Soil temperature and moisture sensitivities of soil CO2 efflux before and after tillage in a wheat field of Loess Plateau, China

Evaluation of no-tillage impacts on soil respiration by 13C-isotopic signature in North China Plain

It is a challenge to characterize soil respiration of crop residue return systems in the North China Plain (NCP) under no-tillage (NT) and conventional tillage (CT) practices. In this study, we addressed the "hot spot" research challenge of impacts of tillage practices on soil carbon storage and soil CO₂ emissions in the NCP by ¹³C-isotopic signature. A short-term (2018-2020) field experiment was conducted with two tillage practices: NT and CT. The results showed that in the tested area, NT had advantages of lower CO₂ emissions compared to CT with average reduced CO₂ emissions by 10.82%-19.14%. The results of this study suggested that the NT facilitated enhanced soil carbon storage by 2.80%, which was evidenced by the δ¹³C data. Based on the path analysis model, the main line of soil respiration reduced by NT was attributed to the increased of soil microbial carbon and nitrogen as well as soil moisture in NT, which further increased δ¹³C and eventually inhibited soil respiration. Overall, adopting NT in NCP is an effective means to improve soil carbon pool and decrease soil CO₂ emissions in agriculture practices.

No tillage increases soil organic carbon storage and decreases carbon dioxide emission in the crop residue-returned farming system

Soil organic carbon (SOC) storage and carbon dioxide (CO₂) emission under different tillage methods in a crop residue-returned farming system may not be consistent with result from studies of the usual tillage researches because crop residues are important carbon sources with significant effects on soil carbon input and output. Herein, we address a knowledge gap over the "hot spot" research on tillage practices on SOC storage and CO₂ emission in crop residue-returned farming systems. In this study, a long-term (2007-2019) field experiment was conducted, and the crop residues were returned to the soil after harvest; then, three tillage methods were conducted: no tillage (NT), subsoiling tillage (ST), and a moldboard plow tillage (CT). Our results showed that in the crop residue-returned farming system, NT and ST still showed advantages of lower CO₂ flux compared with CT, as well as a reduced average CO₂ flux of 14.5% and 8.5%, respectively, over a two-year average. The results of our long-term study suggest that the NT had advantages of SOC accumulation. In addition, as of June 2018, NT increased SOC stocks with 5.85 Mg hm^-2 at a 0-60-cm soil depth compared with CT, whereas no significant difference was found between ST and CT. Overall, adopting NT in a crop residue-returned farming system improved SOC storage to 5.85 Mg hm^-2 after 11 years as well as decreased CO₂ flux by 14.5% in comparison with CT, which is meaningful in improving soil carbon pool and decreasing soil CO₂ emission during agriculture production.

Soil biotreatment effectiveness for reducing global warming potential from main polluting tillage operations in life cycle assessment phase

In order to reduce global warming potential (GWP) due to anthropogenic and natural factors in the cultivation of winter wheat and rapeseed, proved effectiveness of soil biotreatment with different composition of bio-solutions. It was reduced greenhouse gases (GHG) through life cycle impact categories from the main polluting agricultural operations on deeply lukewarm soaked soil. According to the impact diapason evaluated the main indicators such as human toxicity air (HTA), ecotoxicity water chronic (EWC), global warming potential, ecotoxicity water acute (EWA), ozone formation (OF), human toxicity water (HTW), ecotoxicity soil chronic (ESC), human toxicity soil (HTS), terrestrial eutrophication (TE), acidification (A). Assessed researches for three seasons which carried out in production experimental areas. It was appreciated in interrelated stages according to LST EN ISO 14040:2007 standard. Mass balance for one functional unit (FU) was tonne of wheat and rapeseed. SimaPro 8.05 life cycle assessment (LCA) Software was used for comparing soil biotreatment efectiveness using different bio-solutions and its mixes with control. The aim of the assessment - to prove the soil biotreatment effectiveness for reducing main life cycle indicators from tillage operations. It was identificated that phase of field operation is one of the main factor to the global impact. Disc harrowing consists approximately 26%, ploughing - 40% of all operations. Identified effectiveness of soil biotreatment, wheat and rapeseed rotation for reduction of global warming potential. Discovered reduction interdependencies of main life cycle assessement impact categories. The largest CO₂ eq reducing established from primary - disc harrowing 12-15 cm and secondary - ploughing 23-25 cm soil tillage. It was fixed till approximately 15% in mixed bacterial and non-bacterial bio-solution after first soil biotreatment. Till approximately 8% CO₂ eq reduction was in mixed bio-solutions after second biotreatment. The percentage highest soil biotreatment effectiveness till approximately 30% assessed after third biotreatment compared to usual technology. Soil biotreatment effectiveness in reducing green house gases (GHG) proved first year in 86%, second year in 43%, and third year in 71% of all used bio-solutions.

Relationship between CO2 emissions and soil properties of differently tilled soils

Different tillage technologies have different effects on CO₂ emissions from soil. Unfortunately, little information exists about the impact of different types of tillage as compared with no-tillage, and the main controls. The aim of this research is to determine the relationship between physicomechanical, chemical and biological properties of soil and CO₂ emissions from differently tilled soils under the climatic conditions of central Lithuania before and after autumn tillage. The studies were conducted in 2009-2012 and 2014 at the Experimental Station of Aleksandras Stulginskis University in Central Lithuania. Different tillage technologies were applied: deep ploughing at 23-25 cm depth (DP); shallow ploughing at 12-15 cm depth (SP); deep cultivation with a cultivator at 25-27 cm depth (DC); shallow cultivation with a disc harrow at 12-15 cm depth (SC); and no-tillage (NT). The correlation of physicomechanical, chemical and biological soil properties with CO₂ emissions was determined. During all the experimental period total CO₂ emissions from soil in DP, SP, DC, SC and NT technologies were respectively 6.05, 4.25, 4.97, 4.42, 3.94 μmol m^-2 s^-1 before autumn soil tillage and 29.88, 22.50, 16.73, 13.72, 10.00 μmol m^-2 s^-1 after autumn tillage. Negative correlation between soil temperature and CO₂ emissions before the autumn tillage from soil was evidenced (r = -0.98). A strong negative correlation between soil respiration and total soil porosity was observed. Correlation between aeration soil porosity and CO₂ emissions was strong. After autumn tillage, the strongest correlations were found between soil penetration resistance and respiration in the upper (r = -0.75) and deeper (r = -0.71) layers. In autumn, a significant strong correlation (r = 0.78) between soil respiration and aeration porosity was obtained in the upper soil layer under ploughing or cultivation. This study revealed that CO₂ emissions were significantly higher immediately after autumn ploughing technologies compared to deep and shallow cultivation and no-tillage.

Soil respiration, labile carbon pools, and enzyme activities as affected by tillage practices in a tropical rice-maize-cowpea cropping system

In order to identify the viable option of tillage practices in rice-maize-cowpea cropping system that could cut down soil carbon dioxide (CO2) emission, sustain grain yield, and maintain better soil quality in tropical low land rice ecology soil respiration in terms of CO2 emission, labile carbon (C) pools, water-stable aggregate C fractions, and enzymatic activities were investigated in a sandy clay loam soil. Soil respiration is the major pathway of gaseous C efflux from terrestrial systems and acts as an important index of ecosystem functioning. The CO2-C emissions were quantified in between plants and rows throughout the year in rice-maize-cowpea cropping sequence both under conventional tillage (CT) and minimum tillage (MT) practices along with soil moisture and temperature. The CO2-C emissions, as a whole, were 24 % higher in between plants than in rows, and were in the range of 23.4-78.1, 37.1-128.1, and 28.6-101.2 mg m(-2) h(-1) under CT and 10.7-60.3, 17.3-99.1, and 17.2-79.1 mg m(-2) h(-1) under MT in rice, maize, and cowpea, respectively. The CO2-C emission was found highest under maize (44 %) followed by rice (33 %) and cowpea (23 %) irrespective of CT and MT practices. In CT system, the CO2-C emission increased significantly by 37.1 % with respect to MT on cumulative annual basis including fallow. The CO2-C emission per unit yield was at par in rice and cowpea signifying the beneficial effect of MT in maintaining soil quality and reduction of CO2 emission. The microbial biomass C (MBC), readily mineralizable C (RMC), water-soluble C (WSC), and permanganate-oxidizable C (PMOC) were 19.4, 20.4, 39.5, and 15.1 % higher under MT than CT. The C contents in soil aggregate fraction were significantly higher in MT than CT. Soil enzymatic activities like, dehydrogenase, fluorescein diacetate, and β-glucosidase were significantly higher by 13.8, 15.4, and 27.4 % under MT compared to CT. The soil labile C pools, enzymatic activities, and heterotrophic microbial populations were in the order of maize > cowpea > rice, irrespective of the tillage treatments. Environmental sustainability point of view, minimum tillage practices in rice-maize-cowpea cropping system in tropical low land soil could be adopted to minimize CO2-C emission, sustain yield, and maintain soil health.

Typical urban gully nitrogen migration in Changchun City, China

In this study, Yitong River, which is located in Changchun, a representative city in northeastern China, was selected as the research area. Using position monitoring and field measurements, we quantitatively investigated the migration path and flux of nitrogen in a gully region in Changchun City undergoing rapid urbanization. The results showed that at the Yitong River subwatershed, the total nitrogen input flux was 188 kg/hm(2), the degree of which can be ranked in descending order as fertilizer input > biological immobilization > feed > atmospheric deposition. The total nitrogen output flux was 102.5 kg/hm(2), ranked in descending degree as products > waste output > denitrification > surface runoff. The net nitrogen storage was 85.5 kg/hm(2). The migration path and flux of nitrogen were markedly impacted by human activities, showing an imbalance between input and output, as well as a tendency toward nitrogen accumulation and pollution. The nitrogen budget for the Yitong River subwatershed suggested that more than 50 % of the net anthropogenic nitrogen input was lost to the environment, and about 14.5 % was discharged in rivers, indicating that agricultural and human activities in the basin substantially impact the river water quality and thus alter the nitrogen environmental geochemistry. Reducing the application and improving the efficiency of nitrogenous fertilizer use as well as reclaiming human life waste are efficient approaches to decreasing the nitrogen input flux and environmental accumulation and to promoting the balance between nitrogen input and output. These practices are also effective approaches to reducing non-point source pollution.

Tillage, mulch and N fertilizer affect emissions of CO2 under the rain fed condition

A two year (2010–2012) study was conducted to assess the effects of different agronomic management practices on the emissions of CO₂ from a field of non-irrigated wheat planted on China's Loess Plateau. Management practices included four tillage methods i.e. T₁: (chisel plow tillage), T₂: (zero-tillage), T₃: (rotary tillage) and T₄: (mold board plow tillage), 2 mulch levels i.e., M₀ (no corn residue mulch) and M₁ (application of corn residue mulch) and 5 levels of N fertilizer (0, 80, 160, 240, 320 kg N/ha). A factorial experiment having a strip split-split arrangement, with tillage methods in the main plots, mulch levels in the sub plots and N-fertilizer levels in the sub-sub plots with three replicates, was used for this study. The CO₂ data were recorded three times per week using a portable GXH-3010E1 gas analyzer. The highest CO₂ emissions were recorded following rotary tillage, compared to the lowest emissions from the zero tillage planting method. The lowest emissions were recorded at the 160 kg N/ha, fertilizer level. Higher CO₂ emissions were recorded during the cropping year 2010–11 relative to the year 2011–12. During cropping year 2010–11, applications of corn residue mulch significantly increased CO₂ emissions in comparison to the non-mulched treatments, and during the year 2011–12, equal emissions were recorded for both types of mulch treatments. Higher CO₂ emissions were recorded immediately after the tillage operations. Different environmental factors, i.e., rain, air temperatures, soil temperatures and soil moistures, had significant effects on the CO₂ emissions. We conclude that conservation tillage practices, i.e., zero tillage, the use of corn residue mulch and optimum N fertilizer use, can reduce CO₂ emissions, give better yields and provide environmentally friendly options.