长期稻虾共作模式提高稻田土壤生物肥力的机理

Mechanism of long-term integrated rice-crayfish farming increasing soil biological fertility of paddy fields

【目的】长期稻虾共作是提高稻田肥力的有机生态途径。研究该模式对稻田土壤有机碳库和土壤酶活性的影响,为该模式的可持续应用提供理论依据。【方法】基于连续10年(2005—2015)中稻单作和稻虾共作的田间定位试验,于2015年10月中旬水稻收获后,按照0—10 cm、10—20 cm、20—30 cm、30—40 cm土层采集土样,分析不同土层中总有机碳(total organic carbon,TOC)、土壤微生物量碳(microbial biomass carbon,MBC)、可溶性有机碳(dissolved organic carbon,DOC)、易氧化有机碳(easily-oxidized organic carbon,EOC)和颗粒有机碳(particulate organic carbon,POC)含量,测定不同土层土壤水稳性团聚体中有机碳的含量,计算了土壤碳库管理指数,同时分析了与土壤碳、氮和磷代谢有密切关系的纤维素酶、蔗糖酶、脲酶和酸性磷酸酶活性。【结果】1)相对于中稻单作,稻虾共作显著增加了各土层中TOC、POC和DOC含量,增加30—40 cm土层中MBC含量以及10—40 cm土层中EOC含量;2)稻虾共作显著提高了10—30 cm土层中土壤碳库管理指数,碳库管理指数在10—20 cm和20—30 cm土层中较中稻单作模式分别提高了52.7%和58.2%;3)稻虾共作模式下,0—20 cm土层中小于0.053 mm粉-黏团聚体的有机碳含量显著高于中稻单作模式,而在20—30 cm土层各粒级团聚体的有机碳含量均显著高于中稻单作模式;4)与中稻单作相比,稻虾共作土壤脲酶活性在10—20 cm土层显著降低了16.7%,而在20—30 cm土层纤维素酶活性显著提高了28.0%;5)除DOC外,TOC、POC、MBC与纤维素酶、蔗糖酶、脲酶和酸性磷酸酶活性均呈显著正相关。【结论】长期稻虾共作提高了稻田土壤有机碳及其活性组分含量,特别是提高了20—30 cm土层纤维素酶活性,促进了根茬等有机物的分解,提高了该层次各粒级团聚体内的有机碳含量,改善了土壤结构,加大了水稻根系的下扎深度,改善了固持速效养分的能力,从而提升了稻田土壤生物肥力。

【Objectives】Rice-crayfish farming is a well-advised practice for efficient rice production and soil fertility maintenance.We studied the change of the soil organic carbon pool and some enzyme activities caused by the practice,for further understanding the mechanism of fertility improvement.【Methods】Rice-crayfish farming(CR)experiment had been conducted for 10 consecutive years(2005-2015),with single rice planting(MR)as control.The soil samples were collected in soil layers of 0-10 cm,10-20 cm,20-30 cm,30-40 cm after rice harvesting in mid-October 2015.The contents of total organic carbon(TOC),microbial biomass carbon(MBC),dissolved organic carbon(DOC),easily-oxidized organic carbon(EOC)and particulate organic carbon(POC)were analyzed.The contents of organic carbon in the soil water-stable aggregates were determined,and the soil carbon pool management index(CPMI)was calculated.The soil cellulase,sucrase,urease and acid phosphatase activities which waere closely related to soil carbon,nitrogen and phosphorus metabolism were also analyzed.【Results】1)Compared with the rice monoculture,the rice-crayfish farming significantly increased the contents of TOC,POC and DOC in the 0-40 cm soil layer,significantly increased the content of MBC in the 30-40 cm soil layer,and significantly increased the content of EOC in the 10-40 cm soil layer.2)The rice-crayfish farming significantly improved the soil carbon pool management index in the soil layer of 10-30 cm,with increase rate of 52.7% and 58.2% in the soil layer of 10-20 cm and 20-30 cm,compared with the rice monoculture,respectively.3)The rice-crayfish farming significantly increased the organic carbon contents of<0.053 mm silt-clay aggregate in the 0-20 cm soil layer,and those of all the particle size of aggregates in the 20-30 cm soil layer.4)The urease activity in the 10-20 cm soil layer of the CR system was significantly decreased by 16.7%,while the cellulase activity in the 20-30 cm soil layer was significantly increased by 28.0%,compared with the rice monoculture.5)Except DOC,the contents of TOC,POC and MBC were significantly and positively correlated with the activities of cellulase,sucrase,urease and acid phosphatase.【Conclusions】The long-term rice-crayfish co-culture could significantly increase the contents of soil organic carbon and the active organic carbon components,increase the organic carbon contents in all sizes of water stable aggregates and soil cellulose enzyme activities in 20-30 cm soil layer,which is beneficial to the improvement of soil texture,deep growth of rice root and maintenance of available nutrients,consequently improve the soil biological fertility of paddy fields.