Introduction: In the arid and semi-arid lands of Iran, due to calcareousness, lack of nutrients that can be absorbed by plants, unsuitable physical conditions of the soil, and the salinity of the soil, it is very important to pay attention to organic fertilizers and soil microorganisms to improve these lands. This experiment was conducted with the aim of investigating the effect of compost obtained from the contents of sheep rumen and humic acid on the physical, chemical, and biological properties of the soil and the performance of the turnip plant in saline, sodic, and calcareous soil with a clay texture.
Materials and Methods: This study was conducted in clay-textured soil from the Meianjolgae of the Neyshabur plain (Shahrabad village), with a saline soil (ECe: 9.1 dS m^-1) and 15% lime. In this study, two levels of compost with rumen contents of zero and 5 tons per hectare (S0: 0 ton/ha and S1: 5 ton/ha) and two levels of humic acid of zero and 5 mg/kg (H0: 0 mg/kg and H1: 5 mg/kg) were used. To prepare rumen compost, 200 kg of fresh rumen contents were mixed with 10% wheat straw and processed according to standard composting methods. The experiment was conducted in the form of a completely randomized design with a factorial arrangement. The experiment was conducted in field conditions in one-square-meter plots with a border distance of half a meter. The experimental treatments were randomly added to the experimental plots and were completely mixed with the soil to a depth of 30 cm. 10 white turnip plants were planted in each plot and kept in the field for 3 months.Irrigation was done every 15 days and the plant was kept in the field for 4 months.
Results and Discussion: The results showed that the experimental treatments (rumen compost and humic acid) had a significant effect on improving the physical parameters of the soil, including increasing the weighted average diameter of the soil grains in wet (MWDwet) and dry (MWDdry) conditions, respectively (83 and 44 percent). 62% increase in the stability of soil grains (AS). They had a 46% reduction in soil dispersible clay (DC). The simple effect of humic acid did not have a significant effect on soil moisture retention capacity, but the simple effect of rumen compost increased the soil moisture retention capacity by 33% in the case of field crop capacity (FC). The effect of experimental treatments on rumen compost and humic acid improved soil biological parameters. The interaction effect of rumen compost and humic acid increased microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) respectively (43% and 77%) and increased soil microbial respiration (BR) by 75%. Rumen compost and humic acid had a positive and significant effect on improving soil chemical parameters. Rumen compost and humic acid decreased the pH of the soil and increased the availability of nitrogen, phosphorus, and potassium nutrients in the soil. The use of rumen compost and humic acid increased the yield of turnip plants. The simultaneous application of rumen contents compost and humic acid had the greatest effect on increasing turnip yield (22%) compared to the control.
Conclusion: According to the obtained results, rumen compost and humic acid improved the physical and biological properties of the soil, followed by an increase in the availability of nitrogen, phosphorus, and potassium nutrients in the soil, and finally increased the yield of the turnip plant. Due to the nature of rumen compost, because it has a relatively acidic pH, the presence of beneficial microorganisms that increase the availability of soil nutrients, and fibrous fibers that maintain soil moisture, improve adverse soil conditions, and increase plant performance. It became a turnip. Humic acid is an aromatic compound that plays a good role in chelating soil nutrients. It seems that combining humic acid with rumen compost increases the effectiveness of rumen compost in improving soil conditions. And rumen compost preserves humic acid from leaching.