system level. A reference case consists of seven fully described farms in northern Italy. Both upscaling in complexity by substituting measured input with estimated input and upscaling in space by extending the methods to farms not included in the reference case are addressed. The indicator increased with 3-107% at four farms after substituting measured management input with that estimated by an expert, whereas it remained unchanged or decreased at the other three farms. Taking the modal value from a cluster of pedological input did not lead to additional uncertainty in most cases, and only slightly increased it in others. We evaluated spatial upscaling by including 733 farms divided in 18 clusters that were described with less information as compared to the reference farms. Within each cluster, we observed relevant variability of the indicator (coefficients of variation of 12-43%), as a consequence of the heterogeneity of farms comprised in each cluster. In each cluster we calculated the indicator for one virtual farm, defined by using modal values for basic farm inputs. In this case the indicator was highly correlated (R² = 0.98) with the average of the values obtained using measured basic farm inputs. We conclude that upscaling in complexity and space introduces uncertainty in the values of the indicator compared to the reference case. The extent of such differences depends on the variability of the systems under analysis and on indicator sensitivity.     

Enhancing the Simplified Surface Energy Balance (SSEB) approach for estimating landscape ET: Validation with the METRIC model

Evapotranspiration (ET) can be derived from satellite data using surface energy balance principles. METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) is one of the most widely used models available in the literature to estimate ET from satellite imagery. The Simplified Surface Energy Balance (SSEB) model is much easier and less expensive to implement. The main purpose of this research was to present an enhanced version of the Simplified Surface Energy Balance (SSEB) model and to evaluate its performance using the established METRIC model. In this study, SSEB and METRIC ET fractions were compared using 7 Landsat images acquired for south central Idaho during the 2003 growing season. The enhanced SSEB model compared well with the METRIC model output exhibiting an r² improvement from 0.83 to 0.90 in less complex topography (elevation less than 2000 m) and with an improvement of r² from 0.27 to 0.38 in more complex (mountain) areas with elevation greater than 2000 m. Independent evaluation showed that both models exhibited higher variation in complex topographic regions, although more with SSEB than with METRIC. The higher ET fraction variation in the complex mountainous regions highlighted the difficulty of capturing the radiation and heat transfer physics on steep slopes having variable aspect with the simple index model, and the need to conduct more research. However, the temporal consistency of the results suggests that the SSEB model can be used on a wide range of elevation (more successfully up 2000 m) to detect anomalies in space and time for water resources management and monitoring such as for drought early warning systems in data scarce regions. SSEB has a potential for operational agro-hydrologic applications to estimate ET with inputs of surface temperature, NDVI, DEM and reference ET.