Stover Mulch Research Articles

Microbial necromass contribution to soil carbon storage via community assembly processes

Soil organic matter has been well acknowledged as a natural solution to mitigate climate change and to maintain agricultural productivity. Microbial necromass is an important contributor to soil organic carbon (SOC) storage, and serves as a resource pool for microbial utilization. The trade-off between microbial births/deaths and resource acquisition might influence the fate of microbial necromass in the SOC pool, which remains poorly understood. We coupled soil microbial assembly with microbial necromass contribution to SOC on a long-term, no-till (NT) farm that received maize (Zea mays L.) stover mulching in amounts of 0 %, 33 %, 67 %, and 100 % for 8 y. We characterized soil microbial assembly using the Infer Community Assembly Mechanisms by Phylogenetic-bin-based null model (iCAMP), and microbial necromass using its biomarker amino sugars. We found that 100 % maize stover mulching (NT100) was associated with significantly lower amino sugars (66.4 mg g−1 SOC) than the other treatments (>70 mg g−1 SOC). Bacterial and fungal communities responded divergently to maize stover mulching: bacterial communities were positive for phylogenetic diversity, while fungal communities were positive for taxonomic richness. Soil bacterial communities influenced microbial necromass contribution to SOC through determinism on certain phylogenetic groups and bacterial bin composition, while fungal communities impacted SOC accumulation through taxonomic richness, which is enhanced by the positive contribution of dispersal limitation-dominated saprotrophic guilds. The prevalence of homogeneous selection and dispersal limitation on microbial cell wall-degrading bacteria, specifically Chitinophagaceae, along with increased soil fungal richness and interactions, might induce the decreased microbial necromass contribution to SOC under NT100. Our findings shed new light on the role of microbial assembly in shaping the dynamics of microbial necromass and SOC storage. This advances our understanding of the biological mechanisms that underpin microbial necromass associated with SOC storage, with implications for sustainable agriculture and mitigation of climate change.

Dynamic responses of soil microbial communities to seasonal freeze-thaw cycles in a temperate agroecosystem

Soil freeze-thaw cycles (FTCs) are common in temperate agricultural ecosystems during the non-growing season and are progressively influenced by climate change. The impact of these cycles on soil microbial communities, crucial for ecosystem functioning, varies under different agricultural management practices. Here, we investigated the dynamic changes in soil microbial communities in a Mollisol during seasonal FTCs and examined the effects of stover mulching and nitrogen fertilization. We revealed distinct responses between bacterial and fungal communities. The dominant bacterial phyla reacted differently to FTCs: for example, Proteobacteria responded opportunistically, Actinobacteria, Acidobacteria, Choroflexi and Gemmatimonadetes responded sensitively, and Saccharibacteria exhibited a tolerance response. In contrast, the fungal community composition remained relatively stable during FTCs, except for a decline in Glomeromycota. Certain bacterial OTUs acted as sensitive indicators of FTCs, forming keystone modules in the network that are closely linked to soil carbon, nitrogen content and potential functions. Additionally, neither stover mulching nor nitrogen fertilization significantly influenced microbial richness, diversity and potential functions. However, over time, more indicator species specific to these agricultural practices began to emerge within the networks and gradually occupied the central positions. Furthermore, our findings suggest that farming practices, by introducing keystone microbes and changing interspecies interactions (even without changing microbial richness and diversity), can enhance microbial community stability against FTC disturbances. Specifically, higher nitrogen input with stover removal promotes fungal stability during soil freezing, while lower nitrogen levels increase bacterial stability during soil thawing. Considering the fungal tolerance to FTCs, we recommend reducing nitrogen input for manipulating bacterial interactions, thereby enhancing overall microbial resilience to seasonal FTCs. In summary, our research reveals that microbial responses to seasonal FTCs are reshaped through land management to support ecosystem functions under environmental stress amid climate change.

Effects of long-term no-tillage and different stover mulching amounts on soil carbon and nitrogen contents and enzyme activities of carbon and nitrogen cycle in Mollisols.

To understand the effects of different stover mulching amounts in no-tillage on soil carbon and nitrogen contents and enzyme activities, finding a stover mulching amount which can meet the requirement of soil carbon and nitrogen accumulation while maximizing economic benefits, we conducted a long-term conservation tillage field experiment since 2007 in Mollisols area of Northeast China. We analyzed soil carbon and nitrogen contents, enzyme activities and economic benefits under conventional tillage (Control, CT), no-tillage without stover mulching (NT0), no-tillage with 33% stover mulching (NT33), no-tillage with 67% stover mulching (NT67), and no-tillage with 100% stover mulching (NT100) before planting in May 2020. The results showed that compared with CT, NT0 did not affect soil organic carbon (SOC) and total nitrogen (TN) contents, but increased soil organic carbon recalcitrance and decreased the availability of dissolved organic nitrogen (DON) and ammonium nitrogen. Compared with NT0, no-tillage with stover mulching significantly increased SOC contents in 0-10 cm layer and increased with the amounts of stover. In addition, NT67 and NT100 significantly increased SOC stocks, facilitating the accumulation of soil organic matter. The effects of different stover mulching amounts on soil nitrogen content in 0-10 cm layer were different. Specifically, NT33 increased DON content and DON/TN, NT67 increased DON content, while NT100 increased TN content. Compared with CT, NT0 decreased peroxidase (POD) activity in 0-10 cm layer. Compared with NT0, NT33 increased β-glucosidase (βG), cellobiase (CB), 1,4-β-N-acetylglucosaminidase (NAG), polyphenol oxidase (PPO) and POD activities, while NT67 only increased CB, NAG and POD activities in 0-10 cm soil layer, both alleviated microbial nutrient limitation. NT100 increased PPO activity in 10-20 cm layer. NT33 increased carbon conversion efficiency of stover compared with NT100, and had the highest economic benefit. In all, no-tillage with 33% stover mulching was the optimal strategy, which could promote nutrient circulation, boost stover utilization efficiency, improve the quality of Mollisols, and maximize guaranteed income.

Stover mulching in no-tillage farming reduces ammonia volatilization in the Mollisol of Northeast China: Insights from gross N transformation dynamics

Ammonia (NH3) volatilization, a critical pathway of nitrogen (N) loss in agroecosystems, is closely regulated by ammonium (NH4+-N) availability and associated NH4+-N transformation dynamics in soil. To determine the effect of no-tillage and crop stover retention on soil internal gross N transformation and further NH3 volatilization in the long-term conservation tillage (CT) agroecosystem, a combination of 15N-tracing field monitoring and paired 15N-labeled incubation experiments was simultaneously conducted on a 9-year maize cropping system in the Mollisol of Northeast China. Three treatments were set up: traditional ridge tillage (RT), no-tillage with maize stover removal (NT0), and no-tillage with full harvest (ca. 7500 kg ha−1 yr−1) maize stover mulching (NTS). It was found that NH3 volatilization in the experimental Mollisol primarily occurred within 7 days after fertilization. Given that the paired gross NH4+-N transformation dynamics were considered in terms of the mutual production-consumption processes, the low fertilizer-derived NH3 volatilization was mainly attributed to a high gross N transformation rate combined with a low net N transformation rate for all treated plots, indicating that there was a rapid internal NH4+-N turnover in the studied Mollisols. Additionally, no-tillage with maize stover mulching considerably reduced NH3 emissions by 17% compared with RT treatment, and the inhibitory effect was primarily owing to the synchronized stimulation of biotic mineralization-immobilization and abiotic adsorption-release turnover in the CT agroecosystem. These findings suggest that long-term no-tillage with maize stover mulching could be a sustainable management strategy for improving soil NH4+-N retention and mitigating NH3 losses in the Mollisol of Northeast China.

Effects of frequency and amount of stover mulching on the microbial community composition and structure in the endosphere and rhizosphere.

Stover mulching, as a sustainable agricultural conservation practice, has been shown to effectively increase soil organic matter and enhance crop yields. The impact of stover mulching on soil microorganisms has been extensively studied. However, less attention has been given to endophytic and rhizospheric microorganisms that have closer relationships with crops. How do the quality and frequency of stover mulching affect the composition and structure of these endosphere and rhizosphere microbial communities? And what is their influence on critical indicators of soil health such as bacterial plant pathogen and Rhizobiales? These questions remain unresolved. Therefore, we investigated the responses of the microbial functional guilds in the endosphere and rhizosphere to maize stover mulching qualities (0%, 33%, 67%, and total stover mulching every year) and frequencies (once every 3 years and twice every 3 years) under 10-year no-till management. Results showed significant correlations between Bacillales and Rhizobiales orders and soil SOC, NO3-N, and NH4+N; Hypocreales and Eurotiales orders were significantly correlated with soil NO3-N, with the Aspergillus genus also showing a significant correlation with soil SOC. The frequency and quality of stover mulching had a significant effect on root and rhizospheric microbial communities, with the lowest relative abundance of bacterial plant pathogens and highest relative abundance of nitrogen-fixing bacteria such as Rhizobiales and Hypocreales observed under F1/3 and F2/3 conditions. The most complex structures in endosphere and rhizospheric microbial communities were found under Q33 and Q67 conditions, respectively. This research indicates that from a soil health perspective, low-frequency high-coverage stover mulching is beneficial for the composition of endosphere and rhizosphere microbial communities, while moderate coverage levels are conducive to more complex structures within these communities. This study holds significant ecological implications for agricultural production and crop protection.

High leaching potential combined with a low leaching amount of fertilizer-derived nitrate in conservation tillage cropland of Northeast China

Stover mulching in no-tillage farming has been widely proposed as an optimized agricultural management practice to increase soil carbon storage and improve fertilizer nitrogen (N) use efficiency in current agroecosystems. However, the regulation of soil internal gross N transformation dynamics on NO3−-N leaching potential in response to long-term conservation tillage practices is still lacking. Here, based on a combination of 15N-tracing incubation and in situ monitoring experiments, we investigated the effect of 9-year no-tillage and maize stover mulching on the vertical migration of fertilizer-derived NO3−-N into a deeper soil profile and the associated gross NO3−-N transformation dynamics in the Mollisol of Northeast China. The net positive NO3−-N production rates (varied from 3.14 to 6.22 mg N kg−1 d−1) were observed across all management practices in the studied Mollisol, indicating a relatively high NO3−-N leaching potential in the cropland of Northeast China, which was further confirmed by an average of 7.4 % fertilizer-derived NO3−-N being vertically transferred to the 80–100 cm soil layer after a complete maize growing period. Compared with traditional ridge tillage, long-term stover mulching in no-tillage farming significantly reduced total NO3−-N production by decreasing autotrophic nitrification while simultaneously enhancing total NO3−-N consumption by stimulating nitrate reduction and microbial NO3−-N immobilization, revealing a markedly reduction of net NO3−-N production in the no-tillage agroecosystem. Therefore, converting traditional ridge tillage toward no-tillage with maize stover mulching can effectively decrease fertilizer-derived NO3−-N leaching amounts and thus formulate targeted mitigation strategies for sustainable agriculture in Mollisols of Northeast China.

Reduction of NH3 Emissions from Urea by Long-Term No-Tillage and Stover Mulching with Inhibitors: An Isotopic Field Study in Northeast China

Large nitrogen (N) losses during fertilization in agricultural production may result in energy wastage, soil and water contamination, and potentially influence crop development. Thus, with the help of a 15N-labeled tracer, we carried out a field monitoring analysis of NH3 emissions in a long-term (9-year) conservation tillage agroecosystem of Mollisols in northeast China, in order to determine whether a no-tillage regime and four levels of stover mulching (0%, 33%, 67%, and 100%), combined with urease and nitrification inhibitors, could improve fertilizer utilization efficiency in agricultural systems by reducing ammonia volatilization. Our results showed that in comparison with ridge tillage, no-tillage with stover mulching levels of 33%, 67%, and 100% significantly reduced NH3 emission rates and cumulative volatilization from 159.67 to 130.42 g N ha−1 and 15N-NH3 cumulative volatilization emission by 26% (on average). Furthermore, the application of urease and nitrification inhibitors significantly reduced 15N-NH3 volatilization levels from 1.19 to 0.98 g N ha−1. Our research results demonstrate that a long-term no-tillage regime and straw mulching can significantly reduce NH3 volatilization in fertilizers. Furthermore, when combined with the use of urease and nitrification inhibitors, these practices further enhance the reduction in NH3 volatilization. Although the volatilization of 15N-NH3 is minimally studied in Mollisols, these findings provide a solid foundation for improving fertilizer utilization efficiency, reducing crop production costs and mitigating subsequent environmental pollution.

Organic Mulching Effects on Water Productivity, Soil Temperature, Growth and Yield of Lentil Varieties

The experiment was conducted at College of Post Graduate Studies in Agricultural Sciences, Umiam, Meghalaya during the rabi season (November–April, 2022) to study the effect of organic mulching on growth, yield and water productivity of lentil varieties in mid-hills of Meghalaya. The experiment was carried out in split plot design with four mulch treatment under main plot (M0: un-mulch/control, M1: paddy straw mulch, M2: maize stover mulch, M3: weed mulch) and four varietal treatments under sub plot (V1: HUL-57, V2: PL-4, V3: PDL-1 and V4: PSL-9) which were replicated thrice. Results indicated that, plant height, number of branches plant-1, water productivity were highest under paddy straw mulch. Paddy straw mulch (43.57) which was on par with weed mulch (41.29) has reported significantly highest number of pods plant-1 over maize stover mulch (38.18) and un-mulch (36.21) treatments. Different mulches have reported economic yield advantage of 21.01% to 10.55% over the control. Water productivity has found significantly higher under paddy straw mulch (3.25 kg ha-1 mm-1) over the control treatment (2.57 kg ha-1 mm-1). Mulches also modified soil thermal regimes and effected plant growth and development. Soil temperature has shown increasing trend towards the end of crop season, since, air temperatures are increasing towards the end of growing season. Paddy straw mulch, weed mulch and maize stover mulch increased 2.31oC, 1.88oC, 0.27oC temperature, respectively, over the control during morning hours.

Conservation Tillage in Medicinal Plant Cultivation in China: What, Why, and How

Ecological cultivation is a promising regime for medicinal plant production. For a long time, unreasonable farming methods have threatened soil health and medicinal agriculture and restricted the sustainable development of ecological agriculture for medicinal plants. However, there is a lack of comprehensive discourse and discussion about the pros and cons of different tillage regimes. Here, the research trend and application prospects of no-tillage (NT) are comprehensively reviewed, and the ecological benefits, challenges, and opportunities of the NT system in ecological agriculture of medicinal plants are scrutinized, aiming to call for an about-face in the sustainable conservation and utilization of both phytomedicine resources and agricultural/ecological resources. An exhaustive literature search in PubMed, Bing, Scopus, and CNKI was performed to outline the research trend in conservation tillage and medicinal plants during the recent four decades. The application of NT has a long history and can reduce tillage frequency and intensity and protect soil from erosion and deterioration. NT is often combined with organic mulch to significantly reduce soil disturbance. NT and stover mulching have the advantages of saving manpower and resources and improving soil quality, crop yield, and quality. The ecological and economic benefits of NT in long-term medicinal plant cultivation could be prominent. In developing medicinal plant cultivation, competing with food crops should be avoided as much as possible, and the impact on the production of major grain crops should be minimized. Therefore, the full utilization of soil resources in forests, mountains, and wasteland is advocated, and sustainable soil utilization is the core issue in the process of land reclamation. NT and stover mulching not only inherit the traditional concept of “natural farming”, conform to the basic laws of ecology, as well as the growth characteristics of medicinal plants, but also protect the ecological environment of the production area. It would become the core strategy of ecological agriculture for medicinal plants. Our summary and discussions would help propose countermeasures to popularize NT and organic mulch, promote relevant research and scientific allocation of resources, and adapt to local conditions to achieve precise management and harmonize conservation and production of medicinal plants.

Effects of tillage patterns and stover mulching on N2O production, nitrogen cycling genes and microbial dynamics in black soil

Stover-covered no-tillage (NT) is of great significance to the rational utilization of stover resources and improvement of cultivated land quality, and also has a profound impact on ensuring groundwater, food and ecosystem security. However, the effects of tillage patterns and stover mulching on soil nitrogen turnover remain elusive. Based on the long-term conservation tillage field experiment in the mollisol area of Northeast China since 2007, the shotgun metagenomic sequencing of soils and microcosm incubation were combined with physical and chemical analyses, alkyne inhibition analysis to elucidate the regulatory mechanisms of NT and stover mulching on the farmland soil nitrogen emissions and microbial nitrogen cycling genes. Compared with conventional tillage (CT), NT stover mulching significantly reduced the emission of N2O instead of CO2, especially when 33% mulching was adopted, and correspondingly the nitrate nitrogen of NT33 was higher than that of other mulching amounts. The stover mulching was associated with higher total nitrogen, soil organic carbon and pH. The abundance of AOB (ammonia-oxidizing bacteria)-amoA (ammonia monooxygenase subunit A) was substantially increased by stover mulching, while the abundance of denitrification genes was reduced in most cases. Under alkyne inhibition, the tillage mode, treatment time, gas condition and interactions between them noticeably influenced the N2O emission and nitrogen transformation. In CT, NT0 (no mulching) and NT100 (full mulching), the relative contribution of AOB to N2O production was markedly higher than that of ammonia oxidizing archaea. Different tillage modes were associated with distinct microbial community composition, albeit NT100 was closer to CT than to NT0. Compared with CT, the co-occurrence network of microbial communities was more complex in NT0 and NT100. Our findings suggest that maintaining a low-quantity stover mulching could regulate soil nitrogen turnover toward proficiently enhancing soil health and regenerative agriculture, and coping with global climate change.

Effects of no-tillage and different stover mulching amounts on soil microbial community and microbial residue in the Mollisols of China.

To investigate the effects of no-tillage and different amounts of stover mulch on soil microbial community composition and their residues, we set up a field experiment of different amounts of stover mulch under no-tillage on the long-term maize conservation tillage station located in the Mollisols area of Northeast China (built in 2007), including without stover mulch (NT0), 1/3 stover mulch (NT1/3), 2/3 stover mulch (NT2/3) and full stover mulch (NT3/3), and the conservation tillage (plowing without stover mulch, CT) as control. We analyzed phospholipid fatty acid, amino sugar biomarker and soil physicochemical properties at different soil layers (0-5 cm, 5-10 cm, 10-20 cm). The results showed that compared to CT, no-tillage without stover mulch (NT0) did not affect soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon and nitrogen (DOC, DON), water content, microbial community and their residue. The main effects of no-tillage and stover mulch were found in the topsoil. Specifically, the NT1/3, NT2/3 and NT3/3 significantly increased SOC content by 27.2%, 34.1% and 35.6%, respectively, phospholipid fatty acid content was significantly increased under NT2/3 and NT3/3 by 39.2% and 65.0%, respectively, and NT3/3 significantly increased the content of microbial residue-amino sugar by 47.2% in the depth of 0-5 cm compared with CT. The variations in soil properties and microbial community induced by no-tillage and different amounts stover mulch decreased with soil depth, with almost no difference in the 5-20 cm soil layer. SOC, TN, DOC, DON, and water content were the main factors influencing the composition of the microbial community and the accumulation of microbial residue. Microbial biomass was positively correlated with microbial residue, particularly fungal residue. In conclusion, all stover mulch treatments promoted SOC accumulation to different degrees. When there is sufficient stover, it is advisable to opt for no-tillage with full stover mulch, as it is most conducive to the increases of soil microbial biomass, microbial residue and SOC. In case when the amount of stover is inadequate, however, no-tillage with 2/3 stover mulch can still improve soil microbial biomass and SOC content. This study would provide practical guidance for stover management in conservation tillage and sustainable agricultural development in the Mollisols area of Northeast China.

Mechanisms of conservation tillage on nitrogen-fertilizer reduction and maize grain improvement in Mollisols of Northeast China: Insights from a 15N tracing study.

Conservation tillage is an important management practice to guarantee soil fertility in degraded Mollisols. It is still unclear, however, whether the improvement and stability of crop yield under conservation tillage can be sustainable with increasing soil fertility and reducing fertilizer-N application. Based on a long-term tillage experiment initiated in Lishu Conservation Tillage Research and Development Station by Chinese Academy of Sciences, we conducted a 15N tracing field micro-plot experiment to investigate the effects of reducing nitrogen application on maize yield and fertilizer-N transformation under long-term conservation tillage agroecosystem. There were four treatments, including conventional ridge tillage (RT), no-tillage with 0% (NT0), 100% (NTS) maize straw mul-ching, and 20% reduced fertilizer-N plus 100% maize stover mulching (RNTS). The results showed that after a complete cultivation round, the average percentages of fertilizer N recovery in soil residues, crop usage, and gaseous loss were 34%, 50%, and 16%, respectively. Compared with conventional ridge tillage, no-tillage with maize straw mulching (NTS and RNTS) significantly increased the use efficiency of fertilizer N in current season by 10% to 14%. From the perspective of N sourcing analysis, the average percentage of fertilizer N absorbed by crop parts (including seeds, straws, roots, and cobs) to the total N uptake reached nearly 40%, indicating that soil N pool was the main source of N for crop uptakes. In comparison with conventional ridge tillage, conservation tillage significantly increased total N storage in 0-40 cm by reducing soil disturbance and increasing organic inputs, and thus ensured the expansion and efficiency increment of soil N pool in degraded Mollisols. Compared with conventional ridge tillage, NTS and RNTS treatments significantly increased the maize yield from 2016 to 2018. In all, by improving fertilizer nitrogen utilization efficiency and maintaining the continuous supply of soil nitrogen, long-term management of no-tillage with maize straw mulching could achieve a stable and increasing maize yield in three consecutive growing seasons and simultaneously reduce environmental risks derived by fertilizer-N losses, even under the condition of 20% reduction of fertilizer-N application, and thus actualize the sustainable development of agriculture in Mollisols of Northeast China.

Soil microbial necromass regulation of long-term fertilizer N retention influenced by maize stover mulching

Microbial immobilization of nitrogen (N) fertilizer is critical for N retention in soils and is mainly influenced by agricultural management, including crop residue return. However, the underlying relationship between microbially mediated processes and long-term fertilizer N dynamics has not been characterized well in arable soil. Here, by tracing in situ the temporal changes of soil amino sugars initially synthesized from the 15N fertilizer applied in the 1st year, we investigated the dynamic contribution of microbial necromass to long-term fertilizer N retention in soil influenced by maize stove mulching. After the 1st year of fertilizer application, microbial necromass contributed to 36.3–43.9 % of the remaining fertilizer N in the topsoil (0–10 cm), but the remaining fertilizer N in the subsoil (10–20 cm) was predominantly attributed to microbial necromass accumulation, regardless of maize stover mulching. During the following 9 years, the fertilizer-derived microbial necromass N decreased at a slower rate (42.3–52.8 %) than the remaining fertilizer N (73.5–76.7 %) in the topsoil layer, while the former decreased synchronously with the latter in the subsoil layer, indicating that microbial necromass played a critical role in long-term fertilizer N stabilization though it could serve as a transitional N pool for N supply. For the microbial necromass of different origin, the residence time of fertilizer N in fungal necromass (34.7–48.7 y) was longer than that in the bacterial necromass pool (21.4–27.1 y) in the cultivated soil layer (0–20 cm), explicitly indicating that the retention of fungal necromass was inclined to contribute to long-term fertilizer N stabilization while bacterial necromass was associated with fertilizer N turnover. Compared with fertilizer application alone, maize stover mulching enhanced the initial fertilizer N retention by increasing microbial necromass accumulation but had no influence on the subsequent dynamics of both the remaining fertilizer N and fertilizer-derived microbial necromass N, thus improving long-term fertilizer N retention. Specifically, maize stover mulching increased the stability of microbial necromass N by enhancing the retention and prolonging the residence time of fungal necromass over bacterial necromass, thus improving the contribution of microbial necromass to the long-term stabilization of fertilizer N in the cultivated soil.

Effects of different mulching materials on yield and yield components of maize (Zea mays L.)

Two field experiments were conducted during dry season (October, 2019 to March, 2020) at Yezin Agricultural University farm and Sepin research farm, Yamethin, Myanmar to investigate the effect of different mulching materials on yield and yield components of maize. No mulching and six mulching materials (rice straw mulching, rice husk mulching, maize stover mulching, mung bean stover mulching, soybean stover mulching and white plastic polyethylene mulching) were laid in a Randomized Complete Block Design (RCB) with three replications on NK-621 variety. The longest days to 50% tasseling (69.67) at Yezin and (71.67) at Yamethin were obtained in no mulching while the shortest days to 50% tasseling (62.00) at Yezin and (64.33) at Yamethin were observed from rice straw mulching at Yezin and white plastic polyethylene mulching at Yamethin. Number of kernel row-1, rows ear-1, row length, kernels ear-1, thousand grains weight were significantly different among different mulching materials at Yezin. The maximum grain yield (5.72 ton ha-1) and (10.39 ton ha-1) were observed from rice straw mulching at Yezin and Yamethin. According to the results, rice straw mulching resulted in the highest yield and yield components of maize at two locations.

Effects of corn straw cover years on soil organic matter and compactness in typical black soil areas of Songnen Plain

China is a huge agricultural country with rich straw resources. However, the problem to be solved urgently is to find means to use crop straw effectively and reasonably. To study the influence of no-tillage straw mulching measures on soil compactness and soil organic matter, taking the black soil straw mulching no-tillage test field in Gaojia Village, Lishu County, Jilin Province as the research object, the characteristics of soil compactness and organic matter in different tillage layers under different cover years of no-till straw are discussed. The results show the following: (1) in the 0–50 cm tillage layer, the highest treatment method of soil organic matter is NT1 (no-tillage corn stover mulching for one year), with an average value of 2.62%, and the soil organic matter content of NT1 treatment increased by 57.46% compared with RT (ridge tillage). (2) The compactness of surface soil (0–20 cm) no-tillage soil is higher than RT, with an increase of more than 6.87%, and the compactness of deep soil (20–50 cm) no-tillage soil is lower than RT, with a decrease of more than 23.48%. (3) No-tillage can improve the agglomeration structure of the surface soil, increase the moisture content of the surface soil, reduce the volume of the surface soil, and improve the organic matter content of the surface soil, thus increasing the firmness of the surface soil. This study can provide a theoretical basis for promoting the comprehensive utilization of straw resources and developing eco-agriculture.

Mulching as soil moisture conservation to improve physiological traits in maize (Zea mays L.)

Field experiments were conducted at Yezin farm and Sepin research farm, Yamethin, Myanmar to study the effect of different mulching materials on percent reduction of soil moisture content and physiological traits in Yezin and Yamethin. Randomized complete block design (RCB) was used with three replications from October, 2019 to March, 2020. Rice straw mulching (T2), rice husk mulching (T3), maize stover mulching (T4), mung bean stover mulching (T5), soybean stover mulching (T6) and white plastic polyethylene mulching (T7) and no mulching (T1) were tested with NK-621, variety. At Yezin, the minimum percent reduction of soil moisture content (45.89) was obtained from T2 and (76.79, 58.07) was resulted in T7 whereas the maximum percent reduction of soil moisture contents (76.93, 89.00, 83.93) were recorded from T1 at 14 DAI (Days after irrigation). At tasseling stage, the maximum photosynthesis rates (20.45 µmol m-2s-1) and (21.59 µmol m-2s-1) were observed from T2 at Yezin and Yamethin. At two locations, the maximum stomatal conductance (158.36 mmol m-2s-1) and (204.44 mmol m-2s-1) was observed from T2 at maximum growth stage. At maximum growth stage, the maximum SPAD values (33.90) and (53.98) were obtained from T6 at Yezin and T2 at Yamethin. The maximum five ears weight (1830.6 g) was recorded from rice straw mulching whereas the minimum five ears weight (1326.0 g) was resulted from no mulching at Yamethin. According to the results, rice straw mulching resulted in the highest physiological traits of maize, and white plastic polyethylene mulching recorded the minimum percent reduction of soil moisture content at Yezin and maize stover mulching at Yamethin.

Estimating soil water evaporation as influenced by “dry-and green-mulch” cover beneath maize canopy

Soil evaporation reduction can improve rainfed crop production in semi-arid climates. The purpose of this study was to develop empirical models to estimate cumulative soil evaporation (∑Es) from a maize field across the basin and runoff area (BA and RA) of the in-field rainwater harvesting (IRWH) technique as influenced by different levels of stover mulch ("dry-mulch") and canopy shading ("green-mulch"). Soil water evaporation (Es) was measured with micro-lysimeters 300 mm deep and 71 mm in diameter in the BA and RA sections for three consecutive drying cycles. Four different runoff strip lengths, RSL (RSL-1, 1.5, 2 and 3m) and three mulching levels (ML) of bare, 39%, and 96% were used to estimate the Es. The coefficient crop cover (Kcover) values for full and partial canopy shade (FC and PC) on the RA were in the range of 0.46–0.97 and 0.43–0.94, respectively, while in the BA the Kcover values ranged between 0.33 and 0.92. Under IRWH, the ∑Es values from a basin area beneath a maize canopy averaged 42% of the seasonal rainfall. ∑Es proportion of seasonal rainfall is about 62, 64, and 66 percent for bare soil, but as low as 28, 30 and 32 percent for FC, PC, and unshaded canopy (UC), respectively. In conclusion, the microclimate of the cropping system changes according to surface treatments, which greatly affect the Es losses for the IRWH technique and contributes to ET partitioning. Hence, reducing unproductive water losses in dryland crop production improves water use efficiency by storing more water in the root zone for transpiration.

Effects of frequency and amount of stover mulching on soil nitrogen and the microbial functional guilds of the endosphere and rhizosphere.

Stover mulching as a conservation and sustainable agricultural practice is beneficial for maintaining soil nitrogen (N) requirements and plant health. The microbial functional guilds of the root and rhizosphere are important factors in the soil nitrogen cycle. However, it is unclear how the frequency and amount of stover mulching influence microbial functional guilds in the root and rhizosphere. Therefore, we investigated the responses of the microbial functional guilds in the endosphere and rhizosphere to maize stover mulching amounts (0, 1/3, 2/3, and total stover mulching every year) and frequencies (once every 3 years and twice every 3 years) under 10-year no-till management. The bacterial functional guilds of nitrogen fixation, nitrification, and anaerobic nitrate oxidation displayed the significantly correlation with C/N, total nitrogen, NO3−, and NH4+. The fungal functional guilds of plant pathogens and saprotrophs showed significantly correlations with C/N, total nitrogen, and NO3−. Moreover, we found that bacterial guilds play a pivotal role in maintaining N requirements at the jointing stage, whereas root endophytic fungal guilds play a more important role than bacterial guilds in regulating plant health at the mature stage. The frequency and amount of stover mulching had significant effects on the microbial functional guilds in the root and rhizosphere. Our data suggest that stover mulch application twice every 3 years is the optimal mulching frequency because it yielded the lowest abundance of nitrifying and anaerobic nitrate-oxidising bacteria and the highest abundance of nitrogen-fixing bacteria at the jointing stage, as well as the lowest abundance of fungal plant pathogens in roots at the mature stage.

Performance of different mulching materials on soil moisture content, weed infestation and growth of maize (Zea mays L.)

Two field experiments were conducted at Yezin farm and Sepin research farm, Yamenthin, Myanmar to investigate the effect of different mulching materials on growth, soil moisture and weed infestation of maize and to identify the most
 Two field experiments were conducted at Yezin and Sepin research farms, Yamethin, Myanmar to investigate the effect of different mulching materials on growth, soil moisture and weed infestation of maize and to identify the most suitable mulching materials for maize cultivation in the study areas during the dry season (October, 2019 to March, 2020). The experiments used randomized complete block design (RCB) with three replications. No mulching and six mulching materials, including rice straw mulching, rice husk mulching, maize stover mulching, mung bean stover mulching, soybean stover mulching and white plastic polyethylene mulching were tested. NK-621 (120 days) was used as the tested variety. Different mulching materials showed higher plant height and SPAD value than no mulching whereas rice straw mulching was highest at both locations. The highest LAI was achieved from rice straw mulching at Yezin. At Yamethin, the maximum LAI (2.19) was recorded from rice straw mulching at maximum growth stage (MGS), LAI (2.71) observed from maize stover mulching at tasseling stage (TS). The maximum crop growth rate (CGR) (13.31 gm-2day-1) was achieved from rice straw mulching at Yezin and (14.19 gm-2day-1) at Yamethin. Soil moisture content and weed infestation were significantly different among different mulching materials at two locations. White plastic polyethylene mulching and rice straw mulching were observed as the most suitable for soil moisture content and minimal weed infestation. According to the results, rice straw mulching is the best in all parameters among the treatments for Yezin and Yamethin areas.
 suitable mulching materials for maize cultivation in the study areas during the dry season (October, 2019 to March, 2020). The experiments were assigned by using randomized complete block design (RCB) with three replications. A total of seven treatment; no mulching (T1) and six mulching materials including rice straw mulching (T2), rice husk mulching (T3), maize stover mulching (T4), mung bean stover mulching (T5), soybean stover mulching (T6) and white plastic polyethylene mulching (T7) were tested. The most widely sown variety, NK-621 (120 days) was used as the tested variety. Different mulching materials showed higher plant height and SPAD value than no mulching whereas rice straw mulching (T2) was highest at both locations. At three sampling times, the highest LAI was achieved from rice straw mulching (T2) at Yezin. At Yamenthin, the maximum LAI (2.19) was recorded from rice straw mulching at maximum growth stage (MGS), LAI (2.71) observed from maize stover mulching (T4) at tasseling stage (TS) and LAI (2.00) achieved from white plastic polyethylene mulching (T7) at grain filling stage (GFS). The maximum crop growth rate (CGR) (13.31 gm-2day-1) was achieved from rice straw mulching (T2) at Yezin and (14.19 gm-2day-1) at Yamenthin. Soil moisture content and weed infestation were significantly different among different mulching materials at two locations. White plastic polyethylene mulching and rice straw mulching were observed as the most suitable for soil moisture content and minimal weed infestation. According to the results, rice straw mulching is the best in all parameters among the treatments for Yezin and Yamenthin areas.

Effects of long-term no-tillage and stover mulching on maize yield and its stability.

Clarifying the differences of maize yield and its stability under long-term no-tillage with different stover mulching amounts can provide theoretical and technical supports for establishing and evaluating long-term conservation tillage pattern and promoting grain production. Based on a long-term conservation tillage field experiment in the mollisol area of Northeast China since 2007, we analyzed the interannual variation, variation coefficient and stability of maize yield during 2013 and 2019 across five treatments, i.e., no-tillage stover-free mulching (NT0), no-tillage with 33% stover mulching (NT33), no-tillage with 67% stover mulching (NT67) and no-tillage with 100% stover mulching (NT100), with the traditional ridge cropping (RT) as the control. The results showed that compared with RT, long-term no-tillage with stover mulching treatments could increase maize yield. NT100 had the highest increasing rate of 11.4%, followed by NT67 and NT0, with the increasing rate of 11.0% and 10.4%, respectively. Maize yield exhibited a nonlinear relationship with the amount of stover mulch. The variation coefficient of maize yield under multi-year no-tillage with different stover mulching could be sorted as NT67<RT<NT100<NT33<NT0, and the yield sustainability index was NT67>NT0>NT100>RT>NT33, indicating that NT67 treatment could significantly reduce the interannual fluctuation of maize yield and had better sustainability of yield. No-tillage stover mulching significantly increased soil total carbon and total nitrogen contents, which were significantly positively correlated with maize yield. In conclusion, compared with traditional tillage, no-tillage stover mulching could increase maize yield and soil carbon and nitrogen contents. Appropriate stover mulching (NT67)had the potential to improve the stability and sustainability of maize yield.