Rice Rotation Research Articles

Optimal phosphorus management strategies to enhance crop productivity and soil phosphorus fertility in rapeseed–rice rotation

Optimal phosphorus (P) managements can improve the crop yield without reducing soil P supply capacity over the long term. In this study, the rapeseed–rice rotation experiments were conducted to evaluate the effect of five optimal P fertilizer managements, including the addition of RA (rooting agents), PSB (phosphate solubilizing bacteria), CMP (calcium and magnesium phosphate fertilizer), DP1 (starter P) and DP2 (foliar fertilizer) with the reduction of 40% (in the 1st rapeseed season) and 75% (in the 2nd rapeseed season) P fertilizers of farmers’ fertilizer practice (FFP) on crop productivity and soil P fertility in low and high P fertility soils. Seed yield, P partial factor productivity, and P recovery efficiency of both cultivars, Shengguang168 (SG168) and Zhongshuang 11 (ZS11), were significantly improved under optimal P managements, and the increase of them in low P fertility soil was more than that in high P fertility soil. Total P surplus was lower under optimal P managements than under FFP in both P fertility soils. The increasing amount of crop yields under optimal P managements for both cultivars was equivalent to that of 16.0–38.3 kg P2O5 hm−2 of P fertilizer application, and the order of the optimal P managements was as follows: RA > PSB > CMP > DP1 > DP2. In addition, the grain yield of rotated rice cultivar Longliangyou1212 (LLY1212) without P supply was not reduced in both fertility soils. Compared with low P fertility soil, yields of SG168, ZS11 and LLY1212 in high P fertility soil increased by 28.1%–71.7%, 28.3%–78.9% and 26.2%–47.2% at the same treatment, respectively. In summary, optimal P managements in the rapeseed season could stabilize the crop yield, promote P use efficiency and the capacity of soil P supply in the rapeseed–rice rotation, especially in low P fertility soil.

Soil hydraulic properties and field-scale hydrology as affected by land-management options

Recurring puddling for long-term rice cultivation forms a plow pan at a particular soil depth, which alters soil hydraulic properties, field-scale hydrology, and nutrient persistence in the soil. This experiment aimed to assess the impact of long-term rice cultivation on root-zone soil hydraulic properties and field-scale hydrology. Soil core samples were collected from four land management options namely, rice‒rice, non-rice, rice and non-rice, and field ridge, at two sites, one with loam and another with silt-loam soil. The soil cores were sampled for each 10 cm layer up to 100 cm depth from three locations of each rotation at both sites. Soil hydraulic parameters were estimated using a pedotransfer function based on the measured bulk density and soil texture. A mathematical model named HYDRUS-1D predicted infiltration, percolation, and surface runoff with the estimated hydraulic properties for three extreme rainfall events, i.e., 3.33, 5, and 6.66 cm hr<sup>-1</sup>, during a 3-hour period. A plow pan was found at 20–30 cm soil depth for all the land management options but not for the field ridge. The plow pan of the rice‒rice rotation had the highest bulk density (1.53 g cm<sup>-3</sup>) and the lowest hydraulic conductivity (17.56 cm day<sup>-1</sup>). However, the top 10 cm soil layer in the rice–rice field had the lowest bulk density (0.93 g cm<sup>-3</sup>). At both sites, the field ridge had higher infiltration and percolation and lower runoff than other rotations. The study reveals that the field-ridge area of a rice field can be the main water loss pathway. Phosphorus concentration in the rice-rice rotation decreased from 7.7 mg kg<sup>-1</sup> in the 10-cm soil layer to 2.49 mg kg<sup>-1</sup> in the 100-cm layer. These findings will facilitate making better water management decisions.

An appraisal of the utility of biochar in a rotation involving tobacco–rice in southern China

AbstractThe employment of biochar in crop production can not only improve soil quality, but also helps the field ecosystem to fix carbon and reduce emissions. Although the benefits of their application in crop production have been more and more confirmed, it is not clear when it comes to the acidic soil of tobacco and rice rotation. A tobacco–rice rotation experiment was conducted in southern China to probe the application value of biochar under these conditions. Three biochar application rates were employed in this experiment. BC0 (without biochar), BC25 (25 t ha−1), and BC50 (50 t ha−1). The findings show that biochar significantly boosted soil fertility and crop yields. Meanwhile, the soil organic carbon of tobacco rice rotation field with biochar increased by 31.76%. After a whole growth period of tobacco and rice, the cumulative emission reduction of CO2 and N2O from the soil by biochar were 15,944 kg ha−1 and 1810 g ha−1, respectively. The use of biochar not only significantly improved the bacterial diversity of tobacco and rice rotation soil, but also altered the original microbial community structure. The profusion of Proteobacteria and Acidobacteria was reduced and the abundance of Actinobacteria and Bacteroidetes was enhanced in the treatments with biochar. Among them, Sphingomonadales, Planctomycotes, and Ktedonobacteria, which are beneficial to plant growth and soil health, have become key phylotypes. The carbon balance analysis data show that the net carbon sequestration of the two treatments with biochar is positive, while that of the treatment without biochar is negative. In terms of economic benefit, the application of biochar increased the average of 2.055 CNY kg−1 consumed energy (CE) in the whole tobacco–rice rotation system. The ecological benefit was 0.51 kg C kg−1 CE. In conclusion, biochar can be effectively used in the practice of tobacco–rice rotation and acidic soil improvement in southern China.

Effects of Deep Plowing with a Chisel Plow Before Wheat Seeding on Rate of Soil Pulverization, Soil Physical Properties, Drainage, growth and Yield During Soybean Cultivation in an Upland Field Converted from Paddy Field with Three-Crop Rotation of Rice, Wheat, and Soybean in Two Years

Effects of Deep Plowing with a Chisel Plow Before Wheat Seeding on Rate of Soil Pulverization, Soil Physical Properties, Drainage, growth and Yield During Soybean Cultivation in an Upland Field Converted from Paddy Field with Three-Crop Rotation of Rice, Wheat, and Soybean in Two Years

SOC sequestration affected by fertilization in rice-based cropping systems over the last four decades

Enhancing soil organic carbon (SOC) stocks through fertilization and crop rotation will contribute to sustaining crop productivity and mitigating global warming. In this study, we analyzed the differences in total SOC stocks and their driving factors in the topsoil (0–20 cm) with various fertilization measures in two puddled lowland rice-based cropping systems (i.e., rice-wheat rotation and double rice rotation systems) over the last four decades from seven long-term experiments in the Yangtze River catchment. The soil types include Cambisol, Luvisol, and Anthrosol. The treatments include no fertilizer application (CK), application of chemical nitrogen, phosphorus and potassium fertilizers (NPK) and a combination of NPK and manure applications (NPKM). Every year, field was ploughed to a depth of 15–20 cm before wheat sowing and rice transplanting. Residue was removed after plant harvesting. Results showed that during the last four decades, the average crop grain yield ranged from 1,151 ± 504 kg ha−1 yr−1 under CK treatment to 7,553 ± 1,373 kg ha−1 yr−1 under NPKM treatment. The topsoil SOC stock significantly increased by 8.6 t ha−1 on average under NPKM treatment in rice-wheat system and by 2.5–6.4 t ha−1 on average under NPK and NPKM treatments in double rice system as compared with CK. A higher SOC sequestration rate and a longer SOC sequestration duration were found in NPKM treatment than that in NPK treatment in both cropping systems. The highest SOC stock ratio (SOC stock in fertilizer treatments to CK) was observed under the NPKM treatment in both cropping systems, though no significant difference was found between these two cropping systems. However, the fertilization-induced relative increase of the SOC stock was 109.5% and 45.8% under the NPK and NPKM treatments, respectively in the rice-wheat system than that in the double rice system. This indicates that the rice-wheat system is more conducive for SOC sequestration. RF and SEM analyses revealed that the magnitude and influencing factors driving SOC sequestration varied between two systems. In the double rice system, continuous flooding weakens the influence of precipitation on SOC sequestration and highlights the importance of soil properties and C input. In contrast, soil properties, C input and climate factors all have important impacts on SOC sequestration in rice-wheat system. This study reveals that the rice-wheat system is more favorable for SOC sequestration despite its lower C input compared to the double rice system in China’s paddies.

Returned straw reduces nitrogen runoff loss by influencing nitrification process through modulating soil C:N of different paddy systems

Nitrogen (N) runoff loss from paddy fields contributes significantly to non-point source pollution. Straw return to soil may affect N runoff loss by changing soil biochemistry. In situ N runoff monitoring combined with an analysis of soil biochemical indicators was implemented to explore the effect of straw return lasting for five or six years on N runoff loss and its potential mechanism in five rice rotation systems. The results showed that straw return reduced total N (TN) runoff losses by 2.29%− 26.10% through physical and biochemical pathways, and the reduction in inorganic N (IN) was the largest (53.56%–82.42%) through biochemistry. This was mainly achieved by the increase in soil C:N due to straw return, thereby increasing the immobilization of microbial N and reducing the soil IN. At the same time, the abundance of functional genes (AOA, AOB, nxrA) participating in the nitrification process was also conducive to the decrease in TN runoff concentration. More importantly, the reduction in IN and functional genes of the nitrification process did not affect N uptake by rice, and the increase in the atmospheric N fixation gene (nifH) was also beneficial to N supplementation in soil. However, the positive effects of straw return under the five rice rotation systems were different, and the TN loss reduction in double-cropping rice was the lowest. With the lower soil C:N in the single-cropping and paddy-upland systems, the increase in soil C:N after straw was more effective, and had greater potential to reduce TN runoff loss. This study provides a new perspective on N cycling in soil biochemistry by straw return, so as to select optimal measures to protect the water environment in different rice rotation systems.

Southern China can produce more high-quality rice with less N by green manuring

Green manures (GMs) are commonly used in reducing synthetic fertilizer input and mitigating environmental burden in paddy fields in China, but the contributions and comprehensive mechanisms of GMs are not illustrated clearly. We have established an experiment network of GM–rice rotation and have demonstrated extensively across eight provinces in southern China since 2008. Results from 201 site–year field experiments and the survey of GM's responses at 71 demonstration sites and 2062 farmers were collected. Compared with conventional synthetic N (CN) fertilization without GM, GM with 60% CN achieved the same level of rice yield, total amino acid concentration increased by 62.64% in the grains, and CN use efficiency increased by 15.8%, whereas the C footprint, reactive N loss, and N footprint decreased by 30.81%, 19.18%, and 9.65%, respectively. This quantitative analysis of green manuring provides support to rice production with low N input in southern China.

Stem and Sheath Diseases and Yield Response of Irrigated Rice Rotation Systems with Different Intensification Levels.

Rice cultivation in South America is undergoing several intensification processes for economic reasons that cause more rice to be planted continuously on the same soils. This intensification makes the long-term biological and economic sustainability of systems questionable. Among the most common problems that threaten sustainability in intensified systems is pest and disease pressure. In this context, the primary rice diseases were studied during a 6-year period in a long-term experiment of rice rotations established in 2012 in Uruguay. The experiment consisted of six rice rotations with other crops with different duration and intensification levels. The main disease found was stem rot and, to a lesser extent, aggregate sheath spot and sheath spot of rice. These diseases are of importance in intensified rice systems because they produce sclerotia that accumulate in soils. Disease occurrence was variable among years and rotations. Stem rot incidence increased rapidly in the experiment, reaching values close to 85% in the third year, while the severity varied each year. Sheath spot incidence and severity were low and varied with the year. Continuous rice (CR) reached the highest occurrence values for stem rot, but other systems with short pastures in rotation did not differ. Aggregate sheath spot and sheath spot were of importance only in CR and in some years. When levels of intensification were compared, systems with less time (25 to 60%) occupied with rice showed lower disease severity and higher yields. Comparing CR with rice rotation with pastures of different lengths (1 to 3 years), disease occurrence was higher in 2 of the 4 years analyzed. However, yields were consistently lower, denoting that other factors are influencing productivity. Stem and sheath diseases appear not to be a limiting factor in the medium term in intensified rice systems. Also, there are several alternatives of rice intensification incorporating crops and pastures in the rotation.

Soil microbial community structure in rice rotation systems with crops and pastures in temperate Uruguay

Rice in southern South America is mainly associated with livestock production in rotation with pastures of three to four years in length, but there is interest in intensifying production by increasing the frequency of rice, introducing new crops, or shortening the pasture in the rotation. However, little is known about the impact of this perturbation on agroecosystems resilience. In 2012, a long-term experiment was established in the main rice-producing area of Uruguay to study the impact of the intensification of rotations on the sustainability of rice systems. After one cycle, soil microbial communities were studied in six different rotations using high-throughput sequencing to compare microbial community changes after agroecosystem disturbances caused by intensification. 3662 and 807 bacterial and fungal OTUs were detected. No major differences were found in the indicators of the diversity of microbial communities between rotations. Actinobacteria, Firmicutes, and Proteobacteria were the most common bacterial phyla, but only Proteobacteria differed between rotations. Most of the fungal OTUs were not identified, but Ascomycota, and to a lesser extent, Basidiomycota, and Mucoromycota were the most abundant classes. Only P and C: N varied between rotations after six years, and bacterial OTUs were weakly influenced by P, pH, Mg, and fungal OTUs by P. The results suggest that the bacterial / archaea communities were influenced by the frequency of rice in the rotation, and the fungal communities were more influenced by the previous crop. More studies are needed to associate fungal communities with environmental or rotational variables. Some bacterial taxa were associated with a particular rotation and were identified as biomarkers. No fungal indicator taxa were identified at the species level for any rotation.

Molecular mechanism of resistance to mesosulfuron-methyl in shortawn foxtail (Alopecurus aequalis) from China

AbstractShortawn foxtail (Alopecurus aequalis Sobol.) is an obligate wetland plant that is widely distributed throughout Europe, temperate Asia, and North America. In China, it is widespread in the middle and lower reaches of the Yangtze River as a noxious weed in winter cropping fields with a rice (Oryza sativa L.) rotation. The acetolactate synthase (ALS)-inhibiting herbicide mesosulfuron-methyl has been widely used to control annual grass and broadleaf weeds, including A. aequalis, in wheat (Triticum aestivum L.) fields, leading to the selection of herbicide-resistant weeds. In this study, an A. aequalis population, AHFT-4, that survived mesosulfuron-methyl at the field-recommended rate (9 g ai ha−1) was collected in Anhui Province. Single-dose testing confirmed that the suspected resistant AHFT-4 had evolved resistance to mesosulfuron-methyl. Target gene sequencing revealed a resistance mutation of Pro-197-Ala in ALS1 of the resistant plants, and a derived cleaved amplified polymorphic sequence marker was developed to specifically detect the mutation. A relative expression assay showed no significant difference in ALS expression between AHFT-4 and a susceptible population without or with mesosulfuron-methyl treatment. Whole-plant dose–response bioassays indicated that AHFT-4 had evolved broad-spectrum cross-resistance to ALS-inhibiting herbicides of all five chemical families tested, with GR50 resistance index (RI) values ranging from 21 to 206. However, it remained susceptible to the photosystem II inhibitor isoproturon. Pretreatment with the cytochrome P450 inhibitor malathion or the glutathione S-transferase inhibitor 4-chloro-7-nitrobenzoxadiazole had no significant effects on the resistance of AHFT-4 to mesosulfuron-methyl. To our knowledge, this study reports for the first time the ALS gene Pro-197-Ala substitution conferring broad-spectrum cross-resistance to ALS-inhibiting herbicides in A. aequalis.

Abundance and diversity of endophytic and rhizospheric diazotrophs associated with rice roots from different rice rotation systems under field conditions

Abundance and diversity of endophytic and rhizospheric diazotrophs associated with rice roots from different rice rotation systems under field conditions

Variation of Cd and As accumulation in crops under oilseed rape–rice rotation system in response to different contaminated rice straw-return methods

Variation of Cd and As accumulation in crops under oilseed rape–rice rotation system in response to different contaminated rice straw-return methods

Responses of arbuscular mycorrhizal fungi to rice–upland crop rotations in an 8‐year paddy ecosystem

AbstractArbuscular mycorrhizal fungi (AMF), which can form symbiotic associations with many terrestrial plants, are critical for crop yields and agroecosystem sustainability. In this study, we assessed the influence of rice–upland crop rotations on soil AMF diversity and composition. We also explored the mechanisms of rice (Oryza sativa L.)–upland crop rotations that affect AMF using trait‐based guild methods. We found that rotations of rice with different plants differentially influenced soil AMF. Rice–wheat (Triticum aestivum L.) (RW) and rice–Chinese milk vetch (Astragalus sinicus L.) (RV) rotations significantly altered the soil AMF composition, with RW and RV significantly increasing and decreasing AMF diversity, respectively, compared with the rice–fallow treatment. In addition, RW and RV affected AMF abundance in intra‐ and extra‐radical portions in different ways. For example, both the RW and RV treatments increased AMF spore density, but decreased AMF colonization rate. Different AMF guilds showed different responses to rice–upland crop rotations. The RW treatment increased the rhizophilic guild by 4.9% and decreased the edaphophilic guild by 27.9%, whereas the RV treatment produced opposite trends. Thus, rice–upland crop rotations changed soil AMF diversity, AMF composition, and trait‐based guilds in different ways, and rice yield was mainly correlated with AMF colonization rate.

Multiyear methane and nitrous oxide emissions in different irrigation management under long-term continuous rice rotation in Arkansas.

Rice paddies are one of the major sources of anthropogenic methane (CH4 ) emissions. The alternate wetting and drying (AWD) irrigation management has been shown to reduce CH4 emissions and total global warming potential (GWP) (CH4 and nitrous oxide [N2 O]). However, there is limited information about utilizing AWD management to reduce greenhouse gas (GHG) emissions from commercial-scale continuous rice fields. This study was conducted for five consecutive growing seasons (2015-2019) on a pair of adjacent fields in a commercial farm in Arkansas under long-term continuous rice rotation irrigated with either continuously flooded (CF) or AWD conditions. The cumulative CH4 emissions in the growing season across the two fields and 5 years ranged from 41 to 123kg CH4 -C ha-1 for CF and 1 to 73kg CH4 -C ha-1 for AWD. On average, AWD reduced CH4 emissions by 73% relative to CH4 emissions in CF fields. Compared to N2 O emissions, CH4 emissions dominated the GWP with an average contribution of 91% in both irrigation treatments. There was no significant variation in grain yield (7.3-11.9 Mg ha-1 ) or growing season N2 O emissions (-0.02 to 0.51kg N2 O-N ha-1 ) between the irrigation treatments. The yield-scaled GWP was 368 and 173kg CO2 eq. Mg-1 season-1 for CF and AWD, respectively, showing the feasibility of AWD on a commercial farm to reduce the total GHG emissions while sustaining grain yield. Seasonal variations of GHG emissions observed within fields showed total GHG emissions were predominantly influenced by weather (precipitation) and crop and irrigation management. The influence of air temperature and floodwater heights on GHG emissions had high degree of variability among years and fields. These findings demonstrate that the use of multiyear GHG emission datasets could better capture variability of GHG emissions associated with rice production and could improve field verification of GHG emission models and scaling factors for commercial rice farms.

Study of the Interaction of Dissolved Organic Carbon, Available Nutrients, and Clay Content Driving Soil Carbon Storage in the Rice Rotation Cropping System in Northern Thailand

The appropriate management of crop residues in a rice rotation cropping system (RRCS) can promote carbon storage and contribute to soil health. The objective of this study was to determine and analyze the amount of organic carbon in the soil, the amount of labile carbon in a dissolved state in the soil, and the physicochemical properties of the soil and their relationship with soil organic carbon dynamics under the RRCS in northern Thailand. The RRCS can be divided into the following four categories by pattern: (1) Rice_F (rice (Oryza sativa) followed by a fallow period); (2) Rice_S (rice followed by shallots (Allium cepa L.); (3) Rice_Mixed crop (rice followed by tobacco (Nicotiana tabacum), vegetables, or maize (Zea mays)); and (4) Rice_P (rice followed by potatoes (Solanum tuberosum)). These patterns can be classified according to the dissolved organic carbon (DOC), the availability of nutrients from fertilization, and clay contents. In our study, the Rice-F and Rice-S patterns led to higher soil organic carbon (SOC) and dissolved organic carbon (DOC) in the soil, but when the Rice-P pattern was followed, the soil had a lower clay content, lower available phosphorus (Avail P), the lowest DOC, and high contents of calcium (Ca2+) and magnesium (Mg2+). This study also revealed that on the basis of relationships, clay content, Avail P, and DOC were the most important factors for the formation of SOC, while Ca2+ and Mg2+ were the subordinate factors for the decreased formation of SOC and carbon storage when the RRCS was followed. In addition, low SOC/clay when the Rice-P pattern was followed could reflect carbon saturation, while the percentages of DOC/SOC could indicate the decomposition and formation of SOC.

Effects of Deep Plowing with a Chisel Plow on Rate of Soil Pulverization, Soil Physical Properties, Drainage, and Growth Yield During Wheat Cultivation in an Upland Field Converted from Paddy Field with Three-Crop Rotation of Rice, Wheat, and Soybean in Two Years

Effects of Deep Plowing with a Chisel Plow on Rate of Soil Pulverization, Soil Physical Properties, Drainage, and Growth Yield During Wheat Cultivation in an Upland Field Converted from Paddy Field with Three-Crop Rotation of Rice, Wheat, and Soybean in Two Years

Effects of Deep Plowing with a Chisel Plow on Soil Physical Properties in the Subsoil and Drainage of the Plow Layer in an Upland Field Converted from Paddy Field with Three-Crop Rotation of Rice, Wheat, and Soybean in Two Years

Effects of Deep Plowing with a Chisel Plow on Soil Physical Properties in the Subsoil and Drainage of the Plow Layer in an Upland Field Converted from Paddy Field with Three-Crop Rotation of Rice, Wheat, and Soybean in Two Years

Evaluation of a subtropical maize-rice rotation system maintained under long-term fertilizer inputs for sustainable intensification of agriculture

The impacts of long-term (1996–2019) fertilizer inputs on grain yield and edaphic factors of upland maize and wetland rice rotation system were assessed for sustainable intensification of agriculture. Subtropical field treatments included swine manure compost (CP), chemical fertilizer (CF, control), no fertilizer (CK, blank), inorganic N-amended CP (CPN1 and CPN2), peat (PN1) and green manure (GMN1). Maize exhibited a significantly increased yield trend under CF, GMN1 and CP-based inputs (CP, CPN1 and CPN2), whereas rice yield displayed a non-significant marginal improvement or negative result. Principal component analysis of edaphic factors revealed distinct clustering of CP-CPN1-CPN2, CF-GMN1-CK and PN1 samples during maize-rice rotation. CP-based inputs in particular improved OM, EC, microbial metabolism and nutrient availability during crop rotation. Pronounced soil microbial activity and Bacterial abundances were recorded during maize cultivation. In contrast, low aerobic metabolism coupled with high Bacterial and Archaeal species richness, diversity and evenness were found during rice cultivation. In conclusion, increasing maize yield trends observed under long-term CP-based inputs were on par with CF and GMN1 amendments that concurrently acidified soil. Numerically dominant aerobic Bacteria appear to drive nutrient recycling and promote maize grain yield, whereas metabolically lethargic diverse prokaryotes constrained nutrient turnover stagnating the rice yield.

Tillage and N-source affect soil fertility, enzymatic activity, and crop yield in a maize–rice rotation system in the Indian Terai zone

A field experiment (2017–2019) was undertaken to study the short-term effects of tillage [zero tillage (ZT), conventional tillage (CT), and alternate tillage (AT)] and sources of organic and mineral fertilizer N [NS0—control, NS1—recommended doses of fertilizer (160:50:100), NS2—recommended level of fertilizer and crop residue (6 Mg·ha−1), NS3—75% of recommended N as fertilizer (120 kg·ha⁻1) and 25% N (40 kg·ha⁻1) as farm yard manure (FYM), and NS4—75% of recommended N as fertilizer and 25% N as vermicompost] on yield and soil quality under a maize–rice rotation system. Among N sources, NS4 produced the highest maize grain yield (10 Mg·ha⁻1). Residual effects of N sources on mean rice grain yield were evident only in crop residue (NS2)- and vermicompost (NS4)-treated plots. After the harvest of two complete maize–rice crop cycles, higher content of dehydrogenase activity (DHA) and urease activity (UR) were observed in the soil under AT as compared to ZT and CT at 0–10 cm (p < 0.05). Similarly, microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) also recorded positive changes at 0–10 cm soil depth, especially in NS2 and NS4 treatments. AT resulted in the highest total soil carbon (TOC) (8.10 g·kg−1), followed by CT (6.73 g·kg−1) and ZT (5.98 g·kg−1). Fertilizer N treatments, however, influenced the NO3-N accumulation beyond the root zone, where crop residue-based (NS2) fertilizer N treatment resulted in the highest NO3-N (32.52 kg·ha−1), and the lowest NO3-N (14.48 kg·ha−1) was observed in the FYM-based (NS3) treatment. Therefore, the practice of alternate tillage and integration of vermicompost (40 kg·N·ha−1) and chemical fertilizer (total 120 kg·ha−1) sources should be mostly recommended to farmers in the Terai region of India.

Crop rotation-driven change in physicochemical properties regulates microbial diversity, dominant components, and community complexity in paddy soils

Crop rotation is a production practice to promote a more diversified plant community in rice field, thereby enhancing agroecosystem sustainability and production efficiency under an increasing demand for food and energy. The regulation of rotations of rice with different crop on soil microbiomes and their relationships with key soil physicochemical drivers has not been understood enough. To address this, soils of 0–20 cm and 20–40 cm layers subjected to four rotation regimes (rice-rice, tobacco-rice, rice-oilseed rape, and rice-rice-oilseed rape) were collected from a long-term (>20 year) field experiment. Compared with the rice-rice, the other three rotations significantly increased surface soil porosity and the content of soil total nitrogen (N), available phosphorus (P), total potassium, and organic matter, as well as improved soil aggregate composition but decreased soil bulk density (P < 0.05). Rotation patterns and soil layers independently or interactively explained the variation in microbial diversity and community composition in soil, with a greater impact of the rotation regimes (9.3–49.7%; P < 0.05). The rotation systems of rice-oilseed rape and rice-rice-oilseed rape showed a higher soil microbial diversity and co-occurrence of the community species compared with other two systems. The components of the genus Clostridium, Pedobacter, and Gp1 were the dominant hubs (with a larger number of edges) in bacterial communities, and the members of the Mortierella, Ascomycota, and Agaricales were the hubs in fungal communities. The co-occurring networks between the members of bacterial and fungal communities in the four systems showed same keystone taxa that mainly belong to fungal genus Mortierella, Fusicolla, Paranamyces, and Pseudeurotium. The microbial diversity and community composition were positively correlated with soil NH4+-N-to-NO3--N ratio, available P content, total N content, and soil aggregates, and meanwhile, those variables were the creadible predictors of the community changes. These findings highlighted the advantage of rice rotations with oilseed rape in improvement of soil fertility and production by mediating soil microbiome and physicochemical property relationships.