Evaluation of the Efficiency of Rice (Oryza sativa L.) Straw Checkerboard Barriers Technique on Moisture Retention, CO2 Production, and Soil Microbial Population

The incidence of drought periods and its continuity in arid and semi-arid areas is considered one of the factors affecting soil microbial population and activity and soil water content, and thus affect soil fertility and nutrient availability. Implementation of the straw checkerboard barrier technique in these areas as a cheap, effective, and easy technology has an important role in reviving soil microbial communities and desertification control. In the present study, the effect of the straw checkerboard barriers technique on moisture retention, soil microbial population and their CO2 production was investigated.

This research was carried out in a semi-arid region prone to wind erosion with damaged soil communities, in which the straw checkered barrier technique was established to control wind erosion. For this purpose, 5 t.ha-1 of rice (Oryza sativa L.) straws were arranged in 1 m × 1 m checkerboard patterns in January 2018. This research was carried out in a part of the “ Margh” meadow the south of Shahrekord, the capital of Chaharmahal and Bakhtiari province (50° 50 ́E, 32° 17 ́N). Then the effect of this technique on soil microbial properties, including respiration and soil microbial biomass as well as moisture retention and aggregate stability, were considered. The same area was also dedicated for control as bare ground. Several straw squares were randomly selected, and the trend of changes in microbial respiration and soil moisture in the border of barriers, the center of barriers, and bare ground were measured in several stages. Also in the fourth stage of microbial respiration determination, microbial biomass, and aggregate stability were measured too. Microbial respiration and soil moisture data were analyzed based on a split-plot experiment in time in a randomized complete block design, and microbial biomass data and weight and geometric mean particle diameter were analyzed based on a randomized complete block design.

The results indicate that soil water content at the borders of the barriers significantly increased compared to the center of the barriers and the bare ground by 10.91% and 18.56%, respectively. Soil water content at the borders of the barriers was maintained for a longer time compared to the bare ground, but the decreasing trend of soil moisture in the bare ground was steeper over time, reaching the lowest position compared to the others. This can be attributed to the reduction of wind speed and shading of straws on the soil surface, creating a safer microclimate near the soil surface. The addition of rice straw in the form of checkered barriers to the soil significantly increased carbon mineralization compared to the bare ground in all measurement stages. In the first stage, the amount of CO2-C produced at the borders and center of the barriers increased by 37.76% and 14.69%, respectively, compared to the bare ground. On July 5th, CO2-C production decreased significantly. From July 15th to October 28th, the trend of carbon mineralization at the borders and center of the barriers and bare ground showed a steady state with lower values for the bare ground. Residue incorporation in soils may increase C mineralization and have a positive priming effect for accelerating soil organic carbon (SOC) decomposition. The establishment of straw checkerboard barriers alleviated the effects of moisture deficiency on soil microbial activity and increased carbon mineralization. The higher rates of microbial respiration in the barriers indicate the efficiency of the straws added to the soil and the better adjustment of drought conditions in the soil. The highest soil microbial biomass and aggregate stability were observed at the borders of the barriers, which was significantly different from the bare ground. The return of residues to the soil increased aggregate stability, which may be due to the improvement of organic matter and soil porosity.

The results of this study indicate that the implementation of straw checkerboard barriers improved the soil's biological properties, moisture content and aggregates stability and can provide a better microclimate for plant establishment and growth, which may lead to higher conservation of natural resources and sustainable production.