Preparation method of carbon-based selenium-enriched fertilizer for rice

A preparation method of a carbon-based selenium-enriched fertilizer for rice, comprising:

• (1) planting a selenium-enriched plant material planting rank vegetation with the selenium-enriched plant material;
• spraying a sodium selenite solution at a concentration of 100-150 mg/kg for 20-30L per mu (traditional Chinese unit of measure, 1 mu equals to 667 square meters) after 30-40 days of seedling growth;
• spraying the sodium selenite solution once every 7 days and spraying 3 times consecutively;
• and harvesting the rank vegetation after 2-5 months of growth;
• (2) collecting and concentrating a selenium-enriched extracting solution grinding the harvested rank vegetation in the step (1) by an ultrafine grinder;
• placing the ground rank vegetation into a fermentation tank;
• adding 1-2% of microbial agent per kg of the rank vegetation;
• adding an oxamide, wherein an addition amount of the oxamide is as follows:
• a carbon-nitrogen ratio of a fermented material is adjusted to be 30-35;
• directly and continuously aerating, by an aerating pump, at a frequency of 10 min each time interval for 2 min with an aeration amount of 0.5 (V/V·min);
• and performing a fermentation;
• transporting the thoroughly decomposed fermented material after one month of the fermentation;
• pressing and filtering the transported material to obtain a primary filtrate and primary residues;
• adding a deionized water into the primary residues according to a volume ratio of 1:1, followed by pressing and filtering to obtain secondary filtrate and secondary residues;
• then adding the deionized water into the secondary residues according to a volume ratio of 1:1, followed by pressing and filtering to obtain tertiary filtrate and tertiary residues;
• mixing the primary filtrate, the secondary filtrate and the tertiary filtrate so as to obtain an extracting solution;
• and heating and concentrating the extracting solution to ⅓ of an original volume so as to obtain a selenium-enriched concentrated solution;
• (3) preparing modified selenium-enriched biomass charcoal from the tertiary residues
• mixing the tertiary residues obtained in the step (2) with perlite and rice straws according to a volume ratio of 1:0.5:10;
• carrying out a low-temperature carbonization reaction on the mixture in a biomass carbonization device;
• setting a temperature at 300-350° C.;
• performing an anaerobic carbonization treatment for 2-5 hours;
• and spraying 1 mol/L of dilute sulphuric acid into the treated mixture to enable a pH value to be 6-7, to obtain the modified selenium-enriched biomass charcoal;
• (4) preparing the carbon-based selenium-enriched fertilizer
• spraying the selenium-enriched concentrated solution obtained in the step (2) into the modified selenium-enriched biomass charcoal prepared in the step (3) to enable a selenium content in the modified selenium-enriched biomass charcoal to be up to 100 mg/kg;
• and grinding the biomass charcoal so as to obtain 0.5-1 mm of modified selenium-enriched biomass charcoal powder granules;
• uniformly mixing 4 parts of the modified selenium-enriched biomass charcoal powder granules, 4 parts of a turtle dove fermented organic fertilizer, 1.5 parts of a compound fertilizer with a N-P-K ratio of 17:17:17, 0.2 part of sodium-based clay, 0.2 part of a modified gelatinization powder and 0.1 part of a lignocellulose by a mixer;
• transporting the mixture into a granulator;
• and granulating the mixture to obtain the carbon-based selenium-enriched fertilizer with a particle size of 1-6 mm.