Biochar, vermicompost, and humic acid are soil improvement materials with high economy, simple production, and environmental friendliness that have attracted attention in recent years.
Biochar has porous characteristics and a large specific surface area, which is conducive to soil water accumulation, porosity, and bulk density, thereby providing a good environment for plant growth, which has an obvious improvement effect on soil physical and chemical properties and provides a solution for the ecological restoration of polluted soil.
Humic acid has a variety of active functional groups and a large specific surface area and is also an environmentally friendly adsorbent.
Vermicompost is simple to prepare and has a wide source of raw materials. It can improve soil, improve soil structure and microbial population, promote crop growth, and increase crop yield and quality of agricultural products.
Effect on Soil Salinity
The experiment found that when biochar, vermicompost, and humic acid were combined to improve soil, their impact on pH was not significant. The reason may be related to the amount of biochar applied in the joint amendment. Biochar is alkaline, and biochar application may cause soil pH to increase. Soil organic matter content is also an important factor affecting pH. It is negatively correlated with pH and can significantly improve the buffering properties of soil. After the use of combined amendments, the soil-soluble salt content increased significantly.
Effect on Soil Nutrients
Overall, applying different proportions of biochar, humic acid and vermicompost fertilizers can increase the content of soil organic matter, available phosphorus, available potassium and nitrate nitrogen.
Effect on Soil Permeability
After applying different proportions of joint amendments, the redox potential of the soil in each treatment increased, ranging from 3.65% to 26.04%. The redox potential can directly determine the soil aeration status.
Among the combined amendments, biochar has a significant impact on the redox potential. When the biochar content of the joint amendment reaches 40 g/kg, the soil redox potential has the best effect. Biochar is a good soil conditioner that can effectively improve the water and air permeability of the soil.
The combined application of biochar, vermicompost and humic acid can significantly increase soil nutrients and promote the formation of aggregates. The results show that the combined application of the three materials can improve poor soil, improve soil structure, and increase soil fertility.