Date Published: February 6, 2019
Publisher: Public Library of Science
Author(s): Bingpeng Qu, Yuanxin Liu, Xiangyang Sun, Suyan Li, Xinyu Wang, Kaiyi Xiong, Binghui Yun, Hua Zhang, Arun Jyoti Nath.
Mulching is a widely employed soil management practice. The mulches used have variable effects on the soil properties and plant growth. In China, mulches are used to cover bare soil at a few places in landscapes, where most of the soil is uncovered, especially in tree pits. As to improve our understanding on the effect of various mulches on soil properties and tree growth after two years of the treatment justifying its implication in soil fertility and tree growth. A comparison study was conducted to determine the effects of inorganic (cobblestone—CB; water permeable brick—WPB), organic (pine bark—PB; green waste compost—GWC), and living (turf grass—TG) mulches on soil physical and chemical properties at three different depths (0–10 cm, 10–20 cm, and 20–40cm), and on tree growth (Sophora japonica) in urban tree pits. Soil moisture was measured once a month in 2015.The soil samples were collected from the tree pits two years after mulching and used to evaluate the physical and chemical properties. Further, trunk diameter and tree height were determined once a year. During the most months, all types of mulches significantly affected the moisture content of the soil at all the depths analyzed. In July and August, however, the moisture content of PB and TG treated soil decreased when compared with that of unmulched bare soil. Two years after mulching, the bulk density of the soil treated with PB, GWC, and TG was significantly affected at10–20 cm, with GWC exhibiting a relatively better effect. The treatments with PB, GWC, and TG also improved the total porosity, macroporosity, and microporosity of the soil at lower depths. Further, WPB worsened the bulk density and porosity of the soil, elevating the pH at lower depths. The organic matter, total N, mineral N, available P, and available K contents of the soil at lower depths increased when mulched with organic material. Turf grass significantly increased only the total N and available K at 0–10 and 10–20 cm. There was no significant difference in the soil properties among the treatments at 20–40 cm. Furthermore, the trunk diameter and tree height were not affected by the mulches two years after mulching. In conclusion, organic mulches especially GWC, not only increased soil fertility significantly but improved soil physical characters (0–10 cm depth) comparing to other mulches, are suitable to cover bare soil in urban tree pits.
Mulches have been widely used in agriculture lands, orchards, forests, and landscapes in many parts of the world . Generally, mulches reduce competition from weeds, maintain soil temperature, and reduce evaporation from soil . They protect the soil from wind-, water-, and traffic-induced erosion. Further, fugitive dust from soil is suppressed by mulching . Mulches also improve soil properties by improving moisture retention capacity, releasing different nutrients, and enhancing biological activities . Therefore, with the improved soil properties, plants grow better [5, 6].
The inorganic mulches (CB and WPB), organic mulches (GWC and PB) and living mulch (TG) exhibited positive effect by elevating the soil moisture content. However, the moisture content of soil applying GWC, PB, and TG decreased in July and August when compared with that of CK. PB, GWC, and TG improved the soil bulk density, total porosity, macroporosity, and microporosity of the soil to some extent at lower depths, whilst WPB worsened those factors. In addition, by comparing with other treatments, GWC significantly increased the level of all the nutrients. There was no significant difference in the soil properties among the treatments at 20–40 cm. Furthermore, the trunk diameter and tree height of S. japonica were not affected by the mulches. Organic mulches, especially GWC, seem to be better than other mulches analyzed to cover bare soil in the urban tree pits.