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971.
The impact of different irrigation scheduling regimes on the quantity and quality of olive oil from a low-density olive grove in southern Portugal was assessed during the irrigation seasons of 2006 and 2007. Olive trees were subjected to one of the following treatments: A—full irrigation; B—sustained deficit irrigation (SDI) with 60% of ETc water applied with irrigation; C—regulated deficit irrigation (RDI) with irrigation water applied at three critical phases: before flowering, at the beginning of pit hardening and before crop harvesting and D—rain-fed treatment. Olive oil yield was significantly higher than rain-fed conditions in 2006, an “on year” of significant rainfall during summer. No significant yield differences were observed in the following “off year”. Among the irrigated treatments, olive oil production of treatment B was 32.5% and 40.1% higher in 2006 and 2007, respectively than the fully irrigated treatment A, despite receiving 49% less irrigation water. Such strategy could allow for an efficient use of water in the region, of very limited available resources, and for modest but important oil yield increase. Nonetheless, on the “on year” of 2006 treatment C used 13.9% of the water applied to treatment B and produced only 23.9% less olive fruits which could also make it illegible as the next possible strategy to use for irrigating olive trees in the region, provided that water is secured latter in the summer, a period of vital importance for oil accumulation and very sensitive to water stress as the poor results of 2007 revealed. The different treatment water regimes did not impact on the chemical characteristics of olive oils that were within the set threshold limits. Similarly, the sensory characteristics of the olive oils as well as bitterness and pungency were negligible for all treatments allowing them to be assessed as of “superior quality”.Overall, irrigation treatments had no influence on the commercial value of produced oils, being all classified as “extra virgin”. Such funding may be of vital importance to farmers willing to further their irrigation area, save water and still retain the protected designation of origin (PDO) seal of quality for their oil. 相似文献
972.
In Hawaii, pineapple is typically grown in raised beds covered with impervious plastic mulch. Field measurements of a commonly used herbicide (bromacil) mass beneath mulch-covered pineapple beds and inter-bed open areas revealed that open areas contained a mass of bromacil about 3.5 times greater than was originally applied, based on label instructions, to the entire field. The broadcast bromacil ended up in the inter-bed open areas through water runoff from the plastic mulch covering the pineapple beds. The objective of this study was to evaluate the impact of surficial management on water dynamics and bromacil concentration in the soil on a pineapple plantation using the one- (1D) and two-dimensional (2D) flow and transport models. Flow and transport processes were simulated in a 2D vertical cross-section perpendicular to the plant rows. The 1D simulation was limited to the open inter-bed areas. Several simulation scenarios were proposed to evaluate the effect of plastic mulch on bromacil transport in soil. In our simplified approach, the water and solute boundary fluxes for the non-covered areas were increased to simulate the water and solute contribution from the plastic mulch surface. The simulation results were compared with field observations of soil water potentials and resident bromacil concentration profiles. The field and laboratory-measured hydraulic and transport parameters were used for all simulation scenarios. Reasonably good agreement between the model-predicted and observed soil water potentials and bromacil concentration profiles was obtained. Biased 1D and 2D results were predicted when the water runoff from plastic mulch was neglected. The 1D approach to quantify bromacil transport beneath the inter-bed open areas seemed to be sufficient in case the water runoff from the mulch was taken into account. 相似文献
973.
974.
电磁-液压复合防抱死制动系统滑模控制 总被引:5,自引:0,他引:5
为了提高电磁-液压复合制动系统的紧急制动性能,设计了一套既适用于电磁制动特性,又适用于液压制动特性的电磁-液压复合制动系统,按系统结构建立了液压制动系统数学模型,分低速区和高速区分别建立了电磁制动数学模型。在1/4车辆模型受力分析的基础上,设计了滑模变结构控制器,搭建了硬件在环仿真平台,模拟沥青路面和冰雪路面进行了防抱死制动系统(ABS)性能仿真实验,并同商业ABS在同等条件下的实验结果进行了对比分析。实验结果表明:电磁-液压复合制动系统相比传统液压制动系统而言,响应速度更快,滑移率控制更精确,车辆制动稳定性更高,制动时间也有小幅减少,同时还减小了机械磨损,并降低了热衰退和失效的风险。 相似文献
975.
基于GIS、RS的滴灌棉田土壤养分精确管理分区研究 总被引:3,自引:0,他引:3
在GIS和RS支持下,针对新疆生产建设兵团第五师81团滴灌棉田,选用遥感结合土壤、土壤、遥感数据为数据源,利用模糊c均值聚类法进行土壤养分精确管理分区研究。研究结果表明:无论以何种数据源划分分区,分区后各分区养分指标变异系数均有所下降,空间分布朝均一方向发展;不同管理分区间差异明显,同一管理分区内土壤养分含量的空间变异差异较小。以遥感结合土壤为数据源所划分管理分区与实际产量所划分分区符合度最高达到91.36%,以土壤为数据源的管理分区次之,符合度达到84.40%,仅以遥感数据(归一化植被指数)为数据源所划分管理分区符合度最低为75.47%。因此,运用聚类分析法以遥感结合土壤数据为数据源可获得较好的分区结果,可实施变量投入和精确施肥推荐,为棉田土壤养分管理提供科学的理论依据。 相似文献
976.
977.
978.
979.
U形渠道断面流速分布规律的初步研究 总被引:3,自引:0,他引:3
通过对U形渠道断面流速分布进行理论分析和试验研究,发现断面内最大流速发生在水面以下,综合国内外学者使用不同的流速仪对矩形明渠和复式断面明渠的试验资料,得出最大流速发生在水面以下是由于二次流的存在引起的。分析水槽实测流速,发现由于最大流速发生在水面以下,使得中垂线流速分布与对数律流速分布形式和抛物线形式拟合曲线都有一定的偏差。 相似文献
980.