水分管理及生物质炭对稻田土壤含水率及pH值的影响

The Combined Effects of Water Management and Biochar Amendment on Soil Water Content and pH of Paddy Soil

【目的】我国亚热带地区为典型的双季稻种植区,水分管理多采用长期淹水和间歇灌溉2种方式,灌溉方式的不同会影响土壤含水率的差异,势必会影响土壤酸碱性的改变。添加生物质炭可改变土壤性质。探明稻田淹水灌溉和间歇灌溉条件下添加生物质炭对双季稻田土壤水分及酸碱性的影响。【方法】采用田间小区试验,研究水分管理方式(长期淹水(CF)和间歇灌溉(IF))及生物质炭施用量(0、24 t/hm^(2)(LB+IF)和48 t/hm^(2)(HB+IF))对亚热带双季稻田土壤含水率及pH值的影响。【结果】与长期淹水相比,早稻季和晚稻季间歇灌溉的土壤含水率并没有显著降低。生物质炭添加并未显著影响早稻季和晚稻季土壤含水率,但在休闲季生物质炭处理的土壤含水率有所降低。研究期间,CF、IF、LB+IF和HB+IF处理的土壤含水率周年均值分别为47.35%、39.58%、36.81%和39.02%,与长期淹水相比,间歇灌溉降低了全年的土壤含水率,降幅达16.41%,而生物质炭对间歇灌溉稻田土壤含水率影响不大。与长期淹水相比,早稻季和晚稻季间歇灌溉处理的土壤pH值分别显著降低了0.22和0.57个单位,休闲季不同水分管理方式之间的土壤pH值差异不显著。由于生物质炭本身呈碱性,添加到土壤后可增加土壤pH值,且随着生物质炭添加量的增加而增加。与IF处理相比,早稻季和晚稻季生物质炭处理的pH值分别增加了0.23~0.68个单位和0.17~0.60个单位。【结论】水分管理可影响双季稻田土壤含水率和pH值。间歇灌溉降低了亚热带地区双季稻酸性土壤的pH值。生物质炭添加,尤其是高量生物质炭添加,可在一定程度上缓解间歇灌溉对酸性土壤pH值的降低作用。

【Background】Traditional rice production in paddy fields in subtropical regions in China is to keep the soil surface flooded.This is not only a waste of water resources but also acidifies the soil and leaks agrochemicals to water bodies.Improving water use efficiency and ameliorating soil acidity is a challenge facing sustainable rice production in these regions.【Objective】The purpose of this paper is to investigate the efficacy of using intermittent irrigation and biochar amendment to improve the ability of soil to hold water and deacidify paddy soil.【Method】The experiment was conducted in a rice-rice rotation field.It consisted of two irrigation treatments:continuous flooding(CF)irrigation and intermittent irrigation.Added to the intermittent irrigation were three biochar amendments by adding 0(IF),24 t/hm^(2)(LB)and 48 t/hm(HB)of biochar.In each treatment,we measured soil water content and soil pH during the growth season of both the early and late rice,as well as in the duration when the soil was temporally fallowed.【Result】Compared with CF,intermittent irrigation alone did not result in significant changes in soil water content due to the combined impact of precipitation and drainage.Amending the soil with biochar did not alter soil water content during the growth season of ether rice,but reduced it significantly when the soil was fallowed due to the fine texture of the biochar and structural change in the soil.The annual average soil water content under CF,IF,LB and HB treatments was 47.35%,39.58%,36.81%and 39.02%,respectively.Compared to CK,intermittent irrigation alone had no impact on soil pH when soil was fallowed but reduced it by 0.22 and 0.57 unit during the growth season of the early and the late rice,respectively.Biochar amendment deacidified the soil,increasing its pH by 0.23~0.68 unit in the early rice season and 0.17~0.60 unit in the late rice season,with the increase varying with biochar application rate.【Conclusion】Intermittent irrigation alone reduces soil pH,and combining it with biochar amendment,especially at a high amendment rate,can increase soil pH.These results have important implications for improving agricultural management and quality of paddy soils with rice-rice rotation as commonly cultivated in subtropical regions in south China.