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荷蘭的養耕共生

Nick Savidov with basil crop and fish tanks in background.
Aquaponic systems are being increasingly recognised as having potential for solving some of the many problems facing modern agriculture and aquaculture. MIKE NICHOLS profiles two very different commercial aquaponic systems that embrace new ideas and innovations.


Deep flow system showing aeration.
I recently stopped off for a few days in Alberta, Canada, to meet up with Dr Nick Savidov, the Greenhouse Team Leader of the Crops Diversification Research Centre, Brooks, where I was briefed about their $15 million investment in state-of-the-art research greenhouses to be built in the next 12 months. I also learnt that he has greatly improved his aquaponic project with a few minor ‘tweaks’, which now make it significantly more productive and sustainable than the model developed by Jim Rekocy (US Virgin Islands) on which the original Brooks project was based.


Nick has made more efficient use of expensive greenhouse floor space by joining all the beds into a single ‘pond’ by doing away with all the paths and discarding the aquarium stone bubblers and replacing them with air lines of PVC tubing with small holes.

View of root system of basil plants.
In the new facility, he has improved water, space, and labour efficiency and eliminated chemicals including pesticides, fertilisers and pH adjustments. A new component has been incorporated into the system called Biofloc based on Geotube® technology, which allows him to physically separate solid waste from water. The water is then returned back to the system instead of being pumped out with solids as in the previous model. Solids are allowed to stay in the system gradually releasing nutrients due to a bio-fermentation process and thus serving as a slow-release fertiliser. He has found that the solids removed from the water using GeoTube® technology and stored in the Geotube® tank have been degrading with increasing rate releasing additional nutrients to the system. The result is nutrient use efficiency close to 100%. In other words, for the first time, he has created a recirculating self-sustainable system, which allows the conversion of practically all the organic material (fish feed) input into food (fish and plant biomass).

Hydroponic Garden
Basil plants and fish tanks
Bacteria are the key to the whole system, and it is interesting to note that according to Dr Savidov in year one the aquaponics system produces only 70% of the yield of a conventional hydroponic system, but in year two yields may be as much as 30-40% higher than those obtained using conventional hydroponics. He attributes the difference to micro-organisms in the system that take a year to develop the right balance.

Aquaponics in the Netherlands
In the Netherlands I visited the Greenhouse Improvement Centre at Bleiswijk primarily to meet with Willem Kemmers (of Priva), the Project Leader of EcoFutura (Fish and Tomato Project, another name for aquaponics) and with Pim Wilhelm, the fish biologist.


Fish and tomatoes - Bleiswijk, Netherlands.
The Fish and Tomato project is most impressive, and so it should be as it is supported by some major industry players. The fish tanks are held inside the greenhouse, below the hanging troughs in which the tomatoes are grown in Grodan rockwool. I have personal difficulties with the project, however, in terms that it is not a fully re-circulating system, and also the nutrient stream from the fish is sterilised with ultraviolet light before it is used on the tomatoes, and at the same time the solution is analysed, and the pH adjusted, and other nutrients added to suit the tomatoes. Similarly, many of the organic solids are removed and dumped. The drainage is then returned to the fish tanks, but is again modified (by increasing the pH) to suit the fish.

Thus, this is not the same as the fully re-circulating and sustainable system as has been developed in Alberta.

One of the difficulties of aquaponics is providing crops such as tomatoes with the optimum conductivity (about 3.5mS) necessary to ensure a high quality tomato in the middle of the winter. The conductivity of a solution coming directly from the fish phase is normally very low, but in a deep flow system this is not important as the nutrients flow past the roots, and the leafy crops are able to absorb adequate nutrients, however with tomatoes the objective is to use conductivity to control growth and fruit quality, and this is difficult (impossible) with a deep flow system using aquaponics.

However, when using a media-based hydroponic system such as rockwool or coir, it should be possible to control the conductivity of the solution by using reverse flow osmosis, and directing the water phase back to the fish, and the high conductivity stream to the plants.

Aquaponics is taking off in Canada as a teaching tool. A number of schools have now purchased Nick’s mini aquaponic set up, which he developed as a research tool. They are using this to demonstrate to school students some of the simple principles of ecology and biology.

Aquaponics vs organics
Sadly, the mainstream organic principals still do not like aquaponics. The argument is that it is unnatural, because the plants are not grown in the soil. A very strange decision when the system is certainly the most environmentally friendly and sustainable system that currently exists, as no nutrients are leached through the soil profile, and the system is particularly water efficient. Growing organically in soil is neither water nor nutrient efficient when compared to aquaponics!

In any case, how do you define soil? Basically it is:
• solid particles (e.g. sand, clay silt)
• organic matter
• micro-organisms
• water
• gases (oxygen, CO2 etc.).

An aquaponic system comprises all of these apart from solid particles, and these could be easily added to the system! The addition of a rock or two to the deep flow system should be more than adequate.

It is interesting to note that greenhouse soil-based organic systems usually produce only about 60% of the yield of a conventional hydroponic crop. In Canada, organic certification is available for crops grown using aquaponics, provided that they are grown in a cocopeat (coir) medium!

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蔬菜對溫度日照條件的要求

蔬菜對溫度日照條件的要求
全日照  8個小時日照 瓜類、茄果類、豆類、山藥、豆薯(地瓜)。番茄、黃瓜、茄子、辣椒等喜溫中、強光性
蔬菜夏秋季生產,玉米、青椒、西瓜、南瓜、西紅柿、茄子、芝麻、向日葵類。
其次是根莖類,如:馬鈴薯、甜菜、胡蘿蔔、白蘿蔔、甘藷、山藥等等。至少需半日照,才能生長,芋頭雖喜歡全日照,但比其他蔬菜耐蔭。 
需要中等光照大白菜、甘藍、芥菜、蒜、洋蔥。 

長日性蔬菜白菜、甘藍、芥菜、蘿蔔、胡蘿蔔、芹菜、菠菜、萵苣、蠶豆、豌豆、大蔥、洋蔥。

短日性蔬菜豇豆、扁豆、莧菜、空心菜。         

中光性蔬菜黃瓜、番茄、茄子、辣椒、菜豆

菜豆

菜豆喜溫暖,不耐高溫和霜凍。菜豆種子發芽的適溫為20-30℃;在40℃以上的高溫和10℃以下的低溫,種子不易發芽。幼苗生長適宜氣溫為18-25℃。花芽分化的適宜氣溫為20-25℃,過高或過低溫度易出現發育不完全的花蕾、落花。

菜豆對光照強度的要求較高。在適宜溫度條件下,光照充足則植株生長健壯,莖的節間短而分枝多,開花結莢比較多,而且有利於根部對磷肥的吸收。當光照強度減弱時,植株易徒長,莖的節間長,分枝少,葉質薄,而且開花結莢數少,易落花落莢。

菜豆根系強大,能耐一定程度乾旱,但喜中度濕潤土壤條件,要求水分供應適中,不耐澇。生長期適宜土壤濕度為田間最大持水量的60%-70%,空氣相對濕度以80%為宜。開花結莢期對水分最敏感,此期土壤乾旱對開花結莢有不良影響,開花數、結莢數及莢內種子數減少。土壤水分過大時,下部葉片黃化,早脫落。空氣濕度過大會引起徒長、結莢不良。

菜豆具有深根性和根瘤菌,對土壤的要求不甚嚴格,但仍以土層深厚肥沃、排水良好的輕砂壤土或粘質壤土為好。土壤過於粘重、低溫、排水和通氣不良則生長不良,炭疽病重。菜豆喜中性至微酸性土壤,適宜的土壤pH為5-7.0,其中以州6.2-6.8最適宜。菜豆最忌連作,生產中應實行2-3年輪作。

菜豆生育過程中,主要吸收鉀和氮較多,還要吸收一定量的磷和鈣,才能良好發育。結莢期吸收磷鉀量較大。磷鉀肥對菜豆植株的生長發育、根瘤菌的發育、花芽分化、開花結莢和種子的發育等均有影響。缺乏磷肥,菜豆嫩莢和種子的品質和產量就會降低。缺鈣,幼葉葉片捲曲,葉緣失綠和生長點死亡。缺硼,則根係不發達,影響根瘤菌固氮,使花和豆莢發育不良。 耐陰半陰(大概3-4小時日照) 應選擇耐陰的蔬菜種植,如萵…

黑檸檬

黑檸檬
Dried lemons are actually limes and are used heavily in Persian Gulf and also Iranian cuisine where they add a strong bitter flavor in addition to sourness. They are made by boiling ripe limes in salt water, and then sun drying until the insides turn black. The outside color varies from tan to black. They are sold whole or ground.

Black Lime is a spice used in Middle Eastern dishes. It is made by boiling fresh lime in salt water and sun drying until the insides turn black. The outside color varies from tan to black. It is sold whole or ground.

黑檸檬實際上是使用萊姆,並且在波斯灣和伊朗料理中被大量使用,除了酸味外,它們還添加了強烈的苦味。它們是利用鹽水煮成熟萊姆,然後曬乾,直到內部變黑。外部顏色從棕褐色變化到黑色。他們可以整顆或切片販售。
黑檸檬是用於中東菜餚的香料。它是通過在鹽水中煮沸新鮮的檸檬並經天然乾燥,直到內部變黑。外觀從棕褐色變成黑色。
USE Black limes are usually used in legume, seafood or meat dishes. They are pierced, peeled or crushed before adding them to the dish. After cooking they become softer and edible. They can also be powdered and added to rice dishes. Powdered black lime is also used as an ingredient in Gulf-…

為何冰箱冷凍室非得是零下18度?

為何冰箱冷凍室非得是零下18度? 不少家庭的冰箱有led面板,可顯示冷藏室和冷凍室溫度。每次看到那個零下18℃,不少人,包括筆者在內就會禁不住提出一個小疑問:為什麼冷凍室溫度非得是零下18℃?最多零下1℃不就結冰了嗎?搞這麼低溫度實在是浪費電呢。

聰明如很多人是這樣推測的

百思不得其解,於是很多人,包括筆者在內就開始推測後面的機制了。冷凍室的零下18℃其實不費電,相反,它是節約電力的一個好措施。為何?

冰箱隔一段時間,內部溫度升高後,它就要啟動壓縮機,嗡嗡嗡的。頻繁啟動壓縮機不僅耗電,冰箱的壽命也會降低,還有就是很吵人。怎麼辦?簡單,先把冷凍室的溫度搞得低低的,比如零下18℃左右。


然後,冷凍室的冷氣往上走,來到冷藏室,如此,就能長時間保持冷藏室的溫度處於0到8℃以內了。

待冷凍室的冷氣散失過多,溫度升高到零下幾度時,再啟動冰箱的壓縮機把溫度再次降到零下18℃,如此,冰箱的啟動次數就變少了。

實際是這樣嗎?很遺憾,不是。

原因之一:不一樣的水

水到零度以下就結冰了,這是絕大多數人的認識。然而仔細一想,這不適用於冰箱的冷凍室。因為冷凍室存放的不是上百升礦泉水,而是各種各樣的食物。

食物中含有大量水這沒錯,但這些水同時含有大量的鹽、糖等物質。就像每1升海水中大約含有35克鹽,所以平均起來,要到零下1.33℃時海水才會結冰。

因此,要想把食物凍結,並不是溫度只要達到水的冰點就可以,得保證足夠低的溫度,食物中的水才能凍結,這很重要,因為食物中只要有液態水存在,這就等於是為各種細菌的繁殖提供了必備條件。

圖為牛肉薄片在不同溫度和不同時間內測得的牛肉中凍結水量的曲線。

當牛肉薄片的溫度為零下4℃時,只有70%的水分被凍結;溫度下降到零下9℃左右時,也還有3%的水分未凍結;即使牛肉薄片的溫度降低到零下18℃時,也不是100%的水分都被凍結住。

原因之二:嗜冷微生物

根據微生物對不同溫度的適應範圍,可將微生物分為三大類,嗜熱菌、嗜溫菌和嗜冷菌。在食物的冷藏和冷凍過程中,我們面對的「敵人」是嗜溫菌和嗜冷菌。

一般來說,能引起食物腐敗和食物致毒的嗜溫菌,在低於3 ℃情況下不產生毒素,當然,個別菌種例外。

而對於嗜冷菌,一般得在零下10 ℃到零下12 ℃時才會停止生長。

有的黴菌甚至要到零下15~零下18 ℃時才會停止生長。

瞧,我們以為,零下幾攝氏度後微生物就被殺死或停止繁殖了,但…