条锈病影响下冬小麦叶绿素含量的高光谱估计

叶绿素含量是在小麦长势监测中是非常重要的评估内容，尤其是在小麦受到病害影响的情况下，准确估计其叶绿素含量，有助于合理进行灾害评价。遥感高光谱技术为获取植物的生理参数提供了丰富的数据来源。笔者使用襄樊地区实测获取的受条锈病影响的小麦高光谱数据，利用回归分析的方法建立了受条锈病影响的小麦叶绿素含量与其高光谱的关系模型。经验证，模型有较好的精度。     

Adoption of mucuna in the farming systems of northern Honduras

In many parts of Central America long fallow periods are no longer feasible due to increasing land pressures. Farmers in northern Honduras have developed and diffused from farmer-to-farmer a maize cropping system using velvetbean (Mucuna spp.) as a short-term fallow. High total annual rainfall in a bimodal distribution is favorable to the system because it allows the completion of two rainfed cropping cycles annually. The first season is dedicated to the production of the mucuna crop and the second season is dedicated to maize. Soil pH and exchangeable Ca were not reduced during a 15-year period of continuous mucuna use. Soil organic matter, infiltration, and porosity increased with continuous mucuna use. Maize yields in fields with continuous rotation of mucuna were on average double those obtained without mucuna. The mucuna system was more profitable than the existing alternative bush-fallow system due to higher returns to land and labor resulting from higher yields, lower weeding and land preparation costs, and reduced risk of drought stress. The relative profitability of the mucuna system was also enhanced by seasonally high maize prices during the second season when maize is harvested in the mucuna system. Relatively easy access to land through inexpensive land ownership and land rental markets has made it possible for even small-scale farmers to dedicate land to the mucuna system. Land-use intensity is increasing in the region, however, as land is converted to pastures for cattle production. The opportunity costs of keeping land in the mucuna system, while also accessing land for first-season maize and other crops, are also increasing. These experiences remind us that a viable livelihood is the primary factor in farmers' decision making about adoption particular components of farming systems.This revised version was published online in November 2005 with corrections to the Cover Date.     

Regional analysis of irrigation water requirements using kriging: Application to potato crop (Solanum tuberosum L.) at Trás-os-Montes

Aiming at the analysis of the regional variation of potato crop irrigation water requirements over the Trás-os-Montes region, data from 106 rainfall stations and eight weather stations were utilized in an irrigation scheduling simulation model to estimate net irrigation water requirements of the potato crop. The simulation model was first validated using a field experiment which allows to derive the required crop data to be used in the simulations. The reference evapotranspiration (ET₀) was estimated using the FAO Penman–Monteith method. The model was applied to all 106 locations, each with a data set spanning a 19-year period. As a result of this application, series of the net irrigation water requirements for a 19-year period were obtained for each location. The resulting 106 point values of the net water requirements of the potato crop have been treated as a regionalized variable. The respective semivariograms have been computed and the kriging method then applied to estimate the spatial distribution of the water requirements in the region. Contour lines of this regionalized variable have been drawn using a GIS system. Results show an estimation error averaging 5% for the entire region.     

Influence of slope and stone cover on tillage operations in the Ethiopian highlands

Human population pressure has forced smallholder farmers in some areas of the central plateau region of the Ethiopian highlands to cultivate plots located on slopes or hillsides having varying amounts of stone cover. The objectives of this pilot study were to determine if slope and(or) stone cover influenced tillage operations on smallholder farms in the Debre Birhan area of the Ethiopian highlands, and to examine the relationship between different soil/tillage-related factors and draft of the indigenous single-tined ard (maresha). This paper also briefly describes the traditional systems of cropping and soil management, and provides data on selected physical and chemical properties of soils found in the study area. A land classification (LC) system was developed to categorize plots according to the slope and stone cover. Surface stone cover of plots was calculated and a method of estimating subsurface stones was tested. Tillage measurements included plowing frequency or number (PN) per area per annum, soil moisture tension, plowing depth, furrow “wedge” of soil moved, area plowed, contour angle, and the speed of travel and pulling force exerted by oxen. Plots were located on slopes ranging from 0% to 23%. Degree of slope was a key factor in determining the acuteness of angle of the contour at which plowing is done prior to seed covering, but had no significant effect on maresha draft. Stone cover of plots ranged up to 27%, with individual stones moved by the ard weighing up to 2.5 kg. Plowing depth ranged from 10.1–15.3 cm for all PN across LC. Oxen travelled at speeds of 0.35–0.58 m s⁻¹. Mean values for draft of the maresha across LC ranged from 0.83–1.04 kN. Farmers plowed from 0.10–0.15 ha during a 5–6 h work period, irrespective of LC or PN. Soil moisture tension (range 16–33 kPa) was found not to have a significant effect on draft, due to tillage being carried out prior to the major and minor rains. Percent stone cover explained very little of the variation in implement draft (R²=0.10). Adding stone weight to the model increased R² slightly (0.22), but significance was low (P<0.16). Furrow wedge of soil displaced by the ard head accounted for most of the variation in draft of the maresha across all LC and PN (R²=0.75, P<0.008). The design and construction of the maresha allows it to be used equally well for tillage operations on plots having minimal or high stone cover which may be located on flat or gentle sloping land, or on steep hillsides.     

The effectiveness of cover crops during eight years of a UK sandland rotation

Abstract. Growing cover crops during the winter before spring-planted crops is often suggested as an effective method to decrease nitrate leaching. A four-course crop rotation (potatoes-cereal-sugarbeet-cereal) was followed through two rotations on a sandy soil in the English Midlands. Three management systems were imposed on the rotation to test their effects on nitrate loss. The effects of cover crops on nitrate leaching and crop yields were compared with the more conventional practice of over-winter bare fallow before potatoes and sugarbeet.
Cover crop N uptake was variable between years, averaging 25 kg ha⁻¹, which is typical of their performance on sandy soils in the UK. The cover crops usually decreased nitrate leaching but their effectiveness depended on good establishment before the start of drainage. Over 7 years, cover crops decreased the average N concentration in the drainage from 24 to 11 mg l⁻¹. Potato yield and tuber N offtake increased after cover crops. Ware tuber yield increased by an average of c . 8%; this was unlikely to be due to additional N mineralization from the cover crop because the potatoes received 220–250 kg fertilizer N ha⁻¹, and non-N effects are therefore implicated. Sugar yield was not increased following a cover crop.
After 8 years of nitrate-retentive practices, there were no measurable differences in soil organic matter. However, plots that had received only half of the N fertilizer each year contained, on average, 0.14% less organic matter at the end of the experiment.     

旱地冬小麦生育后期有关光合特性及光合产物分配规律研究

在大田自然干旱条件下旱作处理,冬小麦生育后期旗叶光合速率仍可达１４．２４μｍｏｌＣＯ２·ｍ＾－２·ｓ＾－１,在叶片水势达－１．８～－２．１ＭＰａ条件下,旗叶ＲｕＢｐ羧化酶活性可达２０～２３μｍｏｌＣＯ２·ｍｉｎ＾－１·ｇ＾－１ｄｗ;浇水处理小麦植株旗叶光合速率为１５．１５μｍｏｌＣＯ２·ｍ＾－２·ｓ＾－１水势达－１．６５～－１．８ＭＰａ条件下,旗叶ＲｕＢｐ羧化酶活性可达２２～２５μｍｏｌＣＯ２·ｍ     

我国农产品加工业的发展方向

论述了我国农产品加工的意义、现状以及今后发展的方向。指出我国当前农产品加工的重点是抓好大宗农产品的加工,并就小麦等九大作物加工发展提出了一些具体的观点与建议     

农作物长势的定义与遥感监测

监测作物生长过程的状况与趋势,即长势监测是农业遥感更为重要的任务。其目的是：１）为田间管理提供及时的信息;２）早期估计产量。该文以冬小麦为例,根据实地调查与北方数省的资料,用作物的个体与群体特征定义作物长势,讨论了遥感监测的可能性,提出了基于植被指数与植被表面温度的长势遥感监测的评估模型与诊断模型的概念与算法。     

带状种植小麦带型-群体-产量相关规律研究

在高产田条件下,选用了中穗型冬小麦品种泰876161,设计小麦大小行播种,小行距20cm,大行距分别为30、40、70及100cm,形成了50（20+30）、60（20+40）、90（20+70）及120（20+100）cm 4种带型模式,以常规20cm等行距（20+20）模式栽培作对照。试验又设置了5个播种密度,即1m单行基本苗数分别为15、30、45、60及75。研究了小麦带型-群体-产量的相关规律。主要结果是：（1）行产量（y）随宽行距（x）加宽而提高,增长规律拟合为y=a/x+b的函数形式。（2）随播种密度加大,（20+20）、（20+30）及（20+40）模式行产量明显下降,而（20+70）及（20+100）模式则下降不甚明显。各带型均在精量播种下（15苗/m）获得高产。（3）随宽行距（x）加宽,产量（y）拟合为y=axe#+（bx）的函数变化形式,15、30、45、60及75苗/m拟合的最高产量的宽行距分别为39.55、41.11、44.10、43.93及44.93cm。5个密度平均拟合方程为y=36.60684xe#+[-2.353119×10#+（-2）x],r=-0.994618 9#+（**）,最高产量的宽行距拟合为42.50cm。（4）高产田下（20+40）模式能较好地协调穗数、穗粒数及千粒重三者的矛盾关系,表现出较20cm等行距栽培增产,并且40cm宽行距适于间作冬春蔬菜,套种玉米、花生、夏棉、大豆、生姜等,具有较强的间套通用性和方便性。     

旱地农田肥水耦合效应及其模式研究

旱地农业的基本问题是如何在水分胁迫下,合理施用肥料,充分发挥肥和水的激励机制和协同作用,提高水分的利用效率和在不增加施肥量的情况下,获得最大的经济效益,同时减少肥料对土壤、地下水、大气的污染,节约水肥资源,改善生态环境。本研究主要探讨农田水分与养分之间、各养分之间、作物与水肥间的动态平衡关系,以及作物生长发育和产量的形成对这些相互作用的影响。１　材料与方法１．１　试验地点试验设置在河南省洛阳农业科学研究所旱棚内,本区多年平均降水为５００～６００ｍｍ,地下水位为４～５ｍ。供试土壤为潮褐土,母质为洪…