Straw Application Research Articles

Squash Yield, Water-Use Efficiency and Nitrate Accumulation as Influenced by the Application of Humic Acid, Geobacillus stearothermophilus SSK-2018 and Wheat Straw in an Arid Land Condition

The importance of inorganic fertilizers in squash crop productivity is enormous. However, the continuous use of inorganic fertilizers constitutes a serious problem to the environment and human health due to nitrate accumulation. Thus, two seasons (2020 and 2021) of field trials were carried out to investigate the effects of bio-organic amendments on squash under arid land conditions in Saudi Arabia. The bio-organic amendments were comprised of humic acid (HA) at three levels (0, 50 and 100 L/ha), inoculation of a cellulose-decomposing bacterium (CDB; Geobacillus stearothermophilus SSK-2018) and wheat straw at four levels (0, 20 and 30 t/ha and NPK 20:20:20 at 600 kg/ha as a positive control). A randomized split-split plot design replicated three times was used in laying out the field trials. The independent application of HA, CDB and wheat straw significantly (p ≤ 0.05) improved squash growth, yield and water-use efficiency in both seasons. Furthermore, HA significantly (p ≤ 0.05) reduced fruits’ nitrate content. HA (100 L/ha) reduced nitrate content in squash fruits by 87% and 71.6% compared to the control in 2020 and 2021, respectively. The application of 20 t/ha of wheat straw significantly (p ≤ 0.05) reduced nitrate accumulation in fruits compared to the positive control (NPK) by 5.9% and 13.6% in 2019/20 and 2020/21, respectively. Regression analysis shows that increased nitrate accumulation in fruits results in decreased squash growth and fruit yield. This study demonstrates the significance of bio-organic amendments in improving squash growth and yield while reducing nitrate accumulation in fruits.

Effects of post-fire mulching with straw and wood chips on soil hydrology in pine forests under Mediterranean conditions

Mulching is one of the most common post-fire management techniques, which has been widely studied at the global scale. However, more research is needed on the hydrological effects of mulching in forest ecosystems under Mediterranean semi-arid conditions. This study has evaluated water infiltration, surface runoff and soil loss using a portable rainfall simulator in Central-Eastern Spain after post-fire treatments. In this area, a large wildfire recently affected a pine forest, and the burned soil was mulched using wheat straw (dose of 0.3 kg/m2) or wood chips (2 kg/m2) on plots with two different slopes (about 30%, lower slope, and 50%, higher slope). The study has shown that the soil condition (burned control vs. soils mulched with straw or wood chips) and slope (lower vs. higher) did not significantly influence the water infiltration. However, the mean infiltration of the soils mulched with straw were higher (+40% and + 17%, respectively) compared to both the control and the plots mulched with wood chips. Moreover, lower surface runoff (−23%) was measured in the mulched soils compared to the control plots. The soil mulching with straw was more effective at decreasing the runoff coefficient (−31%) compared to plots treated with wood chips (−18%) and the control areas. Soil loss was significantly lower in plots treated using straw (−87% compared to the burned and not treated soils) compared to wood chips (−54%). Peaks of 90–95% of reduction in the soil loss were even recorded in the steeper soils. Finally, we suggest the application of wheat straw rather than wood chips, since the wheat straw mulch material provides a higher soil cover (on average 73% against 48% of wood chips) and therefore is more indicated to reduce the hydrological response in burned soils, as confirmed by the lower runoff (in the average − 16%) and erosion (−73%) measured in this experiment on both gentler and steeper soils.

Shade net and mulching measures for improving soil and plant water status of fig trees under rainfed conditions

Prolonged drought conditions and soil desiccation have caused extensive damage and reduction in yields of the largest rain-fed fig trees (Ficus carica L. ‘Sabz’) grove located in the semi-arid region of Estahban, Iran. In this experiment, the effect of suspended shade net and two types of water penetration systems covered with organic mulch on plant water status and productivity of the rain-fed fig trees on the foothill slopes with traditional micro-catchment were investigated during 2018–2020. The first experimental factors included -(Ctrl.) without shade net and -(S) covering the tree canopy with 25% shade intensity white suspended shade net; and the second experimental factors included -(Ctrl.) the local traditional practice (25 m2 bare soil micro-catchment only), -(M) application of wheat straw as organic mulch under the tree canopy with two concentrating infiltration pipes and -(MP) application of wheat straw mulch over the soil under the tree canopy with two concentrating infiltration pipes and on the surface of 4 m of overall plowing rows perpendicular to the slope to a depth of 40 cm and a width of 3 m at a distance of 2.5 m upslope of the tree trunk. MP treatment significantly increased and retained the average of soil moisture content by 79.9% in comparison with the local traditional practice. The results showed that S+MP had the greatest effect on inducing the physiological attribute of fig trees such as leaf stomatal conductance (121.1%), leaf transpiration (52.5%), leaf light-saturated net CO2 assimilation (96.6%) and the leaf water potential (30.9%) as the main effective variable in association with increment of commercial fruit yield. This treatment had the highest impacts on the increment of yield (187.7%) and commercial and healthy quality of ‘Sabz' fig dry fruit under severe drought conditions in rain-fed orchards.

Construction of the SHP-GLOX lignin regulation system and its application in rice straw

BackgroundThere is great productivity of rice(Oryza sativa L. spp. japonica) straw in China, which is a potential source of biomass for biofuel and forage. However, the high levels of lignins in rice straw limited its usage and induced the formation of agricultural waste. In order to modify the lignins contents to improve biofuel production and forage digestibility, we selected Soybean hull peroxidase (SHP) and Glyoxal oxidase (GLOX) as candidate genes to improve quality of rice straw. SHP, a class III plant peroxidase, is derived from multiple sources. It has several advantages, such as high resistance to heat, high stability under acidic and alkaline conditions, and a broad substrate range. SHP is speculated to be useful for lignin degradation. Glyoxal oxidase (GLOX) is an extracellular oxidase that can oxidize glyoxal and methylglyoxal in the extracellular medium to generate H2O2.ResultsIn the present study, the SHP and GLOX genes in pCAMBIA3301-glycine-rich protein (GRP)-SHP-GLOX, designated the K167 vector, were optimized and introduced into rice embryos using Agrobacterium-mediated transformation. Positive transgenic rice embryos were examined using molecular, physiological, biochemical and fermentation tests. The outcomes suggested that SHP degraded lignin effectively.ConclusionsThis research has created a rice breeding material with normal growth and yield but stalks that are more amenable to degradation in the later stage for use in breeding rice varieties whose stalks are easily used for energy. Our results will improve the industrial and commercial applications of rice straw.

Effects of long-term organic matter application on soil carbon accumulation and nitrogen use efficiency in a double-cropping rice field

Increasing soil carbon (C) sequestration in paddy field and improving rice nitrogen use efficiency (NUE) are vital for sustainable agriculture and environmental protection. It was a benefit practice for achieving these goals by taken rice straw and organic manure managements. However, there is still need to further investigate the effects of different long-term fertilizer managements on soil C sequestration and NUE under the double-cropping rice system in southern of China. Therefore, the effects of different long-term (36-years) fertilizer practices on soil C sequestration and NUE under the double-cropping rice system in southern of China were investigated in the present paper. The field experiment was included four different fertilizer treatments: chemical fertilizer alone (MF), rice straw residue and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and without fertilizer input as a control (CK). This result indicated that soil C content at plough layer in paddy field with RF and OM treatments were increased, compared with MF and CK treatments. Besides input C directly into paddy field, soil original organic C accumulation with RF and OM treatments were increased by 1.54% and 3.01%, compared with MF treatment. This result indicated that soil TOC content increase rate and annual topsoil organic C sequestration rate in paddy field with RF and OM treatments increased by 55.56%, 88.89% and 48.05%, 76.62%, compared with MF treatment, respectively. Compared with MF treatment, NUE with RF and OM treatments increased by 10.43% and 22.61%, respectively, mainly due to increasing soil organic C. Grain yield of double-cropping rice with RF and OM treatments increased by 1009.5 and 1166.5 kg ha−1, compared with MF treatment, respectively. This result indicated that there was significantly correlation between NUE/NUENPK and TOC content with RF and OM treatments, at early rice and late rice growth seasons. Therefore, it was benefit practice for increasing soil carbon sequestration and improving rice NUE in the double-cropping rice system with long-term application of rice straw and organic manure managements.

Effects of combined applications of straw with industrial and agricultural wastes on greenhouse gases emissions, temperature sensitivity, and rice yield in a subtropical paddy field

The incorporation of post-harvest crop straw and application of industrial and agricultural wastes to paddy soils increase rice crop yields and soil fertility. However, the impacts of combined applications of straw and waste products on greenhouse gas (GHG) emissions and global warming potential (GWP) of paddy soils are unclear. Therefore, we conducted a field experiment in subtropical rice in China to test the effects of applications of straw, straw+biochar, straw+shell slag, straw+gypsum slag, straw+silicon, and straw+steel slag on rice yields, GWP, and greenhouse gas emission intensity (GHGI). The results showed that, compared to the control, cumulative emissions of carbon dioxide (CO2) from paddy soils were 15.2, 16.9, and 36.6 % lower following application of straw+steel slag, straw+silicon, and straw+gypsum, respectively, and cumulative emissions of methane (CH4) were 5.0 and 62.1 % lower following application of straw+steel slag and straw+gypsum, respectively. Meanwhile, relative to the addition of straw alone, application of straw+steel slag and straw+gypsum reduced GHG emissions largely due to reductions in CO2 emissions, further declining the GWP of CO2 and GHGI. In addition, temperature sensitivity (Q10) of CO2 emissions was highest following application of straw+silicon and lowest following application of straw+gypsum. There were no treatment effects on mean dissolved porewater concentrations of CO2, CH4, or nitrous oxide (N2O) and soil emissions of CO2 were negatively correlated with mean dissolved concentrations of CO2, CH4, and N2O. Rice yields were reduced following application of straw+gypsum and unaffected by the other treatments. Thus, relative to the addition of straw alone or control, we suggest the combined application of straw+steel slag may improve the sustainability of paddy rice production, because it reduces GWP, while maintaining yields.

Long-Term Nitrogen and Straw Application Improves Wheat Production and Soil Organic Carbon Sequestration

Long-Term Nitrogen and Straw Application Improves Wheat Production and Soil Organic Carbon Sequestration

Process Simulation-based Net Energy Analysis for Future Bioethanol Production as Commercial Biofuel from Waste Rice Straw in Sri Lanka

As the staple food crop in Sri Lanka, paddy rice occupies around 34% (over 0.87 million hectares of land) of the total arable area in the country, corresponding to an average rice production of 3,774,344 t/year. Rice straw is the major biomass waste from rice cultivation, which approximates to an average of 2,830,758 t/year generation at a theoretical straw/grain ratio of 0.75. Open burning of rice straw in paddy fields is the common practice, which could result in an average GHG emissions of 92 kg CO2 eq/t of dry rice straw and other harmful airborne emissions. Application of rice straw into soil as an organic fertiliser is also an inefficient practice, compared to bioenergy generation using rice straw. The average composition of the Sri Lankan rice straw (i.e. 30.0 wt.% cellulose, 3.9 wt.% hemicellulose, 38.2% lignin, 16.1 wt.% wax, and 12.3 wt.% silica) shows the possibility to be used as a second-generation bioethanol feedstock. Existing studies indicate that bioethanol production from rice straw is more environmentally-benign, compared to alternative options, such as gasification for combined heat and power and dimethyl ether (DME) production. This study analyses the net energy indicators of a possible bioethanol production process from rice straw in Sri Lanka. Chemical process simulations using Aspen Plus software were utilised to evaluate the bioethanol production process from rice straw, with a plant output capacity of 1,000 litres/hr of dehydrated bioethanol (99.7 vol.% ethanol) that can be blended with gasoline as a commercial fuel (e.g. E10: 10% bioethanol+gasoline) without any vehicle engine modification. The cradle to gate bioethanol production process from waste rice straw, considered for net energy analysis consists of three major stages: 1. Rice straw preparation, 2. Rice straw transportation, and 3. Bioethanol conversion. The results show that the considered bioethanol production process has a positive net energy gain and increased renewability factor. Detailed analysis indicates that only around 8% of the total process energy consumption is utilised for the bioethanol dehydration operation that is favourable for converting any existing rice straw ethanol plant into commercial gasohol production plant. The sensitivity of bioethanol yield and process energy parameters for the net energy indicator results are further analysed and discussed. The findings from this study can support decision making for a future waste-to-biofuel plant using waste rice straw in Sri Lanka.Keywords: Rice straw, Bioethanol production, Net energy analysis, Process simulation, Waste-to-biofuel

Full straw incorporation into a calcareous soil increased N2O emission despite more N2O being reduced to N2 in the winter crop season

Crop straw application in combination with fertilizer nitrogen (N) dose reduction is recommended to improve crop yields and carbon sequestration in soil. This practice may also promote soil nitrous oxide (N2O) emission, thus partially counterbalancing the expected benefits. However, the full straw return effect on the reduction of soil N2O to dinitrogen (N2) is not yet well known, owing to the methodological difficulties in quantifying soil N2 fluxes against the high atmospheric N2 concentration. This study was carried out in a long-term experimental field of a calcareous soil cultivated with summer maize and winter wheat in rotation. For the three field treatments since 2006, i.e., optimal fertilizer N with and without full straw return, and the control (without N and straw application), we conducted in- or ex-situ observations on field N2O fluxes, soil N2 emissions, crop yields, soil organic carbon (SOC) contents and soil/environmental factors. During a rotation cycle, we found that soil ammonium and nitrite concentrations, moisture and temperature jointly determined the N2O emissions, while nitrate concentration, dissolvable organic carbon to nitrate-N ratio and moisture jointly dominated the N2 emissions. Compared to straw removal, the straw return promoted reduction of more soil N2O to N2 in the wheat season than in the maize season, showing increases in the N2 emissions by 57% versus − 10% (P = 0.06). Nevertheless, it significantly enhanced the N2O emissions measured in situ by approximately 137% and 21% in the wheat and maize seasons, respectively (P < 0.05). It also significantly increased the annual crop yields by 20% on average (P < 0.05). Meanwhile it tended to enhance the SOC stock (0−20 cm) by 15‰ yr−1 (P = 0.14), showing a trend of more intensive carbon sequestration than the direct soil N2O emission (−948 versus 378 kg CO2e ha−1 yr−1 on average). We conclude that the long-term full straw return helps to sequester more carbon that offsetting the enhanced N2O emissions from the calcareous soil in the rotation system as it promotes reduction of more N2O to N2 in the wheat season.

Effect of Long-Term Organic Amendment Application on the Vertical Distribution of Nutrients in a Vertisol

Soil nutrients in deep soils are important for nutrient cycling and plant growth. Organic amendments have been widely used for enhancing soil health and crop yield. However, little is known about the effects of organic amendments on the vertical distributions of soil nutrients. Based on a 32-year long-term organic amendment experiment, the objective of this study was to evaluate changes in the vertical distribution of nutrients in a soybean–wheat system Vertisol. The results showed that NPK with manure or straw application significantly increased soil organic carbon (SOC), total N, total P, alkali-hydrolyzable N, available P and available K above the 40 cm soil layer. Variations in soil micronutrients primarily occurred above the 20 cm soil layer, and the highest contents were observed for NPKWS and NPKPM, respectively. Nevertheless, large amounts of NO3−−N contents accumulated in the 120–200 cm depth with manure but not straw application, indicating a high potential risk of nitrate leaching in manure treatments. These findings suggested that the application of organic amendment (manure or straw) could be recommendable for improving soil nutrients along the soil profile. Straw incorporation could be used as an alternative option for sustainable agriculture in regions with inadequate manure resources or severe nitrate leaching.

Fermenting straw reduced salt damage and improved the stability of the bacterial community in a saline–sodic soil

This study aimed to explore the potential of fermenting straw return for remediation of soil salinity. A sealed–pot experiment was used to evaluate four treatments: CK (0 g fermenting rice straw), T1 (120 g fermenting rice straw), T2 (240 g fermenting rice straw), and T3 (360 g fermenting rice straw). Using 13C isotope tracer technique and molecular biological techniques to detect the physical, chemical, and biological properties of saline–sodic soils. The results showed that a small amount of CO2 was produced upon addition of soda–alkali soil to the soil after straw was applied. Quantitative analysis showed that the proportion of CO32– reduction of total CO32– was peaked (4.90%) in treatment T3. Concomitantly, under this treatment soil pH, SAR and ESP were reduced, whereas soil porosity and K+, Ca2+, and Mg2+ concentrations, and total nitrogen (TN), SOM, and MBC were increased. PCoA analysis showed that the addition of straw significantly changed the community structure of bacteria in a saline–sodic soil, and increased the Chao1 and Shannon indexes. Straw application increased ryegrass shoot and root biomass without allelopathic effects in the saline–sodic soil used. Our results highlighted that rice straw should be collected and artificially decomposed after rice harvest and then applied for the reclamation of strongly saline–sodic soils in the Songnen Plain and other similar areas.

Effect of crop rotation and straw application in combination with mineral nitrogen fertilization on soil carbon sequestration in the Thyrow long-term experiment Thy_D5

AimsThe aim of study was to quantify the temporal change of soil organic carbon content in relation to agricultural management for a dry sandy arable soil and to derive the C sequestration potential.MethodsWe analyzed data from a long-term field experiment with three crop rotations of different cereal proportions, with two levels of straw application (removal/return) in combination with four mineral nitrogen rates (40 … 160 kg ha-1 yr-1). Treatments are arranged in a two-factorial block design with two replicates for each rotation. During the 24-year study period, grain and straw yield of two cereal test crops and soil organic carbon content in topsoil were determined annually from each plot.ResultsSoil organic carbon content was positively influenced by removing non-cereal crops from the rotation and – to a smaller extent – by straw application. Increasing mineral N-fertilization from 40 kg ha-1 yr-1 to higher rates increased grain yield of rye but not barley, increased straw yield of both cereals more, with no effect of higher straw yields on soil organic carbon content.ConclusionsDespite the overall soil organic carbon content of the sandy soil under study is comparatively low, the results indicate that agricultural management has a relevant impact on soil carbon stocks. Straw return contributes to carbon sequestration even in rotations with a low potential for reproduction of organic matter. High mineral N-fertilization is not an adequate measure to sequester carbon in these soils.

Effects of combined application of biochar with organic amendments on enzyme activity and microbial metabolic function of carbon sources in infertile red soil

To improve carbon (C) sequestration and soil fertility of red soil, a two-year (2017 and 2018) field experiment was conducted to investigate the effects of two organic amendments (i.e., corn straw and sheep manure) applied alone or combined with biochar on soil nutrient content, enzyme activities involved in C cycling, and microbial substrate utilization rate in infertile red soil. There were six treatments, including control (non-amendment), corn straw, sheep manure and across biochar treatments (without and with biochar amendment, respectively). The organic amendments and biochar were applied in 2017 and 2018. The results showed that, compared with the control, organic amendments significantly increased soil pH, organic C, total nitrogen, available phosphorus and potassium contents. Compared with straw and manure alone, the biochar co-application with straw or manure significantly increased the contents of soil organic C, available potassium, and available nitrogen, without any significant interactive effects. Application of organic amendments significantly increased the activities of soil β-glucosidase (BG), cellobiohydrolase (CB), β-xylosidase (XYL), and peroxidase (PERO). The combined application of biochar and straw significantly reduced the activity of phenol oxidase (PHOX) by 28.6% and PERO by 22.2% in comparison with straw addition alone, respectively, while the combined application of biochar and manure significantly reduced the activities of α-glucosidase (AG) by 46.1%, BG by 50.9%, XYL by 41.6%, and PERO by 31.3% compared with manure addition alone, respectively. Compared with the control, the application of organic amendments significantly enhanced soil basal respiration and microbial utilization rates of carbohydrates, whereas biochar co-application significantly decreased microbial utilization rates of carbohydrates and carboxylic acids. Microbial C source utilization rates were significantly and positively correlated with the activities of BG and PERO. Thus, biochar co-application with organic amendments can enhance nutrient content and reduce enzymatic and microbial metabolic activities, thereby may facilitate C sequestration and fertility of infertile red soil.

Distinct stabilization characteristics of organic carbon in coastal salt‐affected soils with different salinity under straw return management

AbstractStraw returning effectively promotes the soil organic carbon (SOC) pool, but the straw‐induced change in SOC quality (C fraction) remains unclear, particularly in saline soil. Here, we investigated how straw returning and soil salinity (low, medium, and high) affect SOC fractions, including easily oxidized and particulate organic C (EOC and POC) and mineral‐associated organic C (MOC) at aggregate scales, including macroaggregates (MA), microaggregates (MI), and silt + clay particles. The results revealed that SOC fraction contents in the whole soil decreased with increasing soil salinity, and straw returning increased the total organic C (TOC) in both low‐ and medium‐salinity soils. In low‐salinity soil, straw returning induced decreases of 12.1% and 30.6% in MI‐associated EOC and POC, respectively, and promoted significant increases of MI‐associated MOC, indicating that 'hierarchical aggregation' theory (i.e., single soil particles gradually form clusters, MI and MA) dominated during soil aggregate formation. In medium‐salinity soil, straw application increased all SOC fraction contents in MA, and raised the POC/TOC of the whole soil by 56.6%, suggesting that the 'macroaggregate turnover' theory (MI is formed within MA) played a more important role in forming aggregates. Our results demonstrated that low‐ and medium‐salinity soils had different C‐increasing strategies under straw returning: MA contributed more to the increased SOC than MI in low‐salinity soil, whereas the reverse was true in medium‐salinity soil. These findings suggest that higher soil salinity would weaken the C sequestration potential of straw returning, and that targeted measures should be applied to enhance reclamation efficiency.

Effects of Fertilizer Reduction and Straw Application on Dynamic Changes of Phosphorus in Overlying and Leaching Water in Rice Fields

In the process of rice cultivation, fertilizer reduction can effectively reduce the concentration of phosphorus (P) in overlying water and leaching water. In this study, the variation characteristics of P in overlying and leaching water under the conditions of fertilizer reduction and straw application and its impact on the environment were studied through a two-season rice field experiment. Four treatments were set, including no fertilizer without straw (CK), conventional fertilization (CF), 20% reduction in nitrogen (N) and P fertilization (RF), and 20% reduction in N and P fertilization with the wheat straw (RFWS). The results showed that RF could effectively reduce the risk of P loss due to its ability to decrease the concentration of P in overlying and leaching water. RFWS increased P concentrations in overlying and leaching water of rice fields. Total dissolved phosphorus (TDP) was the main form of total phosphorus (TP), and soluble reactive phosphorus (SRP) was the main form of TDP. The concentration of TP, TDP, and SRP in the overlying and leaching water peaked on the first day after fertilization, and then gradually decreased. The high-risk period of P loss was 0 to 10 days after fertilization. This study could provide appropriate strategies to reduce the risk of P loss during local rice cultivation and protect local water resources from eutrophication.

Effects of reducing nitrogen application and adding straw on N2O emission and soil nitrogen leaching of tomato in greenhouse

Excessive input of nitrogen(N) fertilizer and improper selection of fertilizer types in the greenhouse vegetable production process will lead to a large amount of N loss. In order to relieve the environmental pollution caused by N loss, a planting experiment was carried out in a solar greenhouse in Shouguang, Shandong, China, to investigate the effects of N-reducing fertilizer and straw application on greenhouse vegetable yield and soil N loss, and to explore the fate of N after fertilizer application using the 15N isotope tracing technique. The experiment was planted for two seasons from July 2017 to June 2018 with four treatments: control (CK), conventional fertilizer (CN), reduced N topdressing (SN), and reduced N topdressing + straw (SNS). The results indicated that N reduction fertilizer and straw application resulted in a 35.25%–35.49% reduction in total N2O emissions and 15.76%–41.77% reduction in mineral N leaching losses. 15N isotopes as tracers showed that the maximum abundance in N2O was reduced by 58.5% and 55.68% for SN and SNS, respectively, and cumulative N2O emissions were reduced by 80.44% and 81.67%, respectively, and mineral N leaching was reduced by 74.4% and 70.48%, respectively, after fertilization compared to CN treatment. There was no significant difference in tomato yield between the three fertilizer treatments in the two growing seasons. Therefore, in greenhouse vegetable production, the amount of N fertilizer was reduced by 40.7% and the addition of straw reduced N2O emissions and N leaching without affecting tomato yields.

Does Straw Returning Amended with Straw Decomposing Microorganism Inoculants Increase the Soil Major Nutrients in China’s Farmlands?

Although straw-decomposing microbial inoculants (SDMI) are capable to generally promote the fertility of straw-amended soils, their impact on the release of individual soil major nutrients remains controversial. Additionally, the combined effects of SDMI and environment/management on various forms of nutrients remain poorly documented. To fill these research gaps, we conducted a meta-analysis study using 1214 paired observations from 132 field trials in China. Our results showed that SDMI significantly increases the total and available concentrations of nitrogen, phosphorus, and potassium in soil (p &lt; 0.05), although increases in nutrients varied with different conditions. Moreover, mean annual precipitation (MAP) had significant correlations with the effects of SDMI-amended straw on soil total nitrogen (p = 0.008) and available nitrogen (p = 0.0006). The effect of SDMI-amended straw on soil total phosphorus and soil available potassium was mainly correlated with soil organic matter (p = 0.032) and MAP (p = 0.049), respectively. Our findings indicate that SDMI-amended straw can have a measurable impact on the status of soil major nutrients. In particular, the application of SDMI-amended rice straw with an initial C/N ratio of ≤15 to neutral soils in temperate and subtropical monsoon climates is a promising strategy.

Straw retention combined with phosphorus fertilizer promotes soil phosphorus availability by enhancing soil P-related enzymes and the abundance of phoC and phoD genes

Straw retention has the potential to improve soil phosphorus (P) availability, but the question on how straw retention under different P level influences the activity of soil P-related enzymes and thus the transformfiation of soil organic P (Po) remains poorly understood. A four-year field experiment (2016–2019) was established to investigate the impacts of straw retention under different P fertilizer levels (0, 44, 88 kg P ha–1) on soil P fractions, the activity of P-related enzymes, and the abundance of phoC and phoD genes. Results demonstrated that P application alone significantly increased all soil inorganic P (Pi) fractions, but had no significant impact on soil Po fractions. Straw retention combined with P fertilizer mainly improved the proportion of NaHCO3-Po (labile P) and NaOH-Pi (moderately labile P), while decreased the proportion of dilute HCl-P and residual-P (non-labile P). The application of straw plus P fertilizer of 44 kg P ha−1 increased the contents of resin-Pi and NaHCO3-Pi more than straw plus 88 kg P ha−1. Also, the former had higher activity of alkaline (ALP) and acid phosphatase (ACP) and abundance of phoD gene than the latter. The structural equation model indicated that soil ALP and phytase (PHY) had a significant and positive effects in P cycling. Soil organic carbon (C), C:P ratio, and water-organic C were positively correlated with the activity of ALP and PHY, and the abundance of phoD gene. These findings together demonstrate that crop straw combined with a moderate amount of P fertilizer (44 kg P ha−1) is more beneficial for soil P availability through enhancing the activity of PHY and ALP and the abundance of phoD and phoC genes.

Nitrogen accumulation and nitrogen substitution effect of maize under straw returning with continuous cropping

<p id="C3">Crop straw resources in Northeast China are rich, but burning and discarding are serious, and nutrient utilization rate is very low. We explored the feasibility of the substitution of straw returning to nitrogen fertilizer and its effects on nitrogen accumulation under continuous cropping in cold region. A frame culture and continuous positioning experiment was carried out in the experimental site of Northeast Agricultural University from 2017 to 2019, with ¹⁵N labeled urea. A three-factor split-plot design was adopted in this experiment, the main plot was straw returning method with no straw returning (S0) and straw returning (S1), and the sub-plot was nitrogen application levels with 0 (N0), 175 (N1), and 350 (N2) kg hm^-2. Two application methods were set for each fertilizer application amount, one ratio of base fertilizer and top dressing applied was 1:1, and the other ratio of base fertilizer and top dressing applied was 1:0. The results were as follows: When the straw returning amount was 12 t hm^-2, the returning straw could replace 36.8 kg hm^-2 pure nitrogen. The average amount of maize straw was 46.50 million tons in Heilongjiang Province from 2017 to 2019, and straw returning could replace 142,700 tons pure nitrogen. The replace amount of pure nitrogen in the ratio of base fertilizer and top dressing (1:1) was 26.88% higher than that in 1:0. Straw returning was negatively correlated with nitrogen use efficiency in maize. The average nitrogen use efficiency of maize in S0 treatment was 6.09% higher than S1 treatment, and the yield of S1 treatment was 4.66% higher than S0 treatment when the urea application amount was 350 kg hm^-2 (161 kg hm^-2 pure nitrogen). The highest yield of maize was 268.22 g frame^-1 in the treatment of straw returning and topdressing with commonly fertilizer applied in local agriculture. In conclusion, the nitrogen substitution effect was remarkable under maize straw returning in Northeast China. Long-term combined application of crop straw and nitrogen fertilizer significantly improved the biomass, yield, and nitrogen accumulation of maize, which was a cultivation mode for increasing yield and efficiency of maize in Northeast China.

AGRO-ECONOMIC IMPACT OF ORGANIC MULCHES ON WEED DYNAMICS AND PRODUCTIVITY OF RAINFED WHEAT (Triticum aestivum L.)

Wheat is a widely grown cereal crop under rainfed conditions of semi-arid areas of the world including Pakistan. Unfortunately, its yield remains low due to heavy weed infestation and scarce moisture supply in the root zone from erratic rainfall. Therefore, a field experiment was conducted to observe the influence of different organic mulches on the soil moisture, weeds, growth and yield of wheat crop. Four organic mulches i.e wheat straw sawdust, rice straw and rice husk were applied up to 2 inches surface layer between the rows of wheat crop. Application of wheat straw mulch conserved the highest soil moisture (72.3%) at 0-15cm depth six weeks after sowing and caused maximum weed suppression with 81.17% weed control efficiency and 63.70% weed control index as compared to unmulched control. Maximum plant height (70.8cm), productive tillers (137.33 m-2), grain weight per spike (2.37g), grains per spike (52.3), 1000-grain weight (50.66 g), biological yield (9393.9 kg ha-1), grain yield (3665.6 kg ha-1), harvest index (38.60%) and benefit-cost ratio (1.69) were observed in rainfed wheat crop treated with wheat straw mulch. Wheat crop total rainfall use efficiency followed the order of wheat straw &gt; rice straw &gt; saw dust&gt; rice husk&gt; control. The highest weed density and dry weight while lowest soil moisture and grain yield were recorded with no mulch and rice husk treatments.