Study On Hydroponics With Biogas Slurry As Nutrient Solution

With the energy crisis intensified and the global environment pollution deteriorated, biogas technology, as a cheap biomass energy with high quality, not only can ease the current and future energy crisis, but also can effectively solve some of pollution problem. Therefore methane fermentation technology has been widely concerned and highlighted, and more and more being used in the practice. But he promotion of methane fermentation technology produced large amount of fermentation residues. After-treatment of the remnants of fermentation become a major problem.As large amount of fertilizers and pesticides used in vegetable production, some qualities of vegetable such as flavor, taste, nutritional quality, safety, etc.,worsened. The demand for pollution-free agricultural products, green agricultural products and organic products grow rapidly, and so do the demand for organic fertilizer. The biogas residues used in crops cultivation meet this demand.The main purpose of this test is to made biogas slurry into the nutrient solution for hydroponics of lettuce, through diluting and adding some elements. The lettuce variety we chooce for the test is bolting tolerant lettuce produced by Guangzhou Hennessy Seed Co., Ltd. We analysed the yield, quality and heavy metal content of the lettuce, and reached the following conclusions:1. The nutrients contained in the biogas slurry can meet the basic needs of the growth and developments of lettuce; cultivating lettuce with different concentration of biogas slurry, the one diluted 10 times can get the highest output; the relative growth rate analysis showed that as the increase of concentration, the relative growth rate increasd first and then reduced. We can get the biggest relative growth rate at A4 in the first two measureme, and at A5 in the latter two. It reveals that the concentration of the biogas slurry can be higher appropriately later.2. Adding Fe into biogas slurry can increase the output very significantly, and the increasing rate is 75.18%; adding K, P can increase the output significantly, and the rates are 45.45%, 88.66%; adding the large number of elements or joining biogas slurry and the standard nutrient solution at the ratio of 1 to 1 can significantly increase the output of lettuce, and the rate is 45.45% and 88.66%; adding various of nutrients to make it reach the standard proportion can increase the yield significantly, and the rate is 29.44%; other treatment can not improve the output significantly. It reveals that joinging half of biogas slurry and half of the standard nutrent solution, the output has no significant difference with the one that of the standard nutrient solution. That is the output of the nutrient made of boigas slurry can reach the level of the standard nutrient solution. Adding a variety of chemical fertilizer to biogas slurry, adding urea can significantly increase the output of lettuce, and the increasing rate is 19.85%; adding ternary compound fertilizer can improve the output significantly, and the rate is 37.92%; adding fertilizer Dabao can not improve the output significantly.3. Nitrate content of every treatment made of biogas slurry is obviously lower than standard nutrition; adding urea, ternary compound fertilizer, or joining biogas slurry and standard nutrient solution can increase the nitrate content obviously; adding urea, P, K, or joining slurry and the standard nutrient solution, or adding various of nutrients to make it reach the standard proportion can increase Vc content; adding urea, K, ternary compound fertilizer, Dabao fertilizer or adding three large number elements, or joining biogas slurry and standard nutrition at 1:1 can all increase soluble protein content; except for joining biogas slurry and standard nutrient solution, soluble protein contents of the other treatments are all lower than standard nutrient solution, adding urea, P, K and Fe can increase the soluble protein contents.4. The heavy metal content of every treatment are in line with national standards limit, the heavy metal content of every treatment made of biogas slurry is high than that of the standard nutrient solution.