Effects of Kind and Incorporation Depth of Biochars on Water Movement and Nitrogen and Phosphorus Loss in Purple Soil
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S152.7

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    Abstract:

    【Objective】 Biochar applied in soil plays an important role in improving soil moisture and soil fertility. To explore effects of kind and incorporation depth of biochars on soil water movement and nutrient interception, an in-lab experiment was conducted. 【Method】 The experiment was designed to have a stable water potential, three kinds of biochars (biochar derived from rice husk, biochar derived from maize straw, and biochar derived from bamboo), two incorporation depths (10 cm and 20 cm), and a control plot of bare purple soil. During the experiment, water movement, total nitrogen (TN) loss and total phosphorus (TP) loss were monitored and changes in soil structure observed. 【Result】 Results show that application of biochars altered soil pore structure, which, together with the specific surface area and particle size distribution of biochars, affected the movement of soil water. The application of biochars reduced soil bulk density, to a varying extent relative to kind of the biochars applied. Among the three, rice husk biochar was the highest in the effect of reducing bulk density, and only rice husk biochar significantly increased total soil porosity and saturated soil water content. Rice husk biochar significantly promoted advance of the wetting front and enhanced soil water infiltration. The rice husk biochar incorporated into the soil 10 cm deep showed the greatest effect of promoting water infiltration in the biochar-soil layer and did not have much effect on water leakage, and when into the soil 20 cm deep, it promoted water leakage and increased saturated hydraulic conductivity. Maize straw biochar is the highest in specific surface area and in total pore volume, thus having a strong ability to retain soil water. Maize straw biochar does not have particles more than 1 mm in size. Once incorporated, it did not have much effect on soil total porosity, but did reduce soil saturated water content, thus inhibiting soil water migration. Maize straw biochar incorporated into the soil 20 cm deep showed the most significant inhibitory effect on water leakage. Bamboo biochar did not have much effect on wetting front movement and infiltration process, but did inhibit water leakage process when incorporated into the soil 20 cm deep. Moreover, it was found that rice husk biochar reduced total phosphorous loss, but increased total nitrogen loss; maize straw biochar did not have much effect on total nitrogen loss, but did have some effect of reducing total phosphorous loss; and bamboo biochar adsorbed nitrogen but enhanced total phosphorous loss. 【Conclusion】 When planning to incorporate biochars into the soil, rice husk biochar incorporated into the soil 10cm deep is the best choice, for it can effectively reduce surface runoff and total phosphorous loss, but it should be remembered that it can increase total nitrogen loss, too. Maize straw biochar incorporated into the soil 20 cm deep can reduce soil water migration rate, thus effectively inhibiting soil water leakage and total phosphorous loss, so it is the best choice for use in sandy soil and other highly permeable soils. Bamboo biochar has less impact on water infiltration and leakage than rice husk biochar and maize straw biochar, and does increase TP loss, thus making it the worst choice for use in farmlands.

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SUN Ningting, WANG Xiaoyan, ZHOU Hao, NI Ke, CUI Can. Effects of Kind and Incorporation Depth of Biochars on Water Movement and Nitrogen and Phosphorus Loss in Purple Soil[J]. Acta Pedologica Sinica,2022,59(3):723-733.

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History
  • Received:August 13,2020
  • Revised:December 21,2020
  • Adopted:
  • Online: April 16,2022
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