A Study of the effect of weed control methods for potatoes (Solanum tuberosum L.) on the biological parameters of soil

Weed management or any management in agriculture has to be considered in terms of the impact on the ecosystem of the soil (Yang et al., 2007). The combination of mulch and any management that affects soil is one of the most important factors affecting the chemical, physical and biological properties of soil (Luo et al., 2015; Wright et al., 2005). The aim of this study is to evaluate the effects of various methods of potato weed management on the biological properties of the soil.
The experiment carried out was a randomized complete block design with three replications in 2016 at two agricultural research stations, Alarogh and Samian, in Ardabil Province in Iran. Treatments included: 1) trifluralin herbicide, 2) metribuzin herbicide, 3) use of a cultivator, 4) wheat straw mulch, 5) canola straw mulch, 6) black plastic mulch, 7) transparent plastic mulch, 8) weed infested (control), and 9) weed control (control). Soil sampling was carried out in two stages. The first sampling was 30 days after application of the treatments and the second sampling was 60 days after. Microbial biomass carbon, soil organic carbon and soil respiration were measured. At the end of the growing season, the potato tuber yield was measured.
The treatments applied in the study caused significant differences in the rates of microbial biomass carbon, soil organic carbon, basal respiration, and induced respiration. The highest rate of microbial biomass carbon was observed with wheat straw and canola straw mulch at the first and the second soil samples. The lowest amounts of microbial biomass in the first sampling were from the trifluralin and metribuzin treatments. In the second stage, the use of a cultivator could significantly reduce the microbial biomass compared to the treatment of plant straw mulch. The wheat and canola mulch treatments had the highest rate of organic carbon in the two stages compared to other treatments. In other words, these treatments increased the organic carbon rate of the soil. The lowest organic carbon rate in both the first and second soil sampling occurred with the transparent plastic mulch. The highest basal respirations for the first sampling were with the canola straw, wheat straw, and black plastic mulches. The lowest basal respiration at the first soil sampling, however, occurred with the trifluralin herbicide. Furthermore, the highest basal respiration rates at the second sampling were with the wheat straw mulch, canola straw mulch, and metribuzin herbicide. Nevertheless, the highest rates of induced respiration were induced with the wheat straw and canola straw mulches. The lowest rate came with the cultivator use at the second sampling. The highest tuber yield was observed with weed control and plant mulch and the lowest yield was observed with weed control and transparent plastic mulch.
To manage weeds, it was determined that applying plant straw mulch treatments to cover the soil surface had more positive effects on the biological characteristics measured compared to the other methods employed in the experiment. The use of plant straw, black polyethylene mulch and a cultivator to manage weeds could lead to lower potato yield. Using mulch, especially plant straw, compared with herbicides, in addition to lowering costs, would adequately control weeds.