Ditch-buried Straw Return Research Articles

Fungal Saprotrophic Promotion and Plant Pathogenic Suppression under Ditch-Buried Straw Return with Appropriate Burial Amount and Depth.

Fungi as heterotrophs are key participants in the decomposition of organic materials and the transformation of nutrients in agroecosystems. Ditch-buried straw return as a novel conservation management strategy can improve soil fertility and alter hydrothermal processes. However, how ditch-buried straw return strategies affect the soil fungal community is still unclear. Herein, a 7-year field trial was conducted to test the influences of burial depth (0, 10, 20, 30, and 40 cm) and the amount of ditch-buried straw (half, full, double) on the diversity, composition, and predicted functions of a soil fungal community, as well as the activities of carbon-degraded enzymes. Under the full amount of straw burial, the abundance of phylum Ascomycota was 7.5% higher as compared to other burial amount treatments. This further increased the activity of cellobiohydrolase by 32%, as revealed by the positive correlation between Ascomycota and cellobiohydrolase. With deeper straw burial, however, the abundance of Ascomycota and β-D-glucopyranoside activity decreased. Moreover, genus Alternaria and Fusarium increased while Mortierella decreased with straw burial amount and depth. FUNgild prediction showed that plant fungal pathogens were 1- to 2-fold higher, whilst arbuscular mycorrhizal fungi were 64% lower under straw buried with double the amount and at a depth of 40 cm. Collectively, these findings suggest that ditch-buried straw return with a full amount and buried at a depth less than 30 cm could improve soil nutrient cycles and health and may be beneficial to subsequent crop production.

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

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

Relative contribution of roots and symbiotic fungi to wheat nitrogen uptake and N2O emissions under straw burial

Ditch-buried straw return (DB-SR), as a novel soil tillage practice, has shown the yield improvement in recent studies in comparison to rotary tillage with straw return (RT-SR). However, the underlying mechanisms are not well known. One field and two greenhouse experiments were conducted to compare the effects of DB-SR on grain yield and nitrogen (N) cycling with other straw managements [RT-SR and straw removal (CK)], and to identify the relative contribution of roots and arbuscular mycorrhizal fungi (AMF) to N cycling in a wheat based cropping system. The field experiment and literature reviews showed that DB-SR can significantly improve annual yields by 19.1% and 15.5% compared with CK and RT-SR, respectively under different cropping systems. The pot experiments supported the findings of field experiments that DB-SR can improve wheat N uptake and decrease N2O emissions driven by trade-offs between AMF and roots depending on soil textures. Roots showed larger impacts in promoting N uptake for wheat and N loss from N2O emissions compared with AMF in clay soils under DB-SR. However, a contrasting pattern was detected in sandy soils where AMF improved N uptake and reduced N2O emissions. Our results highlight that trade-offs between roots and AMF under DB-SR can affect wheat N uptake, and DB-SR could be a practical measure to increase grain yield by improving N uptake and mitigate N2O emission.

Long-term ditch-buried straw return increases functionality of soil microbial communities

Ditch-buried straw return (DB-SR) is a novel soil fertility building method by combing straw incorporation and tillage rotation in rice–wheat annual double cropping system. Several benefits of DB-SR have been shown, e.g. improving carbon sequestration, nitrogen retention and soil aggregation. However, how long-term DB-SR affecting the metabolic activity and diversity of soil microbial communities is still unclear. In this study, we investigated the effects of DB-SR application after 5 years (rice season) and 5.5 years (wheat season) on functional patterns, including the overall functional activity, reflected by fluorescein diacetate hydrolase (FDA) activity, the overall growth activity, reflected by soil respiration rate, extracellular element-cycling enzyme activity, glomalin content and metabolic diversity in different soil layers. Our results first showed that DB-SR significantly increased the overall functional activity (FDA hydrolase) and growth activity (respiration rate) in 10–20 cm and 20–30 cm soils. Second, β-glucosidase, lipase, acid phosphatase and arylsulphatase activities were significantly increased by DB-SR in different soil layers. However, urease activity was only increased by DB-SR in wheat soils, but reduced in the 0–10 cm and 20–30 cm soils after growing rice. In addition, DB-SR significantly increased the content of total glomalin and easily extracted glomalin. Finally, DB-SR significantly increased microbial metabolic diversity of carbon substrates in different soil layers. Overall, the metabolic activity and diversity of microbial communities were shown with a larger increase in 10–20 cm (above the straw layer) than 0–10 cm and 20–30 cm soil layers; and tended to increase with straw burial duration. These findings suggest that the long-term application of DB-SR is helpful to drive material transformation and nutrient supply, which can further benefit crop production in rice–wheat rotation systems.

Long-term ditch-buried straw return alters soil carbon sequestration, nitrogen availability and grain production in a rice–wheat rotation system

Our previous studies indicated that ditch-buried straw return (DB-SR) can improve soil processes in the short term, i.e. increasing microbial metabolic capability, reducing nitrogen leaching loss and promoting soil aggregation. However, it remains unclear how long-term implementation of DB-SR affects soil carbon (C) and nitrogen (N) processes and crop yields. Here, the effects of DB-SR on soil C pool and N availability as well as grain yields were investigated after consecutive application of 6 (rice season) and 6.5 years (wheat season). We found that long-term DB-SR significantly increased rice yields, total organic C, NH4+ and NO3– in the rice soils, as well as enhanced wheat yields, microbial biomass C, microbial biomass N, microbial biomass C/total organic C ratio and microbial biomass C/N ratio, but reduced NH4+ and NO3– in the wheat soils when compared with rotary tillage straw return (RT-SR) and no tillage with straw removal (NT-NS). These findings suggest that long-term DB-SR application has positive effects on grain production, but possibly through different mechanisms in improving soil processes. The yield-increasing effects on rice might result from improvements in soil fertility, whereas increased wheat yields can be ascribed to stimulated soil microbial activity.

Long term ditch-buried straw return affects soil fungal community structure and carbon-degrading enzymatic activities in a rice-wheat rotation system

As a novel soil tillage practice to build fertility, ditch-buried straw return (DBSR) can affect soil carbon sequestration, nitrogen availability and hydrothermal processes in rice-wheat rotation systems. However, it is still not well-known how DBSR influences soil fungal community. A 6.5-year's field experiment was conducted to test the effects of DBSR on soil fungal community via comparing with rotary tillage straw return (RTSR) and no tillage with no straw (NTNS). Our results showed that soil fungal species composition under DBSR was significantly different from NTNS and RTSR. Also, DBSR showed distinctive impacts on soil fungal composition at the order level. DBSR significantly increased Shannon diversity index and evenness, decreased dominance, but did not affect species richness. Moreover, DBSR significantly increased the abundance of symbiotrophic fungi, but reduced the abundance of pathotrophic fungi. Especially, DBSR largely increased the abundance ratio of arbuscular mycorrhizal fungi to plant fungal pathogens. DBSR significantly reduced β-D-glucosidase activity but increased peroxidase activity while RTSR increased both cellobiohydrolase and peroxidase activity. Our results suggest that long term ditch-buried straw return can structure a unique soil fungal community from that of RTSR and NTNS, increase soil fungal diversity and promote the dominance of beneficial fungi over soil-borne plant fungal pathogens. These findings can provide solid evidence for future large-scale extension of ditch-buried straw return in practical agriculture.

Mycorrhizal nitrogen uptake of wheat is increased by earthworm activity only under no-till and straw removal conditions

A large part of crop nutrient uptake occurs through the interaction of roots with symbiotic arbuscular mycorrhizal fungi (AMF). However, it is still an open question how straw management and earthworm activity affect AMF community structure and their nitrogen-transferring function in wheat. A split-plot field experiment was conducted to address this question. Three straw management regimes including different tillage treatments (no-till with no straw, NTNS; rotary tillage with straw return, RTSR and ditch-buried straw return, DBSR), and two earthworm treatments (no earthworm, −E; and earthworm addition, +E) were conducted. The AMF community structure in the wheat roots was characterized with high-throughput sequencing, and its function in terms of N acquisition was measured with 15N isotope tracing through hyphal in-growth cores. Our results showed that both the DBSR and RTSR treatments significantly changed AMF community composition and enhanced the mycorrhiza-mediated plant N uptake when compared to NTNS. The effect of earthworm activity on AMF community composition and mycorrhiza-mediated N uptake strongly depended on the straw management regimes. While earthworm presence increased AMF dominance (+32.9%) and mycorrhizal N uptake (+2.05-fold) under straw removal, they decreased AMF dominance (−30.4% and −41.9% respectively) and mycorrhizal N uptake (−37.3% and −34.3% respectively) under both DBSR and RTSR treatments in comparison with the absence of earthworms. It is concluded that straw addition shifts the AMF community structure and increases N uptake by the host plants; and that the effect of earthworms on AMF community structure and functioning depends on the straw management regime. The results suggest that straw management and its interaction with earthworms can affect mycorrhiza-mediated plant N uptake, possibly through altering some dominant AMF taxa.

The impacts of ditch-buried straw layers on the interface soil physicochemical and microbial properties in a rice-wheat rotation system

Ditch-buried straw return (DB-SR) is a novel soil tillage and fertility-building practice, which may allow for the formation of a straw layer structure in rice–wheat rotation systems. However, it is presently unknown how the straw layer affects soil physicochemical and microbial processes in the interface between straw layer and bulk soils. Thus, we conducted a field experiment from 2008 to 2014 to determine whether there were changes in soil structure, temperature, available nitrogen, and microbial properties in the soil layer close to the straw layers (± 5 cm). Three treatments were included: control with no-till and straw removal (CK), ditch-buried straw return to a depth of 20 cm (DB-SR-20), and ditch-buried straw return to a depth of 40 cm (DB-SR-40). Our results showed that soil macroaggregate formation was increased with the duration of straw return in the soils 5 cm below the straw layers under DB-SR-20 and above the straw layers under DB-SR-40. The straw layers could significantly increase soil temperature below the straw layers, but a larger increase was observed for DB-SR-40 than DB-SR-20. We also found that DB-SR-20 largely increased the NH4+ concentration in both the soil layers above and below the straw layers, but DB-SR-40 only increased NO3− in the soils above the straw layers. In addition, the catabolic profile of soil microbial communities was largely affected by the straw layers, but the effects decreased with the duration of the treatment. These findings suggest that the straw layer largely alters the spatio-temporal processes of physicochemical and microbial properties in the interface soils after long-term implementation of ditch-buried straw return. Some of the positive alterations may cascade to facilitate crop growth and enhance the productivity of rice-wheat rotation systems.

Combined ditch buried straw return technology in a ridge–furrow plastic film mulch system: Implications for crop yield and soil organic matter dynamics

A ridge–furrow plastic film mulch (RP) configuration can increase crop and straw yields in semiarid areas of China. This study advocated for a novel soil tillage practice (ditch buried straw return) in a ridge–furrow plastic film mulch system. There were three treatments: (i) flat cultivation, CK; (ii) ridge–furrow plastic film mulch with no straw return (RP−S); and (iii) ridge–furrow plastic film mulch with ditch buried straw return (RP+S). Field experiments were conducted from 2015 to 2018 on the Loess Plateau of China to study the effects of straw incorporation on maize growth, biomass, water use efficiency, soil organic carbon, and total nitrogen sequestration capacity in RP systems. The mean rate of straw decomposition in RP+S reached 81 % at harvest of each year. The RP systems provided suitable hydrothermal conditions for maize growth. Both RP treatments promoted maize growth, particularly biomass accumulation and plant height under RP+S. The RP+S treatment also had greater concentrations of soil organic carbon and total nitrogen in surface soil at harvest, higher total nitrogen accumulation, nitrogen content and crude protein in maize grain, and higher maize yields and water use efficiencies than the other two treatments. In summary, the introduction of ditch buried straw return to RP is an effective measure for promoting the sustainable development of film mulching systems in semiarid regions of China by improving soil fertility and increasing crop yields.

Waterlogging reduction and wheat yield increase through long-term ditch-buried straw return in a rice—wheat rotation system

Waterlogging stress and rice residue management are two major problems for wheat production in rice-wheat rotation systems. Ditch-buried rice straw return (DB-SR) is designed to incorporate all rice straw residues and has exhibited positive effects on soil carbon sequestration and nitrogen retention. However, little is known about its effects on waterlogging and wheat yield after long-term application. We therefore determined whether DB-SR could reduce waterlogging stress and increase wheat yields through a 6.5-year field experiment. We found that the straw ditches served as hidden drainage channels and could significantly reduce soil moisture content and water potential after rainfall in the wheat fields. However, the drainage effect was dependent on DB-SR burial depths. DB-SR promoted more waterlogging reduction at the depth of 40cm than 20cm. Wheat yields began to increase only after DB-SR application for four years. Our results suggest that DB-SR has the potential to solve the problems of waterlogging stress and incorporation of total rice straws, as well as simultaneously maintain or increase wheat grain yield in the rice-wheat rotation system.

Long-term ditch-buried straw return alters soil water potential, temperature, and microbial communities in a rice-wheat rotation system

As a novel soil tillage practice, ditch-buried straw return (DB-SR) has exhibited positive effects on soil carbon sequestration, nitrogen retention and rice yield in previous studies. However, little is known about how long-term DB-SR affects soil hydrothermal and microbial processes. Our objective is to test whether DB-SR will alter the soil water potential, temperature and microbial community in a wheat field following rice cultivation. In this study, we found significant alterations in soil water potential, temperature, and microbial communities driven by DB-SR. On average, soil water potential was significantly reduced by 37.33% and 17.56% under DB-SR to a depth of 20cm (DB-SR-20) and 40cm (DB-SR-40), respectively. DB-SR-20 increased soil mean daily temperature and daily range of temperature more than DB-SR-40, possibly caused by decreased water content, especially at soil depths of 10 and 15cm. Both DB-SR-20 and DB-SR-40 led to distinct shifts in soil bacterial and fungal community composition. DB-SR-20 significantly increased the activities of peroxidase, cellobiohydrolase, urease, and acid phosphatase by 3.5%, 75.0%, 81.4% and 41.7%, respectively, but had no effects on β-d-glucosidase activity. DB-SR-40, in contrast, significantly increased the activities of peroxidase and cellobiohydrolase by 2.4% and 36.0%, respectively, but showed no effects on urease and acid phosphatase. It did, however, reduce β-d-glucosidase activity by 15.0%. Overall functional diversity was increased by 29.9% under DB-SR-20 but was not affected by DB-SR-40. Our results suggest that these improvements in soil ecological processes driven by DB-SR will promote wheat yield in a rice-wheat rotation system.

Soil nitrogen retention is increased by ditch-buried straw return in a rice-wheat rotation system

Ditch-buried straw return (DBSR) is a novel farming system that not only efficiently eliminates the need to burn straw, but also shows positive effects on soil carbon sequestration and crop yields. Implementation of DBSR, however, may penetrate the tillage pan, increasing the risk of N leaching losses. We therefore determined whether N retention could be increased by DBSR in order to reduce the risk of N loss to the environment. A four-year field experiment and a complementary greenhouse experiment were conducted to test the effects of DBSR on N retention in a rice-wheat rotation system. We found that DBSR altered the spatial distribution of fertilizer N. N content was significantly increased above but reduced below the straw layer in the field experiment. The greenhouse experiment further confirmed the N retention effects by the straw layer. In theory, a maximum of 9.09mg urea-N could be adsorbed by one gram dry wheat straw. Our results suggest that DBSR has the potential to increase N retention in the soil, thus increasing crop uptake and minimizing leaching N loss in the rice-wheat rotation system.

Effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system.

Crop residue management and nitrogen loss are two important environmental problems in the rice-wheat rotation system in China. This study investigated the effects of burial of straw on water percolation, nitrogen loss by leaching, crop growth and yield. Greenhouse mesocosm experiments were conducted over the course of three simulated cropping seasons in a rice1-wheat-rice2 rotation. Greater amounts of straw resulted in more water percolation, irrespective of crop season. Burial at 20 and 35 cm significantly reduced, but burial at 50 cm increased nitrogen leaching. Straw at 500 kg ha(-1) reduced, but at 1000 kg ha(-1) and at 1500 kg ha(-1) straw increased nitrogen leaching in three consecutive crop rotations. In addition, straw at 500 kg ha(-1) buried at 35 cm significantly increased yield and its components for both crops. This study suggests that N losses via leaching from the rice-wheat rotation may be reduced by the burial of the appropriate amount of straw at the appropriate depth. Greater amounts of buried straw, however, may promote nitrogen leaching and negatively affect crop growth and yields. Complementary field experiments must be performed to make specific agronomic recommendations.

Effects of ditch-buried straw return on soil organic carbon and rice yields in a rice–wheat rotation system

A novel straw return method (ditch-buried straw return, DB-SR) with a four-year field experiment was implemented to investigate the carbon sequestration effect under various burial depths and with different amounts in a rice–wheat rotation system. The DB-SR significantly increased the soil total organic carbon (TOC) and labile organic carbon (LOC) contents. In the two soil layers 10cm above and below the straw layer, the TOC and LOC levels increased. The DB-SR treatment using the total amount of straw showed higher TOC, LOC and carbon pool management index (CPMI) values than when half and twice the amount of straw were used. The rice yield was significantly higher when the total amount was used with the DB-SR to depth of 20cm than at other soil depth treatments. However, the DB-SR with twice the amount showed a negative, but not significant, effect on rice yields. These results suggest that DB-SR might be a better straw return method to increase soil organic carbon (SOC) and improve soil quality, particularly when returning the total amount of straw to a soil depth of 20cm.