有机无机肥配施对盐渍化土壤微生物量和呼吸的影响

Effects of the combined application of organic and inorganic fertilizers on soil microbial biomass and soil respiration in saline soil

微生物可以通过摄入能量合成有机渗透压物质来实现对盐度的适应,然而,不同程度盐渍土微生物对能量的需求可能会发生改变。因此,该研究于2018-2019年开展田间定位试验,选取河套灌区轻度盐渍土S_(1)(电导率为0.46 dS/m)及中度盐渍土S_(2)(电导率为1.07 dS/m)为研究对象,设置了6个处理,包括不施氮(CK),单施无机氮(U_(1))以及分别用有机氮(U_(3)O_(1)、U_(1)O_(1)、U_(1)O_(3)和O_(1))替代25%、50%、75%和100%的无机氮,监测了土壤微生物量碳氮及土壤呼吸在第二个生长季的动态状况。结果表明:土壤盐渍化程度增加会导致土壤微生物量及微生物活性下降,S_(1)土壤较S_(2)土壤微生物量碳高12.01%~68.81%,土壤微生物量氮高14.31%~58.58%,土壤呼吸速率高11.75%~54.71%。不同盐分条件下,适当的有机肥施入比例可以显著提高土壤微生物量及微生物活性,S_(1)和S_(2)盐渍土分别以U_(1)O_(1)及O_(1)处理较优。相关性分析表明,土壤呼吸速率与土壤微生物量碳氮呈极显著正相关(P<0.01),土壤温度、土壤矿质氮与土壤微生物量碳氮、土壤呼吸速率呈显著正相关(P<0.05)。从玉米产量及改善土壤微生物生存环境角度,得到该地区适宜的施肥模式为,轻度盐渍土:有机氮替代50%无机氮;中度盐渍土:有机氮替代100%无机氮。

Microorganisms can adapt to the salinity by ingesting energy,further to synthesize organic osmolytes in soil.However,microbial demand for energy may change,as the soil salinity changes.In this study,a field experiment was carried out to explore the effects of the combined application of organic and inorganic fertilizers on soil respiration and microbial biomass in saline soil.The samples were taken as the mild saline soil,S_(1)(electrical conductivity(EC)0.46 dS/m)and moderate saline soil,S_(2)(electrical conductivity(EC)1.07 dS/m)in Hetao Irrigation District of Inner Mongolia,China,in 2018.Soil respiration rate was measured by a li-8100 soil carbon flux automatic measurement system.Surface soil samples of 0-20 cm depths were collected under various fertilization regimes in mild and moderate saline soil.Calcium chloride and chloroform fumigation extraction were used to investigate the effect of various fertilization regimes on the mineral nitrogen contents and microbial biomass in soil.Six treatments were set,including no fertilization(CK),urea(U_(1)),and 25%,50%,75%,as well as 100%of urea N substituted by organic fertilizers U_(3)O_(1),U_(1)O_(1),U_(1)O_(3),and O_(1),respectively,during the second growing season(April-September).The parameters were measured under equal N application rates of 240 kg/hm^(2),the dynamics of soil microbial biomass(i.e.,microbial biomass carbon[MBC]and microbial biomass nitrogen[MBN]),and soil respiration(i.e.,soil respiration rate,soil autotrophic respiration rate,and soil heterotrophic respiration rate).The results showed that the contents of mineral nitrogen in S_(1) soil were higher in the U_(1) treatment during the early growing stage(seedling and stem elongation stage),but higher in the U_(1)O_(1) treatment in the later stage.S_(2) soil showed that the soil mineral nitrogen contents were higher in the whole growing stage,as the application rate of organic fertilizer increased.Furthermore,the increase of soil salinization resulted in the decrease of microbial biomass and microbial activity in the soil.The MBC in S_(1) soil increased by 12.01%-68.81%,while the MBN increased by 14.31%-58.58%,and the soil respiration flux increased by 11.75%-54.71%,compared with S_(1) soil.Furthermore,the organic fertilizer significantly increased the microbial biomass and microbial activity under different degrees of saline soils.The S_(1) saline soils treated with U_(1)O_(1) presented the higher MBC,MBN,and soil respiration flux,indicating a significant increase compared with U_(1) treatment(P<0.05).The performance of S_(2) saline soil after the O_(1) treatment was better than that after the U_(1) treatment,where the MBC,MBN,and soil respiration flux increased(P<0.05).The highest maize yield was also achieved in the S_(1) and S_(2) soil treated with U_(1)O_(1) and O_(1),which were 11902.91,and 7609.67 kg/hm2,respectively.A correlation analysis was found that the soil respiration presented a significant positive correlation with the MBC and MBN(P<0.05).The soil temperature and mineral nitrogen had a significant positive correlation with the soil respiration,MBC,and MBN(P<0.05).Regression analysis showed that there was a significant exponential relationship between the soil respiration and temperature(P<0.05),but the relationship between soil respiration rate and soil moisture content was not significant.Additionally,there was a significant nonlinear relationship of soil microbial biomass and respiration rate with the organic fertilizer rate and soil salt concentration.The regression coefficient demonstrated that the appropriate organic fertilizer rate contributed to maximizing the soil microbial biomass and respiration rate in different saline soils.Optimal organic and chemical fertilizer management models were achieved for the mild saline soil in the Hetao irrigation area.Specifically,the mild saline soil(120 kg/hm^(2) urea+120 kg/hm^(2) organic fertilizer),and moderate saline soil(240 kg/hm^(2) organic fertilizer)can be expected for the higher corn yield under the improved soil microbial environment.