Development of Organic Ecological Soilless Cultivation

Xingchun WANG, Qihang LIN, Ande MU, Yu SU, Zibu WANG

Guizhou Biological Resources Development and Use Characteristic Key Laboratory, Guiyang 550018, China

Organic ecological soilless cultivation is a soilless technology using organic solid fertilizers and abandoned river sands, coal cinders, and straws as cultivation substrates, irrigated directly with water,instead of natural soils and traditional nutrient solutions. It is a nationally developed low-cost but high-profit technology according to national conditions, performing excellently in terms of economic, social and ecological fields. The technology coincides with the targets of organic agriculture and agricultural sustainable development and will be a major orientation for greenhouse vegetable in China.

Development of Soilless Cultivation

Global development

Soilless cultivation technology o riginates from Denmark, developed by Grodan company based on rock wool[1]. Research on modern soilless cultivation technology, however, focuses on Europe, the US, Israel and Japan, mostly characterized by automatic modern greenhouse integrating engineering technology, computer technology,material science and horticulture Science,which makes it possible of automatic control of temperature, humidity, sunshine, and nutrient solution, and drip irrigation, as well as seedling cultivation, transportation,pruning, supplementary pollination,disease and pest control, harvesting and packaging. In contrast, traditional hydroculture is the growing of plants in an inorganic salt-based environment,but it costs high and is hardly to be grasped by manufacturers in terms of preparation and management, which prevents the technology from application[2-4]. Organic ecological soilless cultivation just changes traditional planting to resolve a series of problems in cultivation, such as successive cropping obstacle, soil salinization, deterioration of soil borne pests and diseases,and accumulation of hazardous substance, so that it reduces costs and chemical reagents in cultivation process by replacing traditional hydroculture.

Domestic development

Recorded in the Book of Han,soilless culture started before 2000 years in China, which is much earlier than that recorded by ancient Rome.Nevertheless, earlier start, soilless culture developed much slower domestically, and fell behind to theNetherlands, Japan, Britain and the US. Only by introduction and integration made it develop to certain extent in China.For example,tropical regions in South China are dominated by deep flow technology (DFT); southeastern coastal areas are dominated by nutrient film technique (NFT);northern regions are dominated by substrate culture-based soilless culture. However,these cultures are all on basis of nutrient solution which is hardly to be operated by normal workers. Therefore,soilless culture develops quite slowly in our country and it is urgent to research a simple and practicable substrate-based culture technology in order to accelerate application and extension of soilless culture in China.

By a long term exploration,Vegetable Research Institute of Chinese Academy of Agricultural Sciences is engaged in organic ecological soilless cultivation dominated by a new supply method of fertilizer and water for replacing nutrient solution[5]. For example, the sterilized fowl manure can applied in culture substrates as a kind of slow-release organic fertilizer, abundant with nutrients, and meets growth demands of crops. What’s more, organic ecological soilless culture is developed by successive improvements on a complete set of techniques,which takes sterilized chicken manures as nutrients and adds organic fertilizer taking place of nutrient solution of substrate-based culture. Besides, Liu et al. took slag, mushroom residue,saw dust, and corn stalk as organic substrate and applied organic solid fertilizer, so that the cultivated tomatoes achieved the maximal yield[6].Li et al. mixed pure reed residue and 20%perlite as substrates[7].Li cultivated lettuce and cucumber by mixing furfural residues, which improved yield and nutrient components[8].

Advantages of organic ecological soilless cultivation

For traditional soilless culture,vegetables are irrigated with nutrient solution prepared with inorganic chemical fertilizers, which costs higher and hardly learnt in terms of preparation of nutrient solution and management technology. What’s worse, environment would be contaminated by nutrient residues. In contrary, organic ecological soilless cultivation just makes use of organic solid fertilizers fermented with substrates to take place of traditional nutrient solution, so that the method costs lower,and easier for operation and management, free from pollution. What’s more, the products are highly-qualified, meeting AA grade green food standards in China. Therefore, it is much suitable for present condition of our country and much popular among industries.

Selection of Substrates

Sources of substrates

During cultivation process by organic ecological soilless cultivation,wastes can be taken as cultivation substrates, produced from industry,agriculture, breeding industry, as well as forestry and animal husbandry,which maximizes resource use and resolves the problem of treatment on agricultural residues, such as herb residue, mushroom dreg, coal ash,straw,chicken manure,swine manure,branch/leaf residues, camellia seed and fruit residue.

The type of substrate components

Yu et al.researched substrates of soilless cultivation based on straw fiber and concluded that[9-11]solid substrates can be classified into organic substrates, such as saw dust, bark, nonwoven fabric, and straw, inorganic substrates, such as ceramsite, volcanic lava, rock wool and silica gel,and formula substrate, such as ceramsite+perlite, peat+ wood shavings,and peat+silica gel.

Nutrient characteristics of cultivation substrates

Tian et al. explored absorption property of water and nutrient of substrates, as well as nutrient characters[12]and the results indicated that the accumulation of dry matter inside tomato fruits presented a linear trend by organic ecological soilless cultivation; tomatoes grew better in seedling stage, compared with the control; total yield per unit area of tomato was higher,also.

Standard for selection of cultivation substrates

Xie et al. made research on soilless cultivation of Chinese vegetables[13]and demonstrated that highlyqualified substrates of soilless cultivation should be able to provide a stable and coordinated rhizosphere environment in terms of water, fertilizer, gas and heat, supporting anchor plants,and maintain water. What’s more,substrates of organic cultivation stabilize rhizosphere environment to certain extent and guarantee crop growth. Li et al.[14]researched substrates of soilless cultivation based on organic wastes from industry and agriculture and concluded that physicochemical property and biological stability of the substrates should all meet relevant demands. Specifically, for physical property, proportions of solid-liquidvapor should be appropriate; volumeweight should be in the range of 0.1-0.8 g/cm3;total porosity keeps of 75%;big and small pore ratio keeps about 0.5. As for chemical property, cation exchange capacity (CEC)is high;nutrient preserving capability of substrates should be good enough; pH values should be in 6.5-7.0. Besides,C/N value should be maintained well to guarantee biological stability of substrates during cultivation. Additionally,Jing et al.[15]discovered that selection of substrates should take difficulty of collecting materials, nutrients, fertilizer efficiency, impurities, germs, peculiar smell, weight, water absorption and retention,price,adjustment and preparation.

Merits of substrate-based cultivation

Conductive to crop growth Song et al.[16]researched the effects of organic substrates with different proportions on lettuce growth,yield and quality and concluded that organic substrates promote lettuce growth in terms of plant height,accumulations of dry and fresh materials of ground parts.For example,the optimal proportions for cultivating lettuce is (v(mushroom residue)∶v (cornstalk)∶v(sheep manure)∶v(perlite)=3∶4∶1∶4), (v(mushroom residue)∶v (cornstalk)∶v(sheep manure)∶v (perlite)=4 ∶3 ∶1 ∶4) and (v(mushroom residue) ∶v (cornstalk) ∶v(perlite)=4∶4∶4).

To obtain vegetable and improve yield and economic and environmental benefits It is reported by Qin et al.[17]that tomatoes proved better in terms of physical and chemical properties, single fruit weight and per plantyield, with yield increase rate of 35.24% , which were cultivated with mixed substrates of slag, fermented sheep manure, and bio-organic andinorganic compound fertilizer with proportions of 3.5∶1.5∶0.5. Ye et al.[18]researched effects of different substrates (treatments with sands, saw dusts and mixture) on vegetable yield and nitrate content, and concluded that the treatment with mixture of sands and saw dusts improved vegetable yield and quality and reduced content of nitrate, without environment pollution, which is contrary to the treatment with sands. Liu et al.[19]explored eutrophicated water purification by economic plants as per soilless cultivation based on artificial substrates.Specifically, the research cultivated cress and Ipomoea aquatica with cystosepiment and vermiculite as per soilless cultivation to explore water purification effects and the results indicated that soilless cultivation technology applied in eutrophicated water performs well in sewage purification, with environmental and economic benefits.

Comparisons on Cultivation Effects

Liu et al.[20]investigated organic ecological soilless cultivation on vegetables and concluded that by organic ecological soilless cultivation in a heliogreenhouse, vegetable yield grew by over 35%, fertilizers reduced by over 70%,fertilizer cost decreased by 50%-60%, and water saved by 50%-70%.Therefore, organic ecological soilless cultivation is widely promoted currently,and the concerning area is 60%higher than national soilless cultivation area. What’s more, more than 95%users are individual vegetable farmers.In addition,average annual yield of the cultivated vegetable reached as high as 240 000 kg/hm2, growing by 150%than that cultivated in normal soils.It is notable that cucumber yield was as high as 380 190 kg/hm2[21].

Comparisons of total yield

In China, vegetable farmers are engaged in learning organic ecological soilless cultivation and have already been skillful at the cultivation, so that abundant vegetable products can be supplied in markets, with social and economic benefits. In Guizhou Province, however, the technology develops slowly. For instance, Hu explored fruit cucumber as per organic ecological soilless cultivation[22]and concluded that yield of fruit cucumber reached 75 000-90 000 kg/hm2in single season in the form of double-cropping and total yield reached over 150 000 kg/hm2. Zhao conducted research on organic ecological soilless cultivation in a heliogreenhouse and the results showed that average yield of vegetable reached 87 000 kg/hm2, increasing by 25%[23]in a production cycle. Zhang et al. carried out research on organic ecological stereo-cultivation of interplanting of cucumber and pepper in a greenhouse in desertified areas in Hexi Corridor and the results indicated that[24]yields of cucumber and pepper reached 79 890 and 75 000 kg/hm2,respectively.

Zhang et al.[25]conducted an experiment on organic ecological soilless cultivation on vegetables in a greenhouse in the northwest and the results showed that based on double-layer arched shed and double films, organic ecological soilless cultivation allowed multiple cropping (3-4), covering leafy vegetable in early spring, watermelon in spring, sun-shading leafy vegetable in summer, and tomato in autumn.Specifically, yield of leafy vegetables reached 30 000 kg/hm2in spring; watermelon yield reached 45 000 kg/hm2and output value was 15 000 yuan;yields of sun-shading leafy vegetable and tomato were 30 000 and 120 000 kg/hm2, respectively. It is obvious that annual mean yield of vegetable achieved 225 000 kg/hm2, increasing by 35% compared with common cultivation.

Comparisons of yield per plant

Qin et al.[26]explored soilless cultivation of tomato based on mixed substrates of furfural residues and concluded that the physicochemical property of the mixed substrates of slag,sheep manures, and furfural residues is suitable for tomato growth and development. Compared with the treatments of slag, sheep manure and turf and of soil-based cultivation, plant heights of seedlings increased by 4.08 and 11.02 cm, respectively, the numbers of leaf grew by 1.23 and 5.22 and dry weights of roots enhanced by 3.74 and 11.48 g per plant. Considering from economic traits of tomato, insignificant differences were shown between the treatments of slag, sheep manure, and furfural residues and of slag, sheep manure and turf. Compared with the treatment of soil-based cultivation, tomato plant height increased by 16.18 cm, weight per fruit grew by 25.40 g, fruit weight per plant enhanced by 0.89 kg in the treatment of slag, sheep manure, and furfural residues,which suggested that annual mean yield increased by 20 541.9 kg/hm2.

Comparisons of treatments with different substrates

The substrates for soilless cultivation should be volatile upon geographical environment and climate.For example, Zhang conducted research on physicochemical property of substrates of soilless cultivation[27]and the results indicated that soilless cultivation with carbonized rice husk is suitable in the southern areas of the Yangtze River; soilless cultivation with slag,turf and saw dust is strengthened in Northern China; agricultural wastes are used as substrates for soilless cultivation in the north.Wang et al.[28]conducted research on cultivation of tomato based on substrates of sterilized chicken manures and the results showed that tomato yield cultivated with sterilized chicken manures was 570 kg/hm2lower than that cultivated with nutrient solution in early stage,but 10 005, and 18 540 higher in middle and later stages. Additionally, total yield kept 27 950 kg/hm2higher. Li et al.[29]proposed that cucumber cultivated with organic wastes grew mature earlier with a high yield, and tomato cultivated with turf and rice husk increased in terms of yield than that cultivated with just turf.What’s more,the rate of malformed fruit declined. Besides cultivation and production, organic wastes could also take place of turf in cultivating seedlings. Y. inbar and Y chen made use of decomposed cow dung and grape marc as substrates. Furthermore, cucumber,tomato and pepper cultivated with liquid cow dung grew better than those cultivated with vermiculite and turf.

Development Prospect

China is a fast developing country,and application of agricultural technology is conductive to advancing agriculture development and improving income per capita. It has shown that research and development,and application of organic ecological soilless cultivation accelerate soilless cultivation in China. For example, the areas applied by soilless cultivation was only 0.1 hm2, and as high as 12000 hm2in 2005. What’s more, the area reached 1 750 hm2in the end of 2005, representing over 60%nationwide. In 2011,the area exceeded 3 000 hm2, dominated by vegetables and supplemented by floral planting(Table 1).

Generally speaking, traditional soilless cultivation uses nutrient solution as cultivation substrates. Specifically, a set of equipment is required and it costs high in terms of solution preparation,management and energy.Secondly, the use rate of water and nutrient by crop is lower than that of soil-based cultivation.Finally,preparation,regulation and use of nutrient solution have high demands on relevant staff, and technicists are a top priority.Therefore,it is much hard for the technology to be widely applied.

In contrast, organic ecological soilless cultivation uses agricultural wastes or wastes produced from cultivation, through fermentation and decomposition, so that it meets nutrient demands of plants. In planting process, specific nutrients can be added according to physiological status of specific plant. Jiang explored the aspect[30]and the results showed that the specific nutrient can be applied in multiple times directly on substrates or in the form of inorganic chemical fertilizer upon plant growth. Besides, organic substrates are abundant with trace elements and management and production almost keep the same as soilbased cultivation. Hence, only total quantities and balances of N, P and K should be taken into consideration for the technology, which simplifies operation and management process and reduces production and cultivation costs.

Specifically, nonrecurring expenditure,substrate cost and fertilizer cost lowered by 45.5%, 60% and 53.3%[30],and it can be concluded that organic ecological soilless cultivation is characterized by simple operation, low costs, and easy for promotion, enjoying a promising prospect in China.

Table 1 Distribution of soilless cultivation area in 2001 in China

Expectation

Considering increasing population and occupation of agricultural lands by construction lands, it is urgent to seek a new cultivation method which resolves land issue without occupying it.Currently, organic ecological soilless cultivation is an optimal choice according to agricultural market, science and technology research and national policy.On the other hand,large-scale development and industrialization are accelerating of high value-added agricultural products, such as vegetable and flower, as modern and protected agriculture evolves and farming structure adjusts. In the future, organic ecological soilless cultivation will make use of organic solid wastes and select and classify material sources, as well as standard control on fermentation process in order to accomplish cyclic utilization of natural resources and sustainable development of agriculture. It is notable that soilless cultivation has been applied with modernized control on instruments and meters and computer automatic control technology as facility develops domestically.Large-scale, intensification, automation, industrialization and domestication would be development orientation for organic ecological soilless cultivation in accordance with present development of protected vegetable and diversified lifestyles. On the other hand,once industrialization has accomplished, organic ecological soilless cultivation would be popular among people and increasingly applied in vegetable planting in balcony and on roof by residents.

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