首页 | 本学科首页   官方微博 | 高级检索  
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   13篇
  完全免费   10篇
  农学   23篇
  2017年   3篇
  2015年   1篇
  2013年   2篇
  2012年   2篇
  2011年   2篇
  2010年   1篇
  2009年   1篇
  2007年   1篇
  2006年   1篇
  2005年   1篇
  2001年   1篇
  2000年   1篇
  1999年   2篇
  1996年   1篇
  1995年   1篇
  1992年   1篇
  1989年   1篇
排序方式: 共有23条查询结果,搜索用时 15 毫秒
The effect of six doses of beet vinasse (0, 3, 6, 10, 20 and 40 t ha−1, respectively) on wheat (Triticum aestivum cv. Cajeme) yield in dryland conditions (Guadalquivir Valley, Andalusia, Spain) for 3 years on a Typic Xerofluvent was studied. The results showed that at low doses, beet vinasse is of agricultural interest due mainly to its organic matter concentration. The application of this byproduct to the soil increased soil microbial biomass and mineralization of its organic matter increased NO3–N concentrations in soil. This caused an increase in grain yield in the three seasons. When the vinasse was applied with high doses, NO3–N concentrations in soil, soil microbial biomass, soil structure, bulk density, electric conductivity, nutrient uptake, crop yield and grain quality were negatively affected. We assume that the high amounts of monovalent cations, particularly Na+, and of fulvic acids, which had been transported into the soil by the vinasse, destabilized the soil structure. This may have led to anaerobic soil conditions being presumably responsible for restricted N mineralization or even for denitrification. This explains the lower N supply to the crops reflected by the low N concentrations in the leaves of treatments A4 and A5.  相似文献
This field study evaluated the effects of water quality, irrigation frequency and crop species on some physical properties of soils. The experiment had a split-split-plot design, with three irrigation water qualities (normal water, drainage water and a 1 : 1 mixture of freshwater and drainage water) as the main treatments, two irrigation frequencies (at 7- and 14-day intervals) as the subtreatments and two crops (barley and alfalfa) as the subsubtreatments. The soil infiltration rate was highest in the barley plot receiving freshwater irrigation at weekly intervals. The lowest soil infiltration rate was found in alfalfa plots receiving saline irrigation water at 14-day intervals. Bulk density and proportions of micropores [pore radius (r) < 1.4 µm] were higher and the proportion of macropores (r > 14.4 µm) was lower in barley than in alfalfa. Saline irrigation caused the greatest decrease in total porosity. The soil infiltration rate was higher with more frequent irrigation, and was highest in alfalfa plots receiving freshwater irrigation. The decrease in soil bulk density and infiltration rate was greater with saline drainage water, irrespective of the crop grown and the irrigation frequency.  相似文献
Influence Of Tillage On Soil Aeration   总被引:2,自引:0,他引:2  
Air- porosity of soil can be altered by tillage. Therefore, it plays a significant role in protecting plants against deficient aeration during critical periods of their life cycle. The effect of five tillage treatments (mouldboard, cultivator, rotary tiller, wedge and zero tillage) and three mulch treatments (paddy straw, rice husk and bare) on the soil oxygen diffusion rate (ODR) during the various growth phases of peanut crop ( Arachis Hypogaea L.) were investigated on a lateritic sandy loam soil (utilsol). These experiments were conducted for two consecutive seasons. ODR values were higher in tilled plots. Among tillage treatments, the highest ODR was recorded under mouldboard (60.51 × 10-8 g cm-2 min-1), followed closely by cultivator (57.65 × 10-8g cm-2 min-1), and it was lowest under rotary tiller (46.29 × 10-8 g cm-2 min-1). During the later growth stages and also in lower soil depths, the differences between the values of ODR narrowed down. Among mulch treatments, plots with rice husk (53.98 × 10-8 g cm-2 min-1), had the higher ODR values. Bulk density was lower, whereas total and aeration porosity were higher, under mouldboard and cultivator. Soil temperatures were also higher under mouldboard and cultivator tilled plots.  相似文献
小麦水分含量对容重及硬度的影响   总被引:2,自引:0,他引:2  
司建中 《粮食储藏》2011,40(5):47-49
容重是国内外粮食定等及评价粮食工艺品质的主要指标,小麦籽粒硬度是国内外小麦市场分类和定价的重要依据之一,通过改变小麦水分含量,判定其对小麦容重及硬度的影响。结果表明,在一定的水分范围之内,小麦容重与水分含量呈负相关,小麦籽粒硬度与水分含量呈正相关。  相似文献
华北高寒区多年保护性耕作对农田土壤容重的影响   总被引:2,自引:2,他引:0       下载免费PDF全文
为了在保护土壤、减抑风蚀的同时,兼顾作物的产量,探索适合华北高寒区的保护性耕作模式,给当地作物生产提供理论依据,在农业部张北野外观测站连续9年不同耕作方式定位研究的基础上,于2007-2009年探讨了免耕、松耕和翻耕对土壤耕层容重的影响.结果表明,3种耕作方式播种期不同耕层土壤容重均以免耕最高,翻耕最低,播前0~10 cm、10~20 cm土壤容重免耕分别为1.65、1.81 g/cm3,翻耕则分别为1.38、1.47 g/cm3,收获期土壤容重差异不明显.华北高寒区不同耕作方式对农田耕层土壤容重具有明显的影响,翻耕和松耕可以显著降低耕层土壤容重.受作物根系生长生物力的影响,收获期与播种期相比,免耕及松耕农田耕层土壤容重呈下降趋势,翻耕则无明显变化.  相似文献
土壤容重的修订方法研究   总被引:2,自引:2,他引:0       下载免费PDF全文
为了自动土壤水分观测资料更准确、更好地服务于实际应用以及应用于科学研究,从理论上分析自动土壤水分观测与人工实测值存在误差的原因及修正办法,通过公式P=Q0/W,用每次计算的土壤容重的平均值代表修正的土壤容重,分析评估用修正的土壤容重计算土壤重量含水率的可行性。结果表明:土壤容重修正公式可靠,利用自动观测土壤水分含水量以及土壤容重修正公式来计算土壤重量含水率可行,理论上可以取消逢八观测,也为自动土壤水分观测资料的实际应用、为两年一度的自动传感器评估提供一种指导方法。  相似文献
Soil Aeration under Different Soil Surface Conditions   总被引:1,自引:0,他引:1  
The assessment of the importance of soil aeration for various plant characteristics and environmental conditions is necessary to evaluate the oxygen relations to the crops. The root environment as a solid-liquid matrix depends upon soil structure and moisture condition. A limited oxygen supply restricts the root development and also reduces the nitrogen fixation in peanuts. Soil surface conditions can be altered by mulching and plays a significant role in protecting the plants against deficient aeration during critical periods of growth phases. The effects of eight mulching treatments (rice husk, rice husk-incorporated, paddy straw, sawdust, water mulch, clear polyethylene, black polyethylene and control) on the soil oxygen diffusion rate (ODR) during the various growth phases of peanut crop ( Arachis hypogaea L.) were investigated on a lateritic sandy loam soil (ultisols). These experiments were conducted for two consecutive seasons. ODR values were higher in mulched plots. With the progress of growth stages and also in deeper soil depths, the differences between the values of ODR among treatments narrowed down. The influence of mulches on other physical edaphic properties like bulk density, aeration (noncapillary) porosity and soil temperature were also studied. Mulches reduced the surface crusting and thereby soil bulk density; and increased the aeration porosity and ODR. Soil temperature was higher under plastic mulches whereas vegetative mulches suppressed it.  相似文献
长期施用化肥对山东三大土类土壤物理性质的影响   总被引:1,自引:0,他引:1       下载免费PDF全文
为阐明长期施用化肥对土壤物理性质的影响,通过定位施肥试验研究了肥对山东棕壤、潮土和褐土3种土壤物理性质的影响。研究发现在长期定位定量施肥试验中,一年两季施用化肥不会引起土壤容重增加,造成土壤板结。结果表明单独施用化肥25年后,各施肥处理的土壤孔隙度与对照相比均有不同程度的增加,而且土壤容重均下降,不同化肥处理的土壤容重并无增大的趋势。在三大土类中,以棕壤的土壤孔隙度最低,其次是潮土,褐土最高。此外,三大土类的土壤容重均与土壤孔隙度呈显著负相关;棕壤和潮土的土壤容重与耕层有机质呈显著负相关,而褐土的土壤容重与有机质相关性较差。笔者认为长期施用化肥并未显著提高土壤容重,而能提高土壤孔隙度,因此长期单独施用化肥并非造成土壤板结的主要原因。  相似文献
食品行业粉体材料流动性研究的新仪器——PFT   总被引:1,自引:0,他引:1  
奶粉、面粉、糖、盐、调味品等原料和添加剂粉体的流动性研究是目前很多材料行业的难点,现有常见的一些方法不能满足实际的需求。简单介绍了Brookfield公司根据ASTM D 6128推出的PFT粉体流体测试仪的基本功能,介绍了粉体流动函数、壁面摩擦、松装密度、时间固结、拱架、鼠孔、料斗半角的测量和计算。  相似文献
土壤容重对高产玉米根系生长的影响及调控研究   总被引:1,自引:0,他引:1  
不同土壤容重不同,其稳定性也不同。土壤容重的变化会引起土壤调节水、气、热能力的变化,提高土壤的自动调节能力可以使土壤肥力水平得以提高并满足植物对生长因子的持续需求。为研究土壤物理性质对玉米高产稳产的影响机理,以耕地棕壤为试验材料,采用盆栽方法,研究不同容重对玉米根系生长指标的影响,并进一步研究了施用不同有机肥量及模拟不同耕作深度对玉米根系生长的调控效果。结果表明:在设计容重范围内,容重增加,根系生长指标都表现为下降,容重大于1.2 g/m3时,不同处理根系生长指标差异显著;当容重大于1.3 g/cm3时,不同处理根系活力差异显著。施用有机肥对高容重土壤调控效果更好,有机质含量为4%与5%的处理差异减小,低容重土壤在所设计的有机质水平内调控效果也都较好。耕层厚度增加可以提高根系生长参数,但与对照相比,差异不显著。所以,对于紧实结构性较差的土壤,改善其调节能力应该通过增施有机肥的方法,紧实结构较好的土壤考虑使用耕翻的办法。  相似文献
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号