Abstract

To investigate the temporal dynamics of CO₂ efflux from the soil surface in a temperate cropland and to quantify the effects of soil temperature, soil water content, N fertilization and plant growth on soil carbon dioxide efflux (R_s) field and lab experiments were performed. The field experiment was conducted in a cropland site with a conventional farming system in Central Hungary. The temporal changes of R_s were estimated using a closed chamber IRGA system about bi-weekly/monthly between November 2017–November 2019 in 10 positions. The measured average soil CO₂ efflux values ranged from 0.06 ± 0.007 to 7.04 ± 0.44 µmol CO₂ m^–2 s^–1 Soil respiration model including soil temperature (T_s), soil water content (SWC) and the incorporation of VIgreen (plant growth and functioning) gave a higher goodness-of-fit value (r² = 0.54) than the simple temperature response. According to our field results, different variables including T_s, SWC and VIgreen play a principal role in the carbon cycle of the investigated cropland. We further investigated the effects of the main drivers in a laboratory experiment with the same soil. Closed chamber technique was used for measuring the emission of carbon dioxide by a Picarro G1101-i gas analyzer. We also introduced a fertilization experiment: three different N treatments were applied (N0, N75 and N150) with different levels of soil water content on the soil planted with maize and bare soil. According to our laboratory results, the cumulative CO₂ efflux from soil was found to have a positive correlation with plant growth and with N fertilizer rate: as higher plant biomass and more N added, more CO₂ was emitted, whereas, the cumulative emissions values from planted soil were around two times higher than in bare soil in all treatments. Significant positive correlations were found between CO₂ efflux and SWC indicating that the soil water content was the main factor limiting the rate of the CO₂ emission from soil in both planted and bare soil, in which the cumulative CO₂ efflux was increased with the increase in soil water content, and it was almost three times higher in planted soils at higher soil moisture level than in the bare soil. We can conclude that the effects of plant presence and soil moisture on soil respiration had similar magnitude; however, the effect of N addition was small.

中文翻译：

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温带农田土壤呼吸对生物和非生物驱动因素的响应

摘要

为了研究温带农田土壤表面CO ₂排放的时间动态，并量化土壤温度，土壤含水量，氮肥和植物生长对土壤二氧化碳排放（R _s）场的影响，并进行了室内实验。在匈牙利中部具有常规耕作制度的农田中进行了田间试验。R _s的时间变化是使用封闭室IRGA系统在2017年11月至2019年11月之间每两周/每月在10个位置进行估算的。测得的平均土壤CO ₂外排值范围为0.06±0.007至7.04±0.44 µmol CO ₂ m ^–2 s ^–1与简单的温度响应相比，包括土壤温度（T _s），土壤含水量（SWC）和VIgreen的掺入（植物生长和功能）的土壤呼吸模型具有更高的拟合优度值（r ² = 0.54）。根据我们的现场结果，包括T _s在内的不同变量，SWC和VIgreen在被调查农田的碳循环中起主要作用。我们在相同土壤的实验室实验中进一步研究了主要驱动因素的作用。使用密闭室技术通过Picarro G1101-i气体分析仪测量二氧化碳的排放。我们还介绍了一个施肥实验：在玉米和裸露的土壤上施用了三种不同的氮处理方法（N0，N75和N150），土壤水含量不同。根据我们的实验室结果，发现土壤中累积的CO ₂外排量与植物生长和氮肥施用量呈正相关：随着植物生物量增加和氮素添加量增加，CO ₂含量增加。排放，而在所有处理中，种植土壤的累积排放值大约是裸土的两倍。在CO ₂与SWC之间存在显着的正相关关系，表明土壤水分是限制种植和裸露土壤中CO ₂排放速率的主要因素，其中累积CO ₂排放随增加而增加。土壤水分含量方面，在土壤湿度较高的情况下，种植土壤的土壤水分含量几乎是裸土的三倍。我们可以得出结论，植物的存在和土壤水分对土壤呼吸的影响具有相似的程度。但是，添加氮的作用很小。