Study on Obstacles to Continuous Cropping of Vegetables and Soil Remediation Technology

, , , FENG, ,

1. Vegetable Research Institute, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China; 2. Lianyungang Vegetable Gardening Station, Lianyungang 222100, China

StudyonObstaclestoContinuousCroppingofVegetablesandSoilRemediationTechnology

PingshengFAN1*,GangCHEN1,DeliXU2,WeiminFENG1,YuyuLU1,AnqinGUAN1

1. Vegetable Research Institute, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China; 2. Lianyungang Vegetable Gardening Station, Lianyungang 222100, China

Firstly, this paper analyzes the cause of obstacles to continuous cropping of vegetables, and then introduces the soil ecological remediation technology used for overcoming obstacles to continuous cropping of vegetables. Finally, this paper analyzes the effect of applying soil ecological remediation technology in overcoming obstacles to continuous cropping of vegetables.

Obstacles to continuous cropping of vegetables, Soil ecological remediation technology, Autotoxins, Application

1 Introduction

The obstacle to continuous cropping of vegetables is one of the major obstacles to facility cultivation and greenhouse production, causing serious vegetable diseases, reducing the yield and quality, and affecting the yield and quality of vegetables[1]. There are many researches at home and abroad on obstacles to continuous cropping of vegetables. In this paper, based on the cause of continuous cropping obstacles, with autotoxins and rhizosphere microbial community as the main line, we study the physiological and biochemical reaction, rhizosphere micro-ecology characteristics and autotoxicity of continuous cropping and autotoxins, and carry out experimental demonstration in Lianyungang.

2 Causes of obstacles to continuous cropping of vegetables

2.1AutotoxicityofallelopathicautotoxinsAutotoxin is one of the main causes of obstacles to continuous cropping of vegetables, and studies show that the autotoxins responsible for obstacles to continuous cropping of cucumbers and other vegetables mainly include hydroxybenzoic acid, ferulic acid, cinnamic acid, benzoic acid and the like. By ion absorption, moisture absorption, photosynthesis, protein and DNA synthesis and many other ways, autotoxins have a huge impact on vegetable seed germination, cell division, and plant growth[2-3]. (i) Autotoxin can inhibit the activity of important enzymes necessary for plant growth. It can inhibit the activity of root ATP enzyme, root dehydrogenase, nitrate reductase and superoxide dismutase and it can inhibit the activity of many enzymes in plants such as POD, CAT, SOD and ATP hydrolase. (ii) Autotoxin affects plant roots’ absorption of water, NO3-, K+ and other nutrients. (iii) Autotoxin also affects photosynthesis as well as protein and DNA synthesis of vegetables, and inhibits plant growth and development. Benzoic acid and cinnamic acid can reduce net photosynthetic rate, transpiration rate, intercellular CO2 concentration and stomatal conductance of vegetables. (iv) Autotoxin affects the cell membrane permeability, and studies show that cinnamic acid and para-hydroxybenzoic acid can significantly change the submicroscopic structure of plant chloroplast: capsula is dissolved; grana stacks and stroma lamella are reduced; photosynthetic rate lowers. (v) Autotoxins interfere with the synthesis of auxins, so that the root and stem cell growth is inhibited.

2.2Pathogenincreaseincontinuouscroppingsoilanddeteriorationofmicrobialspecies,quantity,populationstructureandsoilenzymeactivity[3-5]Due to the repetition of cropping systems and management practices in vegetable continuous cropping, after many years of planting and fertilization, vegetables selectively absorb the specific nutrients, resulting in soil nutrient imbalances. Continuous cropping affects the soil and rhizosphere microbial growth and reproduction, reduces the microbial population diversity, increases the number of pathogenic bacteria, lowers population density of beneficial microorganisms, changes the soil-borne micro-ecological structure, makes soil enzyme activity deteriorate and causes the soil microbial community’s ability to resist the outside world to decline.

2.3ConsiderablefertilizerconsumptioncausedbycontinuouscroppingThe continuous cropping inhibits the plant growth and metabolism, and in order to promote plant growth, farmers would increase fertilizer and other inputs, and the soil fertilizer content increases. The relatively high temperature environment of facility cultivation increases relative soil evaporation, and the closed environment of facility prevents the rain from thoroughly rinsing soil. The fertilizer and salts in deep soil will rise by soil capillary with the evaporation of deep soil moisture, causing soil salinization phenomenon.

3 Soil ecological restoration to overcome obstacles to continuous cropping

3.1Agriculturalmeasures

3.1.1Companion planting. In the agricultural production process, using agronomic measures, choosing the appropriate crops and adopting the methods of crop rotation, intercropping and companion planting can significantly inhibit the obstacles to continuous cropping of vegetables, improve soil micro-ecological environment, control the occurrence of pests and diseases, improve the photosynthetic pigment content and photosynthetic rate of vegetables, and promote the growth of vegetables. Companion planting (crop rotation, intercropping) can improve the continuous cropping soil micro-environment. Companion crop root exudates and root’s decaying substances can improve soil micro-ecological environment and enhance soil activity. Studies have shown that companion planting improves the physical properties of continuous cropping soil, activates soil nutrients and improves rhizosphere micro-environment. The soil bulk density decreases; the soil porosity increases; the organic matter, available P and available K content increases in varying degrees; the proportion of soil microbial flora is changed. Companion planting can promote the growth and development of vegetables. Research indicates that companion planting and other measures can promote the crop root growth, improve root activity, promote root absorption of nutrients, and improve the quality of vegetables. Suitable companion planting can significantly increase the vitamin C and soluble protein content of vegetables, and reduce fruit nitrates. The crop stubble from legume crop rotation, straw decomposition products, garlic root exudates and alfalfa straw mulch play a role in promoting root length, overground part fresh weight and root fresh weight of vegetables[1-4]. Companion planting can reduce the vegetable diseases in continuous cropping soil[5]. Intercropping can reduce the incidence of vegetable diseases and partly solve continuous cropping obstacles. By the crop rotation and intercropping between vegetables and wheat, oats, onion, garlic or celery, it can significantly reduce the incidence of downy mildew, angular leaf spot powdery mildew and other diseases, and significantly improve vegetable production. Crop rotation, intercropping and other agronomic measures can significantly control vegetable diseases, and they have been accepted and widely used by the majority of producers.

3.1.2Solarization technology. The facility greenhouses use solarization to kill pathogens in soil, improve soil micro-ecological environment, reduce pests and diseases for succeeding crops and promote crop growth. In practice, we can use lime nitrogen, ammonium bicarbonate and other fertilizers which can produce ammonia to penetrate into the soil and kill pathogens and weed seeds. After cleaning greenhouse in the summer, 70-80 kg of solid lime nitrogen or ammonium bicarbonate is uniformly mixed and applied on the surface of soil, the organic fertilizers are mixed and buried deep in soil through rotary tillage, and the transparent film is used to completely close soil surface, in order to rapidly increase soil accumulated temperature. Then the furrow is filled with water from under the film, and the greenhouse is sealed. The sunlight is used to make the 20-30cm deep soil remain at 40℃-50℃ for a long time, and it can effectively kill the soil pathogens and weed seeds. Then the film is uncovered, greenhouse is aired, and the soil is turned over. After about seven days, the vegetable crops can be planted. By comparing the experimental results, it shows that solarization is an effective way to solve continuous cropping diseases.

3.2BeneficialmicroorganismmultiplicationtechnologyAfter making the greenhouse stuffy under high temperature, the microbial population in soil is significantly reduced. In order to maintain healthy soil microbial balance and improve soil and crop quality, we can promote the use of microbial fertilizers, including bacterial fertilizer, fungi fertilizer, biological fertilizer and other organic fertilizers. This technology can accelerate the decomposition of crop straw, promote fermentation of organic nutrients, purify soil environment, maintain the diversity of soil biological population, promote the growth of crops, and enhance crop’s disease resistance and drought tolerance capacity.

3.3SlowreleaseandbalancingtechnologyoforganicnutrientsinsoilIt is necessary to promote the slow release and balancing technology of organic nutrients in soil and reasonably applying organic fertilizer. Organic fertilizer can improve soil aggregate structure, keep the soil loose and balance nutrients. It has the functions of preserving moisture and fertility, regulating temperature and improving gas permeability of soil. It can also increase soil trace element content, improve soil fertility, improve soil’s fertilizer storage performance, and enhance soil’s pH buffering capacity. Studies have shown that the technology can promote crop growth, increase crop disease resistance, improve crop quality, and increase production efficiency.

4 Conclusions

This paper analyzes the cause of obstacles to continuous cropping of vegetables, and then introduces the soil ecological remediation technology used for overcoming obstacles to continuous cropping of vegetables. The technology has gone through experiment and demonstration in Jiangsu Province. In different regions of Jiangsu, the demonstration greenhouses are built and corresponding technical regulations and norms are developed. Through technical training, demonstration and extension, it eases the obstacles to continuous cropping of vegetables, promotes the development of vegetable industry, and achieves remarkable economic, social and ecological benefits.

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November 9, 2015 Accepted: January 16, 2016

Supported by Independent Agricultural Innovation Foundation in Jiangsu Province (CX151044).

*Corresponding author. E-mail: pingshengfan@163.com