Measured and estimated water use and crop coefficients of grapevines trained to overhead trellis systems in California’s San Joaquin Valley

The use of overhead trellis systems for the production of dry-on-vine (DOV) raisins and table grapes in California is expanding. Studies were conducted from 2006 to 2009 using Thompson Seedless grapevines grown in a weighing lysimeter trained to an overhead arbor trellis and farmed as DOV raisins for the first two years and for use as table grapes thereafter. Maximum canopy coverage for the two lysimeter vines across years was in excess of 80 %. Seasonal (15 March–31 October) evapotranspiration for the lysimeter vines (ET_Lys) was 952 mm in 2007 (farmed as DOV raisins) and 943 and 952 mm (when farmed as table grapes). The maximum crop coefficient (K _cLys) across all 4 years ranged from 1.3 to 1.4. These maximum values were similar to those estimated using the relationship where K _c is a function of the amount of shaded area measured beneath the canopy at solar noon (K _c = 0.017 × percent shaded area). Covering the lysimeter’s soil surface with plastic (and then removing it) numerous times during the 2009 growing season (1 June–14 September) reduced ET_Lys from an average of 6.4 to 5.6 mm day^?1 and the K _c from 1.07 to 0.93. A seasonal basal K _c (K _cb) was calculated for grapevines using an overhead trellis system with a 13 % reduction in the K _cLys across the growing season.     

小黄鱼热泵干燥工艺及设备选型分析

研究了不同热泵干燥温度下小黄鱼的干燥特性,并对其干燥品质进行分析。结果表明在干燥温度55℃、铺放密度为6.48 kg/m2的条件下干燥时间为13.5 h,干燥品质最优。在综合考虑能耗、企业加工条件和产品品质的前提下,将生产工艺参数确定为:干燥温度60℃、铺放密度为6~7 kg/m2,干燥时间为10~12 h。根据企业日处理量5.5~6.0 t的加工要求,通过对产能核算及加工成本计算,确定设备选型方案为:1台GHRH-510型热泵干燥机与2台GHRH-340型热泵干燥机,该方案投资回报期短,社会效益明显。     

R4102直喷式柴油机起动过程粗暴性的测试分析

利用自行开发的数据采集系统，同步测量了Ｒ４１０２直喷式柴油机起动过程的瞬时转速及１、３缸的气缸压力，对起动过程粗暴性问题进行了测试分析，并研究了其对发动机连杆，活塞，活塞销等主要受力零件强度的影响，结果表明：该影响很大，设计中应予以考虑。     

电磁制动器性能评价体系的建立及指标权重的确定

首次建立电磁制动器性能的评价体系,重点介绍其中指标体系的确立方案及依据,通过利用层次分析法建立评价模型并对各指标进行权重的确定和层次的总排序,取得了比较客观合理的评价结果。     

嫁接苗盘自动叠放装置研究与设计

为了提高嫁接作业的自动化水平,实现嫁接操作的流水线生产,设计了用于嫁接作业后期对载有嫁接苗的苗盘自动叠放的装置。该装置的机构部分包括由滚筒和线性模组构成的推送平台,以及由链条、链轮、机架构成的升降机构,采用PLC进行系统控制。试验表明,该装置运行稳定可靠,升降定位精度±1.0mm,最长动作周期26s,适用于现阶段蔬菜嫁接生产流水线。     

An approach to multi-criterion evaluation of irrigation system performance

Irrigation systems aim to meet multiple objectives and performance must therefore be assessed using quantifiable measures for each. It therefore becomes an extremely difficult task to capture the valuation of all of them simultaneously and to mentally process the trade-offs between them in order to arrive at an overall impression of system performance. There is a need for a methodology which provides a systematic approach to comparing and combining the components of overall performance.Multi-Attribute Utility Theory offers an attractive approach to assessing performance of irrigation systems in the form of a utility function which reflects the strength of preferences and trade-offs between individual performance criteria. The method is described and demonstrated on the basis of a case study of irrigation in Sudan.     

Alfalfa (Medicago sativa L.) water use efficiency as affected by harvest traffic and soil compaction in a sandy loam soil

Summary Traffic during alfalfa harvest operations can cause soil compaction and damage to newly growing stems. Root exploration for soil water and nutrients, forage growth dynamics, and final yield can all be affected. The objectives of this study were to determine the long-term effects of harvest traffic and soil compaction on water-use efficiency (WUE) of alfalfa grown in a Wasco sandy loam (coarse-loamy, mixed, nonacid, thermic Typic Torriorthents). Alfalfa was planted into tilled soil and managed with or without harvest traffic. Plants subjected to traffic during harvest had a significantly lower WUE two out of the three years studied compared to plants that were never subject to traffic. The second experiment examined whether planting alfalfa into compacted soil and managed with or without harvest traffic altered WUE. Soil compaction had no affect on alfalfa WUE. It was significantly lower when grown in compacted soil and subjected to harvest traffic. It is suggested that the decrease in WUE caused by harvest traffic may be explained by plants allocating carbohydrates to damaged shoots and crowns instead of to above ground forage production. The area of the field affected by harvest traffic, which damages newly growing stems, should be minimized to increase crop water use efficiency.     

Interpretation of solute profile dynamics in irrigated soils

Summary Knowledge of the flux of water flowing through macropores in soils is required to devise management strategies for efficient fertiliser use and to prevent fast movement of solutes and pollutants to groundwaters. Water and solute balances in soil profiles were used to develop a simple model for assessing the magnitude of macropore flow. Fluxes of water bypassing the soil matrix were calculated at 35 sites to be between 0 and 415 mm y^–1, with the flux being < 200 mm y^–1 at most sites. The maximum flux was three times the flux flowing through the soil matrix but only one third of that infiltrating the soil. The flux of macropore flow was not simply related to soil types or soil properties, although the highest fluxes did occur in cracking soils. A qualitative method of using soil chloride profiles to indicate the occurrence (but not magnitude) of bypass flux was also demonstrated. Both these quantitative and qualitative assessments of bypass flow should assist in interpreting root-zone hydrology in soils.     

The growth and nitrogen economy of rice under sprinkler and flood irrigation in South East Australia

Summary ¹⁵N balances were compared in rice (Oryza sativa L., cv. Calrose) grown under continuous flood (CF) or sprinkler irrigation. Two sprinkler treatments with irrigation frequencies of once (S1W) and thrice (S3W) per week were studied. Five atom %¹⁵N-labelled urea (60 kg N ha^–1) was applied to microplots either 36 or 84 days after emergence (DAE). An equivalent amount of unlabelled urea was applied at the other application time, so that each microplot received a total of 120 kg N ha^–1 in an equal split. There was no significant effect of irrigation treatment on recovery of urea N by straw. Straw recovery from urea applied 36 DAE was almost half that from an application 84 DAE, and time of urea application produced a similar effect on recovery in grain. Grain recovery in S1W was less than half that in CF and S3W for both application times. Total plant recovery of urea N applied 36 DAE was similar for all irrigation treatments (average 29%), but for urea applied 84 DAE total plant recovery in CF (67%) was significantly higher than in S1W (49%). Total N uptake in the plant tops was considerably lower in both the sprinkler-irrigated treatments when compared with CF, and this was mostly due to reduced soil N uptake in S3W (one-half) and S1W (one-third). The proportion of N derived from fertilizer in the plant tops increased from 40% in CF to 60% in S1W. Immobilization of applied N in the soil of the sprinkler-irrigated treatments was greater than in CF by factors of 1.5 (S3W) and 2 (S1W). Immobilization of urea N applied 36 DAE was almost 50% greater than immobilization of urea N applied 84 DAE. There was a trend for lower losses of fertilizer N with sprinkler irrigation (mean loss 18% of the applied N) compared with CF (27%). Within all irrigation treatments, the loss from urea applied 36 DAE was more than double the loss from urea applied 84 DAE. An additional study in CF compared the ¹⁵N balance for split application versus a single dose applied 36 DAE (before permanent flood). Split application resulted in significantly increased plant recovery of applied ¹⁵N, and this was largely associated with increased recovery in the grain. Slightly more fertilizer N was immobilized in the soil with a single application. The effect of application method on N loss was not significant.     

Managing the water balance of The Fayoum Depression,Egypt

A study of the water balances of The Fayoum irrigated lands and Lake Qarun was made to investigate the management of the irrigation system and the efficiency of irrigation water use. The two water balances are strongly interrelated. The drainage flow to Lake Qarun and the water level of the Lake are in delicate balance. A rise in Lake level causes the inundation of adjacent land. Management of The Fayoum water balance assumes control over irrigation water flows, but this control has technical and organizational limitations. Also discussed is the influence of irrigation practices in The Fayoum on the water balance (e.g., the autumn flushing of fields and farmers' preference for not irrigating at night in winter). Notwithstanding a high overall efficiency, irrigation efficiency during the winter is low. The reasons for this are given, together with the constraints against improving system management. Improved uniformity of the division and application of irrigation water will enable a better technical control of flows and will result in better water management in The Fayoum. Abbreviations: FID — Fayoum Irrigation Department, 1 feddan (fe) — 0.4 ha, 1 mcm — 1 million cubic metres: an average annual flow of 3.17 m³/s gives 100 mcm, m³/fe.year — supplied volume (m³) per surface area (fe) per year: 1000 m³/fe.year equals 240 mm/year, MSL — Mean Sea Level