Straw Incorporation Research Articles

Photosynthetic Physiological Basis of No Tillage with Wheat Straw Returning to Improve Maize Yield with Plastic Film Mulching in Arid Irrigated Areas

Surface mulch is an efficient plant production technique widely used in arid and water-scarce areas. In this study, a field experiment was conducted to determine whether plastic film combined with wheat straw returning could boost grain yield of maize via optimizing photosynthetic physiological characteristics and coordinating yield components. The results showed that no tillage with wheat straw mulching and straw standing treatments had better regulation on photosynthetic physiological characteristics and had a greater impact on the increase in grain yield than conventional tillage with wheat straw incorporation and without wheat straw returning (the control treatment) in plastic film-mulched maize. Meanwhile, no tillage with wheat straw mulching had a relatively higher yield than no tillage with wheat straw standing through better regulation of photosynthetic physiological characteristics. No tillage with wheat straw mulching decreased the leaf area index (LAI) and leaf area duration (LAD) of maize before the VT stage and maintained higher LAI and LAD after the VT stage, which effectively regulated the growth and development of maize at early and late stages of development. From VT to R4 stage of maize, no tillage with wheat straw mulching had greater chlorophyll relative content, net photosynthetic rate, and transpiration rate by 7.9-17.5%, 7.7-19.2%, and 5.5-12.1% than the control, respectively. In addition, leaf water use efficiency was increased by 6.2-6.7% from the R2 to R4 stage of no tillage with wheat straw mulching in comparison to the control treatment. Thus, no tillage with wheat straw mulching had a greater grain yield of maize by 15.6% than the control, and the high yield was attributed to the synchronous increase and cooperative development of ear number, grain number per ear, and 100-grain weight. Collectively, no tillage with wheat straw mulching had a positive effect on regulating the photosynthetic physiological traits and can be recommended to enhance the grain yield of maize in arid conditions.

Biomimetic tool design improves tillage efficiency, seedbed quality, and straw incorporation during rototilling in conservation farming

Rotary tillage facilitates conservation agriculture in rice-based crop farming systems through minimal soil disturbance for seedbed preparation and crop residue management. However, efficiency of rotary tiller blades is hampered by degraded paddy soils and excessive crop residue conditions. Biomimetics presents an edge in the optimisation design of cultivation tools and can be employed to improve the efficiency of rotary tiller blades. This study was designed to evaluate the adaptability and performance of biomimetic rotary tiller blades inspired by the geometric structure of a mole rat’s claw. Field experiments were conducted to evaluate the blades’ torque and power requirements, soil fragmentation, displacement characteristics, and the rate of straw incorporation at three tillage depths (i.e., 40, 70, and 100 mm). Results revealed that the biomimetic blades minimised torque by up to 21.05%, had lower specific power requirements, and produced finer tilths with granular and more even clod sizes than conventional blades. It also achieved more redistribution of topsoil and improved the straw burial rate. The biomimetic rotary tiller blades are thus energy-efficient and can improve soil structure and the quality of seedbeds, besides managing crop residues through incorporation, and therefore advance conservation tillage in intensive farming systems.

Tillage with straw incorporation reduces the optimal nitrogen rate for maize production by affecting crop uptake, utility efficiency, and the soil balance of nitrogen

AbstractUnderstanding the combined effects of tillage and straw incorporation on grain yield and nitrogen (N) fertilizer utilization is vital for sustainable agriculture in northeastern China. How various tillage patterns with straw incorporation affect soil N balance and optimal N rate for crop production remains largely unknown. A four‐year (2015–2018) field experiment was conducted to assess the impact of rotary tillage with maize straw incorporation (RTS) and plough tillage with straw incorporation (PTS) combined with different N fertilizer rates (0, 112, 187, 262, and 337 kg N ha−1) on maize yield, N uptake, soil N balance, nitrogen use efficiency, and optimal N rate. In general, higher straw N uptake and lower N partial factor productivity, N use efficiency, and recovery of applied N in grains were obtained under PTS than under RTS. Moreover, grain yield and both straw and grain N uptake increased with the N application rate. However, no further increase in grain yield was observed when the applied N exceeded 187 kg N ha−1. PTS resulted in a higher level of unaccounted N from applied N fertilizer (38–81 kg N ha−1) than RTS. A high N fertilizer input (>262 kg N ha−1) combined with straw incorporation resulted in a high soil mineral N profit and substantially increased unaccounted N (614–715 kg N ha−1) over the four‐year field trial period. The optimal N input required for the highest maize yield could be reduced by 35.0%–44.6% using tillage with straw return. Nevertheless, PTS was more effective than RTS at lowering the optimal N application rate. Overall, the results of this short‐term maize field study conducted in northeastern China suggest that the amount of N fertilizer input required for maize production could be reduced by using tillage with continuous straw incorporation.

Earthworms and long-term straw management practices interactively affect soil carbon and nitrogen forms across soil depths

The earthworm functions in agriculture are determined by soil managements, including straw management practices (e.g., straw mulched on soil surface and incorporated into soil), which affect the spatial distribution of resources for earthworms as well as other organisms. However, it remains unclear that how earthworms and straw management practices jointly affect soil C and N forms and their spatial distributions. Based on a decade-long field experiment, we explored the effects of endogeic earthworms (Metaphire guillelmi) on contents of different soil C and N forms across soil depths (0–7.5 cm, 7.5–15 cm and 15–30 cm) under straw surface mulching and incorporation. Under straw mulching, earthworms did not affect the soil organic carbon (SOC) content but reduced the ammonium nitrogen and nitrate nitrogen (NH4+-N and NO3--N) content regardless of soil depths. And earthworms decreased the contents of total nitrogen (TN), microbial biomass carbon and nitrogen (MBC and MBN) at 0–7.5 cm layer, while increased those of MBC and MBN at 7.5–15 cm layer. In contrast, with straw incorporation, SOC, TN, MBC and MBN contents increased in the presence of earthworms. The most apparent positive effects of endogeic earthworms on the above total and microbial measurements occurred at 7.5–15 cm, with increases ranging from 25.5% to 65.7% under straw incorporation. Earthworms also tended to increase soil NH4+-N and NO3--N at 7.5–15 and 15–30 cm layers. Overall, the effects of endogeic earthworms depended on the straw management practices and soil depths. The interaction between earthworms and organic straw incorporation causes nutrients accumulated towards subsurface layer.

Efficiency of Combed Straw Harvesting Technology Involving Straw Decomposition in the Soil

This article deals with the problem of harvesting combed straw by mixing it with the soil and the process of combed straw decomposition in particular. The idea and purpose of the research are also analysed in terms of circular economy, which represents a closed cycle. Combed straw is seen as a by-product which is reused as fertilizer to increase soil fertility, thus reducing the negative impact on the environment and increasing the efficiency of organic matter use. To analyse the qualitative aspect of the process, the introduction of an indicator is proposed—the straw decomposition coefficient. Experimental studies of straw decomposition in the soil were carried out using the mathematical theory of experimental design, where the response function is represented by the functional dependence of the straw decomposition coefficient on the length of its cutting and nitrogen and phosphorus application doses. For experimental studies, Box–Behnken design was used, which made it possible to calculate the regression coefficients by known formulas. Verification of the obtained coefficients according to Student’s t-test showed that all of them were significant. According to Fisher’s test, it was established that the model is adequate and can be used for further research. As determined by the experimental study, shredded straw incorporation improves soil properties and increases its biological activity. Ultimately, this improves plant nutrition and increases crop yields. The experiment results showed that reduced amounts of nitrogen and phosphorus fertilizers can be applied, thus leading to a reduction in the direct production costs of growing cereals in the following year. The integration of several technological processes, such as straw cutting, shredding, and incorporating it into the soil with simultaneous application of nitrogen and phosphorus fertilizers, increases the economic efficiency of grain production and a shortens the payback period for investment.

The inhibitory effect of a water-saving irrigation regime on CH4 emission in Mollisols under straw incorporation for 5 consecutive years

The inhibitory effect of a water-saving irrigation regime on CH4 emission in Mollisols under straw incorporation for 5 consecutive years

Nitrogen budgeting under the influence of in situ rice residue management options in rice (Oryza sativa)–wheat (Triticum aestivum) cropping system

A field experiment was conducted during rainy (kharif) and winter (rabi) seasons 2019–20 and 2020–21 at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi to study the effect of rice establishment techniques (RETs) and microbial consortia mediated in situ rice residue management options on nitrogen (N) budgeting in a rice (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system (RWCS). The experiment was laid out in split plot design with 3 replications having 2 main plot treatments, viz. aerobic rice (AR) and conventional transplanted rice (CTR) in kharif and 7 sub plot treatments, viz. clean cultivation (removal of paddy straw), paddy straw incorporation, paddy straw mulching, paddy straw incorporation + Pusa decomposer, paddy straw mulching + Pusa decomposer, paddy straw incorporation + urea @20 kg/ha, paddy straw incorporation + Pusa decomposer + urea @10 kg/ha. The residual effects of these treatments were observed in seed drill and zero till sown wheat in rabi seasons. Results showed that N uptake (95.1 kg/ha and 100.4 kg/ha in CTR and 79.4 kg/ha and 83.8 kg/ha in AR) was significantly superior in CTR than AR in kharif seasons. The residual effects of in situ rice residue management options in wheat, paddy straw incorporation + Pusa decomposer + urea @10 kg/ha resulted in significantly higher N uptake (136.4 and 141.5 kg/ha) than other treatments, and it was followed by paddy straw incorporation + Pusa decomposer in both the years. The nutrient uptake by the RWCS was an important indicator of soil fertility and plant nutrient status. This investigation concluded that there is need for use of microbial consortia mediated in situ rice residue management in RWCS for positive N balance in spite of enhanced nutrient uptake.

No-tillage with straw mulching boosts wheat grain yield by improving the eco-physiological characteristics in arid regions

Straw returning to the field is a technical measure of crop production widely adopted in arid areas. It is unknown whether crop yield can be further increased by improving the eco-physiological characteristics when straw returning is applied in the crop production system. So, a three-year field experiment was conducted with various straw returning treatments for wheat production: (i) no-tillage with straw mulching (NTSM), (ii) no-tillage with straw standing (NTSS), (iii) conventional tillage with straw incorporation (CTS), and (iv) conventional tillage with no straw returning (CT, control). The eco-physiological and yield formation indicators were investigated to provide the basis for selecting the appropriate straw returning method to increase wheat yield and clarifying its regulation mechanism on eco-physiology. The results showed that NTSM and NTSS treatments had better regulation of eco-physiological characteristics and had a higher yield increase than CTS and CT. Meanwhile, NTSM had a relatively higher yield than NTSS through better regulation of eco-physiological characteristics. Compared to CT, the leaf area index of NTSM was decreased by 6.1–7.6% before the Feekes 10.0 stage of wheat, but that of NTSM was increased by 38.9–45.1% after the Feekes 10.0 stage. NTSM effectively regulated the dynamics of the photosynthetic source of green leaves during the wheat growth period. NTSM improved net photosynthetic rate by 10.2–21.4% and 11.0–21.6%, raised transpiration rate by 4.4–10.0% and 5.3–6.1%, increased leaf water use efficiency by 5.6–10.4% and 5.4–14.6%, at Feekes 11.0 and 11.2 stages of wheat, compared to CT, respectively. NTSM had higher leaf water potential (LWP) by 7.5–12.0% and soil water potential (SWP) by 8.9–24.0% from Feekes 10.3 to 11.2 stages of wheat than CT. Meanwhile, the absolute value of difference on LWP and SWP with NTSM was less than that with CT, indicating that NTSM was conducive to holding the stability of water demand for wheat plants and water supply of soil at arid conditions. Thus, NTSM had a greater grain yield of wheat by 18.6–27.3% than CT, and the high yield was attributed to the synchronous increase and cooperative development of ear number, grain number per ear, and 1 000-grain weight. NTSM had a positive effect on regulating the eco-physiological characteristics and can be recommended to enhance wheat grain yield in arid conditions.

Soil organic carbon stability mediate soil phosphorus in greenhouse vegetable soil by shifting phoD-harboring bacterial communities and keystone taxa

Addition of organic amendments, such as manure and straw, to arable fields as a partial substitute for mineral phosphorus (P), are a sustainable practice in high-efficiency agricultural production. Different organic inputs may induce varied soil organic carbon (OC) stability and phoD harboring microbes, subsequently regulate P behavior, but the underlying mechanisms are poorly understood. A 11-year field experiment examined P forms by 31P-nuclear magnetic resonance (NMR), OC chemical composition by 13C NMR, and biologically-based P availability methods, phoD bacterial communities, and their co-occurrence in soils amended with chemical P fertilizer (CF), chemical P partly substituted by organic amendments including pig manure (CM), a mixture of pig manure and corn straw (CMS), and corn straw (CS), with equal P input in all treatments. Organic amendments significantly increased soil labile Pi (CaCl2-P, citrate-P, 2.91–3.26 and 1.16–1.32 times higher than CF) and Po (enzyme-P, diesters, 4.08–7.47 and 1.71–2.14 times higher than CF) contents and phosphatase activities, while significantly decreased aromaticity (AI) and recalcitrance indexes (RI) of soil C, compared with CF. The keystone genera in manured soils (Alienimomas and Streptomyces) and straw-applied soils (Janthinobacterium and Caulobacter) were significantly correlated with soil enzyme-P, microbial biomass P (MBP), diesters, and citrate-P. Soil AI and RI were significantly correlated with the phoD keystone and soil P species. It suggested that the keystone was impacted by soil OC stability and play a role in regulating P redistribution in amended soils. This study highlights how manure and straw incorporation altered soil OC stability, shaped the phoD harboring community, and enhanced soil P biological processes promoted by the keystone taxa. The partial substitution of mineral P by mixture of manure and straw is effectively promote soil P availability and beneficial for environmental sustainability.

Trade-offs between fertilizer-N availability and Cd pollution potential under crop straw incorporation by 15N stable isotopes in rice.

Application of crop residues and chemical nitrogen (N) fertilizer is a conventional practice for achieving high yield in a rice system. However, the fallacious combination of N fertilizers with crop straw not only significantly reduces the N use efficiencies (NUEs) but also leads to serious environmental problems. The present study employed five treatments including no N fertilization and no straw incorporation (ck), N fertilization incorporation only (S0), N fertilization with 40% straw (S40), N fertilization with 60% straw (S60), and N fertilization with 100% straw (S100) to improve N use efficiency as well as reduced Cd distribution in rice. The crop yields were largely enhanced by fertilization ranging from 13 to 52% over the straw addition treatments. Compared with ck, N fertilizer input significantly decreased soil pH, while DOC contents were raised in response to straw amendment, reaching the highest in S60 and S100 treatments, respectively. Moreover, straw addition substantially impacted the Cd accumulation and altered the bacterial community structure. The soil NH4+-N concentration under S0 performed the maximum in yellow soil, while the minimum in black soil compared to straw-incorporated pots. In addition, the soil NO3--N concentration in straw-incorporated plots tended to be higher than that in straw-removed plots in both soils, indicating that crop straw triggering the N mineralization was associated with native soil N condition. Furthermore, the NUE increased with 15N uptake in the plant, and the residual 15N in soil was increased by 26.8% with straw addition across four straw application rates. Overall, our study highlights the trade-offs between straw incorporation with N fertilizer in eliminating potential Cd toxicity, increasing fertilizer-N use efficiencies and help to provide a feasible agricultural management.

No-tillage with straw mulching promotes wheat production via regulating soil drying-wetting status and reducing soil-air temperature variation at arid regions

Straw returning is a technical measure of crop production widely adopted in arid and water-deficient areas. However, the mechanism by which straw returning drives spatio-temporal changes in soil moisture and temperature to improve crop productivity remains unclear. So, a three-year field experiment was conducted with four various straw returning treatments for wheat production: 1) no-tillage with straw mulching (NTSM), 2) no-tillage with straw standing (NTSS), 3) conventional tillage with straw incorporation (CTS), and 4) conventional tillage without straw returning (CT, control). The spatio-temporal variations of soil moisture content and soil temperature were assessed. It will provide the basis for selecting the appropriate way of straw returning to increase wheat yield and clarifying its hydrothermal regulation mechanism. NTSM and NTSS were effective in maintaining soil moisture and regulating soil temperature, and had a greater effect on grain increase, than CTS and CT. Meanwhile, NTSM had a relatively higher yield than NTSS through better regulation of soil hydrothermal characteristics. NTSM had higher soil moisture content in the 0–120 cm depth by 9.8–10.2%, 6.7–8.2%, 6.5–10.2%, and 6.9–7.4% at sowing to jointing, jointing to booting, booting to early-filling, and early-filling to maturing stages of wheat, respectively. NTSM decreased evapotranspiration modulus coefficient (ETMC) and evapotranspiration intensity (ETI) at jointing to early-filling stage of wheat, but increased both indexes from early-filing to maturing stage of wheat, which is helpful to adjust the contradiction of soil moisture demand for wheat in different growth stages. Additionally, NTSM had 9.8–10.2%, 6.7–8.2%, 6.5–10.2%, and 6.9–7.4% lower soil temperature in the 5–25 cm depth than CT, at the four aforementioned wheat growth stages, respectively. The difference of soil temperature was mainly reflected at the 5–15 cm depth by analyzing the difference on soil temperature in various soil depths. The treatment on NTSM had little variation and stabilized soil temperature, according to the difference between air and average soil temperature of 5–15 cm depth. NTSM allowed wheat to grow a suitable thermal environment across their growth period, which is a significant regulatory mechanism for wheat to maintain better growth and development. Thereby, NTSM boosted wheat grain yield by 18.6–27.3% as compared to CT. Collectively, the NTSM treatment had better effect on regulating soil drying-wetting status and reducing soil-air temperature variation, which could be used as a recommended measure to improve wheat productivity at arid conditions.

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.

Soil properties and crop yields as influenced by the frequency of straw incorporation in rape-wheat-triticale rotation

Straw, particularly cereal straw, is a valuable by-product of crop production, which can be used for various purposes, e.g. as livestock feed and bedding or for making fuels, however it should primarily be retained on farmland in order to prevent soil organic matter (SOM) losses and thus to maintain or improve soil quality. The aim of this study was to analyze effects of the frequency of crop residues (straw) incorporation into the soil on the content of soil organic matter and on crop yields. There were the following experimental treatments: SR – straw of all crop in the rotation removed, S1 – straw of one crop per rotation incorporated, S2 – straw of two crops in the rotation incorporated, and S3 – straw of three crops incorporated into the soil (loamy sand). After 21 years of crop rotation with straw removal (SR) the SOM level in the soil slightly decreased to 14.4 g∙kg –1 soil DM, compared to that in 1997 (14.6 g∙kg –1). However, when straw of one crop (rape) per rotation was incorporated (S1) the content of SOM increased to 15.0 g∙kg -1 soil DM, and to 15.6 and 16.0 g∙kg –1 in S2 and S3 treatments respectively. Straw retention had also a beneficial effect on the content of labile fractions of SOM (hot water extractable C and N). Grain yields and yield components of wheat and triticale, and seed yields of rape in the SR treatment were not significantly different from those obtained in S1, S2 and S3 treatments.

Biochar combined with N fertilization and straw return in wheat-maize agroecosystem: Key practices to enhance crop yields and minimize carbon and nitrogen footprints

Straw incorporation is widely applied to improve crop productivity, and biochar amendment may be an effective countermeasure for mitigating greenhouse gas (GHG) emissions; however, the comprehensive evaluation of straw return and biochar amendment coupled with different N application rates on soil organic carbon (SOC) sequestration rate, GHG emissions, and reactive N losses have been inadequately recorded. Consequently, the field experiment had six treatments and three replications including two mineral N fertilization rates (conventional N fertilizer application (N1) and 30% reduced N fertilizer application (N0.7)) and three types of straw and biochar management variations (no straw incorporation (S0), straw incorporation (S), and straw incorporation with biochar amendment (SB)) and the results were based on three years of soil SOC and GHGs emission data in wheat-maize agroecosystem. Our finding revealed that N0.7 reduced the GHG emissions (CO2: 13.9%; N2O: 34.2%; CH4: 32.5%), greenhouse gas intensity (GHGI; 32.7%), carbon footprint (CF; 35.1%) and nitrogen footprint (NF; 24.5%), but had no significantly different crop yields compared with N1 (p > 0.05). Straw incorporation had no significant impact on CF and yield-scaled CF but increased NF (29.7%) because the stimulated GHG emissions would be offset by SOC sequestration. Under S, the wheat and maize yields increased by 9.7% and 5.4%, respectively, whereas the GHGI increased by 59.6% compared with S0. Biochar amendment reduced GHG emissions (CO2: 19.9%; N2O: 29.9%), GHGI (32.7%), CF (26.7%) and yield-scaled CF (29.2%), while improving crop yields (wheat: 5.8% (p < 0.05); maize: 1.5% (p > 0.05)) and SOC sequestration rate (74.5%) compared with that under S. Overall, N0.7SB exhibited enormous potential for enhancing wheat-maize agroecosystem productivity and drastically mitigating their CF and NF in the semi-arid conditions of the Guanzhong Plain.

Transition of spatio-temporal distribution of soil enzyme activity after straw incorporation: From rhizosphere to detritusphere

The rhizosphere and detritusphere are hotspots of soil enzyme-mediated microbial processes, but little is known about their spatio-temporal distribution and interactions in situ, especially after straw incorporation. To answer this question, we planted maize in rhizoboxes with three wheat straw localizations: a) straw incorporated in the upper 2 cm of soil (straw localized); b) straw mixed with all the soil (straw homogenized); and 3) without straw (control). Zymography was used to investigate the spatio-temporal distribution of soil C- and N- acquiring enzyme activities in the rhizosphere (living roots) and detritusphere (straw induced), which depends on straw localization (localized vs. homogenized) and time (7 vs. 15 days after planting). The hotspot area of enzyme activities was similar in the detritusphere compared to the rhizosphere at the early stage (day 7), suggesting the importance of detritusphere in driving C and N cycling. Compared with homogenized straw, higher C- and N-acquiring enzyme activities in detritusphere were observed in the treatment with localized straw, which indicates that straw localization had a marked impact on the enzyme activity in the detritusphere. Although enzyme activities in rhizosphere and detritusphere decreased with time from straw application, straw incorporation increased the enzyme activities in the rhizosphere (especially with localized straw) compared to control at the late stage (day 15). Furthermore, homogenized straw greatly reduced plant height (−36 %), leaf area (−49 %), SPAD (−49 %), and shoot weight (−53 %) than control at the late stage, but localized straw had little impact on plant performance. In conclusion, straw incorporation forms another soil enzyme activity hotspot (detritusphere) and promotes enzyme activities in the rhizosphere and soil profile. Collectively, homogenized straw incorporation intensified nutrient competition between microorganisms and roots and restricted plant performance.

Effect of Different Tillage Systems and Soil Biostimulants on Agrochemical Properties and Intensity of Soil CO2 Emission in Wheat Crop

In this study, a field experiment was performed at the Experimental Station of Vytautas Magnus University Agriculture Academy in Lithuania from 2018 to 2020. The researched soil comprised carbonate deeper gleyic leachate (IDg4-k) (Calc(ar)i Endohypogleyic Luvisol) (LVg-n-w-cc). A two-factor field experiment was performed on spring and winter wheat. Factor A was soil tillage technology; factor B was the use of biostimulants and their mixtures (Ruinex, Penergetic, Azofix). The experimental fields were arranged randomly in four replicates. The aim of the work was to assess the soil CO2 emissions, soil carbon, soil nitrogen, humus, and humic substances using two different soil tillage management methods (no till—wheat straw left on the soil surface; and reduced till—soil incorporation of the wheat straw) and different biostimulants or nitrogen fertilization. The humus content of the soil remained sufficiently stable or slightly decreased when the straw was retained and the single-component biostimulators Azofix, Ruinex, and Penergetic were used. In contrast, when continuous straw application was combined with two- or three-component mixtures of these biological preparations or with compensatory nitrogen the humus content increased. Compared with the initial state, it increased by 1.4–12.8 % due to the improved complexity of extra conditions for microbiological biodiversity. Meanwhile, after three years of investigation, the soil tillage technology did not significantly impact the humus content, total nitrogen, and CO2 emissions. Tillage technologies had a significant impact on the content of water-soluble soil carbon. Under no-till, the carbon content increased by an average of 9.0%, and under reduced tillage, the carbon content increased by only 2.3%. It is likely that the combination of no-till with catch crops increased the stocks of soluble C in the soil. Compared to the use of compensatory nitrogen, this indicator was increased by all biostimulants, especially when using all three preparations in the mixture (Ruinex, Penergetic, Azofix). The effect of the two-preparation mixtures was also more pronounced than that of the single component. The results over three years show that biostimulants promote the release of mobile humic substances and mobile humic acids better than compensatory nitrogen for straw decomposition. The effect was the same for the organic carbon content.

Methane emission under straw return is mitigated by tillage types depending on crop growth stages in a wheat-rotated rice farming system

Straw return (SR) is a recommended management practice to improve soil fertility, but often increases methane (CH4) emissions from rice paddies. Tillage type (before or after irrigation) will change the contact surface between soil and straw, as well as soil structure, but little is known about how tillage type affects CH4 emission under SR from rice fields. A field experiment using split-plot design (straw as main plot and tillage type as subplot) was conducted to quantify the interactive effects of SR and tillage type on CH4 emission from transplanting to jointing, jointing to booting, and booting to maturity stages of rice in 2018 and 2019 and its underlying mechanisms. The results showed that SR significantly increased CH4 emission throughout the rice growing season by 58.8% due to enhanced methanogenic activity compared with straw removal (S0). Cumulative CH4 emission from transplanting to booting stage accounts for 95% of that from the whole rice growth season. Dry tillage (tillage before irrigation, -W) mitigates CH4 emission under SR from transplanting to jointing stage due to lower mcrA abundance compared with wet tillage (tillage after irrigation, +W). However, +W mitigates CH4 emission from jointing to booting stage in the absence of significant interaction between straw and tillage type through improved soil aggregation and higher carbon accumulation compared with -W. Overall, S0 +W had lower CH4 emission by 18.3%− 36.5%, 42.9%− 52.7%, and 44.0%− 48.6% than S0-W, SR-W, and SR+W, respectively (P < 0.0.5). Our results emphasize the importance of adjusting paddy tillage method in mitigating CH4 emission boosted by straw incorporation.

The Yield-Forming Role of Nitrogen in Rice in the Growing Seasons with Variable Thermal Conditions

A reduced basal and increased topdressing fertilizer rate (RBIT) can usually increase rice yield, but whether this practice alleviates the impact of poor weather on rice production is unknown. Thus, the effect of three integrated RBIT treatments (RBITs, including RBIT alone, RBIT in combination with straw incorporation (RBITS) or a reduced fertilizer rate (RBITR)) on rice growth and nutritional status under different weathers was investigated in a 9-year experiment. Conventional fertilization (CF) was the control. We found that daytime temperature and light (DTL) after heading were the main meteorological factors limiting rice yield increases. RBITs did not affect rice yield under High-DTL, compared with CF, but RBITS significantly increased rice yield under Low-DTL. Compared with High-DTL, the positive effect of RBIT and RBITR on the N concentration and proportion in vegetative organs under Low-DTL was higher than the K concentration in vegetative organs, but RBITS showed the opposite trend. Regression analysis indicated that the harvest index had stronger correlations with the N concentration (negative), K concentration (positive), and N/K (negative) in vegetative organs under Low-DTL than under High-DTL. Our findings suggested that RBITS could improve rice adaptability to daytime temperature and light changes after heading by balancing crop nutritional status (N/K).

Effect of different straw retention techniques on soil microbial community structure in wheat-maize rotation system.

Rotational straw return technique is considered an effective measure for improving soil quality and maintaining soil microorganisms. However, there are few reports on the influence of wheat-maize crop rotation and straw-returning tillage on crop soil microbial communities in China. This study aimed to investigate how wheat or maize straw-incorporation practices affect bacterial and fungal communities under wheat-maize rotational farming practices. To clarify the effects of straw incorporation on microbial composition, microbial communities from soils subjected to different treatments were identified using high-throughput sequencing. Our results showed that, before corn planting, wheat and maize straw returning reduced bacterial density and increased their diversity but had no effect on fungal diversity. However, before wheat planting, returning wheat and corn stalks to the field increased the diversity of soil bacteria and fungi, whereas returning corn stalks to the field reduced the diversity of fungi and other microorganisms. Straw return significantly increased the relative abundance of Ascomycota in the first season and decreased it in the second season; however, in the second season, wheat straw return increased the relative abundance of Bradyrhizobium, which can promote the soil microbial nitrogen cycle and provide nitrogen to the soil. Wheat and maize straw return increased the relative abundance of Chaetomium, whereas, individually, they decreased the relative abundance. In addition, we detected two fungal pathogens (Fusarium and Trichoderma) under the two planting patterns and found that the relative abundance of pathogenic Fusarium increased with wheat straw return (FW and SW). Trichoderma increased after treatment with maize straw return before wheat planting (S group). These results suggest that wheat straw return (FW and SW) and maize straw return might have a negative impact on the pathogenic risk. Therefore, further studies are needed to determine how to manage straw returns in agricultural production.

Potential of crop straw incorporation for replacing chemical fertilizer and reducing nutrient loss in Sichuan Province, China

Sichuan Province is rich in crop straw, yet little is known about its spatial distribution pattern, potential in replacing chemical fertilizer and mitigating nutrient loss. Based on the statistical data and literature review, the spatial distribution and potential of nutrient resources in crop straw for replacing chemical fertilizers was evaluated in this study. The nutrient loss with both crop incorporation and chemical fertilizer application were examined using a nutrient release coefficient method and compared. Results showed that Chengdu Plain, Northeast and South Sichuan produced more than 95% of the total straw nutrient resources during the period of 2016–2020. The potential of crop straw to substitute potassium (K), nitrogen (N) and phosphorus (P) fertilizer were K2O 33.08–285.95 kg hm−2, N 9.52–82.32 kg hm−2 and P2O5 4.91–28.71 kg hm−2, respectively. If chemical fertilizer was substituted by all the available straw nutrient resources, N and P loss can be decreased by 55.12% and 65.84% in average in Sichuan Province. 343.93 t of N loss and 20.05 t of P loss can be reduced in plain areas, 122.88 t of N loss and 46.29 t of P loss can be reduced in mountainous and hilly areas, and 5.65 t of t N loss and 3.54 t of P loss can be reduced in plateau areas. It can be concluded that there were rich crop straw nutrient resources in Sichuan Province with obvious spatial variability, solid consideration should be put on to the proper use of crop straw nutrient resources, with the aim of chemical fertilizer reduction, nutrient loss reduction and sustainable development.