采收机不同振动强度采收对枸杞树光合系统参数的影响

分别于2008年的6月22日、7月11日、8月5日、10月12日（其中6～8月为夏果期,10月为秋果期）,按3个处理（采收机采收,T1、T2、仍振动强度依次增大）和对照（熟练工人工采摘）分别采收枸杞,研究枸杞采收机不同振动强度采收对枸杞树的光合系统参数的影响。结果表明：对照和各处理的净光合速率（砌）变化规律为7月中旬以前逐渐降低,7月中旬达到最低点,此后开始上升,至8月份达到一个新的高度,随后又开始下降,与枸杞树物候期分析结果一致。蒸腾速率（Tr）、气孔导度（Gs）的变化趋势与Pn一致。6～8月胞间CO,浓度（Ci）的变化趋势与Pn一致,但在10月明显升高。方差分析表明,各处理在各测定时期的Pn、Tr、Gs、Ci与对照相比差异不显著,说明采收机采收对枸杞树叶片的光合系统参数没有显著影响。光合系统参数的相关性分析表明,Pn和Cs、Tr具有较强的相关性,同时Gs和Pn、Tr也具有较强的相关性,说明光合速率和蒸腾速率的高低受气孔影响很大。在6～8月,Pn和Gi具有较强的正相关性,与气孔限制值Ls（Ls=1—Ci／Ca,Ca为空气中CO2浓度）有较强的负相关关系。夏果期（7月16日）光合速率的降低伴随着胞间CO2浓度的降低和气孔限制值的增大,光合速率的下降为气孔因素。秋果期（10月14日）光合速率降低,而胞间CO2浓度升高,表明光合速率降低为非气孔因素,是叶片的光合功能下降所致。     

收获时间对老芒麦种子产量的影响

以生长2年和生长3年老芒麦为试验材料,研究收获时间对其种子产量的影响。结果表明,随着老芒麦种子的成熟,收获的种子产量逐渐增加,在盛花期后26-27d收获可以获得较高的种子产量,延迟收获种子产量则呈下降趋势。生长3年老芒麦同生长2年老芒麦相比,其种子产量下降50%左右。     

Structuring a landscape by forestland classification and harvest scheduling spatial constraints

Landscape environmental features, such as disturbance susceptibility, biological diversity and aesthetics, depend on the forest spatial structure and on the characteristics of its component stands. Strategies for forestland classification are key for managing for spatial heterogeneity as they provide the setting for the layout of land use activities. The design of management units boundaries may further contribute to meet specific spatial conditions. In this paper, two alternative land-classification strategies are presented. They are applied to one test forest with about 12,000 ha. The forest management is constrained by the definition of an exclusion period — the minimum number of years between clearcuts of adjacent management units. Land transformation and fragmentation by harvest scheduling over a temporal horizon with eight ten-year periods is analyzed within the framework of each strategy. Landscape mosaics in each planning period are characterized by spatial statistics, such as the number of patches, average patch area, and the amount and type of edge and interior space. Results from three test computer runs are discussed. They show that land classification has a substantial impact on the spatial dynamics of the forested landscape. They further suggest that timber opportunity costs are not sensitive to the strategy used to classify the land as long as a scheduling model is used to help in management planning.     

The effect of harvest time and pre harvest treatment on the moisture content of Miscanthus × giganteus

This study aims to determine the most appropriate time to harvest Miscanthus × giganteus between January and April, over three possible harvest windows (Jan, Feb and Mar), relative to the harvest method being employed to cut the crop. The moisture content (MC) of biomass cut in January increased compared to the standing crop (control). From an initial MC of 53% in 2009 and 63% in 2010, the control was 12% and 13% lower than Cut Jan after 4 weeks of the treatment in respective years. The MC of Cut Feb was 19% lower than the control after 4 weeks in 2009. Despite Cut Feb being 4% higher than the control after one week in 2010, both treatments reached 34% MC after 3 weeks. A difference of 16% occurred between the Cut Mar and the control after one week in 2009 while in 2010 Cut Mar was 5% higher than the control after one week. Examining the relationship between stem MC, meteorological parameters and evapotranspiration showed that a combination of relative humidity and evaporation rate (Penman equation.) demonstrated the strongest relationship with crop MC. If harvesting early, lower MC can be achieved by cutting and collecting the crop immediately. An increase in the rate of moisture loss can be achieved later in spring by cutting the material and allowing it to dry for a period of time prior to collection if suitable drying conditions occur. An analysis across several sites showed that such conditions are most likely to occur in February.     

Response of Yield Attributes of Isogenic Tall, Semidwarf, and Doubledwarf Winter Wheats to Nitrogen Fertilizer and Seeding Rates

Relationships between grain yield attributes and response to agronomic practices of dwarf and tall genotypes in the major U.S. wheat region were investigated. Isogenic tall, semidwarf, and doubledwarf (Norin 10/5/Pawnee) 'Pawnee' winter wheat ( Triticum aestivum L.) lines were planted in a split-split-plot design with nitrogen fertilizer rates of 0, 50, and 100 kg ha⁻¹ as main plots and seeding rates of 30, 60, and 90 kg ha⁻¹ as subplots in four replications at Hutchinson and Manhattan, Kansas, during 1980–1981. There was no evidence that dwarf lines responded better than the tall line to nitrogen fertilizer; however, percentage fertile spikelets, spike length, harvest index, and kernel number per spike of the semidwarf line were favored by high nitrogen rates. Grain yield was more responsive to seeding rate in the doubledwarf line than in the other lines, and test weight and spike number per unit area were more responsive to seeding rate in one or both dwarf lines than in the tall line. Grain yield of each genotype depended highly on the predominant yield attributes — usually spike number per unit area and/or kernel weight — at one or both locations.     

台湾特色农业考察与启示

本文介绍了台湾特色农业的发展情况,学习考察的主要收获及对我省农业发展的一些启示。     

Effect of harvest date on shearing force of maize stems

Shearing force, one of physical characteristics, is an important indictor of forage value. Maize stem abounds in agro-pastoral ecotone in north-east China and can be utilized as ruminant forage in cold season. The objective of this study is to investigate temporal dynamics and vertical change of shearing force of maize stem because stem is the dominant morphological component contributing to stover nutritive value. Three maize varieties were selected in the study. The stem was cut into 4 segments, and every segment was measured at the approximate midpoint. The results show that shearing force increases with advancing maturity of maize. On same sampling date, shearing force of bottom part of stem is higher than that of upper part. Maize should be harvested as early as possible to avoid the decrease of forage value of stover. Of course, grain yield cannot be sacrificed greatly because maize is grown for its grain in this area. The upper part of stover should be selected as ruminant forage in order to improve the forage digestibility. If maize stover is utilized efficiently, it can play an important role for filling forage shortage gap in agro-pastoral ecotone in north-east China. There is positive relationship between shearing force and cellulose content, and between shearing force and lignin content. Measuring shearing force is very simple, so it can be used to predict forage value of maize stover.     

越冬韭菜栽培技术

介绍了越冬韭菜的品种选择,管理(温度、光照和培土)和收割技术。     

玉米籽粒机收影响因素及其栽培调控研究进展

全程机械化对玉米生产的发展具有非常重要的意义,而机械化收获是玉米全程机械化的重要环节,也是当前推进玉米全程机械化的难点。本文介绍了国内外玉米机械化发展的现状,分析了籽粒含水率、苞叶性状、茎秆特性与穗轴特性对玉米机收的影响,总结了行距、播期、收获时期、施氮量与密度等玉米机收栽培调控措施,并从宜机收品种筛选、收获机械研发与配套栽培技术研究等角度为玉米机械化收获的研究与发展提出了建议。     

Contribution of cultivar,fertilizer and weather to yield variation of winter wheat over three decades: A case study in the North China Plain

Long-term field measured yield data provides good opportunity to assess the impacts of climate and management on crop production. This study used the yield results from a long-term field experiment (1979–2012) at Luancheng Experimental Station in the central part of the North China Plain (NCP) to analyze the seasonal yield variation of winter wheat (Triticum aestivum L.) under the condition of sufficient water supply. The yield change of winter wheat over the last 33 growing seasons was divided into three time periods: the 1980s, the 1990s, and the years of 2001–2012. The grain yield of winter wheat during the 1980s was relative stable. During the 1990s, the annual yield of this crop was continuously increased by 193 kg/ha/year (P < 0.01). While for the past 12 years, yield of winter wheat was maintained at relative higher level, but with larger seasonal yield variation than that back in 1980s. CERES-Wheat model was calibrated and was used to verify the effects of management practices on grain yield. Seven scenarios were simulated with and without improvements in management. The simulated results show that the yield of winter wheat was decreased by 5.3% during 1990s and by 9.2% during the recent 12 seasons, compared with that during 1980s, under the scenario that the yield of winter wheat was solely affected by weather. Seasonal yield variation caused by weather factors was around −39% to 20%, indicating the great effects of weather on yearly yield variation. Yield improvement by cultivars was around 24.7% during 1990s and 52.0% during the recent 12 seasons compared with that during 1980s. The yield improvement by the increase in soil fertility and chemical fertilizer input was 7.4% and 6.8% during the two periods, respectively. The initial higher soil fertility and chemical fertilizer input might be the reasons that the responses of crop production to the further increase in chemical fertilizer were small during the simulation period. Correlation analysis of the grain yield from the field measured data with weather factors showed that sunshine hours and diurnal temperature difference (DTR) were positively, and relative humidity was negatively related to grain yield of winter wheat. The climatic change trends in this area showed that the DTR and sunshine hours were declining. This type of climatic change trend might further negatively affect winter wheat production in the future.