Straw Incorporation Research Articles

Microbial Responses of Soil Fertility to Depth of Tillage and Incorporation of Straw in a Haplic Chernozem in Northeast China

Microbial Responses of Soil Fertility to Depth of Tillage and Incorporation of Straw in a Haplic Chernozem in Northeast China

Long-term fertilization enhances the activity of anaerobic oxidation of methane coupled to nitrate reduction and associated microbial abundance in paddy soils

Anaerobic oxidation of methane coupled to nitrate reduction (nitrate-coupled AOM) is performed by Candidatus Methanoperedens nitroreducens (M. nitroreducens)-related archaea, and is recently recognized as a crucial component of the global carbon cycle. The input of fertilizers is an essential agricultural practice that greatly impacts methane (CH4) production and emission. However, the significance of nitrate-coupled AOM in CH4 cycling and its response to fertilization in rice fields remain unclear. In this study, the potential nitrate-coupled AOM rates and the communities of M. nitroreducens-related archaea in rice fields were examined at different soil layers (0–10, 10–20, and 30–40 cm) at tillering, elongation, flowering, and ripening stages under three long-term fertilization treatments (CK-without fertilizer, CF-chemical fertilization, or CFS-chemical fertilization with straw incorporation). The results indicated that both CF (1.07 nmol 13CO2 g−1 d−1) and CFS (1.21 nmol 13CO2 g−1 d−1) treatments significantly promoted the potential nitrate-coupled AOM rates compared to CK (0.53 nmol 13CO2 g−1 d−1). A greater response of potential activity to fertilization was observed at plough layer (upper 20 cm) and during elongation stage. The abundance of M. nitroreducens-related archaea under CF (1.12 × 107 copies g−1) and CFS (1.62 × 107 copies g−1) treatments was significantly greater than that under CK (6.93 × 106 copies g−1). Conversely, the growth response of these archaeal to fertilization was stronger at deeper layer (30–40 cm). Moreover, no significant change was observed in the community composition of M. nitroreducens-related archaea among treatments. Correlation analysis suggested that the variations of soil organic carbon, NH4+, and NO3− contents caused by fertilization were key factors influencing the potential nitrate-coupled AOM rates and M. nitroreducens-related archaeal abundance. Our findings provide the first evidence for positive response of nitrate-coupled AOM to long-term fertilization, demonstrating its potential to act as an important process for mitigating CH4 emission in rice fields.

Interactive effects of agricultural management on soil organic carbon accrual: A synthesis of long-term field experiments in Germany

Crop production often leads to soil organic carbon (SOC) losses. However, under good management practice it is possible to maintain and even re-accumulate SOC. We evaluated how different cropland management techniques affected SOC stocks in the topsoil (0–30 cm depth) of 10 long-term experiments (LTE) in Germany. We found that SOC stocks were particularly enhanced by mineral fertilization and organic amendments like straw incorporation and to a smaller degree by irrigation, but only slightly affected by the choice of preceding crops. In agreement with global meta-analyses, liming and reduced tillage had little or even negative effects on SOC storage, but effects also depended on fertilization. Management effects on SOC stocks were dependent on soil texture: sandy soils showed the lowest SOC stocks of 20.9 ± 2.3 (standard error of the mean) Mg ha−1, but exhibited the largest relative response to different management options. Annual changes in SOC stocks ranged from −3.0 ‰ with no mineral N fertilization, to + 6.1 ‰ with farmyard manure application, using the mineral-fertilized and limed treatment as reference. Even higher rates of up to + 10.6 ‰ yr−1 were reached with the combination of irrigation and straw incorporation. Note that the contribution of organic amendments to SOC accrual and thus to climate change mitigation must be adjusted for reduction in SOC at sites from which straw was removed. Overall, the potential of agricultural management to influence and enhance SOC stocks is significant. This potential is controlled by soil type and land-use duration, is largest for sandy soils with overall lowest SOC stocks, and is characterized by antagonistic and synergistic effects of different management practices.

Uncovering the potentials of long-term straw return and nitrogen supply on subtropical maize (Zea mays L.) photosynthesis and grain yield

ContextCrop straw is a significant byproduct of agricultural production and a rich source of nutrients, but it is carelessly disposed of, potentially harming the environment and wasting valuable resources. In China, returning straw to the soil as a means of disposing of agricultural waste is a crucial management technique that not only makes use of agricultural waste but also enhances soil quality and grain yield. ObjectiveA five-year (2018–2022) field experiment was designed to study the effect of straw treatment methods and optimal nitrogen (N) application rate on the photosynthesis process and grain yield of maize. MethodsThe different straw methods (straw return (SR) and traditional practice (TP) — no straw return) were assigned to main plots while the N levels such as N100 (100 kg ha−1), N150 (150 kg ha−1), N200 (200 kg ha−1), N250 (250 kg ha−1), and N300 (300 kg ha−1) were allotted to sub-plots. ResultsThe results showed the photosynthesis rate (Pn), intercellular carbon dioxide concentration, stomatal conductance, transpiration rate, relative chlorophyll content (SPAD), leaf area index (LAI), dry matter (DM), soil nitrogen content, maize grain nitrogen accumulation, and grain yield were increased with an increase in N levels. Similarly, SR also showed a promotion effect on the aforementioned parameters compared with TP. After five years, SR with an optimum N level (250 kg ha−1) increased the SPAD values (2%) and Pn (8%) which resulted in higher LAI (27%) compared with TPN300. As a result, more DM (15%) was formed and finally increased the grain yield (7%). It was revealed that the SPAD, Pn, LAI, DM, and grain yield were maximum at a higher 300 kg N ha−1 level but it was found statistically similar with 250 kg N ha−1. So in this study, SR with 250 kg N ha−1 is optimum for better photosynthetic efficiency, dry matter production, and grain yield. The correlation analysis also showed a positive correlation (i) of SPAD values with Pn (ii) LAI with SPAD values and Pn, (iii) DM with SPAD values, Pn, and LAI, and (iv) grain yield with DM under SR compared with TP. Conclusion and implicationIn summary, SRN250 resulted in better chlorophyll content and photosynthesis process that yielded more photosynthetic area for higher DM production and subsequently higher maize grain yield. The SR reduced the amount of N fertilizer and improved the grain yield and it is the best approach to improve grain yield and minimize agricultural waste production. Long-term trials are needed to understand the effects of straw incorporation and nitrogen application in different regions and locations.

Microbial community and network differently reshaped by crushed straw or biochar incorporation and associated with nitrogen fertilizer level

AbstractStraw returning has been demonstrated as a beneficial approach for the utilization of renewable biomass source, which contributes to reducing environmental pollution and strengthening the sustainability of agriculture. However, information on how microorganisms respond to different straw return modes (SRMs) at varying nitrogen fertilizer levels (NFLs) in the black soil is still limited. The community composition, network pattern, and modular function of bacteria and fungi are investigated under three SRMs, including straw removal (CK), crushed straw incorporation (SD), and biochar incorporation (BC) at three NFLs (0, 144, and 240 kg N ha−1, respectively) mainly using Illumina MiSeq technique based on a long‐term maize field experiment. Results showed that bacterial richness, diversity, and fungal richness decreased with NFL reduction. However, these decreases can be compensated by SD and BC, demonstrating superiority for BC at reduced NFLs. SD and BC differed in their effects on the bacterial and fungal abundances (showing increments only in SD) and fungal Shannon diversity (remaining stable only in BC irrespective of NFLs). Microbial communities were substantially affected by SRMs and interacted with NFLs, which were driven by soil NH4+‐N, available potassium, total nitrogen, and pH. In addition, SD induced a network characterized by its highly complex (average degree 10.259 vs. 3.364) and stable structure (average clustering coefficient 0.503 vs. 0.239), Ascomycota as predominating keystone taxa, and abundant N‐cycling related bacteria, while BC formed a network comprising a superior modular structure (modularity 2.599 vs. 0.912), dominant symbiotic fungi, and soil bulk density as specific shaping factor, indicating that network pattern, keystone taxa, modular function, and determining factors shifted between SD and BC co‐occurrence networks. These results deepen insights into the response divergence of bacteria and fungi to SRMs and NFLs, providing a scientific basis for selecting the suitable strategy for sustainable straw utilization in the black soil area.

Straw Returning Measures Enhance Soil Moisture and Nutrients and Promote Cotton Growth

In order to investigate the comprehensive effects of straw returning on soil physical and chemical properties, as well as cotton growth in Jiangsu, China, and to determine suitable high-yield and efficient straw returning measures, this study implemented three different straw returning methods: straw mulching (SM), straw incorporation (SI), and straw biochar (BC), with no straw returning served as a control (CT). The study aimed to assess the impact of these straw-returning measures on soil nutrients, soil moisture content, soil water storage, and deficit status, as well as primary indicators of cotton growth. The findings revealed that the total available nutrient storage under SM, SI, and BC showed an increase of 11.93%, 11.15%, and 32.39%, respectively, compared to CT. Among these methods, BC demonstrated a significant enhancement in soil organic carbon content, available phosphorus, and available potassium. Furthermore, SM exhibited a considerable increase in soil moisture content across all layers (0–40 cm), resulting in an average water storage increase of 7.42 mm compared to CT. Consequently, this effectively reduced the soil water deficit during the cotton development period. Moreover, the height of cotton plants was increased by SM, SI, and BC, with SM promoting the greatest growth rate of up to 66.87%. SM resulted in an 11.17 cm increase in cotton plant height compared to CT. Additionally, SM contributed to higher chlorophyll content in leaves at the end of the growth period. Overall, the indicators suggest that straw mulching is particularly effective in enhancing soil moisture and nutrient distribution, especially during dry years, and has a positive impact on promoting cotton development. Based on the results, straw mulching emerges as a recommended straw-returning measure for improving soil quality and maximizing cotton production in the study area.

Improving wheat seedling quality through deep ploughing and soil compaction at sowing in lime concretion black soil.

The straw incorporation in lime concretion black soil compromises the emergence and quality of winter wheat seedlings in Huaibei Plain, China, lowering the potential of wheat productivity. To overcome the disadvantage, a two-year field experiment was conducted in 2017-18 and 2018-19 to investigate the effects of different tillage modes on seedling emergence and subsequent seedling growth, and final grain yield (GY) in winter wheat. The modes are rotary tillage with compaction after sowing (RCT), rotary tillage after deep ploughing (PT) and rotary tillage after deep ploughing with compaction after sowing (PCT), with the traditional rotary tillage (RT) method as the control. Compared to RT, greater soil moisture content (SMC) at the seedling stage was observed in deep ploughing or compaction treatment, and the highest SMC was achieved in PCT; the time of reaching the maximum number of seedlings was 1 d sooner in RCT or PT, and 3 d in PCT; the seedling number in RCT, PT and PCT was significantly increased by 32.6%, 34.5% and 61.5% respectively. The population size, shoot and root growth of winter wheat in ploughing mode was significantly enhanced than that of rotary treatment at the over-wintering stage; compared to no compaction after sowing, plant growth in compaction treatments was significantly promoted with greater plant population size and height of seedlings. At harvest, GY in RCT, PT and PCT was significantly improved by 5.87%, 10.8% and 16.4%, respectively, compared to RT and the highest GY was achieved in PCT by up to 8, 350.1 kg ha-1 due to the increased spike number. In conclusion, the seedling quality in the straw incorporation practice was improved through rotary after deep ploughing and compaction after sowing for lime concretion black soil in Huaibei Plain, China or a similar soil type.

Formation of soil organic carbon pool is regulated by the structure of dissolved organic matter and microbial carbon pump efficacy: A decadal study comparing different carbon management strategies.

To achieve long-term increases in soil organic carbon (SOC) storage, it is essential to understand the effects of carbon management strategies on SOC formation pathways, particularly through changes in microbial necromass carbon (MNC) and dissolved organic carbon (DOC). Using a 14-year field study, we demonstrate that both biochar and maize straw lifted the SOC ceiling, but through different pathways. Biochar, while raising SOC and DOC content, decreased substrate degradability by increasing carbon aromaticity. This resulted in suppressed microbial abundance and enzyme activity, which lowered soil respiration, weakened in vivo turnover and ex vivo modification for MNC production (i.e., low microbial carbon pump "efficacy"), and led to lower efficiency in decomposing MNC, ultimately resulting in the net accumulation of SOC and MNC. In contrast, straw incorporation increased the content and decreased the aromaticity of SOC and DOC. The enhanced SOC degradability and soil nutrient content, such as total nitrogen and total phosphorous, stimulated the microbial population and activity, thereby boosting soil respiration and enhancing microbial carbon pump "efficacy" for MNC production. The total C added to biochar and straw plots were estimated as 27.3-54.5 and 41.4 Mg C ha-1 , respectively. Our results demonstrated that biochar was more efficient in lifting the SOC stock via exogenous stable carbon input and MNC stabilization, although the latter showed low "efficacy". Meanwhile, straw incorporation significantly promoted net MNC accumulation but also stimulated SOC mineralization, resulting in a smaller increase in SOC content (by 50%) compared to biochar (by 53%-102%). The results address the decadal-scale effects of biochar and straw application on the formation of the stable organic carbon pool in soil, and understanding the causal mechanisms can allow field practices to maximize SOC content.

Evaluation of Methane Emission Reduction Potential of Water Management and Chinese Milk Vetch Planting in Hunan Paddy Rice Fields

In order to explore the methane reduction potential with two scenarios of water management and Chinese Milk Vetch return, we calculated the methane emissions of Hunan Province rice fields in 2019 using the SECTOR tool based on Excel and released by the International Rice Research Institute. Thus, we preliminarily established an agricultural carbon emissions monitoring, reporting, and verification (MRV) system. The results showed that: (1) There was significant spatial variation in methane emissions in Hunan rice fields, with higher emissions in both the south and north and lower emissions in the east and west. Late rice was the main contributor to methane emissions, and the cities of Changde, Hengyang, Yueyang, and Shaoyang were high-emission areas due to differences in rice planting types and areas. Compared with flooding (1275.75 Gg), optimized water management measures (mid-drainage and AWD irrigation) reduced methane emissions by 29~45% (905.79 and 701.66 Gg, respectively). (2) Under the same nitrogen input conditions, compared with a solely straw return (375.24 Gg), combining green manure with straw return could partially reduce methane emissions from Hunan super hybrid rice (327.63 Gg). Compared with the control fertilizers (404.28 Gg), the reduction rates of winter-planted Chinese Milk Vetch, the return of rice straw, and the incorporation of both Chinese Milk Vetch and straw were 7.19%, 13.01%, and 18.96%, respectively. Based on scientific accounting tools, a preliminary MRV system for rice field carbon emissions was established. Under the national demand for reducing fertilizer use and increasing efficiency, equal nitrogen organic amendments could effectively contribute to the development of green, low-carbon, and high-quality agriculture.

Risk preferences and the low-carbon agricultural technology adoption: Evidence from rice production in China

Climate change which is mainly caused by carbon emissions is a global problem affecting the economic development and well-being of human society. Low-carbon agriculture is of particular significance in slowing down global warming and reaching the goal of “carbon peak and carbon neutrality”. Therefore, taking straw incorporation as an example, this paper aims to investigate the impact of risk preferences on farmers’ low-carbon agricultural technology (LCAT) adoption. Based on a two-phase micro-survey data of 1 038 rice farmers in Jiangsu, Jiangxi, and Hunan provinces, this paper uses experimental economics methods to measure farmers’ risk aversion and loss aversion to obtain the real risk preferences information of the farmers. We also explore the data to examine the actual LCAT adoption behavior of farmers. The results revealed that both risk aversion and loss aversion significantly inhibit farmers’ LCAT adoption: more risk-averse or more loss-averse farmers are less likely to adopt LCAT. It is further found that crop insurance, farm scale and governmental regulations can alleviate the negative impact of risk aversion and loss aversion on farmers’ LCAT adoption. Therefore, we propose that local governments need to promote low-carbon agricultural development by propagating the benefits of LCAT, extending crop insurance, promoting appropriate scale operations, and strengthening governmental regulations to promote farmers’ LCAT adoption.

Effects of straw incorporation on soil erosion resistance along a land degradation gradient in the black soil region of China

Soil erosion resistance (reflected by rill erodibility and critical shear stress) is a useful parameter for evaluating soil erosion subjected to concentrated flow. The changes in soil properties and root trait induced by straw incorporation and land degradation likely affect soil erosion resistance considerably. Nevertheless, few studies have been conducted to quantify the effects of straw incorporation on soil erosion resistance of degraded croplands in the black soil region. In this study, a large hydraulic flume (5.0 m in length and 0.4 m in width) was utilized to quantify the impacts of straw incorporation on soil erosion resistance of four croplands with different degradation degrees (non-degradation, light degradation, moderate degradation and strong degradation) and further to determine the related influencing mechanisms in Northeast China. The results showed that straw incorporation reduced rill erodibility by 44.9%, 41.2%, 27.1% and −11.4% for non-degradation, light degradation, moderate degradation and strong degradation croplands, respectively. Land degradation degree had much stronger influence on soil erosion resistance than that of straw incorporation and regulated the roles of straw incorporation in mitigating erosion. Rill erodibility was significantly and negatively correlated with clay content, organic matter content, aggregate stability, soil cohesion, physical crust thickness and root mass density, whereas positively correlated with silt content. The increase in soil organic matter and clay content was the key to improve soil erosion resistance and prevent land degradation. Straw incorporation was suggested in non-degradation, light degradation and moderate degradation croplands, but vegetation restoration was recommended in strong degraded cropland. The results are helpful to understand the mechanism of straw incorporation to improve soil erosion resistance and make reasonable agricultural management strategies in semi humid region.

The impact of maize straw incorporation on arsenic and cadmium availability, transformation and microbial communities in alkaline-contaminated soils

Increasing evidence of the uncertainty of crop straw returning in heavy metal-contaminated soil is a significant concern. The present study investigated the influence of 1 and 2% maize straws (MS) amendment on As and Cd bioavailability in two different alkaline soils (A-industrial and B-irrigation) after 56 days of ageing. Adding MS to the two soils decreased the pH by 1.28 (A soil) and 1.13 (B soil) and increased the concentration of dissolved organic carbon (DOC) by 54.40 mg/kg (A soil) and 100.00 mg/kg (B soil) during the study period. After 56 days of ageing, the overall NaHCO3–As and DTPA-Cd increased by 40% and 33% (A) and 39% and 41% (B) soils, respectively. The MS additions increased the alteration of As and Cd exchangeable and residual fractions, whereas advanced solid-state 13C nuclear magnetic resonance (NMR) revealed that alkyl C and alkyl O–C–O in A soil and alkyl C, Methoxy C/N-alkyl, and alkyl O–C–O in B soil significantly contributed to the As and Cd mobilisation. Collectively, 16 S rRNA analyses revealed Acidobacteria, Firmicutes, Chloroflexi, Actinobacteria and Bacillus promoted the As and Cd mobilisation following the MS addition, while principle component analysis (PCA) demonstrated that bacterial proliferation significantly influenced MS decomposition, resulting in As and Cd mobilisation in the two soils. Overall, the study highlights the implications of applying MS to As- and Cd-contaminated alkaline soil and offers the framework for conditions to be considered during As- and Cd-remediation efforts, especially when MS is the sole remediation component.

Improvement of Straw Changed Soil Microbial Flora Composition and Suppressed Chinese Cabbage (Brassica rapa L. ssp. pekinensis) Clubroot Disease

Straw incorporation is known as an environmentally friendly agricultural practice that can effectively enhance soil nutrient contents and crop yields; its potential to suppress soil-borne disease has also been reported in recent years. Here, we perform a field experiment for two consecutive years (2017–2018) to evaluate the effectiveness of maize (Zea mays), rice (Oryzae sativa L.) and wheat (Triticum aestivum L.) straws incorporation in alleviating Chinese cabbage (Brassica rapa L. ssp. pekinensis) clubroot disease caused by Plasmodiophora brassicae Woronin. Microbial composition in Chinese cabbage rhizosphere and soil P. brassicae abundance were estimated by high-throughput amplicon sequencing and quantitative polymerase chain reaction (qPCR). Results showed that, during the two-year field experimental cycle, all three straw amendments promoted Chinese cabbage plant growth, inhibited clubroot disease and increased the alpha diversity of the bacterial community in Chinese cabbage rhizosphere. Rice and wheat straws also increased the alpha diversity of the fungal community. These straws diversified the composition of the Chinese cabbage rhizosphere microbial community. All three straws promoted Cryptococcus carnescens; both rice and wheat straws stimulated Lysobacter sp.; maize straw boosted Sphingomonas sp. and wheat straw increased Talaromyces sp. These microbial taxa are either considered to have positive influences on plant growth or potential biocontrol effects. In addition, straw amendments also increased soil pH, electrical conductivity, available nitrogen and available potassium contents in both years of the field experiment. Taken together, we concluded that these three gramineous straw amendments ameliorated Chinese cabbage rhizosphere microorganisms, inhibited clubroot disease and promoted the growth of Chinese cabbage, and that rice straw worked best amongst the three. This study could potentially provide a new tactic of massive grain crop straw utilization and a direction in dealing with clubroot disease.

Estimation of in-season nitrogen requirement for drip-irrigated spring maize without or with straw incorporation using critical nitrogen dilution curve

Estimation of in-season nitrogen requirement for drip-irrigated spring maize without or with straw incorporation using critical nitrogen dilution curve

Soil aggregates associated carbon and enzyme activities under long-term nitrogen and rice straw incorporation in Rice-Wheat system

ABSTRACT Intensive tillage and burning or removal of crop residues have led to a decline in soil organic carbon (SOC) content, posing a significant threat to soil quality and global food production. To mitigate this, adoption of conservation-agriculture practices, including residue retention/incorporation, is necessary to promote soil structural stability, increase SOC content, and enzyme activities, and restore carbon (C) sustainability in the rice-wheat system (RWS). Therefore, the long-term effects (10 years) of rice straw incorporation (RS) (0, 5, 7.5, and 10 Mg ha−1) and nitrogen (N) levels (0, 90, 120, and 150 kg N ha−1) in wheat on soil aggregate associated C pools and enzyme activities were studied. The results revealed that RS incorporation levels of RS7.5 and RS10 had 15.1% and 15.5% higher water-stable aggregates. Within the aggregate fractions, enzyme activities and C pools were significantly higher in the macro-aggregates fraction (Ma-A >0.25 mm) and least in micro-aggregates (Mi-A <0.25 mm). Under Ma-A fraction, treatments RS10 and N150 had higher enzyme activity compared to RS0 and N0. Under Ma-A, very labile C, labile C, less labile C, and recalcitrant C were increased by 34%, 25%, 33%, and 48% in RS10 over RS0 and by 20%, 28%, 23%, and 15% in N150 over the N0 level, respectively. Thus, the study concluded that the addition of crop residues (7.5 and 10 Mg ha−1) along with the N level of 150 kg ha−1 is a suitable management practice to promote soil structural stability and enzyme activities encouraging long-term SOC sustainability in the RWS.

Changes in Soil Properties and Crop Yield under Sustainable Conservation Tillage Systems in Spring Wheat Agroecosystems

The cultivated soils in several semi-arid areas have very low organic matter due to climatic constraints that limit primary crop yield. Conservation tillage systems, outlined here as no tillage, no tillage with straw return and straw incorporation into the field, have been accepted as capable systems that preserve soil’s resources and sustain soil productivity. However, in semi-arid climates, there is presently no knowledge about the influence of different conservation tillage techniques on soil’s physical, chemical and biological properties at different soil depths in spring wheat fields and only little information about spring wheat yield in these management systems. Therefore, the present study was carried out with the objective of examining the impact of conservation tillage systems on soil properties (physical, chemical and biological) and spring wheat yield. The three conservation tillage treatments consisted of no tillage system (NT), wheat stubble return with no tillage (NTS) and straw incorporation with conventional tillage (CTS), as well as one conventional tillage (CT) control treatment, which were evaluated under randomized complete block design with three replications. The three conservation tillage treatments were compared with the conventional tillage control. Conservation tillage significantly increased the bulk density, gravimetric water content, water storage, hydraulic conductivity and soil aggregates and decreased the pore space and soil temperature compared to CT; however, no significant difference was found in the case of field capacity. Soil chemical properties in the 0–40 cm soil layer increased with conservation tillage compared to CT. Conservation tillage also notably increased the soil microbial counts, urease, alkaline phosphatase, invertase, cellulase and catalase activities relative to CT. Microbial biomasses (carbon and nitrogen) and wheat yield significantly elevated under conservation tillage compared to CT. Therefore, conservation tillage could significantly improve soil properties and maintain wheat yield for the research zone.

Twenty percent of agricultural management effects on organic carbon stocks occur in subsoils – Results of ten long-term experiments

Agricultural management can influence soil organic carbon (SOC) stocks and thus may contribute to carbon sequestration and climate change mitigation. The soil depth to which agricultural management practices affect SOC is uncertain. Soil depth may have an important bearing on soil carbon dynamics, so it is important to consider depth effects to capture fully changes in SOC stocks. This applies in particular to the evaluation of carbon farming measures, which are becoming increasingly important due to climate change. We sampled and analysed the upper metre of mineral cropland soils from ten long-term experiments (LTEs) in Germany to quantify depth-specific effects on SOC stocks of common agricultural management practices: mineral nitrogen (N) fertilisation, a combination of N, phosphorus (P) and potassium (K) fertilisation, irrigation, a crop rotation with preceding crops (pre-crops), straw incorporation, application of farmyard manure (FYM), liming, and reduced tillage. In addition, the effects of soil compaction on SOC stocks were examined as a negative side effect of agricultural management. Results showed that 19 ± 3 % of total management effects on SOC stocks were found in the upper subsoil (30–50 cm) and 3 ± 4 % in the lower subsoil (50–100 cm), including all agricultural management practices with significant topsoil SOC effects, while 79 ± 7 % of management effects were in the topsoil (0–30 cm). Nitrogen and NPK fertilisation were the treatments that had the greatest effect on subsoil organic carbon (OC) stocks, followed by irrigation, FYM application and straw incorporation. Sampling down to a depth of 50 cm resulted in significantly higher SOC effects than when considering topsoil only. A crop rotation with pre-crops, liming, reduced tillage and soil compaction did not significantly affect SOC stocks at any depth increment. Since approximately 20 % of the impact of agricultural management on SOC stocks occurs in the subsoil, we recommend soil monitoring programs and carbon farming schemes extend their standard soil sampling down to 50 cm depth to capture fully agricultural management effects on SOC.

Sustainable Analysis of Maize Production under Previous Wheat Straw Returning in Arid Irrigated Areas

Conservation tillage is widely recognized as an important way to improve soil quality, ensure food security and mitigate climate change. However, relatively little attention has been paid to the subject in terms of sustainable evaluation of environmental and economic benefits of the combination of no tillage and straw returning for maize production in arid irrigated areas. In this study, grain yield (GY) and water use efficiency based on grain yield (WUEGY), soil carbon emission characteristics and economic benefits were investigated, and a sustainability evaluation index based on the above indicators was assessed in maize production under a wheat–maize rotation system from 2009 to 2012. Four wheat straw returning approaches were designed: no tillage with 25 to 30 cm tall wheat straw mulching (NTSMP), no tillage with 25 to 30 cm tall wheat straw standing (NTSSP), conventional tillage with 25 to 30 cm tall wheat straw incorporation (CTSP), and conventional tillage without wheat straw returning (CTP). The results showed that NTSMP treatment could effectively regulate water consumption characteristics of maize fields and meet the water conditions for high grain yield formation, thus gaining higher GY and WUEGY. NTSMP increased GY and WUEGY of maize by 13.7–17.5% and 15.4–16.7% over the CTP treatment, and by 5.6–9.0% and 2.3–11.2% over the CTSP treatment, respectively. Meanwhile, compared with CTP, the NTSMP treatment could effectively reduce carbon emissions from maize fields, where average soil carbon emission fluxes (ACf), carbon emission (CE) and water use efficiency based on carbon emission (WUECE) were reduced by 17.7–18.9%, 11.1–11.2% and 8.8–12.8% and carbon emission efficiency (CEE) was increased by 10.2–14.7%. In addition, the NTSMP and NTSSP treatments could effectively increase total output and reduce human labor and farm machinery input, resulting in higher economic benefit. Among them, the NTSMP treatment was the most effective, net income (NI) and benefit per cubic meter of water (BPW) were increased by 16.1–34.2% and 19.1–31.8% over the CTP treatment, and by 13.2–13.3% and 9.8–15.6% over the CTSP treatment, respectively. The sustainability analysis showed that the NTSMP treatment had a high sustainability evaluation index and was a promising field-management strategy. Therefore, no tillage with 25 to 30 cm tall wheat straw mulching is a sustainable maize-management practice for increasing economic benefits and improving environmental impacts in arid irrigated areas.

Effects of Annual Straw Incorporation Combined with Application of Nitrogen Fertilizer in Rice Season on Dry Matter and Nutrient Accumulation Characteristics of Subsequent Rapeseed

In the rice–rapeseed rotation system, straw incorporation plays an important role in achieving the rational utilization of resources and maintaining crop production. However, in the study of rice–rapeseed rotation, there was no study on the effect of straw and nitrogen (N) fertilizer in the rice season on the dry matter accumulation (DMA) and nutrient accumulation of subsequent rapeseed. So, this study relied on the localization experiment of rice–rapeseed rotation and annual straw incorporation (full straw returning to the field, SR; the control is full straw removal from the field, CK) with different N fertilizer application rates (N1: 0 kg ha−1, N2: 75 kg ha−1, N3: 150 kg ha−1, and N4: 225 kg ha−1) in the rice season. Based on the fourth year of experiment implementation, the effects of annual straw incorporation combined with the N fertilizer application rate in the rice season on the leaf area index (LAI), photosynthetic potential (PP), DMA and its distribution proportion and rate, and nutrient uptake and its allocation proportion in rapeseed were discussed. At the bolting stage (BS), initial flowering stage (IFS), terminal flowering stage (TFS), and mature stage (MS), the DMA of rapeseed in SR was significantly higher than that in CK by 69.90, 64.27, 62.90, and 41.27%, respectively. The accumulation of N, phosphorus (P), and potassium (K) in SR was significantly higher than that in CK at the BS, IFS, TFS, and MS. Straw treatment had a significant impact on the apparent surplus of N, P, and K in the rice, rapeseed, and annual seasons, while the application of N fertilizer in the rice season had a significant or extremely significant impact on the apparent surplus (AS) of N in the rice, rapeseed, and annual seasons, indicating that fertilization of previous crops had a certain aftereffect. Therefore, straw incorporation is a sustainable farmland management measure.

Effects of Combined Long-Term Straw Return and Nitrogen Fertilization on Wheat Productivity and Soil Properties in the Wheat-Maize-Soybean Rotation System in the Pannonian Plain

The study, conducted to evaluate the effects of long-term straw management combined with the application of increasing nitrogen rates on the yield of twenty winter wheat varieties, as well as on soil properties, was carried out in a long-term field trial established in 1971. The trial was monitored for twenty growing seasons under rainfed conditions in a typical chernozem zone of the southern part of the Pannonian Plain. The cropping system was a winter wheat-maize-soybean rotation. The ten SN-treatments (combinations of straw management (S) and N-fertilization) were as follows: In the plot (treatment) with straw return (S1), seven variants of nitrogen fertilization (0–180 kg N ha−1) were included, while on the plot without straw return (S0) the variants of N-fertilization were 0, 90 and 150 kg N ha−l. Based on the high relative share in the total sum of squares, variance analysis showed that wheat grain yield (GY) was significantly affected by years, SN-treatments, and their interaction, and they can explain the largest part of the total variance of GY. The results showed that straw return integrated with N fertilization could increase wheat yield to varying degrees over 20 years. On average, for all years, the highest GYs were obtained in the treatment S1 and fertilization with 180 and 150 kg N ha−1. The overall results showed that long-term straw returning significantly increased GY by an average of 8.4 ± 4.5%, with a considerable simultaneous increase in yield stability compared to straw removal. In addition, straw incorporation (SI) significantly increased soil humus, total nitrogen (TN), and soil organic carbon (SOC) contents at a soil depth of 0–30 cm by an average of 4.2, 3.8, and 11.3%, respectively. The results of our study have demonstrated that the long-term practice of straw return, in combination with the application of mineral fertilizers, has the potential to serve as a sustainable soil management strategy that is economically viable and environmentally acceptable. However, additional research is required to investigate its interactive effects on both grain yield and soil productivity.