Rice-wheat Rotation Research Articles

Incorporation of rice residue and green gram cultivation saves nitrogen, improve soil health and sustainability of rice-wheat system

• Rice residue incorporation and green gram was tested on yield and soil health. • Nitrogen fertilizer up to 75 kg ha −1 was saved by green gram growing before rice. • Sustainability was enhanced by rice residue and green gram incorporation. • Organic C increased by rice residue and green gram incorporation after 7 years. • Saving upto75 Kg N ha −1 in Punjab and Haryana could save $45.1 million yearly. Rice-wheat cropping system and associated residue burning is a major cause of air pollution and soil health depletion in Northern India. This calls for urgent technological interventions to address the issue and improve the profitability of this cropping system. Objective was to study the effect of rice residue incorporation (RRI) and green gram inclusion (GGI) on amount of N applied, productivity and soil health in rice-wheat cropping (RWC) system. Combinations of RRI, nitrogen management and GGI with conventional rice-wheat rotation were tested for 7 years. Eleven treatments with combination of RRI, RR removal, GGI and N management were evaluated. Treatment effects on system productivity, profitability and soil health parameters were measured. Treatment R-W (-RR) - Gg + <25 % N to R and R-W (+RR) - Gg+ <25 % N to R +>25 % N to W produced maximum rice (7677 kg ha −1 ) and wheat yield (5949 kg ha −1 ), though non-significant (P > 0.05) compared to control (Rice = 7508 & Wheat = 5724 kg ha −1 ). Nitrogen fertilizer up to 75 kg ha −1 was saved when GGI was taken up before rice. GGI and RRI was sustainable in terms of higher sustainability value index (SVI = 0.78), wheat equivalent yield (WEY = 20.0 t ha −1 ) and production efficiency (PE = 57.5 kg ha −1 day −1 ). The treatments with GGI + RRI produced 1015$ additional net returns with more than double B:C ratio. Soil health in the form of SOC (0.42 %) and available N (152.6 kg ha −1 ) were also improved with GGI + RRI in treatment R-W (+RR) - Gg+ <25 % N to R +>25 % N to W. Adoption of RRI + GGI over 3.64 m ha area under RWC system of studied ecology may save 45.1 million US $ worth N fertilizer annually in addition to substantial reduction in air pollution.

Conversion from rice–wheat rotation to rice–crayfish coculture increases net ecosystem service values in Hung-tse Lake area, east China

Paddy field farms are being converted to provide both grain and aquatic products. Presently, China has 1.11 million ha of rice–crayfish farming system which is growing. Conversion from paddy field-based farming to rice–crayfish coculture systems requires field engineering to excavate ditches for breeding. However, the net ecological benefits of this conversion remain unknown. To address this gap, this study used unmanned aerial vehicle surveillance to monitor the proportion of area of different types of ditches (circle, U-shaped, L-shaped, and I-shaped ditch) of the total field area in 140 rice–crayfish fields in the Hung-tse Lake area. Then the ecosystem service (ES) values were evaluated after the conversion to rice–crayfish coculture. The results showed that the average proportions of area covered by circular, U-shaped, L-shaped, and I-shaped ditches of the total field area were 26.29%, 17.38%, 9.63%, and 1.92%, respectively. Conversion to rice–crayfish coculture increases the net ES value by 145.3–176.9%, but also negatively impacts the ecological environment which should not be ignored. Indeed, with a decrease in the proportion of the ditch, the net ES value increased. Overall, the study suggested that rice–crayfish coculture fields with L- and I-shaped ditches produce substantial crayfish yields and stable rice yields, whereas those with circular and U-shaped ditches squeeze the rice planting area and reduce rice yield. The study provides vital information to avoid the blind expansion and development of rice–crayfish farming from the perspective of the ecological environment, and provides policy suggestions for sustainable development.

Sensitivity of soil aggregation to soil organic carbon fractions under land-use conversion from rice to organic vegetable cultivation

Conversion of rice-wheat rotation (RWR) to conventional vegetable cultivation, especially vegetable cultivation in plastic sheds, readily causes soil structure degradation, and organic manure is commonly applied to mitigate such degradation. Although many studies have focused on changes in SOC properties or structural soil parameters, additional details about the changes, such as the relationships between SOC fractions and soil aggregates during unique land-use changes, are unknown. Here, we studied the changes in soil aggregation, and SOC parameters in 14-year-old plastic-shed vegetable fields (PVFs) and open-air vegetable fields (OVFs) covered with organic manure, with adjacent RWR fields serving as a control. The vegetable fields were converted from RWR fields. SOC fractions were analyzed by using 13C solid-state NMR spectroscopy, and the aggregate classes were divided as follows: large macro-aggregates (>2 mm), small macro-aggregates (2–0.25 mm), micro-aggregates (0.25–0.053 mm), and silt and clay particles (<0.053 mm). PVFs had higher SOC and MBC than OVFs and RWR fields. In terms of the SOC fractions, the proportion of O-alkyl C decreased as RWR (53.90%) > PVF (43.21%) > OVF (35.37%), in contrast to the trends in the carbonyl C and aromatic C fractions. The aggregate-associated C, especially that associated with large macro-aggregates and micro-aggregates, in the PVFs was highest among the treatments. The O-alkyl C fraction in large macro-aggregates decreased in the order RWR (44.67%) > OVF (35.76%) > PVF (32.40%), consistent with the results for micro-aggregates. Furthermore, there was a significant (P ≤ 0.05) positive relationship between macro-aggregates (>0.25 mm) and the active C fractions, in contrast to the relationships with stable fractions. It suggested that plastic-shed cultivation might have a more positive effect than open-air cultivation on soil structure and the carbon stock when large amounts of organic manure are applied; moreover, the SOC quantity and quality affect soil aggregation differently.

Nitrogen use efficiency exhibits a trade-off relationship with soil N2O and NO emissions from wheat-rice rotations receiving manure substitution

Nitrogen (N) fertilizer has shown to affect soil nitrous oxide (N2O) and nitric oxide (NO) emissions that contribute to global warming and stratospheric ozone depletion. However, soil N2O and NO emissions with a linkage to crop N use efficiency (NUE) under different fertilization strategies in winter wheat-summer rice rotation systems remain yet to be further examined. Here, we carried out a two-year field study to assess the response of soil N2O and NO emissions as an interplay with NUE to different fertilization strategies in a typical winter wheat-summer rice rotation cropland of subtropical China. Three fertilizer treatments were established consisting of phosphorus (P) and potassium (K) fertilizer application (PK), NPK fertilizer application (NPK), and NPK fertilizer application with N partially replaced with manure (NPKM). Annual N2O, NO and N2O + NO emissions averaged 0.96, 0.24 and 1.19 kg N ha−1 yr−1 for the PK plots and 6.54, 1.48 and 8.03 kg N ha−1 yr−1 for the NPK plots, respectively. Relative to the NPK plots, partially replacing chemical N fertilizer with manure decreased annual N2O and NO emissions and their combined emissions by 13–15%, while it significantly enhanced crop NUE as compared to the NPK plots. Annual mean emission factors (EFs) of N fertilizer for N2O and NO were estimated to be 1.17% and 0.26% for the NPK plots, and 0.99% and 0.22% for the NPKM plots, respectively. Both N2O and NO emissions were positively correlated with N surplus, while yield-scaled N2O + NO emissions and the fertilizer N-induced combined EF for N2O + NO were negatively related to crop NUE. Together, our results highlight that improving crop NUE while reducing soil N surplus constitutes an effective strategy to mitigate soil gaseous N loss through N2O and NO in the wheat-rice rotation cropping systems.

Tillage Methods on Greenhouse Gas Emissions and Yields of Rice–Wheat Rotation System in East China Polder Area

Tillage Methods on Greenhouse Gas Emissions and Yields of Rice–Wheat Rotation System in East China Polder Area

Effects of Reducing Nitrogen Fertilizer and Improving Organic Fertilizer on Crop Yield, Soil Quality and Microbial Community in Five Years Wheat-Rice Rotation Field

Excessive application of nitrogen (N) fertilizer usually causes contamination of soil and groundwater. In this study, the rice yield and soil quality were investigated under different content of N fertilizer and amending organic compost (OC) or (and) crop residue (CR) in five-year wheat-rice rotated fields, and the soil microbial communities were inspected by means of Illumina sequencing. The results showed that rice yields were maintained at a high level although the N fertilizer was reduced to 80% of the normal content with amendment of OC and (or) CR. The PH was decreased and available phosphorus increased whenever the N fertilizer was normally applied or decreased when OC and (or) CR was amended, respectively. Available potassium was significantly increased when N fertilizer was reduced but OC and (or) CR was added. The abundance of bacterial and fungal communities was affected by OC or CR. Function prediction indicated that bacteria involved in DNA repair, carbohydrate digestion and absorption, amino acid degradation, caffeine metabolites were affected by OC or CR. Some plant growth promoting microbes (bacterial genus Pantoea, fungal gena Talaromyces and Scolecobasidium) were increased when OC or (and) CR was added. In addition, some nitrification or denitrification related bacteria (Candidatus nitrotoga, Nitrolancea, Noviherbaspirillum, Thioalkalispira) and fermentative metabolite bacteria (Lactobacillus) were increased when N fertilizer was reduced and OC or (and) CR was amended. These microbes may decompose the complex organic matter and improve nutrient transforming cycle to promote plant growth.

A meta‐analysis of the effects of global warming on rice and wheat yields in a rice–wheat rotation system

AbstractThe effects of global warming on crop production have received great attention in recent years. However, inconsistent results have been obtained with regard to major crops such as rice and wheat in rice–wheat rotation systems of China. Therefore, we undertook a comprehensive meta‐analysis of literature data. The yield response to warming differed for rice and wheat in the rice–wheat rotation system. Overall, warming significantly increased wheat yield (by 4.8%) but significantly reduced rice yield (by 14.8%). A number of factors were responsible for these observations. For example, rice yield responses varied with the temperature increase, variety and nitrogen (N) rate. Of these, N was the most important variable influencing yield responses to warming. The yield loss for rice was lower at temperature increases of 0.40–1.40°C and at a high N rate than that at temperature increases of 1.60–2.49°C and at a low N rate, respectively. The yield loss of indica rice was lower than that of japonica rice. For wheat, however, yield responses to warming varied with the warming regime, ambient temperature, temperature increases, and CO2 concentrations. Of these factors, ambient temperature was the most important variable influencing yield in response to warming. Warming increased wheat yield at a mean growth season temperature ≤10°C, temperature increases of 0.80–1.50°C, and at ambient CO2 concentrations. In addition, either daytime warming or nighttime warming significantly increased wheat yield. However, all‐day warming had no effect on wheat yields. We conclude that global warming will benefit wheat production but result in a serious loss of rice yield in rice–wheat rotations in China.

Wheat and maize-derived water-washed and unwashed biochar improved the nutrients phytoavailability and the grain and straw yield of rice and wheat: A field trial for sustainable management of paddy soils

A field experiment was carried out to evaluate the effects of different biochars on grain yield and phytoavailability and uptake of macro- and micro-nutrients by rice and wheat grown in a paddy soil in a rotation. Soil was treated with i) maize raw (un-washed) biochar (MRB), ii) maize water-washed biochar (MWB), iii) wheat raw biochar (WRB) or iv) wheat water-washed biochar (WWB) and untreated soil was used as control (CF). Inorganic fertilizers were applied to all soils while biochar treated soils received 20 ton ha−1 of designated biochar before rice cultivation in rice-wheat rotation. The WRB significantly (P < 0.05) increased rice grain yield and straw by up to 49%, compared to the CF. Biochar addition, particularly WRB, significantly increased the availability of N, P, K and their content in the grain (26–37%) and straw (22–37%) of rice and wheat. Also, the availability and grain content of Fe, Mn, Zn, and Cu increased significantly after biochar addition, particularly after the WRB, due to WRB water dissolved C acting as a carrier for micronutrients in soil and plant. However, the water-washing process altered biochar properties, particularly the water extractable C, which decreased its efficiency. Both wheat- and maize-derived biochars, particularly the WRB, are recommended to improve nutrients availability and to improve grain yield in the rice-wheat rotation agro-ecosystem. These results shed light on the importance of crop straw transformation into an important source for soil C and nutrients necessary for sustainable management of wheat-rice agro-ecosystem. However, with the current and future alternative energy demands, the decision on using crop biomass for soil conservation or for bioenergy becomes a challenge reliant on regulatory and policy frameworks.

Sustained rice yields and decreased N runoff in a rice-wheat cropping system by replacing wheat with Chinese milk vetch and sharply reducing fertilizer use

Pollution from the paddy fields has posed a threat to surface water quality, and the reactive N in runoff has been recognized as the dominant contributor. In the rice-wheat systems of eastern China, replacing wheat (Triticum aestivum) with Chinese milk vetch (CMV) (Astragalus sinicus) is known to reduce total fertilizer N use and associated N losses during winter; however, the function of the rice-CMV system in controlling the N runoff loss was overlooked during the summer rice-growing season. Over 6 years, we monitored soil mineral N, plant N accumulation, rice grain yield, N agronomic efficiency (AEN), and N runoff in rice-CMV fertilizer N rate-response experiments and made comparisons with the conventional N inputs in rice-wheat rotation. Aboveground CMV residues added 65–116 kg N ha−1 yr−1; therefore, by adjusting the fertilizer time, the rice in this system required 44–56% less N fertilizer to produce rice yields equivalent to the 270 kg N ha−1 (district average, C270) used in the rice-wheat system. In all fertilizer N application treatments, 120 kg ha−1 seemed to be the threshold that ensured the soil N supply, the N accumulation at rice critical stages, and consequently, the current level rice yield. The corresponding runoff N averaged 9.3 kg ha−1 season−1, which was 51.8% less than that in C270 (19.3 kg ha−1 season−1). Cumulative N runoff (total N and NH4+-N) correlated strongly with fertilizer N input for any single year (sample size = 108, P < 0.01). Application of 30–120 kg fertilizer N ha−1 gave an equivalent AEN, which indicated that the integration of CMV and fertilizer N could increase the agronomic efficiency of N fertilizer applied to the rice. Rotating paddy rice with CMV instead of wheat, together with the suitable adjustment of N fertilizer, could sustain rice yield and gain the utmost environmental benefits from rice-based agroecosystems.

Effects of straw return with N fertilizer reduction on crop yield, plant diseases and pests and potential heavy metal risk in a Chinese rice paddy: A field study of 2 consecutive wheat-rice cycles

Understanding the comprehensive effect on crop production and quality, soil acidification, and Cd accumulation and distribution for wheat-rice rotation under N fertilization and continuous straw return is important for proper contaminated agricultural soil management. A 2-year paddy field experiment was conducted to study the effects of above factors change in the Zhejiang province, China. Fertilization treatments included: conventional N fertilizer application (N3), 20% reduction of N application (N2), 40% reduction of N application (N1), combined with three portions of straw incorporation: all straws retention (N3), half of the straws into the fields (S2), 20% straws retention(S1). The N1 treatments significantly decreased crop yields compared to N2 and N3 treatments. Except for C2-wheat, soil pH generally decreased with increasing N fertilizer input in the order of N1>N2>N3, regardless of how many straws was amended. Moreover, we found that straw addition plus N fertilization had a intersystem impacts on Cd accumulation, distribution and availability. Although total Cd had different trends among 4 experimental seasons, when the N reduced 20% applied, the DTPA-Cd contents were lowest among 3 out of four experimental seasons, except for that of C2-wheat, where N2 treatments ranked the second lower contents. For most seasons, Cd contents in straws were higher than soils and lowest in grains, and S2N2 treatment performed an intermediate value among all treatments. Furthermore, our study demonstrated that S2 or N2 treatments or S2N2 reduced the potential risk of plant diseases and pests with lower disease index, disease cluster rate. Notably, the relative outbreak of pests was remarkably suppressed under S2 treatments, especially S2N2. Thus, these findings demonstrated that in wheat-rice rotation reducing 20% N fertilization with 50% straw returning may be a win-win practice in this region for the equilibrium between agricultural productivity, quality and low Cd polluted risk.

Seasonal and Interannual Variations in the Surface Energy Fluxes of a Rice–Wheat Rotation in Eastern China

AbstractQuantitative knowledge of the water and energy exchanges in agroecosystems is vital for irrigation management and modeling crop production. In this study, the seasonal and annual variabilities of evapotranspiration (ET) and energy exchanges were investigated under two different crop environments—flooded and aerobic soil conditions—using three years (June 2014–May 2017) of eddy covariance observations over a rice–wheat rotation in eastern China. Across the whole rice–wheat rotation, the average daily ET rates in the rice paddies and wheat fields were 3.6 and 2.4 mm day−1, respectively. The respective average seasonal ET rates were 473 and 387 mm for rice and wheat fields, indicating a higher water consumption for rice than for wheat. Averaging for the three cropping seasons, rice paddies had 52% more latent heat flux than wheat fields, whereas wheat had 73% more sensible heat flux than rice paddies. This resulted in a lower Bowen ratio in the rice paddies (0.14) than in the wheat fields (0.4). Because eddy covariance observations of turbulent heat fluxes are typically less than the available energy (Rn − G; i.e., net radiation minus soil heat flux), energy balance closure (EBC) therefore does not occur. For rice, EBC was greatest at the vegetative growth stages (mean: 0.90) after considering the water heat storage, whereas wheat had its best EBC at the ripening stages (mean: 0.86).

Long-Term Zinc Fertilization in Calcareous Soils Improves Wheat (Triticum aestivum L.) Productivity and Soil Zinc Status in the Rice–Wheat Cropping System

Rice–wheat cropping system (RWCS) is considered as the furthermost vital system in the Indo-Gangetic Plains of South-Asia, including India, Pakistan, Bangladesh, and Nepal. Recently, the deficiency of micronutrients like zinc (Zn) has emerged as one of the prime limitations for the sustainability issues of this RWCS in Zn deficient calcareous soils, particularly in India, as a result of the calcareous typic ustifluvents taxonomic nature of the soils. Therefore, a new Zn fertilization approach for soils is very much needed in the intensive RWCS. Thus, a six-year-long investigation was designed with three different modes of Zn application, viz., the application of Zn only in the first year of study, application in alternative years, and application in every year. Four different rates of Zn applications in a hectare of area for a single year, viz., 2.5, 5.0, 7.5, and 10 kg ha−1 year−1, and times of Zn application, viz., only at first year, alternative years, and in each year. The major aims of the study were to determine Zn concentration in soil; yield; and Zn accumulation by wheat crop under different application methods of Zn. From this study, it was found that a large portion of the applied Zn was present in the residual fraction, and it was also revealed that increasing the frequency of Zn application resulted in the increment in the crystalline fraction. Significant correlation of water-soluble and exchangeable Zn (WS+EX-Zn), complexed Zn (COM-Zn), amorphous Zn (AMO-Zn), organic Zn (ORG-Zn), total Zn (TOT-Zn), grain yield, and grain Zn uptake by wheat indicated that these Zn fractions were dominant forms in the soil to be utilized by plants under rice–wheat rotation. Concerning yield and Zn uptake by wheat, it was noted that the Zn application at 10 kg ha−1 in alternate years was the best Zn application method, while application of Zn at 7.5 kg ha−1 in each year also resulted in comparable yield.

Effects of sulfur application on cadmium accumulation in brown rice under wheat-rice rotation

We investigated how sulfur (S) application prior to wheat cultivation under wheat-rice rotation influences the uptake of cadmium (Cd) in rice grown in low- and high-Cd soils. A pot experiment was conducted with four S levels (0, 30, 60, 120 mg S kg−1) and two Cd rates (low and high, 0.35 and 10.35 mg Cd kg−1) supplied to wheat. Part of the wheat straw was returned to the soil before planting rice, which was cultivated for 132 days. To explore the key mechanisms by which S application controlled Cd accumulation in brown rice, (1) soil pore water at the key growth stages was sampled, and dissolved Cd and S species concentrations were determined; (2) rice plant tissues (including iron plaque on the root surface) were sampled at maturity for Cd and S analysis. With increasing S level, Cd accumulation in brown rice peaked at 60 mg S kg−1, irrespective of soil Cd levels. For high-Cd soils, concentrations of Cd in brown rice increased by 57%, 228%, and 100% at 30, 60, and 120 mg S kg−1, respectively, compared with no S treatment. The increase in brown rice Cd by low S levels (0–60 mg kg−1) could be attributed to (1) the S-induced increase in soil pore water sulfate increasing the Cd influx into rice roots and (2) the S-induced increase in leaf S promoting Cd translocation into brown rice. However, brown rice Cd decreased at 120 mg S kg−1 due to (1) low Cd solubility at 120 mg S kg−1 and (2) root and leaf S uptake, which inhibited Cd uptake. Sulfur application to wheat crop increased the risk of Cd accumulation in brown rice. Thus, applying S-containing fertilizers to Cd-contaminated paddy soils is not recommended.

Impact of Residue Incorporation on Soil Carbon Storage, Soil Organic Fractions, Microbial Community Composition and Carbon Mineralization in Rice-wheat Rotation – A Review

In agroecosystems, straw return is a useful management strategy for increasing soil fertility and crop productivity. The total organic carbon (TOC), dissolved organic C (DOC), and microbial biomass C (MBC) contents all increased significantly when compared to the no straw return (N) and straw return (S) treatments, while the easily oxidizable C content remained same. The S treatment resulted in a 28–52 percent increase in soil light fraction, light fraction organic C, and particle organic C over the N treatment. When compared to the N treatment, crop straw return increased total phospholipid fatty acid (PLFA), bacterial biomass, and actinomycete biomass by 52, 75, and 56 percent, respectively. Under short-term crop straw return, MBC and TOC were the two key determinants determining microbial populations. In comparison to residue removal, residue retention (RR) enhanced SOC storage by 11.3 percent. SOC content and contribution of macro-aggregates in the 0-20 cm depth and micro-aggregates in the 20-40 cm depth rose significantly when no-tillage and straw returns were used together. When no-tillage with straw returning (NTS) was used instead of CT, SOC content, mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimensions (FD) rose by 25%, 21%, 19%, and 12%, respectively, in the 0-20 cm depth. Soil micro-aggregates were greater in the 20-40 cm depth after CTS treatment. In the 0-20 cm depth, the percentages of macro- and micro-aggregates increased by 60% and 40%, respectively, under NTS. MWD, GMD, &gt; 5, 2-5, 1-2, and 0.25-0.5 mm aggregates all had a positive linear relationship with the SOC. Microbial biomass C (MBC) was considerably enhanced by 20.0 percent when compared to conventional tillage (CT) and no-tillage (NT), but total organic C (TOC), dissolved organic C (DOC), readily oxidizable C (EOC), and SOC of aggregates were not affected. MBC increased by 18.3% and SOC content of 2–1-mm aggregate increased by 9.4% when residue was returned. Total PLFAs grew by 9.8%, while fungal biomass increased by 40.8 percent, thanks to NT. Total PLFAs, bacterial biomass, fungal biomass, F/B, and MUFA/STFA were all increased by 31.1, 36.0, 95.9, 42.5, and 58.8 percent, respectively, while microbial stress was reduced by 45.9%. Wheat straw return had a considerable impact on the bacterial community in the soil, but not on the fungus community. It increased the relative abundance of the bacteria phylum Proteobacteria and the fungal phylum Zygomycota, while decreasing the relative richness of the bacterial phylum Acidobacteria and the fungal phylum Ascomycota. It increased the relative abundance of nitrogen-cycling bacterial taxa including Bradyrhizobium and Rhizobium, among others. This diversity includes bacteria, cyanobacteria, archaea, planctomycetes, and -proteobacteria, as well as endophytes. The system's intricacy and dynamic nature necessitate in-depth research on the three-part interactions between plants, microorganisms, and the soil-water environment.

Sesbania brown manuring improves soil health, productivity, and profitability of post-rice bread wheat and chickpea

SummaryContinuous rotation of rice with wheat in rice–wheat system has resulted in stagnant yields and reduced profit margins while deteriorating the soil health. Legume incorporation in existing rice–wheat rotations might be a viable option to improve soil health and productivity. We investigated the influence of puddled transplanted flooded rice and direct-seeded rice on weed dynamics, soil health, productivity, and profitability of post-rice wheat and chickpea grown under zero tillage and conventional tillage. The previous direct-seeded rice crop was either sown alone or intercropped with sesbania as brown manure. The experiment comprised different rice–wheat and rice–chickpea systems which had been in place for two years: with and without rice residue retention. The initial soil analysis indicated that the plots with sesbania brown manuring in direct-seeded rice had the lowest soil bulk density (17.2%) and highest soil porosity (19.3%). Zero tillage in wheat or chickpea in the plots previously cultivated with co-culture of sesbania and direct-seeded rice increased total soil organic carbon by 13–22% in both years. The plots with sesbania brown manuring in direct-seeded rice followed by zero till or conventional till wheat and the plots with direct-seeded rice followed by zero till wheat with rice residue retention recorded the greater concentrations of total nitrogen, available phosphorus, and exchangeable potassium. Zero tillage in wheat and chickpea in post-rice sesbania brown manuring plots produced 41% and 43% more grain yield than those in the puddled transplanted flooded rice with conventional tillage and had the highest profitability. Overall, the rice–chickpea systems had better soil health and profitability than rice–wheat cropping systems. In conclusion, direct-seeded rice intercropped with sesbania followed by wheat and chickpea under zero tillage suppressed weed flora and improved soil physical properties, nutrient availability, productivity, and profitability.

Nutrient loss by runoff from rice-wheat rotation during the wheat season is dictated by rainfall duration

Clarifying the properties/features of nutrient loss from farmland surface runoff is essential for the mitigation of nutrient losses. Plough pan formation underneath topsoil is a common feature of long-term paddy soils that significantly affects water movement and nutrient runoff loss, especially during the upland season of paddy-upland rotation. To characterize the nutrients that are lost from wheat fields of paddy-wheat rotation with runoff, a field experiment was conducted in a wheat field using a simulated rainfall system from November 2019 to May 2020 in Nanjing, China. The aim of this study was to investigate the temporal characteristics of nitrogen (N) and phosphorus (P) loss under different rainfall intensities (low, 30 mm h−1; middle, 60 mm h−1; high, 90 mm h−1). The results showed that the time interval from the beginning of rain to the occurrence of runoff (time to runoff, Tr) was negatively correlated with “rainfall intensity” (Ri) (P＜0.01) but unaffected by soil moisture. Different rainfall intensities had no effect on the runoff coefficient (the ratio of the runoff volume over the precipitation, 0.14–0.17). The N and P loss concentrations in the nutrient discharge followed a power-function relationship that decreased over time (P＜0.01), and the peak nutrient concentration appeared during the initial runoff period (0–5 min). The N and P loss rates were the highest during the middle-to-late discharge period (15–30 min) for all intensities. In terms of cumulative nutrient losses, the amounts of TN lost were similar for all rainfall intensities, while TP significantly increased with intensity. The results revealed that nitrate-nitrogen (NOX−-N) and particulate phosphorus (PP) were the predominant forms of N and P losses. Overall, during the initial runoff period, nutrient concentration peaks, whereas the nutrient loss rate is the highest during the middle-late phase of the phenomenon.

Five years integrated crop management in direct seeded rice–zero till wheat rotation of north-western India: Effects on soil carbon dynamics, crop yields, water productivity and economic profitability

Different integrated crop management (ICM) modules have been developed to enhance the productivity and profitability of the rice-wheat rotation (RWR) of the upper Indo-Gangetic Plains (IGPs). As the available options are used quite often singly or with the few combinations, hence in the present study, eight ICM modules have been evaluated; wherein, ICM1&2- conventional transplanted rice fb flatbed wheat, ICM3&4- conventional direct seeded rice (DSR) fb furrow irrigated raised bed wheat without residues, ICM5&6- conservation agriculture (CA)-based modules [zero tilled (ZT) DSR and ZT wheat] with the wheat and rice residues, and ICM7&8- CA-based modules (ZTDSR and ZT wheat) with the wheat, mungbean and rice residues. Results revealed that ICM8 produced the highest mean rice grain yield, which was statistically similar to ICM1&7, however it was 10.1–20.7% greater than the ICM2–6 modules. Similarly, the ICM7 recorded 14–16% greater wheat grain yield than the ICM1–6 (five years' mean), but it was at par to the ICM8. Furthermore, the ICM7&8 produced 10–13% (5 years av.) higher system yields in terms of rice equivalents over the ICM1&2. Water use (WU) was the highest in ICM1&2 and was 8–12% higher than the ICM3–8. In contrast, the highest water productivity (WP) was recorded with the ICM7&8, wherein it was14–16% greater than the ICM1&2. The ICM1&2 had incurred the highest variable production costs (US$ 912–1105 ha−1 yr−1), followed by ICM7&8 (US$ 856–1021 ha−1 yr−1). Nevertheless, on an average, the ICM7&8 gave 19–22% additional returns than the ICM1&2. Also, the ICM modules had a significant (p < 0.05) and positive impact on the soil carbon (0.0–0.45 m). The CA-based (ICM5–8) residue retained modules registered a 10–25% greater total OC stock than the ICM1–4 in 0.0–0.45 m soil layer. The current study thus up-holds the importance of adequate inputs integration, and hence, adoption of the CA-based ICM in the RWR improved the soil carbon dynamics, crop yields, farm profits, besides water savings of the upper Indo-Gangetic Plains (IGPs) of north-west India.

Evaluation on environmental consequences and sustainability of three rice-based rotation systems in Quanjiao, China by an integrated analysis of life cycle, emergy and economic assessment

The rice-based cultivation system in the middle and lower reaches of the Yangtze River of China is changing gradually during recent years which arouses more attentions and concerns on environmental performance and sustainability. In this study, the integrated analysis of life cycle assessment (LCA), emergy evaluation (EME) and economic analysis (ECA) were applied and Quanjiao county was selected as a case study to estimate the pollution emissions, emergy efficiency and economic benefits of three typical rice-based rotation systems depended on a detailed farming practice filed investigation of 157 valid samples under structured questionnaire. The three typical rice-based rotation systems are rice-wheat rotation (RW), rice-fallow rotation (RF) and rice-crayfish rotation (RC), respectively. The LCA results showed that the area-based potential environmental impact for RW, RF and RC are 34.08, 13.71 and 39.98, the profit-based potential environmental impacts are 2.62, 1.16 and 1.98. The EME results indicated that the RC shows the highest emergy input, around 1.23E+17 sej/ha/yr, more than that of RW and RF, around 3.88E+16 sej/ha/yr and 3.40E+16 sej/ha/yr, respectively. From the emergy indices of the three systems, the RC results in higher environmental pressure and lower sustainability compared with the RW and RF. Fertilizer, diesel oil, water, electricity and forage are the crucial factors of environmental consequences, herein forage, water and electricity inputs are becoming new factors that are increasingly prominent and often neglected. From an economic perspective, the cost and income of the RC are highest because of more input and higher sale value, the area-based profit of the RC (20142 ¥/ha) is higher than that of RF (11848 ¥/ha) and RW (13031 ¥/ha). Generally, during the rice planting system transferring, the development of farming technologies and standards should be promoted to avoid the disorder of agricultural production, and then gearing up to the better economic performance and environmental sustainability for the rice-based rotation systems. Moreover, proper agricultural development policies should be made and promoted to stimulate farmers’ willingness to adopt advanced farming practices and techniques to reduce environmental emissions and enhance agricultural system sustainability as well as increasing farmers' income.

Effects of different tillage and fertilization management practices on soil organic carbon and aggregates under the rice–wheat rotation system

Studying the impact of tillage and fertilization on soil organic carbon (SOC) content and aggregate is essential to define better strategies for improving soil structure and SOC sequestration. A field experiment was conducted for 9 years to investigate effects of different tillage and fertilization management practices on SOC and its active fractions [labile organic carbon (LOC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC)] within the bulk soil and in soil aggregates under rice (Oryza sativa L.)–wheat (Triticum aestivum L.)-based cropping systems. Five treatments were included: conventional tillage with no fertilizer (CT), conventional tillage with chemical fertilizer (CTFR), reduced tillage with chemical fertilizer (RTFR), conventional tillage with organic manure (CTOM), and reduced tillage with organic manure (RTOM). The results showed that the organic manured plots (CTOM and RTOM) significantly increased the concentrations of SOC and active carbon fractions (LOC, DOC and MBC) within the bulk soil and soil macroaggregates, and increased the mass proportion of macroaggregates (>250 μm) compared with chemical fertilizer treatments (CTFR and RTFR) or CT. The highest SOC concentration and macroaggregates (>250 μm) were observed in CTOM. The increased SOC, especially active carbon fractions, was mainly concentrated in soil macroaggregates (>250 μm). Soil aggregates were dominated by macroaggregates (>250 μm), which had higher MBC and lower PAOC (the percentage of slow plus passive carbon fractions) after 9 years of RTOM treatment than after CT or CRFR treatment. The results indicated that RTOM played a positive role in promoting the formation of the soil macroaggregate structure. By studying the responses of SOC and water-stable aggregate contents to different tillage and fertilization managements, the continual application of organic manure may be feasible and the periodic organic manure addition may be combined with reduced tillage practice to produce an integrated soil management strategy for the paddy–upland rotation region in Middle China.

Promoting pre-anthesis nitrogen accumulation in wheat to achieve high yield and nitrogen-use efficiency through agronomic measures

Improvements in grain yield and nitrogen (N)-use efficiency (NUE) are being sought to combat the excessive application of N fertilizer in the rice-wheat rotation system in China. Improving N-uptake efficiency (NUpE) is expected to explore the synergy of grain yield and NUE, but the accumulation and remobilization of N in wheat with high NUpE is still obscure. A 2-year field experiment was conducted to study how to improve NUpE through crop management of planting densities, N application splits, and wheat growth stages when the last N was topdressed. In both years, NUpE was significantly positively related to grain yield and NUE. Comparing with the low and medium NUpE groups (grouping the treatments using cluster analysis of NUpE), the high NUpE group had more total N accumulation as a result of absorbing abundant N from re-greening (Zadoks growth stage, GS25) to anthesis (GS60), and higher N accumulation in grains mainly due to increasing N remobilization from the vegetative organs. Our results indicated that improving the planting density (from 150 to 225 plants m−2) promoted N accumulation before stem elongation (GS30). Late application of more N fertilizers (N application splits 3:1:3:3 versus 5:1:2:2) and relatively early application of the last N portion [topdressing when the flag leaf was visible (GS37) or at booting (GS45) versus topdressing at heading (GS55) or anthesis] boosted N accumulation from stem elongation to anthesis. Finally, a combination of agronomic measures was proposed to achieve high yield and NUE through promoting pre-anthesis N accumulation and NUpE.