基于中国农业CGE模型的农业补贴政策对粮食安全影响的研究

通过构建农业一般均衡模型（CGE）,本研究分析了农业补贴增长条件下的粮食安全问题。模拟结果显示,农业补贴增长将降低CPI、GDP价格指数、出口价格指数、投资价格指数,从而带动资本、投资、真实GDP、土地租金增长,促进社会就业,带动名义工资、实际工资、家庭可支配收入增加,促进家庭消费和政府消费增加,整个宏观经济发展呈现良好态势。人民币真实贬值、出口增长、关税收入增加,贸易条件改善,国家宏观经济保持良好增长势头。因此,在保障粮食安全政策中,继续加大农业补贴政策的实施力度,提高农业补贴的实际效用,对国家粮食安全有重要意义。     

The effect of salinity and porosity of sewage sludge compost on the growth of vegetable seedlings

Salinity and porosity of composted sewage sludge (CSS) were studied to evaluate their effect on vegetable seedlings, specifically on vegetable seedling performance and toxicity threshold of soluble salts. For the evaluation, CSS was mixed with different proportions of leached CSS to control the salinity. Soluble salt content of 1.45% or higher in growth media inhibited the growth of cucumber, tomato, and pepper seedlings, while that of 1.1% was relatively safe. Different porosities of CSS media were prepared by mixing CSS (<10 mm) with ground CSS (<1 mm) in different proportions (CSS and ground CSS were leached beforehand to prevent salt stress). The vegetable seedlings grew well in CSS media without showing symptoms of growth inhibition if the total porosity ranged from 66% to 81% and the water holding porosity ranged from 48% to 59%. However, the best seedling performances were achieved with the coarser media with high total porosities. The study indicated that when salt content was appropriate, CSS can be used alone as a vegetable seedling growth medium without the need for grinding or blending with other materials.     

不同种植模式和贮存时间对花生O/L值的影响

通过对花生的春播起垄覆膜、春播平地覆膜、麦垄套种和夏直播4种种植模式试验和1个月、4个月、8个月不同贮存时间的花生油酸、亚油酸含量测定分析。结果表明,春播起垄覆膜种植模式花生的油酸含量最高、油酸/亚油酸(O/L)值最大;贮存时间越长花生的亚油酸含量越高、O/L值越小。     

土壤强还原消毒过程中产生气体对土传病原菌的抑制作用

土壤强还原(reductive soil disinfestation,RSD)是一种高效、环保的土壤消毒方法,为明确RSD杀菌机理,采用气相色谱和荧光定量PCR等技术研究RSD过程中产生的气体对土传病原菌的杀菌作用。结果表明:RSD过程中土壤能够产生H_2S和NH_3;当在装有25 g病土的三角瓶中分别加入25 m L的H_2S和NH_3时,土壤中尖孢镰刀菌的数量均显著下降,其杀菌效果分别为90.3%和100.0%;当在病土中加入0.125%(w/w)氨水时,尖孢镰刀菌、茄劳尔氏菌、辣椒疫霉和立枯丝核菌的数量分别下降至对照土壤的1.0%、0.3%、0.1%和0.9%;此外,加入10μL氨水即可显著抑制尖孢镰刀菌菌丝生长和孢子萌发,抑制率分别为52.8%和100.0%。表明RSD过程中产生的H_2S和NH_3对RSD过程的杀菌效果起着一定的作用。     

烟草青枯病菌在烟草根际的定殖及最适发病条件

为明确烟草青枯病菌在根际的定殖情况和最适发病条件,采用绿色荧光蛋白(gfp)标记病原菌,监测其在根际的定殖位置及数量动态变化,并运用荧光定量PCR法测定病原菌在根际和土体土壤的数量,通过响应曲面法探索病原菌致病的临界浓度、发病最适温湿度以及对烟株青枯病发病的影响。结果表明,从贵州省烟田土壤中分离到烟草青枯病病原菌茄科劳尔氏菌Ralstonia solanacearum,gfp-标记的茄科尔劳尔氏菌主要定殖于根尖和根毛区,少数菌落定殖于初生根的延长区,定殖部分表现为非连续性;第10、15、20天根际土壤的茄科劳尔氏菌数量均显著高于土体土壤数量,分别是土体土壤中的1.15、1.33、1.42倍;当土壤中每克土病原菌数量为106.82 CFU、温度为30.55℃、相对湿度为81.42%以上时,烟草青枯病的病情指数最高为91.13,烟株易发生青枯病。表明茄科尔劳尔氏菌在根际土壤中比土体土壤更易定殖,烟草青枯病发病条件主要取决于病原菌浓度、温度以及相对湿度3项指标。     

小麦间作玉米农田耗水特性及产量变化对根系分隔的响应

通过田间试验,研究了小麦间作玉米塑料薄膜隔根(PW//C)、尼龙网隔根(NW//C)、不隔根(W//C)及单作玉米(C)和单作小麦(W)对土壤水分、棵间蒸发和水分利用效率的影响。结果表明,根系分隔显著影响作物的耗水特性,从而显著影响作物产量及水分利用效率的提高。小麦收获前,W//C、NW//C和PW//C处理玉米带土壤水分含量均高于小麦带,分别提高2.38%、3.82%和6.13%;小麦收获后,NW//C和PW//C处理玉米带土壤水分含量却均低于小麦带,分别降低5.41%和16.07%,而W//C处理玉米带和小麦带间水分差异不显著。根系分隔显著增大了间作模式的作物棵间蒸发量,NW//C和PW//C较W//C处理分别显著提高6.71%和20.13%。以单作小麦、单作玉米加权平均为对照,W//C、NW//C和PW//C处理分别显著提高经济产量33.60%、26.93%和24.69%,增大耗水量-0.2%、1.02%和6.69%,显著提高水分利用效率34.93%、26.67%和17.80%。W//C处理较NW//C和PW//C处理分别提高经济产量5.25%和7.14%,降低耗水量1.21%和6.64%,提高水分利用效率6.52%和14.54%。     

基于离散元法的牛肉咀嚼破碎模型构建

为了实现准确、便捷、客观地牛肉嫩度分级检测。该文利用离散单元法构建牛肉块在口腔中咀嚼破碎模型,并进行仿真模拟。研究中选取50头牛的眼肉作为试验样品,30头牛用于构建模型,20头牛用于验证仿真模型的准确性。试验牛样品在75~80℃的恒温水浴中加热至样品内部温度达到70℃时取出,冷却至室温(20℃)。利用质构仪测得牛肉样品的剪切模量、法向刚度等参数,同时测得密度、碰撞恢复系数、摩擦系数等构建离散元模型需要的相关参数。利用测得的参数构建牛肉咀嚼破碎的离散元仿真模型。将咀嚼破碎的牛肉微颗粒作为离散单元模拟仿真中的最小单位,利用Hertz-Mindlin with bonding模型中的颗粒体积力将牛肉块替换为微颗粒黏结的颗粒簇。在咀嚼作用下,当任意2个微颗粒之间的法向应力和切向应力超过最大极限值时,颗粒簇就开始破碎,仿真牛肉的咀嚼破碎过程。研究中利用离散元模拟仿真4个咀嚼周期并记录力和牛肉颗粒的变化。采用感官评定法和剪切力测定分别验证仿真的准确性,准确率都达到90%。研究表明,利用离散元模拟仿真能有效地实现牛肉嫩度等级的预测评定,为牛肉嫩度品质检测提供新方法。     

甘蔗体内的蔗糖积累

成熟甘蔗茎秆积累高浓度蔗糖,其蔗糖积累涉及到蔗糖的合成、分解和运输等生理过程,而调控甘蔗茎中蔗糖积累的关键性因素是存在于快速发育的茎细胞中蔗糖糖代谢相关酶的活性和蔗糖的跨膜运输能力,而不是作为源叶输出光合产物的能力和韧皮部运输蔗糖的效率。为此,本文主要从蔗糖进入茎节的途径、蔗糖在液泡中的积累及其调控等方面作了概述,并指出运用分子生物学、反向遗传学和细胞生物学手段研究有关酶基因、功能性蛋白、糖信号对甘蔗蔗糖运输和积累的作用将是今后的重要研究方向。     

天津市不同种植年限蔬菜地土壤水分特征对比研究

通过对天津市辛口镇蔬菜种植区不同种植年限(5年以上、10年以上及15年以上)土壤水分特征的比较分析后得知:(1)随着种植年限的延长,3种蔬菜地土壤饱和含水量、田间持水量、萎蔫含水量及有效水含量逐渐下降,种植5年以上的蔬菜地土壤,尤其是淀积层及母质层土壤的水分吸持能力高于种植10年以上和种植15年以上.(2)相比种植5年以上的蔬菜地土壤.种植15年以上的蔬菜地土壤总库容、贮水库容、有效水库容和无效水库容发生不同程度的水分亏缺.(3)随着种植年限的延长.蔬菜地土壤的孔隙减少,土壤结构变差,土壤的水分保持、供释能力及开发、利用潜力逐渐下降.该结果可为天津这种干旱地区的蔬菜地土壤,特别是耕作层土壤改良及水分的合理有效利用提供参考     

Large‐scale assessment of soil erosion using a neuro‐fuzzy model combined with GIS: A case study of Hubei Province,China

Reliable and cost‐effective soil erosion assessment is an important precondition for soil conservation measures, which remains a major challenge at large scale. Considering that the neuro‐fuzzy model has the special advantage in multi‐index comprehensive assessment and GIS technology is adept at geo‐spatial information processing, through the combination of them, it is possible to provide an effective approach for this difficult problem. Taking Hubei Province as a case study area, five evaluating indicators were selected for the large‐scale assessment, in which the GIS technology was used to construct the classification maps of evaluating indicators and to divide basic assessment units, and the neuro‐fuzzy model was adopted to extract fuzzy rules for individual units assessment from available ground truth data. According to the optimized assessment criteria generated by the neuro‐fuzzy model, the soil erosion state of the entire study area was then assessed. To represent the spatial distribution of soil erosion, a detailed map was produced by statistical mapping, which was represented with six erosion levels (from slight to severe) at a map scale of 1:250 000. The resulting map showed that about 30.1% of the total land area in Hubei was affected by different levels of soil erosion problem. Western high mountains and eastern low mountains suffered from the most serious erosion damage, a strong level of soil erosion was widely observed in these mountains. Large areas of moderate level erosion occurred in the northern hills. In contrast, most of the central plains were characterized as slight level erosion effect. The validation indicated that an overall accuracy of 88% and a κ of 0.89 were achieved, proving that the resulting map was in conformity with actual conditions, which indicates this assessment approach was reasonable and applicable. Copyright © 2009 John Wiley & Sons, Ltd.