Humic acid, as a natural organic substance, is found in large quantities in peat, weathered coal, and lignite. Because of its unique structure and properties, it is widely used in agricultural production and soil remediation. Potassium humate is a kind of humate, which can promote crop growth and development, improve crop photosynthesis, improve crop quality and enhance crop stress resistance when applied to farmland. Microbial agents are biological products containing live microorganisms that promote plant growth while maintaining soil health primarily through the metabolic activity of microorganisms. Biological agents have the advantages of low cost, high efficiency and pollution-free, and have broad application prospects in agricultural production.

1. Effects on tomato plant height

From the second to the sixth week after tomato planting, the plants were in the early stage of growth, and there was no significant difference in plant height between treatments. From the 4th week to the 8th week, the plant height of tomatoes began to differ between the treatments. When tomatoes grow to the 4th week, potassium humate, compound bacteria, or a mixture of the two are used to achieve a higher plant height than untreated tomato plants. When the tomato was grown to the 8th week, the plant height of the tomato plants treated with the two treatments was the highest, which was significantly higher than that of the other treatments, and was significantly higher than that of the control, potassium humate alone and compound agent alone, but there was no significant difference between the tomato plants used alone. It can be seen that the application of potassium humate or compound fungicide alone has a certain effect on tomato plant height, but the combined application of potassium humate and compound fungicide has a better effect.

2. Effects on tomato root length

Compared with the control, the root length growth rate of compound fungicide + potassium humate was the most significant, and the application of potassium humate or compound fungicide alone had a significant effect on root growth, but the combined application of potassium humate and compound fungicide had a better effect.

3. Effect on tomato chlorophyll

In the second week after tomato planting, there was no significant difference in chlorophyll values between treatments. However, from week 4 to week 8, the chlorophyll values of each treatment showed differences. The chlorophyll values of the agent and potassium humate alone and in combination were high compared to controls. When the tomato was grown to the 6th week, the chlorophyll value of the tomato plants that were only mixed was the highest, and there was no significant difference between the other treatments. When tomato growth reached the 8th week, potassium humate alone and compound agent were significantly different from those without treatment. It can be seen that potassium humate or compound agent alone can increase the chlorophyll of tomato to a certain extent, but the combination of potassium humate and compound agent can increase the chlorophyll value of tomatoes more significantly.

4. Effect on dry weight of tomato plants

At the maturity stage, the dry weight of potassium humate + compound bacterial agent was the heaviest in the aboveground part, and the dry weight effect of the aboveground part alone was not significant. The dry weight of the underground part was significantly higher than that of the tomato plants without treatment, and the dry weight of the underground part was the heaviest when using a mixture of the two.

It can be seen that the application of potassium humate or compound fungi alone did not have a significant effect on the dry weight of the aboveground part of tomato, but the effect of promoting the dry weight of the underground part was obvious, and the combination of potassium humate and compound fungi had the best effect on the dry weight of the aboveground part and the dry weight of the underground part, and reached a significant level.

5. Impact on tomato fruit quality

For vitamin C content, the content of potassium humate alone and potassium humate + compound bacterial increased significantly, and the content of mixed use was the highest, but the application of compound bacteriol alone reduced the Vc content of tomato fruit. For the sugar-acid ratio, the mixed tomato fruit value was the largest, followed by the use of potassium humate alone, followed by the use of compound bacteria, and the combination of potassium humate and compound bacteria had the best effect in comprehensively improving the quality of tomato fruits.