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121.
对济南市鹊山水库氨氮污染进行模拟分析,分析在不同工况与不同温度下,氨氮污染物的降解运移规律,预测了典型工况下,氨氮突发污染情况,并给出了相应的应对方案,为水库管理者对水库进行水量水质联合调度提供了依据。 相似文献
122.
Deficit irrigation based on drought tolerance and root signalling in potatoes and tomatoes 总被引:1,自引:0,他引:1
Christian R. Jensen Adriano Battilani Georgios Psarras Franciszek Janowiak Zorica Jovanovic Xuebin Qi Sven-Erik Jacobsen 《Agricultural Water Management》2010,98(3):403-384
Agriculture is a big consumer of fresh water in competition with other sectors of the society. Within the EU-project SAFIR new water-saving irrigation strategies were developed based on pot, semi-field and field experiments with potatoes (Solanum tuberosum L.), fresh tomatoes (Lycopersicon esculentum Mill.) and processing tomatoes as model plants. From the pot and semi-field experiments an ABA production model was developed for potatoes to optimize the ABA signalling; this was obtained by modelling the optimal level of soil drying for ABA production before re-irrigation in a crop growth model. The field irrigation guidelines were developed under temperate (Denmark), Mediterranean (Greece, Italy) and continental (Serbia, China) climatic conditions during summer. The field investigations on processing tomatoes were undertaken only in the Po valley (North Italy) on fine, textured soil. The investigations from several studies showed that gradual soil drying imposed by deficit irrigation (DI) or partial root zone drying irrigation (PRD) induced hydraulic and chemical signals from the root system resulting in partial stomatal closure, an increase in photosynthetic water use efficiency, and a slight reduction in top vegetative growth. Further PRD increased N-mineralization significantly beyond that from DI, causing a stay-green effect late in the growing season. In field potato and tomato experiments the water-saving irrigation strategies DI and PRD were able to save about 20-30% of the water used in fully irrigated plants. PRD increased marketable yield in potatoes significantly by 15% due to improved tuber size distribution. PRD increased antioxidant content significantly by approximately 10% in both potatoes and fresh tomatoes. Under a high temperature regime, full irrigation (FI) should be undertaken, as was clear from field observations in tomatoes. For tomatoes full irrigation should be undertaken for cooling effects when the night/day average temperature >26.5 °C or when air temperature >40 °C to avoid flower-dropping. The temperature threshold for potatoes is not clear. From three-year field drip irrigation experiments we found that under the establishment phase, both potatoes and tomatoes should be fully irrigated; however, during the later phases deficit irrigation might be applied as outlined below without causing significant yield reduction:
- •
- Potatoes
- °
- After the end of tuber initiation, DI or PRD is applied at 70% of FI. During the last 14 days of the growth period, DI or PRD is applied at 50% of FI.
- •
- Fresh tomatoes
- °
- From the moment the 1st truce is developed, DI is applied at 85-80% of FI for two weeks. In the middle period, DI or PRD is applied at 70% of FI. During the last 14 days of the growth period, DI or PRD is applied at 50% of FI.
- •
- Processing tomatoes
- °
- From transplanting to fruit setting at 4th-5th cluster, the PRD and DI threshold for re-irrigation is when the plant-available soil water content (ASWC) equals 0.7 (soil water potential, Ψsoil = −90 kPa). During the late fruit development/ripening stage, 10% of red fruits, the threshold for re-irrigation for DI is when ASWC = 0.5 (Ψsoil = −185 kPa) and for PRD when ASWC (dry side) = 0.4 (Ψsoil, dry side = −270 kPa).
123.
覆膜旱作稻N、P、K养分利用特征 总被引:3,自引:2,他引:3
在田间试验条件下对覆膜旱作稻体内N、P、K养分浓度、吸收动态及N肥利用率作了研究。结果表明,相同施肥处理条件下不同生育期覆膜旱作稻N、P、K养分浓度及吸收量均高于水作稻,尤以生育中后期较为明显;覆膜旱作稻全生育期N、P、K养分吸收量明显高于水作稻,分布在籽粒中的N、P、K养分含量也有所提高,而在整株中的占有率差异不大,N肥利用率提高12%左右。 相似文献
124.
125.
两种氮水平下CO2浓度升高对冬小麦生长和氮磷浓度的影响 总被引:16,自引:0,他引:16
预计到 2 1世纪末期大气CO2 浓度将会比目前水平增加 1倍 ,约 70 0 μmolmol- 1 左右。因此CO2 浓度升高对作物的影响研究十分重要。本文探讨在两种氮 (N)水平下 ,CO2 浓度升高对冬小麦 (TriticumaestivumL cv Xinong 872 7)生长和地上部N、磷 (P)浓度的影响及原因。试验设 3 5 0 μmolmol- 1 和 70 0 μmolmol- 1 两种CO2 浓度水平和 45kghm- 2 和 90kghm- 2 两种N肥施用水平。结果表明 ,CO2 浓度升高 ,冬小麦株高和叶面积指数 (LAI)均增加 ,净同化率 (NAR)值增加 ,叶面积比率 (LAR)下降 ,比叶重 (SLW )不增加。高CO2 浓度对相对生长率 (RGR)的影响因施N水平而异 ,低N时RGR不增加 ,高N时明显增加。CO2 浓度增加 ,小麦抽穗提早 7~ 8d ,叶鞘、茎杆和地上部干物重提高 ,叶片、叶鞘和茎杆N、P浓度降低 ,但叶片、叶鞘和茎杆N、P吸收量增加均不明显。CO2 浓度升高 ,氮磷利用效率 (NUE和PUE)提高 ,而对相对氮磷累积速率 (RNAR和RPAR)影响不大。高CO2 浓度冬小麦体内N、P浓度下降是由于稀释效应以及NUE和PUE提高之故。 相似文献
126.
Jiongxin Xu 《CATENA》2002,49(4)
According to the yearly maximum suspended sediment concentrations (SSC) in the Yellow River and its tributaries, the rivers are divided into three types of more than 300, 20–300, and less than 20 kg/m3. The middle Yellow River basin is located in the transitional zone from subhumid to semiarid climates, and covered by a thick loess mantle. Neighboring on the desert areas to the northwest, the surface material of the Loess Plateau exhibits some marked areal differentiation in grain size and forms three zones covered by sandy loess, (typical) loess and clayey loess from northwest to southeast. Controlled by these physico-geographical conditions, the grain size of river-transported sediment shows some particular characteristics; at small water discharge or SSC, the grain size of suspended sediment abruptly decreases to a minimum with increasing water discharge or SSC. At water discharge of more than ca. 40 m3/s or at SSC of more than ca. 40 kg/m3, the grain size increases with water discharge or SSC.During the low-stage season, the relatively clear baseflow may scour the coarse bed materials, so the suspended sediment is relatively coarse. In the rainy season, rainstorm runoff washes out fine loess materials to the river, making suspended sediment fine. During relatively strong rainstorms, there often occur hyperconcentrated flows at SSC of more than 300 kg/m3. The relatively coarse grains could then remain suspended in the mixture of water and fine suspended sediment. 相似文献
127.
选用AG50W-X8阳离子交换树脂,并以批处理的方式,成功地将蜂蜜中的肽类物质与其它组合得到了分离。抗褐变实验结果清楚地表明,蜂蜜中的肽类成分完全没有抑制褐变的活性。这与以前的报道截然不同。 相似文献
128.
129.
为探讨钙元素对桃果实品质、耐贮藏性的影响,确定最佳的叶面喷施钙元素的浓度,研究了喷施钙后,桃果肉组织中钙元素的分布特征、叶片叶绿素的含量以及对果实可溶性固形物含量(SSC)、大小、硬度和耐贮藏性的影响。结果表明,果肉中Ca2 的含量随着喷施钙元素浓度的提高而增加,当喷施CaCl2浓度为0.5%时叶绿素的含量最大,当喷施CaCl2浓度为1%时,SSC、果实大小和果肉硬度达到最大值;当喷施CaCl2浓度为2%时,放置3天后果实硬度最大。本研究确立了最佳的喷施浓度,为深入研究果实钙离子浓度梯度在果实品质形成方面的作用提供了依据。 相似文献
130.
北方森林是全球第二大生物群区,约占全球森林面积的30%,尽管其细根生物量仅占森林生态系统很小的一部分,但其周转率更快,更易分解,因此,其对土壤碳循环和大气CO_2通量贡献很大。笔者综述了氮沉降和CO_2浓度升高的背景数据,总结了细根对二者变化的响应,主要从细根的形态特征、解剖结构和生理功能方面入手,探讨了其对氮沉降和CO_2浓度升高的响应。结论如下:(1)大气氮沉降量一直处于上升状态,与人类活动密切相关的有机氮量所占比例逐渐加大,而无机氮中NH_4~-N和NO_3~-N的变化趋势表现不同;(2)大气CO_2浓度一直呈上升趋势,细根形态特征、解剖结构和生理功能对其表现出明显的响应;(3)树种、年龄、土壤类型等都会改变细根形态、解剖结构和生理功能对氮沉降和CO_2浓度升高的响应结果,但改变的程度不同。研究结果可为北方森林乃至温带森林生态系统功能对氮沉降和CO_2浓度升高的响应提供参考依据和数据支持。 相似文献