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农外3.1

(2008-04-16 21:12:55)
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杂谈

 

Irrigation according to the principles outlined in the preceding paragraphs can achieve about 60% efficiency in the application of water. The other 40% is lost by evaporation, deep percolation in the upper ends of the rows and in the most permeable soil, and in waste water from the lower ends of the rows. The wastewater loss can be lessened if the irrigator will reduce the size of the irrigation streams when they approach the lower end of the rows. The extra water can then be used elsewhere.

按照前面几段简述的原理进行灌溉时,使用水的效率可以达到60%左右,其余40%的水量损失于蒸发、灌水沟上游段和强透水土壤的深层渗漏以及沟道末端的废泄水量。灌溉水流接近沟道末端时,如果灌水员减小流量,就能减少废泄水量。剩余的水量可以用到别的地方。

Principles outlined for furrow irrigation apply to related methods of irrigation. Small furrows known as corrugations are used for uncultivated grain and forage crops. Such vegetation protects the soil better than row crops, but corrugations are too small to carry large streams of water.

简述的沟灌原理也适用于相近的灌水方法。称为灌水垄沟的小沟用于不中耕的粮食作物和饲料作物。和行播作物相比,这种植被能更好地保护土壤。但是,垄沟太小,不能输送较大的流量。

Flood Irrigation  The three main type of flood irrigation are basin irrigation, border  irrigation,  and  wild  flooding. Basin irrigation is probably the oldest method of all. It was practiced in Egypt more than 5000 years ago. It is a simple method that is still widely used to keep land flooded for long periods for paddy rice production or for shorter periods for many other crops. (烟种)

淹灌  淹灌的3种主要类型是:格田淹灌、畦灌、漫灌。格田淹灌大概是最古老的方法,这种方法在埃及已经应用了5000多年。这种方法简便易行,现在仍然广泛使用,使土地长期淹水,种植水稻,或使土地短期淹水,种植许多其它作物。

Land preparation for basin irrigation is accomplished by forming a narrow ridge between 15 and 50 cm high on all sides of each area to be flooded. The elevations within any one basin should be as uniform as possible-certainly within a range of 5 or 10 cm. The area of a basin may be limited by elevation changes, by the size that can be covered uniformly by the available water supply on permeable soils, or by cropping factors. Basins range in size from those designed to irrigate individual trees or small areas of vegetable crop to rice paddies occupying several hectares.

格田淹灌的田间准备是在每一个灌溉田块周围形成15—50厘米高的窄田埂。每块格田内的地面高度应尽可能均匀一致——一定要要限制在5~10厘米的范围内。格田面积受限于地面高度的变化、现有水量均匀覆盖于渗透性土壤的面积大小及耕作因素。格田大小的变化从设计灌溉单棵树或小面积的蔬菜作物到占据几公顷面积的水稻田。   

A ditch or other water supply large enough to flood the basin must be available on one side. Water is turned in until the desired depth is reached, then cut back to just enough to hold a constant depth of about 10 cm for paddy rice or shut off completely for other crops. The water in the basin may be allowed to completely infiltrate or, in some low permeability soils, the excess may be drained onto a lower basin after a specified time.

在格田的一侧必须有足以淹没格田的供水渠道或其他供水设施。把水改入格田,达到预计的水深,然后,减小流量到恰好能够保持稻田大约10厘米的水深;或者对其它作物完全停止放水。格田里的水可以完全渗入土壤,或对一些渗透性较差的土壤,在保持一段特定的时间后,把多余的水排到较低的格田里。

Border irrigation can be described as elongated basins with a gentle slope in the long direction. Water is turned in at the upper end of the border and allowed to flow down its length as though it were a very wide furrow. Borders range from 3 to 30 m wide and must be nearly level across their width so the entire area will be irrigated uniformly. Their lengths are similar to the lengths of furrows on comparable soils and slope gradients.

畦灌可以描绘成长条形的格田,沿其长边方向具有较缓的坡度。水从畦首进入,沿长边方向向下流动,宛如一个很宽的灌水沟。畦宽3—30米,沿宽度方向必须接近水平,以便使全部面积都能得到均匀的灌溉。对相似的土壤和坡度,畦田长度和灌水沟的长度雷同。   

Border irrigation can be used with slope gradients between 0.2 % and 2 % for cultivated crops, up to 4 % or 5 % for small grain or hay crops, and up to about 8 % for pastures. Extensive land leveling is often required because the topography must be smoother than for furrow irrigation. The cost of land leveling is offset by the low labor requirement for turning water into a few border rather than into many furrows or corrugations. The smooth topography is easy to work across at harvest time.

适宜采用畦灌的地面坡度是:种植中耕作物为0.2%一2%;种植小粒谷物或饲料作物为4%~5%;种植牧草约为8%。由于畦灌的地形必须比沟灌的平坦,因此,常常需要大面积平整土地。把水放入几块畦田比放人许多灌水沟或垄沟花费的劳力要少,这就补偿了平整土地的费用。平坦的地形有利于在收获时横穿畦田。

Several variations of border irrigation have been devised. Irrigation terraces made with surfaces that either slope like borders or are level like basins are one example. In another variation, ditches replace the ridge between borders and the area between is irrigated by blocking the ditches. Unfortunately, erosion can be a problem in the ditches, and uniform water application is often difficult to attain with this method.

畦灌的几种变通方式已经被设想出来了。梯式灌溉就是一个例子,这种灌溉把地面平整成有坡度的畦田,或水平的格田。在另一种变通方式中,用渠道代替畦埂,堵塞渠道,进行灌溉。遗憾的是采用这种方法,渠道冲刷是一个问题,而且往往很难实现均匀灌水。

Wild flooding is used to irrigate forage crops and sometimes small grains on uneven topography. Water flows down the ridges in ditches and is diverted to flood across the land. It is often necessary to have small spreader ditches to redistribute water that naturally accumulates in swales. The irrigator uses a shovel to make small furrows and ridges to guide water to any areas that would otherwise remain dry.

漫灌用于灌溉饲料作物,有时也用于在不平坦的土地上灌溉小粒谷物。水在沟渠内沿渠埂向下流动并被引出来灌溉农田,时常需要临时开挖小分水沟把聚集在洼地里的水再次分配。灌水员用铁锹挖沟、筑埂,把水引向那些不这样做仍是干旱的地方。

Wild flooding is inefficient in use of water and labor, but it irrigates land that can't be managed by other methods of surface irrigation. The soil may be too shallow or stony to have its surface smoothed by land leveling, and it may not be used intensely enough to justify a large investment. Rolling (起伏不平的)topography with slope gradients up to about 10% can be irrigated by wild flooding with permanent close-growing vegetation(多年生的茂密植被).

漫灌的用水效率和劳动效率都是很低的,但它能用来灌溉那些不能采用其他地面灌水方法灌溉的土地。由于土层太薄或石块太多而不能进行土地平整,也可能土地利用率不高不足以证明进行巨额投资是合理的。坡度达到10%的起伏地形,并拥有多年生的茂密植被时,可以采用漫灌。

2.  Subsurface Irrigation

Subsurface irrigation, also called sub-irrigation, can be considered as a controlled drainage system. Ditches are usually used, but some systems use tile lines. The systems remove water during wet seasons and add it during dry seasons so the water table is always at a controlled depth. That depth might be as little as 30 cm for shallow-rooted vegetation in a coarse sandy soil or as great as 120 cm in some loamy soils. The surface soil should be dry but most of the root zone should be moist. The field can even be cultivated and irrigated at the same time. (yanzhong)

2。地下灌溉  "

地下灌溉可以看作是一个有控制的排水系统。通常使用明沟,有些系统也使用暗管。这些系统在雨季用于排水,在旱季用于补水,因此,地下水总是处于一个被控深度。对于粗砂土上的浅根作物,这个深度也许浅到30厘米;在一些壤土上,这个深度可以深到120厘米。表层土壤应该是干燥的,而根系分布层的绝大部分土壤应该是潮湿的。这些农田甚至可以耕作、灌溉同时进行。

The required conditions for subsurface irrigation are, so stringent that relatively little land is sub-irrigated. The land surface must be quite smooth and have a slope gradient of less than 0. 5%. The subsoil (底土) must be highly permeable, but it must have a shallow water table or be underlain by an impermeable layer that permits a perched (位置高的) water table to be maintained. Both the soil and the irrigation water must be low in salts to avoid the formation of saline and sodic soil. Suitable conditions for subsurface irrigation most often occur on glacial outwash plains(冰川冲积平原), terraces, or deltas in humid or sub-humid areas.

地下灌溉要求的条件非常严格,因此,只有很少的土地采用地下灌溉。地面一定要相当平整,并且具有小于0.5%的坡度;底土必须是强透水土壤,但是它必须有一个较高的地下水位或在下面铺一个不透水层,以能维持一个较高的地下水位。土壤和灌溉水中的含盐量都必须很少,以防土壤盐碱化。适宜于地下灌溉的条件最常出现在冰川冲积平原、梯田或湿润、半湿润地区的三角洲地带。

3. Sprinkler Irrigation

large-scale sprinkler irrigation is much newer than surface and subsurface irrigation because the necessary pipes, pumps, and power supply were not available until comparatively recent times.

3.喷灌

比起地面灌溉和地下灌溉,大型喷灌是相当新的技术,因为喷灌所需要的管道、水泵、动力机械都是近代才出现的。

Advantages such as portability, adaptability to a wide range of soil and topographic conditions with little or no land preparation, and good control of water application have made sprinkler irrigation popular. High efficiency of water application may result in energy savings and help avoid erosion and leaching nitrates from the soil. Disadvantages limiting its use include high equipment and operating costs, the need to move lines in muddy conditions, salt damage to some plants if poor-quality water is used, and disease problems with some plants.

喷灌具有可移动性、对土壤和地形有很大的适应性、只需很少或根本不需要田间工程、并能准确地控制灌水等优点,所以受到普遍欢迎。高效用水可以节省能源,并有助于,防止土壤侵蚀和硝酸盐的淋失。限制喷灌使用的缺点包括设备费用和运行费用高,要在泥泞的条件下移动管道,水质不好对某些作物产生盐害,以及某些作物的病害问题。

Most field sprinklers use a rotating sprinkler head of the general type. Although the sprinklers may be fixed in permanent locations for limited areas of high-value crops, they are usually mounted on either moving or movable lines.

大部分田间喷灌采用通用的旋转式喷头。虽然喷头可以被安装在固定的位置为有限面积上的经济作物供水,但它们通常是安装在移动的或可以移动的管道上。

4. Trickle Irrigation

Trickle irrigation, also called drip irrigation, is the newest method and the one that achieves the highest irrigation efficiency: about 90% of the applied water is available to the plants. High efficiency is achieved by supplying water to individual plants through small plastic lines. Water is supplied either continuously or so frequently that the plant roots grow in constantly moist soil.

4.滴灌

滴灌是最新的灌溉方法,也是灌溉效率最高的方法,大约90%的灌溉水可以被植物利用。它通过很小的塑料管向每一棵植物供水,这就是灌水效率高的原因。灌水是连续的或十分频繁的,因而,植物的根系总是生长在湿润的土壤中。   

Trickle irrigation is especially suitable for watering trees or other large plants. Much of its use has been in orchards and vineyards but it has also been used to irrigate a variety of row crops including several kinds of vegetables and fruits. Its advantages are greatest where areas between plants can be left dry. It has no advantage for close-growing vegetation such as lawns, pastures, or small grain crops.

滴灌特别适用于灌溉树木或其他高大的植物。果园和葡萄园已经大量使用滴灌,各种行播作物也在使用滴灌,包括几种蔬菜和水果。它的最大的优点是植株间的土壤是干燥的。对于像草坪、牧草、小粒谷物这些茂密的植物,滴灌则没有优点。

An Israeli engineer named Symcha Blass developed the idea of trickle irrigation in the 1930s, but it had to wait until plastic tubing was available to make a practical system. Trickle irrigation in the United States increased from 40 ha in 1960 to over 50,000 ha in 1976 out of a worldwide total of about 160,000ha. Nearly half of the trickle irrigation in the United States is in California, some of it in avocado orchards with slopes up to 50% to 60%. Erosion is not a problem because there is no runoff.

一位名叫西姆查"布莱斯的以色列工程师在19世纪30年代就提出了滴灌这个想法,但是,直到塑料管道问世后,才制造了实用的滴灌系统。美国的滴灌面积由1960年的40公顷发展到1976的50000多公顷。1976年全世界的滴灌面积约160000公顷。美国接近半数的滴灌面积在加利福尼亚州,其中一些滴灌面积上种植鳄梨,地面坡度达50%或60%。因为不产生径流,所以没有冲刷侵蚀问题。   

A bonus with trickle irrigation is its ability to use water with a higher salt content than any other method up to about 2500mg/liter. The constant flow of water from the trickle emitter toward the outer edges of the plant root zone carries the salt along with it. Salt concentrations become very high in the dry areas between plants but not in the actual root zone.

滴灌还有一个优点,就是与其它灌溉方法相比,它可以使用含盐量更高的水源,含盐量可以高达2500毫克/升。来自滴头的稳定流量把水中的盐分带到植物根区的外缘。在植株之间的干燥区域内,盐分含量变得很高,但是在根系区域内盐分并不高。

Trickle irrigation saves water, is able to use water high in salt, functions well in all but the extremes of coarse-and fine-textured soils, works on almost any topography without causing erosion, and required little labor. The disadvantages are mainly high equipment costs and plugging of the lines by sediment, salt encrustation, or algae.

滴灌节省水量,能使用含盐较高的水源,在除了质地极粗和极细的土壤以外的所有土壤上都能获得满意的灌水效果,可以在几乎所有的地形条件下进行灌水而不产生冲刷,而且不需要多少劳力。缺点主要是设备费用高,管道易被泥沙、盐分结晶或藻类植物堵塞。   

A trickle irrigation system normally includes a control box that regulates the water pressure, filters the water, and provides for the addition of fertilizer and herbicides. Chlorine may be added to eliminate algal growth. The water pressure for trickle irrigation is normally 0.4 to I kg/cm2 as compared to I to 8kg/cm2 for sprinkler irrigation. Some trickle controls are set to increase the pressure periodically and flush the lines to reduce clogging.

滴灌系统一般包括一个控制箱,用以调节水压力、过滤灌溉水、并添加化肥和除草剂。也可以加入氯以排除藻类的生长。滴灌的水压力一般是0.4-1.0千克/平方厘米, 而喷灌要求的水压一般为1—8千克/平方厘米。一些滴灌控制设施被安装,用于周期性增加压力、冲洗管道,以减少堵塞。

Exercise 1

Decide whether the following statements are true or false.

  1 ) Surface irrigation is the oldest type of irrigation and it is out of use today.

  2) Trickle irrigation is the most efficient type of irrigation.

  3) Subsurface irrigation can be used in any condition and in any climate.

  4) For any type of irrigation, we can only use fresh water.

  5) Sprinkler irrigation is advantaged and can be used in most kinds of condition.

 

 

 

VOA1

New words

Salinization n. treating or impregnating with salt 盐化

 

Questions

1. What percent of all cropland is irrigated according to UNFAO? How much food is produced by the irrigated land?

2. What is the problem with the irrigated land? Where is the problem most severe?

3. What is salinization? By what rate does it reduce the world’s irrigated land?

4. What is the worst danger to the soil? What will happen when the ground is too wet?

5. How to prevent or reduce salinization? 

 

VOA-2

New Words

Nitrate  n. a salt of nitric acid硝酸盐

Ammonium  n. an ion NH4+ derived from ammonia铵

Questions

1. What are the two effects caused by higher levels of carbon dioxide in the atmosphere?

2. Who reported the findings regarding the changes in the use of N fertilizer.

3. How much has the carbon dioxide level in the atmosphere increased during the past two centuries?

4. By what percent did the carbon dioxide levels increased in the experiments? What was the plant response?

5. What are the scientists at the University of California at Davis studying?

6. What did the scientists at the University of California at Davis find?

 

 

VOA3

New Words

Catch  n. the total quantity caught at one time 捕捞量

Eel  n. long thin snake-like fish 鳝

Salmon  n. a large fish from northern ocean with silvery skin and pink flesh 大马哈鱼

Aquaculture=aquiculture  n. the cultivation of the natural produce of water 水产养殖

 

Questions

1. Why have many nations turned to fish farming?

2. How much did the farmed fish account for the world’s in 1970 and in 2000, respectively?

2. How much farmed fish was harvested in China in the year 2000?

3. What are the possible problems connected with the fish farming?

4. Why do the fish farmers feed their fish with antibiotics?

5. What did the scientist say positively about the farmed fish?

 

 

 

VOA-4

New Words

Larvae n. the immature, wingless feeding form that hatches from the egg of many insects〔单larva〕〔昆虫〕幼虫

Ladybug (ladybeetle) n. any of numerous small nearly hemispherical often brightly colored beetles of temperate and tropical regions 瓢虫

Pecan n. a large hickory that is widely grown in the warmer parts of the U.S. and in Mexico for its edible nut [植]美洲山核桃(树)

 

Questions

1. Why do farmers like some of the insects?

2. In what ways do aphids damage plants?

3. How many aphids could an adult lady beetle and a young beetle larva eat?

4. Why did American scientists import the multicolored Asian lady beetle?

5. Is there any ladybeetle that is bad? What are they?

6. What kind of ladybeetle is mentioned most in this passage? Where does it come from probably?

7. In what ways could the Asian lady beetles help farmers?

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