Straw Incorporation Treatments Research Articles

Straw Returning Proves Advantageous for Regulating Water and Salt Levels, Facilitating Nutrient Accumulation, and Promoting Crop Growth in Coastal Saline Soils

Saline soils limit plant growth due to high salinity. Straw returning has proven effective in enhancing soil adaptability and agricultural stability on saline lands. This study evaluates the effects of different straw-returning methods—straw mulching (SM), straw incorporation (SI), and straw biochar (BC)—on soil nutrients, water dynamics, and salinity in a barley–cotton rotation system using field box experiments. SM improved soil water retention during barley’s jointing and heading stages, while SI was more effective in its filling and maturation stages. BC showed lesser water storage capacity. During cotton’s growth, SI enhanced early-stage water retention, and SM benefited the flowering and boll opening stages. Grey relational analysis pinpointed significant water relationships at 10 cm and 20 cm soil depths, with SM regulating water across layers. SM and BC notably reduced soil conductivity, primarily within the top 20 cm, and their effectiveness decreased with depth. SI significantly lowered soil conductivity at barley’s jointing stage. SM effectively reduced salinity at 10 cm and 20 cm soil depths, whereas BC decreased soil conductivity throughout barley’s jointing, filling, and heading stages. For cotton, SI lowered soil conductivity at the seedling and boll opening stages. SM consistently reduced salinity across all stages, and BC decreased conductivity in the top 30 cm of soil during all growth stages. Both SM and BC significantly enhanced the total nutrient availability for barley and cotton, especially improving soil organic carbon and available potassium, with BC showing notable improvements. At barley’s heading stage, SI maximized dry matter accumulation, while SM boosted accumulation in leaves, stems, and spikes during the filling and maturation stages. Straw returning increased barley yield, particularly with SM and BC, and improved water use efficiency by 11.60% and 5.74%, respectively. For cotton, straw returning significantly boosted yield and water use efficiency, especially with SI and SM treatments, enhancing the total bolls and yield. In conclusion, straw returning effectively improves saline soils, enhances fertility, boosts crop yields, and supports sustainable agriculture. These results provide a robust scientific foundation for adopting efficient soil improvement strategies on saline lands, with significant theoretical and practical implications for increasing agricultural productivity and crop resilience to salt stress.

Straw return influences the structure and functioning of arbuscular mycorrhizal fungal community in a rice-wheat rotation system

Straw incorporation is a sustainable soil fertility-building practice, which can affect soil microbial communities. However, how straw incorporation affects arbuscular mycorrhizal fungi (AMF) is not well explored. Here, we studied the impacts of different straw management practices over eight years on the structure and function of AMF communities in a rice-wheat rotation system. The straw managements included no tillage with no straw (NTNS), rotary tillage straw return (RTSR) and ditch-buried straw return (DBSR). The community structure of AMF was characterized using high-throughput sequencing and the mycorrhizal functioning was quantified using an in situ mycorrhizal-suppression treatment. Different straw management practices formed unique AMF community structure, which was closely related to changes in soil total organic carbon, available phosphorus, total nitrogen, ammonium and nitrate. RTSR significantly increased Shannon diversity in 0-10 cm soils while DBSR increased it in 10–20 cm soils when compared with NTNS. DBSR significantly increased hyphal length density in the whole (0–20 cm) ploughing layer, but RTSR only increased it in the subsoil layer (10–20 cm). The mycorrhizal responses of shoot biomass and nutrient (N and P) uptake were positive under both straw incorporation treatments (RTSR and DBSR), but negative under NTNS. AMF community composition was significantly correlated to hyphal length density, and the latter was further a positive predictor for the mycorrhizal responses of plant growth and nutrient uptake. These findings suggest that straw return can affect AMF community structure and functioning, and farmers should manage mycorrhizas to strengthen their beneficial effects on crop production.

Enhanced phosphorus fixation in red mud-amended acidic soil subjected to periodic flooding-drying and straw incorporation

Globally, red mud is a solid waste from the aluminum industry, which is rich in iron oxides. It is an effective soil amendment in agriculture that protects connected waters from legacy diffuse phosphorus (P) soil losses. However, other management practices such as flooding and drying and/or organic carbon inputs could potentially alter P fixation in these red mud-amended soils thereby releasing P to waters. The present study was designed and conducted to monitor the mobilization of P in a red mud-amended acidic soil subjected to periodic flooding-drying, straw incorporation, and a mix of both management practices. Sequential extraction and K edge X-ray absorption near-edge structure spectroscopy (k-XANES) were employed to distinguish P fractions/species and the Langmuir model was fitted to evaluate soil P sorption capacity. The content of labile P indicated by CaCl2–P was increased significantly by 101% and 28.7% in the straw incorporation and periodic flooding-drying treatments, while it decreased significantly by 22.3% in the combined periodic flooding-drying with straw incorporation treatment, compared with Control. The inherent phosphate contained in sorghum straw, and the enhanced iron (Fe) reduction and dissolution of Calcium (Ca)-bound P induced by straw addition contributed to mobilization of P in the straw incorporation treatment. In contrast, the increased poorly crystalline Al/Fe oxides-bound P and occluded Fe-bound P fraction in the combined periodic flooding-drying with straw incorporation treatment explains the decrease in CaCl2–P. Furthermore, the increased soil P sorption capacity and the decreased P desorption rate were also responsible for the reduced P loss risk in the treatment. The results of structural equation modelling (SEM) indicated that organically complexed Fe and Fe-bound P were directly affecting P mobilization in the amended soil. Overall, the present study shows that appropriate flooding-drying events coupled with straw incorporation could be a mitigation practice for stabilizing P in red mud-amended soil. However, before it can be applied on a wide scale, multi-point and field trials should be carried out to further evaluate actual environmental implications.

Effects of straw incorporation and straw-burning on aggregate stability and soil organic carbon in a clay soil of Bangladesh

The clay soil of Bangladesh is typically low in soil organic carbon (SOC) and generally has poor soil aggregate stability (measured as mean weight diameter, MWD). The addition of organic amendments in the field has the potential to increase soil organic matter (SOM) and MWD. However, the influence of organic amendments on aggregation in the clay soils of Bangladesh is largely unknown. A short-term (105 days) field study has been conducted to evaluate the effects of straw incorporation and straw-burning treatments on MWD and SOC in clay soil under eggplant (Solanum melongena L.). This study consisted of three treatments: (i) control (no amendments), (ii) rice straw (straw applied at 21 t ha−1), (iii) rice straw-burning (ash retained after burning at 7.4 t ha−1). Soil samples were collected after plant harvest, and then MWD, SOC, glomalin-related soil protein (GRSP), microbial biomass carbon (MBC), Fe-oxides, and available soil nutrients (e.g., N, P, K, S, Na, Ca, and Mg) were determined. Our results showed that MWD in straw addition treatment was on average 2 times higher, whereas SOC was 1.3 times higher compared to the control and straw-burning treatments, respectively (P < 0.05). Conversely, the straw-burning treatment reduced the MWD by 19% and the SOC by 20% compared to the control treatments (P < 0.05). Significant improvements in the available K, S, and Mg content of soil were found in the straw incorporation treatment (P < 0.05). We did not find any significant influence of the treatments on the MBC and GRSP content of the soil. Soil organic carbon had a significant correlation with MWD (R2 = 0.80**, P < 0.01), while GRSP and Fe-oxides did not show any relationship with MWD (P > 0.05). Our study demonstrates that the incorporation of rice straw has the potential to increase soil aggregation and SOC stock, at least for the short term in the clay soils of Bangladesh.

Fall Straw Incorporation with Plastic Film Cover Increases Corn Yield and Water Use Efficiency under a Semi-Arid Climate

Corn straw incorporation in soil has been regarded as an environment-friendly approach for straw utilization. However, straw incorporation has been a challenge under a cold and dry climate due to slow decomposition. This field study was to use a novel approach to incorporate corn straw into the soil during the fall season with a plastic film cover in an effort to enhance the straw degradation, soil water use efficiency, and corn growth and yield. Two-year field experiments were conducted in northeast China to investigate the effects of four treatments on soil properties and corn growth: (1) straw incorporation with film cover, (2) straw incorporation only, (3) film cover only, and (4) control. Soils and corn plants were collected during the growing season and analyzed for soil temperature and moisture, straw degradation, corn biomass, grain yield, and water use efficiency. Results indicated that straw incorporation with film cover increased grain yield by 53% as compared to straw incorporation only and by 102% to control. The straw decomposition under film cover was 20% faster, significantly higher than that of the straw incorporation treatment. In all cases, soil water content before planting, corn water uptake, and corn water use efficiency under straw incorporation with film cover were significantly higher than straw incorporation and control. Surface film cover resulted in 10-day earlier corn tasseling in compared to treatments without film cover. This field study demonstrated that straw incorporation with film cover would enhance straw degradation in soil, improve soil properties, and increase corn yield and water use efficiency, which could be potentially used as a sustainable soil management practice in northeast China.

Key soil properties influencing infiltration capacity after long-term straw incorporation in a wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation system

Straw incorporation is increasingly being adopted in wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation systems to improve soil physiochemical properties. To identify the main soil properties influencing infiltration capacity under long-term straw incorporation in a wheat–maize rotation system, the study set four treatments: no straw incorporation and fertilizer application, wheat straw incorporation with 276 kg nitrogen/ha, wheat and maize straw incorporation with 276 kg N/ha, and wheat and maize straw incorporation. The initial, average, and final infiltration rates were calculated to represent soil infiltration capacity. Compared with other treatments, wheat straw incorporation with 276 kg nitrogen/ha treatment significantly decreased soil bulk density, soil aggregate (DMWD) mean weight diameter measured using the dry sieving method, and weight rate of soil aggregates with diameters greater than 0.25 mm measured using the wet sieving method, and significantly increased total soil porosity, soil capillary porosity, field capacity, and weight rate of soil aggregates with diameters less than 0.25 mm measured using the wet sieving method. In contrast, wheat and maize straw incorporation treatment significantly increased soil bulk density and noncapillary porosity, but decreased total soil porosity, capillary porosity, and field capacity. The results of partial least squares regression indicated that the soil moisture content and DMWD were the primary factors influencing initial infiltration rate with positive regression coefficient. Higher total soil porosity, capillary porosity, field capacity, and DMWD contributed to higher final infiltration rate, while higher soil bulk density and noncapillary porosity were correlated with a lower final infiltration rate. The key influencing factors of average infiltration rate were soil bulk density, soil moisture content, total soil porosity, capillary porosity, and DMWD. The wheat straw incorporation with 276 kg nitrogen/ha treatment had higher infiltration rates than no straw incorporation and fertilizer application treatment. However, with an increase in straw amount, the influence of straw on infiltration showed a law of diminishing marginal returns. Therefore, wheat and maize straw incorporation with 276 kg nitrogen/ha treatments had a lower infiltration rate than wheat straw incorporation with 276 kg nitrogen/ha treatment. In addition, wheat and maize straw incorporation treatment had the lowest average and final infiltration rates of all treatments, indicating that excessive straw incorporation without nitrogen fertilizer had adverse effects on infiltration rates. This study furthers understanding of the influence of long-term straw incorporation on soil hydrological processes and helps rationally use straw resources in wheat–maize rotation systems.

Effects of various straw incorporation strategies on soil phosphorus fractions and transformations

AbstractReturning straw to the field is an effective method for optimizing the soil phosphorus (P) availability, in which bacteria play an important role. However, the effects of various straw incorporation strategies on P transformation between different soil P pools remain unclear. In this study, variations in soil P fractions, phosphatase activities and the abundance of phosphatase genes (phoD, phoX and phoC) as well as a P‐solubilizing gene (pqqC) at DNA (total) and cDNA (transcribed) levels were analysed in three straw incorporation treatments, including chopped straw (StrawD), straw compost (Compost) and straw‐derived biochar (Biochar), and control (no straw, CK). Compared with the CK, the moderately labile inorganic P (NaOH I‐Pi) content significantly decreased and the non‐available P (Residual P) content significantly increased in the StrawD treatment. At the same time, phosphodiesterase (PD) activity and the transcribed phoC and phoX genes as well as total pqqC gene abundance significantly increased in the StrawD treatment, suggesting that the input of chopped straw stimulated P transformations from both organic and inorganic P pools. In addition, the stable Pi (NaOH II‐Pi) content and total pqqC gene abundance in the Biochar treatment were significantly higher than that in the CK, indicating that the input of biochar increased the NaOH II‐Pi that could release available P by Pi‐solubilizing bacteria. In comparison to the CK, the Compost input significantly decreased one labile Pi (resin‐Pi) only. However, its P fractions were significantly different from that of CK, Biochar and StrawD treatments, suggesting that the effects of compost input on P should not be ignored. In conclusion, chopped straw input increased soil P transformation but not available P, biochar input may promote inorganic P transformation, and compost input has a latent effect on P transformation. The study provided a comprehensive understanding of straw incorporation strategies for regulating soil P availability.

Deep fertilization combined with straw incorporation improved rice lodging resistance and soil properties of paddy fields

Deep nitrogen fertilization (DNF) coupled with straw incorporation has the potential to improve the grain yield and nitrogen use efficiency of mechanically transplanted rice. However, the effects of different fertilization approaches combined with straw incorporation on lodging resistance ability, and soil properties are still uncertain. Therefore, a two-year field experiment was comprised of broadcast fertilizer treatments (broadcast fertilizer without straw (BFS0) or with straw (BFS)), deep fertilizer treatments (DNF without straw (DFS0) or with straw (DFS)). Results depicted that deep fertilizer treatments significantly improved the pushing resistance force by 63.81–129.58 % and decreased the lodging index by 22.01–80.82 % of rice compared with broadcast fertilizer treatments. Deep fertilizer treatments optimized the length of the first four internodes and increased the internodes diameter and culms wall thickness in the third and fourth internode, and higher silicon and lignin content in the fourth internode, compared to broadcast fertilizer treatments. Furthermore, the straw incorporation treatments also improved soil total nitrogen, soil available potassium, and soil organic matter by 5.60–11.48 %, 17.75–22.56 %, and 7.17–18.26 %, respectively, regardless of fertilizer application method. Hence, this study suggests that deep nitrogen fertilization can be adopted as an agronomically effective tactic to improve lodging resistance in rice whilst the combination of straw incorporation and deep fertilization can be considered to further improve the soil properties.

Biodegradable film mulching combined with straw incorporation can significantly reduce global warming potential with higher spring maize yield

The sole effect of crop straw incorporation or film mulching on soil organic carbon (SOC) content, greenhouse gas (GHG) emission and crop yield is well documented in the literature; however, the combined effects of biodegradable film mulching coupled with straw incorporation on these aspects is not yet studied in detail. We conducted a field experiment expanding over five years to evaluate the influence of different film mulching with straw incorporation treatments: (i) double-ridge furrow sowing with full film mulching plus straw incorporation (DS), (ii) double-ridge furrow sowing with full film mulching (D), (iii) conventional tillage plus straw incorporation (S), and (iv) conventional tillage (CK) on organic carbon contents (SOC), GHG emissions and maize productivity. An average of the results of five years revealed that DS, as compared to CK, increased grain and biological yield by 74.06 % and 29.47 % (P < 0.05), followed by D and S (except for 2017). With every progressing year, DS significantly increased the organic carbon content in the 0–20 cm soil layer with an approximately increase of 17.60 % from 2015 to 2020. A maximum total organic carbon storage of 130.99 Mg C ha−1 in 0–100 cm soil profile was recorded for DS, which was significantly (P < 0.05) higher than other treatments. Conversely, compared with CK, DS increased CO2 and N2O emissions by 34.38 % and 33.95 %, respectively, but significantly reduced the global warming potential (GWP) and greenhouse gas intensity (GHGI) by 41.96 % and 64.91 %, respectively. It is concluded that the use of biodegradable mulch coupled with straw incorporation could be an efficient strategy leading to improved maize yield and organic carbon content, and reduced net global warming potential (NGWP) and GHGI in semi-arid rainfed areas.

Soil Organic Matter, Aggregates, and Microbial Characteristics of Intercropping Soybean under Straw Incorporation and N Input

Soil organic matter (SOM), soil aggregates, and soil microbes play key roles in agriculture soil fertility. In intercropping systems, the influences of straw incorporation and N input on the dynamics of soil physicochemical and microbial properties and their relationships are still unclear. We explore the changes in soil physicochemical and microbial properties with two straw managements, i.e., wheat straw incorporation (SI) and straw removal (SR), and four N supply rates for intercropped soybean, i.e., 60 (N60), 30 (N30), 15 (N15), and 0 (N0) kg N ha−1, in the wheat–maize–soybean relay strip intercropping systems. The results showed that SOM and SOM fractions contents, soil macroaggregate stability, and microbial and fungal α-diversity, e.g., Chao1 and Shannon indices, increased through straw incorporation and N input. The α-diversity was significantly positively correlated with soil physicochemical characteristics. Compared with SR, the relative abundance of ActinobacteriaandMortierellomycota in SI increased, but the relative abundance of Proteobacteria, Acidobacteria, and Ascomycota in SI decreased. In SI treatment, soil physicochemical characteristics and microbial diversity improved through N input, but that difference was not significant between N60 and N30. In conclusion, SI+N30 was the most effective way to maintain soil fertility and reduce the N fertilizer input in the wheat–maize–soybean relay strip intercropping.

Nitrogen fertilization degrades soil aggregation by increasing ammonium ions and decreasing biological binding agents on a Vertisol after 12 years

Degraded soil aggregation arising from nitrogen (N) fertilization has been reported in many studies; however, the mechanisms have not yet been clarified. Elucidating the impact of N fertilization on soil aggregation would help to improve soil structure and sustain high crop production. The objective of this study was to determine the impact of long-term N fertilization on soil aggregation and its association with binding and dispersing agents. A 12-year (2008–2019) N fertilization field experiment on a Vertisol was performed, covering a wide range of N application rates (0, 360, 450, 540, 630, and 720 kg ha-1 year-1) and including straw management (straw return and straw removal) in a wheat (Triticum aestivum L.)-maize (Zea mays L.) cropping system. Soil samples of 0–20 cm depth were collected from 12 field treatments with 3 replications in 2019. Soil aggregate stability (mean weight diameter (MWD)) and contents of soil organic carbon (SOC), glomalin-related soil protein (GRSP), microbial biomass carbon (MBC), and mineral N (NH4+ and NO3-) were determined. Long-term N fertilization under straw removal conditions reduced soil MWD by 12%–18% at N rates from 0 to 720 kg ha-1 compared to that under straw return (P < 0.05). Soil MWD was positively associated with pH (P < 0.05) and MBC (P < 0.05), but negatively correlated with NH4+ (P < 0.05) and NO3- (P < 0.05). Compared with the straw removal treatment, the straw incorporation treatment significantly improved the contents of aggregating agents (SOC, GRSP, and MBC) (P < 0.001), but did not affect that of the dispersing agent (NH4+) (P > 0.05); consequently, it improved soil aggregation. Overall, our results indicate that long-term N fertilization may degrade soil aggregation because of the increases in monovalent ions (H+ and NH4+) and the decrease in MBC during soil acidification, especially when the applied N dose exceeded 360 kg ha-1 year-1. Our finding can minimize the negative structural impacts on Vertisol.

Differential Responses of Soil Organic Carbon Fractions and Carbon Turnover Related Enzyme Activities to Wheat Straw Incorporation in Subtropical China

Soil organic carbon (SOC) fractions and C turnover related enzyme activities are essential for nutrient cycling. This is because they are regarded as important indicators of soil fertility and quality. We measured the effects of wheat straw incorporation on SOC fractions and C turnover related enzyme activities in a paddy field in subtropical China. Soil samples were collected from 0–10 cm and 10–20 cm depths after rice harvesting. The total SOC concentrations were higher in the high rate of wheat straw incorporation treatment (NPKS2) than in the not fertilized control (CK) (P

EFFECTS OF PLASTIC MULCHING AND STRAW INCORPORATION ON RICE YIELD AND NITROGEN USE EFFICIENCY IN A COLD REGION

For the synergistic improvement of soil fertility and rice yields in a cold region, we investigated the effects of plastic mulching with different straw incorporation rates on the rice yield and nitrogen use efficiency in a rice growing area of a cold region. The field experiment was conducted using the Jijing 88 rice cultivar, and set up four straw incorporated treatment: 20% (S1), 40% (S2), 60% (S3) and 100% (S4) under two conditions: mulching (M) and without mulching (NM). The results showed that under the same straw incorporation rates: (1) Plastic mulching increased the total soil nitrogen and organic matter contents while improving the grain yield; the yield increases were 2.8–14.9% in 2016 and 1.4–12.3% in 2017. (2) The mulched treatment improved the net photosynthetic rate, the maximum tiller number, the crop growth rate of the later growth stages, and the shoot dry weight. (3) The recovery efficiency, agronomic efficiency, and partial factor productivity of the nitrogen applications were all higher under the mulched treatment than under the non-mulched treatment. In a comparison of the different straw incorporation treatments, above three indicators consistently increased before they decreased, and significantly higher levels were reached under the 40% straw incorporation treatment with mulching than under the other treatments.

Effects of nitrogen deep placement coupled with straw incorporation on grain quality and root traits from paddy fields

AbstractThe present study was conducted to investigate the effects of deep application of nitrogen (N) fertilizer and straw incorporation on grain yield and quality, nutrient accumulation, and root morphological and physiological traits in both rice (Oryza sativa L.) cultivars during 2019 and 2020. The experimental treatments were comprised of deep N fertilization with (DF+S) and without straw incorporation (DF) as well as broadcasting fertilization with (BF+S) and without straw return (BF). No fertilizer and no straw return treatment were taken as control. Results depicted that the DF+S and DF treatment significantly increased the grain yield by 46.4 and 42.2%, respectively, compared with BF. The DF+S also significantly increased total N accumulation by 37.9 and 44.0%, total phosphorus accumulation by 39.3 and 41.7%, total potassium accumulation by 63.6 and 73.3% for the cultivars Yuxiangyouzahn (YXYZ) and Wufengyou615 at maturity, respectively, compared with BF. Moreover, nutrient accumulation and grain yield of BF+S were slightly higher than BF. Straw incorporation resulted in better total root volume and total root length than no straw incorporation treatments in YXYZ, regardless of fertilizer application method. Root morphology traits are positively associated with other positive traits such as yield or nutrient uptake. The DF+S treatment also significantly increased the milled rice rate and remarkably reduced the chalkiness degree for both rice cultivars, compared to BF treatment. Overall, DF+S is recognized as the optimal method to improve rice productivity and quality with better nutrient acquisition.

Enhanced topsoil P leaching in a short term flooded calcareous soil with combined straw and ammonium nitrogen incorporation

Straw incorporation (SI) coupled with ammonium nitrogen (AN) application is a management strategy for storing organic carbon (OC) and optimizing vegetable yields in intensively managed calcareous soils of North China. However, during short term flooded conditions, the resulting soil acidification and subsequent Fe reduction processes may affect the transformation of soil Fe/Al-bound phosphorus (Fe/Al-P) and the mobility of phosphate in soil. This study was conducted simulating the condition of short term flooding in order to investigate P leaching and the contents of soil inorganic P fractions, Fe(III) reduction and P adsorption kinetics in calcareous soil with four treatments; control (C), straw powder incorporation (SI), SI with subsequent AN elution (SN) and SI with subsequent sulfuric acid elution (SH). The results showed that the SI treatment promoted the transformation of Ca-bound P (Ca-P) in soil to Fe/Al-P due to acidification but had no effect on P leaching. The SN treatment significantly decreased the topsoil Fe/Al-P content and maximum P sorption capacity through Fe(III) reduction, whereas it increased the total amount of P leached under flooded conditions by 86.8%. In contrast, SH promoted Fe/Al-P accumulation as well as increase the soil maximum P sorption capacity in the topsoil, leading to a decrease in P leachate of 38.1% compared with the SI treatment. The SN treatment was responsible for high P mobility through promotion of Fe(III) reduction and inhibition of acidification processes. Such findings in the present study highlight that 1) SI coupled with AN induced the Fe(III) reduction releasing associated P while 2) SI coupled with acidification significantly inhibited the P leaching, which is of environmental benefit. However, the results presented herein were limited to a single soil type. Future studies should validate the processes found in the present study across other soil types.

Responses of nitrite-oxidizing bacteria community to excessive nitrogen application and straw incorporation under intensive cultivation

ABSTRACT N fertilization and straw incorporation often disturb the soil and may affect nitrite oxidation (NO); however, the underlying mechanism remains unclear. Here, we collected soil samples through a 4-year field experiment including no N fertilization, normal N application, excess N application (EN), and EN plus straw incorporation (ES) treatments. We measured the community composition, abundance, and activity of Nitrobacter-like and Nitrospira-like nitrite-oxidizing bacteria (NOB). N application and straw incorporation significantly enhanced potential NO activity (PNO). PNO was affected by the abundance of Nitrobacter but not Nitrospira and the community compositions of both NOB. With increasing N application rate, Nitrobacter abundance increased from 1.0 to 11.8 × 104 copies g−1 dry weight soil, whereas Nitrospira abundance increased initially then subsequently decreased, ranged from 2.1 to 5.2 × 106 copies g−1 dry weight soil. Moreover, N application and straw incorporation markedly affected the NOB community composition. Soil pH and organic C were the key factors shaping the NOB community composition. Overall, N fertilization combined with straw incorporation can affect NO by altering the Nitrobacter abundance and NOB community composition. These findings expand our understanding of mechanisms underlying the effects of straw incorporation on nitrification, particularly under N enrichment.

Inclusion of microbial inoculants with straw mulch enhances grain yields from rice fields in central China

AbstractSlow decomposition of crop straws under field conditions affects sowing and emergence of rice. Microbial inoculants can be used to promote crop straw decomposition for solving these problems and thus have been adopted for rice cultivation in China. However, its effect on greenhouse gas (GHG) emissions and grain yields remains unclear. Here, a two‐year field experiment was conducted to assess the effects of different straw returning methods (no straw, preceding crop straw mulch on the soil or incorporation into the soil, and straw mulch with microbial inoculants or straw incorporation with microbial inoculants) on GHG emissions and grain yields from rice fields in central China. Straw returning treatments significantly enhanced higher CH4 emissions by 21.1%–39.6% relative to no straw treatment, but did not affect N2O emissions. Compared with straw mulch treatments, straw incorporation treatments significantly increased higher dissolved organic C (DOC) content by 20.0%–30.4% and mcrA abundance by 28.01%–37.3%; significant relationships of CH4 emissions with DOC content and mcrA abundance were observed. These resulted in 13.2%–16.0% higher CH4 emissions under straw incorporation treatments. Straw incorporation did not affect N2O emissions relative to straw mulch due to similar mineral N contents. The application of inoculants showed no effects on CH4 and N2O emissions, whereas it significantly enhanced the grain yields by 6.0%–9.1% and thus decreased GHG intensity (GHGI) by 4.3%–11.87%. Straw mulch with decomposing inoculants treatment resulted in the lowest global warming potential (GWP) and GHGI and the highest grain yield among all straw returning treatments. Taken together, our results indicate that mulch of straws with microbial inoculants on the soil is an effective measure to achieve a balance between the mitigation of GWP and the increase in grain yields from rice fields in central China.

Effects of UV‐B radiation on soil carbon conversion and greenhouse gas emission in paddy soil

AbstractThis paper evaluates the relationship between ultraviolet‐B (UV‐B, 280–315 nm) radiation enhancement on the earth's surface caused by ozone attenuation and climate change. A pot experiment was conducted to investigate the effects of enhanced UV‐B radiation on greenhouse gas (GHG) emissions from the paddy soil with rice straw incorporation (SI). The paddy soil was sampled from the Yuanyang Terrace, Yunnan Province, Southwest China. There were four treatments: natural light (control check, CK), 5.0 kJ·m−2 UV‐B radiation (UVB), SI, and SI + UVB. The effects of UV‐B radiation (5.0 kJ·m−2) on straw degradation, soil carbon invertase activity, active organic carbon content, and GHG emissions were studied. The results showed that UV‐B radiation promoted the degradation of straw components (lignin, cellulose, hemicellulose, and water‐soluble phenol). The SI treatment significantly increased the activity of soil carbon invertase (P &lt; 0.05), the content of soil active organic carbon (P &lt; 0.05), and the emission rates and amounts of GHGs (P &lt; 0.05). Compared to the SI treatment, SI + UVB treatment reduced soil carbon invertase activity and active organic carbon content, resulting in a 17% reduction in CH4 emission and a 40% and 16% increase in CO2 and N2O emission (P &lt; 0.05), but had no significant effect on the global warming potential (GWP). Correlation analysis showed that the degradation rate of straw components was positively correlated with the activity of carbon invertase, the contents of microbial biomass carbon (MBC), easily oxidized organic carbon (EOC), and the CO2 emission rate; the activities of sucrase and cellulase were positively correlated with the contents of MBC and EOC, which were in turn positively correlated with the emission rates of CH4 and CO2. Under SI, UV‐B radiation reduced the soil carbon conversion, which led to a decreased CH4 emission and increased emissions of CO2 and N2O, but did not alter the GWP of GHGs from the paddy soil. © 2020 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Effects of biochar, compost and straw input on root exudation of maize (Zea mays L.): From function to morphology

Returning crop straw, such as biochar, into the field is increasingly recognized as a valid, environmentally-friendly agricultural strategy to improve soil quality, increase crop yields, and reduce combustion-induced air pollution. Root exudation has potential importance for plant performance, rhizosphere function and plant–soil interactions; however, the effects of crop straw input on maize root exudation remain unclear. After three seasons of a field experiment, a mesh bag experiment was conducted in situ in the fourth season to study the effects of three straw incorporation treatments (chopped maize straw, SD; compost produced by maize straw, SC; biochar produced by maize straw, BC) and control (no straw, CK) on root exudation and their underlying mechanisms in a maize cropping system. Discrimination in the metabolic profiling of the root exudates between the CK and all the straw-incorporated samples was clear, but the separation between the samples from the three different straw strategies was limited. Among the 32 assigned components of maize root exudates, the fluctuations in organic acids (up to 16-fold) were stronger than those in sugars and amino acids when straw was incorporated. The response of the organic acid exudates was linked to the transcript levels of the ZmMATE1 and ZmMATE2 genes, which are associated with root exudation (Spearman correlations, P < 0.05). Straw incorporation influenced the root phenotypic appearance and morphology, which are characterized by longer and thinner root, larger root surface area, and more root tips in BC treatment, whereas shorter and thicker root, and fewer root tips in SD treatment. The changes in the root morphology and metabolomes were responsible for the responses of the maize root exudates to straw incorporation. Regulation of genes (ZmCycD2; 2a, ZmEXPB8, ZmXTH1, and ZmARF1) that associated with root growth and development, and changes in the viability and anatomical structure of root tips were involved in the modifications of root morphology. This information will be useful for modulating rhizosphere processes and soil fertility, and for guiding and recommending residue management practices in crop production with relatively larger yields.

Straw and optimized nitrogen fertilizer decreases phosphorus leaching risks in a long-term greenhouse soil

Phosphorus (P) mobility in soil is controlled by its forms and soil sorption capacity. The P forms and soil sorption capacity are both affected by nitrogen (N) and carbon (C) addition. This paper aimed to (i) analyze effects of N and straw application on the different forms and content of P in the soil and its leachates in greenhouse soil, and (ii) explain variations in soil P transformation and transport in terms of contributing soil factors. In this study, the impacts of N and straw application on the transformation and transport of soil P were investigated after 17 years in a greenhouse. Four fertilization regimes were implemented: farmer standard fertilization practice (CK), straw incorporation treatment (SC), optimized N fertilizer application (ON), and combined straw and optimized N fertilizer application (SN). P forms and its contents were determined in the selected leached water and its related soil samples. Compared with CK, ON treatment significantly (p < 0.05) decreased total phosphorus (Pt) and the proportion of organic phosphorus (Po) in soil, while straw amendment did not affect soil Pt content. SC, ON, and SN all decreased soil available phosphorus (Pa) but enhanced P transformation, as evidenced by the increase in the ratio of Pa to Pt and microbial phosphorus (MBP) and alkaline phosphatases (ALP) in soil. After SN implementation, soil P adsorption capacity increased significantly and was associated with higher soil organic matter (SOM) and CaCO3. ON showed lower Pt in the leachate than CK, but SC did not lead to significantly different. Under the SN regime, Pt loss by leaching decreased by 29.4% compared with CK and significantly reduced proportion of total dissolve P (DPt) in leachate. Our study highlights that straw and optimized N fertilizer in SN treatment not only generates lower P loss by leaching but also promotes the transformation of soil P, which were attributed to higher soil Pa in greenhouse soil. This finding further indicates that P transformation and transport in the different fertilizer regimes was primarily linked to pH and SOM in greenhouse soil.