Study On Nutrient Release Rule Of Attapulgate-Biochar Slow-Release Fertilizer And Its Effect On The Growth Of Pakchoi And Brassica Oleracea

Compared with conventional fertilizers with the same nutrients,slow-release fertilizers can signific antly increase crop yield,reduce labor input,and alleviate environmental pollution problems to a certain extent.In order to solve the common defects of fertilizers,such as low utilization rate,large runoff and nutrient volatilizing loss,and difficult synchronization of nutrient release and crop absorption,this study prepared 10 kinds of slow-release fertilizers using attapulgite,biochar and attapulgite+biochar as slow-release materials,and explored their biological effects through pot experiment of Chinese cabbage and open-field cabbage.The effects,increasing production and mechanism of attapulgite-biocarbon slow-rel ease fertilizer were evaluated in order to provide theoretical guidance for the development and applicatio n of new slow-release fertilizer for Chinese facilities vegetables.The results are as follows:(1)According to the apparent characteristics,the thermal modification at 300℃ and the phosphoric acid modification at 4mol/L caused the attapulgite to show a broken and circular collapse structure,and there were a large number of gaps and cracks.The acid modification caused the biochar to show a large semi-penetrating to penetrating circular aperture,and the modified structure was conducive to better nutr ient storage and release.After the combination of biochar and attapulgite,the load of attapulgite particle s makes the structure of biochar become loose and porous.The load of attapulgite can provide many atta chment sites for biochar,which effectively prevents the agglomeration of biochar and makes the particle s loose and uniform.Compared with the original biochar,attapulgite+biochar has higher specific surfac e area and deeper pore diameter,which can provide more opportunities for nutrient ions to interact with the composite materials.(2)XRD results show that the thermal modification can enhance the intensity of the attapulgite SiO 2 and CaMg0.77Fe0.23(CO3)2 diffraction peak,and the acid modification can dissolve the CaMg(CO3)2 component in the attapulgite and change the pore structure of the composite material,which is conduciv e to the adsorption effect of the composite adsorbent.Carbon and mineral materials interact more strongl y;High temperature makes the graphitization degree of branch biochar higher,but contains more ash.Ac id modification can eliminate the diffraction peak of CaCO3 and reduce the ash content of biochar.In the thermal modified attapulgate-biochar composite,the thermal modified attapulgate-biochar changes the original structure composition,SiO2,MgFe4(SO4)6(OH)2(H2O)20 and CaMg(CO3)2 components increase,which is beneficial to the adsorption effect of the composite adsorbent.(3)The adsorbability of ammonium nitrogen,phosphorus and potassium of attapulgite,biochar and attapulgate-biochar composites is significantly different.The adsorption rates of different materials for nitrogen,phosphorus and potassium are phosphorus>nitrogen>potassium,and the adsorption rates ran ge from 70%to 97%.The adsorption capacity of attapulgite modified at 300℃,biochar prepared at 500℃and attapulgite modified at 300℃+biochar are stronger.By monitoring the release properties of differe nt slow-release fertilizers on N,P and K,it can be seen that compared with pure fertilizers,300℃ heat-m odified attapulgite slow-release fertilizer and 300℃ heat-modified attapulgite+biochar slow-release fer tilizer had better slow-release properties of N and reached the peak value on the 50th day.Biochar(HNASB400)sustained-release fertilizer,attapulgite+biochar sustained-release fertilizer and 300℃ heat-m odified attapulgite+biochar sustained-release fertilizer all had better sustained-release properties of pho sphorus,and reached the peak on the 40th and 60th days.There was no significant difference in the relea se properties of potassium from different fertilizers.(4)The attapulgate-biochar slow-release fertilizer could replace pure fertilizer to meet the demand of cabbage during the whole growth period,and was superior to control and pure fertilizer in phenotypic indexes,quality and yield.Different types of slow-release fertilizers could significantly increase the util ization rate of nitrogen,phosphorus and potassium fertilizer and agricultural efficiency of plants,and T4(heat-modified attapulgite slow-release fertilizer),T5(acid-modified attapulgite slow-release fertilizer)and T12(heat-modified attapulgite+biochar slow-release fertilizer)showed better performance.PCA an alysis of pakchoi soil indexes,growth indexes,plant nutrients,quality indexes,biomass and yield showe d that,compared with pure fertilizer treatment,different types of slow-release fertilizer treatment could e ffectively improve the growth and development of pakchoi plants,and the slow-release fertilizer treatme nt with heat-modified attapulgite+biochar slow-release fertilizer had the best effect.(5)The attapulgate-biochar slow-release fertilizer could partially replace the pure fertilizer to meet the nutrient requirements of the corresponding growth stage of cabbage,and was superior to the control and pure fertilizer in phenotypic indexes,quality and yield.Compared with different kinds of slow-relea se fertilizer combined with different application amounts,T5(biochar fertilizer replaces chemical fertiliz er 30%),T9(thermomodified attapulgite fertilizer replaces chemical fertilizer 50%)and T12(thermomo dified attapulgite+biochar slow-release fertilizer replaces chemical fertilizer 50%)could significantly i ncrease the utilization rate of nitrogen,phosphorus and potassium fertilizer and agricultural efficiency of plants.The soil indexes,growth indexes,plant nutrients,quality indexes,biomass and yield of cabbage were analyzed by PCA.The results showed that compared with pure chemical fertilizer treatment,attapu lgate-biochar slow-release fertilizer treatment could effectively improve the growth and development of cabbage plants.The effect of different types of slow-release fertilizer replacing 50%of chemical fertilize r was better than that of replacing 30%of chemical fertilizer.Moreover,300℃ heat-modified attapulgite+ biochar slow-release fertilizer was the best type of slow-release fertilizer.