Ground Cover Rice Production System Research Articles

Simulating the Responses of Rice Yield and Nitrogen Fates to the Ground Cover Rice Production System under Different Precipitation Year Types

The ground cover rice production system (GCRPS) has considerable potential for securing rice production in hilly mountainous areas. However, its impact on yields and N fates remains uncertain under varying rainfall conditions. A two-year field experiment (2021–2022) was carried out in Ziyang, Sichuan Province, located in the hilly mountains of southwest China. The experiment included two cultivation methods: conventional flooding paddy (Paddy, W1) and GCRPS (W2). These methods were combined with three N management practices: N1, no-N fertilizer; N2, 135 kg urea N per hm2 as a base fertilizer; and N3, 135 kg urea N per hm2 with split application for W1 and 67.5 kg N per hm2 of urea and chicken manure separately for W2. The WHCNS (soil water heat carbon nitrogen simulator) model was calibrated and validated to simulate ponding water depth, soil water storage, soil mineral N content, leaf area index, aboveground dry matter, crop N uptake, and rice yield. Subsequently, this model was used to simulate the responses of rice yield and N fates to GCRPS under different precipitation year types using meteorological data from 1980 to 2018. The results indicated that the WHCNS model performed well in simulating crop growth and N fates for both Paddy and GCRPS. Compared with Paddy, GCRPS reduced N leaching (35.1%–54.9%), ammonia volatilization (0.7%–13.6%), N runoff (71.1%–83.5%), denitrification (3.8%–6.7%), and total N loss (33.8%–56.9%) for all precipitation year types. However, GCRPS reduced crop N uptake and yield during wet years, while increasing crop N uptake and yield during dry and normal years. Fertilizer application reduced the stability and sustainability of rice yield in wet years, but increased the stability and sustainability of rice yield in dry and normal years. In conclusion, GCRPS is more suitable for normal and dry years in the study region with increasing rice yield and reducing N loss.

Ground Cover Rice Production System Affects Soil Water, Nitrogen Dynamics and Crop Growth Differentially with or without Climate Stress.

The ground cover rice production system (GCRPS) has been proposed as a potential solution to alleviate seasonal drought and early low-temperature stress in hilly mountainous areas; clarifying its impact on crop growth is crucial to enhance rice productivity in these areas. A two-year (2021-2022) field experiment was conducted in the hilly mountains of southwest China to compare the effects of the traditional flooding paddy (Paddy) and GCRPS under three different nitrogen (N) management practices (N1, zero-N fertilizer; N2, 135 kg N ha-1 as a urea-based fertilizer; and N3, 135 kg N ha-1 with a 3:2 base-topdressing ratio as urea fertilizer for the Paddy or a 1:1 basal application ratio as urea and manure for GCRPS) on soil water storage, soil mineral N content and crop growth parameters, including plant height, tiller numbers, the leaf area index (LAI), aboveground dry matter (DM) dynamics and crop yield. The results showed that there was a significant difference in rainfall between the two growth periods, with 906 mm and 291 mm in 2021 and 2022, respectively. While GCRPS did not significantly affect soil water storage, soil mineral N content, and plant height, it led to a reduction in partial tiller numbers (1.1% to 31.6%), LAI (0.6% to 20.4%), DM (4.4% to 18.8%), and crop yield (7.4% to 22.0%) in 2021 (wet year) compared to the Paddy. However, in 2022 (dry year), GCRPS led to an increase in tiller numbers (13.7% to 115.4%), LAI (17.3% to 81.0%), DM (9.0% to 62.6%), and crop yield (2.9% to 9.2%) compared to the Paddy. Structural equation modeling indicated that GCRPS significantly affected tiller numbers, plant height, LAI, DM, and productive tiller numbers, which indirectly influenced crop yield by significantly affecting tiller numbers and productive tiller numbers in 2022. Overall, the effects of GCRPS on soil water and N dynamics were not significant. In 2021, with high rainfall, no drought, and no early, low-temperature stress, the GCRPS suppressed crop growth and reduced yield, while in 2022, with drought and early low-temperature stress and low rainfall, the GCRPS promoted crop growth and increased yield, with tiller numbers and productive tiller numbers being the key factors affecting crop yield.

Incorporating DNA-level microbial constraints helps decipher methane emissions from Chinese water-saving ground cover rice production systems

• Relating CH 4 fluxes to methanogens and methanotrophs under GCRPS remains unclear. • GCRPS reduced CH 4 emissions and the yield-scaled CH 4 emissions. • GCRPS decreased the abundance of mcrA gene while stimulated that of pmoA gene. • Microbial parameters are useful to better predict CH 4 emissions from rice paddies. While water management has been documented to regulate CH 4 emissions from rice paddies, the mechanisms behind the association between CH 4 emissions and functional microbes remain unclear under water-saving ground cover rice production systems (GCRPS). In GCRPS, the soil is kept aerobic by maintaining 80 %–90 % of the water holding capacity but without standing water over the entire rice-growing season, and the soil surface is covered with rice straw or plastic film to reduce water evaporation. A split-plot field experiment was conducted to examine the effects of various GCRPS-related water-saving regimes on CH 4 emissions by linking to CH 4 -related microbes over the 2015 and 2016 rice growing seasons in a typical Chinese rice field. Methane fluxes and related functional genes [methanogens ( mcrA and methanogenic archaeal 16S rRNA ) and methanotrophs ( pmoA )] abundances were simultaneously measured using the closed chamber method and molecular techniques, respectively. The results showed that relative to the conventional waterlogged control (WRPS), GCRPS-related water-saving practices consistently reduced CH 4 emissions, which was largely attributed to the decreased relative abundance of the methanogenic functional gene mcrA while the methanotrophic functional gene pmoA increased. When averaged over the two rice seasons, the grain yield was 17.38 % and 12.22 % greater under the GCRPS -straw and GCRPS -film water-saving systems relative to WRPS, respectively. Water-saving regimes decreased the yield-scaled CH 4 emissions as compared with the WRPS, especially under GCRPS -film . The CH 4 fluxes showed a positive correlation with the relative abundance of mcrA and its ratio to pmoA , but a negative correlation with the relative abundance of pmoA . The performance of CH 4 -simulated models could be improved by incorporating microbial parameters to predict CH 4 emissions from rice fields. Overall, this study updates our understanding of the microbial mechanisms underlying CH 4 emissions from water-saving GCRPSs. We proposed the GCRPS regime with biodegradable film mulching as a desirable water-saving strategy to reconcile high yields and low CH 4 emissions in rice production.

Evaluation of carbon, nitrogen footprint and primary energy demand under different rice production systems

Abstract Ground cover rice production system (GCRPS) has been widely proved to enhance rice yield and save irrigation water. However, information on the environmental impacts and energy consumption of GCRPS remains unknown. In this study, a two-year field experiment was conducted in Hubei Province of China including conventional paddy (W1) and GCRPS (W2, maintaining saturated soil water content; W3, maintaining 80% of the field capacity), factorially combined with different N management practices (N1, zero-N application; N2, single urea application; N3, split application of urea for W1 treatments; manure substitution for W2 and W3 treatments). By combining a soil-crop model simulation with a footprint analysis method, a life cycle inventory was built to evaluate yield-scaled carbon footprint (CF), nitrogen footprint (NF), and primary energy demand (PED) of different rice production systems. Results showed that, compared to conventional flooding paddy, GCRPSs significantly reduced CF, NF, and PED by 31%–35%, 37%–40%, and 17%–18% respectively. Across different N treatments under GCRPS, manure substitution reduced the CF (20%–22%), NF (11%–37%), and PED (25%–27%) compared to the single urea treatments. The hotspot’s contribution of N2O to CF, NH3 to NF, and N-fertilizer production to PED under GCRPS can be reduced by 77%, 33%, and 51% respectively compared to the single urea treatments. Therefore, W3N3 was recommended as the best management practice achieving less CF of 541.4 kg CO2 eq t−1, NF of 2.4 kg N eq t−1, and PED of 2440.0 MJ t−1 meanwhile maintaining high rice yield of 8526 kg ha−1 in the study region.

Innovative water-saving ground cover rice production system increases yield with slight reduction in grain quality

Ground cover rice production system (GCRPS) is known to increase grain yield and reduce irrigation water and greenhouse gas emission. However, whether this innovative technology affects commercial and nutritional rice quality remains unknown. Thus, a three-year field experiment was conducted to compare three production systems: traditional paddy (Paddy) and GCRPS under two soil moisture conditions, namely, saturated and 80% of soil water-holding capacity combined with three nitrogen fertilizer regimes. We analyzed the grain-milling quality (brown rice rate, milled rice rate and head rice recovery), the appearance quality (chalky rice rate and grain size), eating quality (amylose concentration) and nutritional quality (protein and 15 amino acids concentration). Results showed that compared with Paddy, the average rice grain yield, water and nitrogen use efficiency were significantly higher in GCRPS. The milling quality was improved in GCRPS, whereas the appearance quality decreased. Amylose concentration was 7.6% higher in saturated GCRPS than in Paddy. Moreover, protein concentration was 11.5%–13.1% lower in GCRPS than in Paddy and total amino acid concentration was reduced by 6.9%, whereas protein and total amino acid yield were significantly improved. Meanwhile, the concentrations of six essential amino acids were similar to those in Paddy, whereas non-essential amino acid concentration decreased in GCRPS. Overall, our findings showed that suitable N management practices for GCRPS are to be developed to further enhance the protein and amino acid concentrations.

Post-seasonal effects of water-saving rice production regimes on N2O emissions in an annual rice-barley rotation system

Ground cover rice production system (GCRPS)-related water-saving practices have been proposed to alleviate the challenge of increasing water resource scarcity. While water irrigation regime can directly affect nitrous oxide (N2O) emissions in the rice-growing season, it may also have the post-seasonal effects on N2O emissions in the barley-growing season within an annual rice-barley rotation system. A split-plot experiment was conducted to examine the effects of various water-saving rice production regimes on N2O emissions during the following barley-growing season. The abundances of soil N2O-related functional genes (AOA and AOB, and nirS, nirK and nosZ) were simultaneously determined using qPCR. The results showed that, relative to the waterlogged control, GCRPS-film and moisture irrigated rice production system (MRPS) consistently stimulated N2O emissions and associated yield-scaled N2O emissions in the barley-growing season, while they were decreased by 10% and 15% under the GCRPS-straw water-saving system, respectively. Compared with the waterlogged control, the water-saving rice practices increased the abundances of AOA and nosZ genes in the barley-growing season. The abundances of AOA and nirS genes had significant positive correlations with N2O fluxes, as a contrary to the negative correlation of nosZ gene abundances with N2O fluxes. The barley grain yields were slightly increased following water-saving practices but showed no statistical significance among different irrigation systems. Overall, the water-saving ground cover rice production system with rice straw mulching can be encouraged to reconcile high grain yields and low N2O emissions in the following upland cropping seasons.

Ground cover rice production system reduces water consumption and nitrogen loss and increases water and nitrogen use efficiencies

Conventional flooding paddy systems consume large amounts of water and results in water body pollution due to low water (WUE) and nitrogen use efficiencies (NUE). Therefore, rice production systems with water-saving and high resource use efficiencies need to be developed. A two-year field experiment was conducted in Fangxian County of Hubei Province in Central China. The experiment consisted of a conventional flooding paddy system (Paddy) and ground cover rice production system (GCRPS) with two different water management practices (i.e., GCRPSsat and GCRPS80%), factorially combined with three different N management practices (N1, no N fertilizer; N2, 150 kg urea N ha−1; and N3, 75 kg urea N ha−1 plus 75 kg N ha−1 as manure). In this study, we applied soil-crop system model (WHCNS, soil water heat carbon nitrogen simulator) coupled with simplified net mineralization model (LIXIM) to quantitatively evaluate water consumption, N fates, and rice growth under different N management practices for both Paddy and GCRPS. Results showed that the simulated soil water storage, soil mineral N content, leaf area index, dry matter, crop N uptake, and yield agreed well with the measured values. The Nash-Sutcliffe efficiency and index of agreement were greater than 0.51 and 0.86, respectively. Compared with Paddy, GCRPS significantly reduced the quantities of irrigation water (78.1%), nonproductive water consumption (evaporation, drainage, and runoff) (69.3%), and nitrate leaching (74.5%), and significantly enhanced yield (12.6%), WUE (42.8%), and NUE (20.0%). The WUE was ranked as follows: GCRPS80% > GCRPSsat > Paddy. In GCRPSs, GCRPS80% further decreased the nonproductive water consumption by 20.6% and did not reduce the yield compared with GCRPSsat. For different N management practices, no significant differences were found between the N2 and N3 treatments in terms of yields and NUEs. Meanwhile, the WUE of N3 (1.50 kg m-3) was significantly higher than that of N2 (1.41 kg m-3) in GCRPS. Hence, GCRPS80%_N3 was recommended as the best management practice for achieving high yield and high resource use efficiencies with the least environmental impact in the study region.

Greenhouse gas emissions from rice field cultivation with drip irrigation and plastic film mulch

Ground cover rice production system is a promising technique with potentials to alleviate the effect of the increasing water-scarcity on rice production. Hence, finding appropriate management practices under this system is crucial for reducing global warming without yield loss. In this study, CH4 and N2O were quantified and contrasted in drip irrigation with plastic-film-mulch system (DP) and a continuous flooded rice cultivation system (CF) during two rice growing seasons of 2016 and 2017. The range of methane fluxes observed between irrigation regimes was (− 0.36 to 0.43 mg m−2 h−1) and (− 0.77 to 4.66 mg m−2 h−1) in 2016 and 2017 respectively. The cumulative CH4 emissions in 2017 under CF and DP were 16 times and 5 times higher than in 2016 respectively. DP reduced cumulative CH4 flux by 194% and 69% in 2016 and 2017 respectively compared to CF. Emissions of N2O were low and insignificant for both irrigation regimes. Grain yields were comparable between irrigation regimes with an insignificant reduction of 19% and 5% under DP in 2016 and 2017 respectively. The GWP of the 2-year average was 89% reduced under DP compared to CF. Our findings demonstrated that the DP mitigated GHGs while sustaining rice yield as a result of low nitrogen fertilization application and intermittent soil saturation level.

Benefits of integrated nutrient management on N2O and NO mitigations in water-saving ground cover rice production systems

To cope with challenges of food security and water scarcity in rice production, water-saving ground cover rice production systems (GCRPSs) are increasingly adopted in China and globally. Reduced soil moisture as well as increased soil aeration and temperature under GCRPSs may promote soil N transformations, and in turn give rise to environmental challenges. These include emissions of the potent greenhouse gas nitrous oxide (N2O) and atmospheric pollutant nitric oxide (NO). Using conventional flooding rice cultivation as a reference, a three-year field experiment was conducted to investigate the performances of GCRPSs under inorganic (urea) or integrated nutrient management (a combination of synthetic and organic fertilizers), with regards to soil N2O and NO emissions as well as grain yields. N2O and NO emissions in GCRPSs exhibited high seasonal and interannual variations along with changes in soil inorganic N content and rainfall. When urea alone was applied, the average N2O and NO emissions from GCRPSs were 4.11 and 0.14 kg N ha−1, respectively. These emissions were significantly higher than those of conventional rice cultivation, with 1.47 and 0.052 kg N ha−1 for N2O and NO, respectively. When integrated nutrient management was performed for GCRPSs, N2O and NO emissions were reduced by approximately 77% and 50%, respectively, i.e., the emission magnitude comparable with N-trace gas losses from conventional rice cultivation. Moreover, GCRPSs with integrated nutrient management resulted in optimal grain yields, and thus, the yield-scaled N2O + NO emissions were the lowest compared to other treatments. Averaged over 3 years, the direct emission factors of N2O and NO for GCRPSs with urea alone were 2.58% and 0.064%, respectively. Those for GCRPSs with integrated nutrient management were 0.48% and 0.016%, respectively. The results of this study suggest that GCRPS with integrated nutrient management is an eco-friendly strategy for optimizing crop yields while mitigating N2O and NO emissions.

Enhanced nitrogen cycling and N2O loss in water-saving ground cover rice production systems (GCRPS)

An alternative to conventional cultivation of rice on submerged paddy soil is the ground cover rice production system (GCRPS), in which soil is covered with a plastic film to reduce the use of irrigation water. However, reduced soil water, increased aeration and temperature under GCRPS could promote soil nitrogen (N) mineralizing, nitrifying and denitrifying microbes and thus enhance soil N turnover and environmental losses e.g., through emission of the potent greenhouse gas nitrous oxide (N2O). At two sites with paired GCRPS and conventional paddy fields in Central China, we followed the abundance and activity of N-mineralizers, nitrifiers, denitrifiers and N2-fixing microbes based on qPCR from DNA and RNA directly extracted from soil. With decreasing soil water during the growing season, GCRPS strongly increased N mineralization as illustrated by several fold increased transcript levels of chiA. Furthermore, GCRPS reduced the nifH transcripts (encoding for nitrogenase) by 38% to 70% but increased the qnorB transcripts by 160% and archaeal amoA (AOA) transcripts by one order of magnitude (encoding for nitric oxide reductase and ammonia monooxygenase). This indicated a higher potential for N losses due to decreased biological N2 fixation, increased N leaching and increased N2O emission in GCRPS. The latter was confirmed by increased in situ N2O emissions. In addition, the N2-fixing and denitrifying microbial community composition as measured by a community fingerprinting approach was strongly influenced by GCRPS cultivation. Hence, our study reveals the microbial mechanisms underlying the risks for increased N mineralization, nitrification and N2O emissions and decreased biological N fixation in GCRPS. However, analysis of topsoil N stocks provided evidence that at least under N fertilizer application, GCRPS might overall maintain soil N stocks. This might result from a GCRPS-induced increase in fertilizer N use efficiency, root development and C and N return via residues, which appear to outbalance the observed effects on nitrification, gaseous N losses and biological N fixation, thereby preventing a net loss of total soil N.

The physiological processes and mechanisms for superior water productivity of a popular ground cover rice production system

Ground cover rice production systems (GCRPS) have been shown to both save water and increase yields compared to traditional paddy rice production systems (TPRPS). Physiological processes and mechanisms explaining the superiority of a popular GCRPS were investigated in a series of hydroponic, soil column and field experiments. Soil water, temperature and nitrogen, leaf gas exchange, plant water and nitrogen, growth and yield, transpiration, and water productivity were analyzed. Compared to TPRPS, plant available soil inorganic nitrogen was generally improved under GCRPS due to a combination of higher soil temperature and less nitrogen loss through non-physiological water consumption, especially during the early growing season. Consequently, more nitrogen was absorbed by plants under GCRPS except serious drought conditions, accompanied by higher nitrogen contents in plant tissues. Preferable specific leaf nitrogen might lead to higher leaf photosynthetic rate under optimal water conditions and less decrease relative to leaf transpiration rate under water stress. Therefore, rice under GCRPS grew faster with much more biomass and grain yield while transpiration consumption was limited in spite of the fact that the number of tillers and therefore leaf area were increased relative to TPRPS, resulting in superior water productivity. Compared to TPRPS, the root system under GCRPS was limited, but it could absorb enough water and nutrients (especially nitrogen) to support a relatively large canopy even when under water stress, which might be attributed to its higher nitrogen content and thus stronger activity.

Yield differences get large with ascendant altitude between traditional paddy and water-saving ground cover rice production system

In mountainous regions with high altitude, rice yield is mostly limited by low temperatures and insufficient irrigation facilities. The innovative ground cover rice production system (GCRPS) has a recognised potential to significantly increase rice grain yield where rice production is limited by water scarcity and low temperatures. We hypothesised that yield advantage of GCRPS over traditional Paddy might become larger at higher altitudes. We sampled 14 pairs of adjacent GCRPS and Paddy fields at altitudes of 900 m and 23 pairs at 500 m altitude with 3 replicates in central China. The study revealed that Badano et al. (2005) grain and straw yield were 40% and 35% greater in GCRPS compared to Paddy at 900 m, while the difference was only 10% and 15% at 500 m Bennie et al. (2006). Compared to Paddy, increase in productive tiller numbers, spikelets per square metre and percentage of filled grains were significantly larger in GCRPS at high than at low altitude Bennie et al. (2008). Soil temperature differences between GCRPS and Paddy were significantly higher at 900 m than at 500 m during the first month after transplanting. Our findings demonstrate that GCRPS has a good potential to increase rice yield in mountain regions with high altitudes where rice production is limited by low temperature and seasonal water shortage.

Urea deep placement reduces yield-scaled greenhouse gas (CH4 and N2O) and NO emissions from a ground cover rice production system

Ground cover rice production system (GCRPS), i.e., paddy soils being covered by thin plastic films with soil moisture being maintained nearly saturated status, is a promising technology as increased yields are achieved with less irrigation water. However, increased soil aeration and temperature under GCRPS may cause pollution swapping in greenhouse gas (GHG) from CH4 to N2O emissions. A 2-year experiment was performed, taking traditional rice cultivation as a reference, to assess the impacts of N-fertilizer placement methods on CH4, N2O and NO emissions and rice yields under GCRPS. Averaging across all rice seasons and N-fertilizer treatments, the GHG emissions for GCRPS were 1973 kg CO2-eq ha−1 (or 256 kg CO2-eq Mg−1), which is significantly lower than that of traditional cultivation (4186 kg CO2-eq ha−1or 646 kg CO2-eq Mg−1). Furthermore, if urea was placed at a 10–15 cm soil depth instead of broadcasting, the yield-scaled GHG emissions from GCRPS were further reduced from 377 to 222 kg CO2-eq Mg−1, as N2O emissions greatly decreased while yields increased. Urea deep placement also reduced yield-scaled NO emissions by 54%. Therefore, GCRPS with urea deep placement is a climate- and environment-smart management, which allows for maximal rice yields at minimal GHG and NO emissions.

Enhancement of root systems improves productivity and sustainability in water saving ground cover rice production system

In rice growing regions where water and temperature are growth limiting factors, the use of the innovative water-saving ground cover rice production system (GCRPS) leads to a substantial increase in yields and water use efficiency. However, so far the effect of GCRPS on root growth and its possible contribution to the observed increases in yield and water use efficiency remained unclear. In order to fill in this knowledge gap, we conducted a three-year experiment comparing two production systems: traditional paddy (Paddy) and GCRPS combined with two nitrogen fertilizer regimes (0, 150kgNha−1). The parameters investigated were root dry matter, length density and surface area at maximum tillering and flowering stage as well as grain yield and water use efficiency. Our study revealed the following findings: 1) Root dry matter, root length density and surface area were significantly higher in GCRPS than in Paddy at all soil depths. 2) Across the production systems, root dry matter, root length density and surface area at soil depth of 0–40cm at flowering stage were significant positively correlated to grain yield and total water use efficiency which suggested that improved root morphology traits, especially at flowering stage, contribute to higher grain yield and water use efficiency in GCRPS. Our results show that GCRPS has a positive effect on the development of rice roots and that the improved root development is of vital importance for higher yields. Furthermore, the improved root development in GCRPS may avoid potential lodging phenomena and increase soil organic carbon stocks, thus improving key soil functions.

Characterizing roots and water uptake in a ground cover rice production system.

Background and aimsWater-saving ground cover rice production systems (GCRPS) are gaining popularity in many parts of the world. We aimed to describe the characteristics of root growth, morphology, distribution, and water uptake for a GCRPS.MethodsA traditional paddy rice production system (TPRPS) was compared with GCRPS in greenhouse and field experiments. In the greenhouse, GCRPS where root zone average soil water content was kept near saturation (GCRPSsat), field capacity (GCRPSfwc) and 80% field capacity (GCRPS80%), were evaluated. In a two-year field experiment, GCRPSsat and GCRPS80% were applied.ResultsSimilar results were found in greenhouse and field experiments. Before mid-tillering the upper soil temperature was higher for GCRPS, leading to enhanced root dry weight, length, surface area, specific root length, and smaller diameter of roots but lower water uptake rate per root length compared to TPRPS. In subsequent growth stages, the reduced soil water content under GCRPS caused that the preponderance of root growth under GCRPSsat disappeared in comparison to TPRPS. Under other GCRPS treatments (GCRPSfwc and GCRPS80%), significant limitation on root growth, bigger root diameter and higher water uptake rate per root length were found.ConclusionsDiscrepancies in soil water and temperature between TPRPS and GCRPS caused adjustments to root growth, morphology, distribution and function. Even though drought stress was inevitable after mid-tillering under GCRPS, especially GCRPS80%, similar or even enhanced root water uptake capacity in comparison to TPRPS might promote allocation of photosynthetic products to shoots and increase water productivity.

Improving rice production sustainability by reducing water demand and greenhouse gas emissions with biodegradable films

In China, rice production is facing unprecedented challenges, including the increasing demand, looming water crisis and on-going climate change. Thus, producing more rice at lower environmental cost is required for future development, i.e., the use of less water and the production of fewer greenhouse gas (GHG) per unit of rice. Ground cover rice production systems (GCRPSs) could potentially address these concerns, although no studies have systematically and simultaneously evaluated the benefits of GCRPS regarding yields and considering water use and GHG emissions. This study reports the results of a 2-year study comparing conventional paddy and various GCRPS practices. Relative to conventional paddy, GCRPSs had greater rice yields and nitrogen use efficiencies (8.5% and 70%, respectively), required less irrigation (−64%) and resulted in less total CH4 and N2O emissions (−54%). On average, annual emission factors of N2O were 1.67% and 2.00% for conventional paddy and GCRPS, respectively. A cost-benefit analysis considering yields, GHG emissions, water demand and labor and mulching costs indicated GCRPSs are an environmentally and economically profitable technology. Furthermore, substituting the polyethylene film with a biodegradable film resulted in comparable benefits of yield and climate. Overall, GCRPSs, particularly with biodegradable films, provide a promising solution for farmers to secure or even increase yields while reducing the environmental footprint.

Modelling the effect of mulching on soil heat transfer, water movement and crop growth for ground cover rice production system

Soil-crop system models often failed to simulate the effect of plastic film mulching (FM) on soil heat transfer, water movement and crop growth due to lack of appropriate method and the measured data in the fields. The objectives of this study were to (i) improve the Soil Water Heat Carbon Nitrogen Simulator (WHCNS) model to simulate soil temperature, water content and rice growth under FM condition, and (ii) to analyze the effect of FM on water balance and water use efficiency (WUE) under different water and nitrogen (N) management, using the data of a two-year field experiment with a factorial design of two water (Wsat and W80%, soil water content was kept at saturation and 80% field capacity) and three N levels (N1: zero-N fertilizer; N2: 150kg urea Nha−1; and N3: 75kg urea N ha−1 plus 75kgNha−1 as manure) treatments. The results showed that the modified model accurately simulated the changes in soil temperature, soil water content, LAI, dry matter and yield under FM condition. The normalized root mean square error (nRMSE) were 4.7%, 4.5%, 24.5%, 16.5% and 7.9%, respectively, which were significantly smaller than the results simulated by the original model. Importantly, although there were no significant differences in average crop yields between two water input levels (W80% and Wsat), the amounts of irrigation and evaporation under W80% treatment were reduced significantly by 71.9% and 36.2%, respectively. And the WUE of W80% (1.13kgm−3) was higher than that of Wsat (0.84kgm−3). The ranking of WUE under different N management for W80% treatments was N2≈N3>N1. In conclusion, the modified WHCNS model performed significantly better in simulating the dynamics of water, heat, and crop growth under FM. Reduced irrigation with 80% field capacity and applying 75kg urea Nha−1 plus 75kgNha−1 as manure can achieve “more yield with less water”.

Benefit of using biodegradable film on rice grain yield and N use efficiency in ground cover rice production system

A ground cover rice production system (GCRPS) has been reported to reduce the consumption of irrigation water while increasing grain yield and water use efficiency in regions where water and temperature are limiting factors for rice production. However, all fertilizer must be applied in a single basal dose before the soil surface is covered by plastic film in GCRPS resulting in excessive vegetative crop growth and nitrogen deficiency during the reproductive stage. Furthermore, a severe drawback of GCRPS is soil and water pollution from residuals polyethylene film used for ground cover. A two-year field experiment was conducted using biodegradable film together with treatments comparing all basal application of N with application of N as three splits and a single basal fertilization of urea plus manure. We examined N uptake and crop growth from transplanting harvest, rice grain yield, yield components, dynamics of tillers and shoot dry matter, and N recovery efficiency.Compared to basal application of all N fertilizer in GCRPS, split application of N or a basal combination of urea plus manure in conjunction with the use of biodegradable film 1) significantly increased rice grain yield, number of productive tillers, and spikelets per square meter; 2) improved crop growth rate and N uptake rate from panicle initiation to maturity; and 3) significantly increased agronomic efficiency of N fertilizer and recovery efficiency of N in grains. Our results highlight that using biodegradable film instead of standard plastic film allows for split application of fertilizers, which increases yield and N use efficiency as well as significantly reduce environmental pollution with plastic film in GCRPS.

Water consumption and water-saving characteristics of a ground cover rice production system

Summary The ground cover rice production system (GCRPS) offers a potentially water-saving alternative to the traditional paddy rice production system (TPRPS) by furrow irrigating mulched soil beds and maintaining soils under predominately unsaturated conditions. The guiding hypothesis of this study was that a GCRPS would decrease both physiological and non-physiological water consumption of rice compared to a TPRPS while either maintaining or enhancing production. This was tested in a two-year field experiment with three treatments (TPRPS, GCRPSsat keeping root zone average soil water content near saturated, and GCRPS80% keeping root zone average soil water content as 80–100% of field water capacity) and a greenhouse experiment with four treatments (TPRPS, GCRPSsat, GCRPSfwc keeping root zone average soil water content close to field water capacity, and GCRPS80%). The water-saving characteristics of GCRPS were analyzed as a function of the measured soil water conditions, plant parameters regarding growth and production, and water input and consumption. In the field experiment, significant reduction in both physiological and non-physiological water consumption under GCRPS lead to savings in irrigation water of ∼61–84% and reduction in total input water of ∼35–47%. Compared to TPRPS, deep drainage was reduced ∼72–88%, evaporation was lessened ∼83–89% and transpiration was limited ∼6–10% under GCRPS. In addition to saving water, plant growth and grain yield were enhanced under GCRPS due to increased soil temperature in the root zone. Therefore, water use efficiencies (WUEs), based on transpiration, irrigation and total input water, were respectively improved as much as 27%, 609% and 110% under GCRPS. Increased yield attributed to up to ∼19%, decreased deep drainage accounted for ∼75%, decreased evaporation accounted for ∼14% and reduced transpiration for ∼5% of the enhancement in WUE of input water under GCRPS, while increased runoff and water storage had negative influence on WUE (−7.5 and −3.7%, respectively) for GCRPS compared to TPRPS. The greenhouse experiment validated the results obtained in the field by simplifying the non-physiological water consumption processes, and thus confirming the relative importance of physiological processes and increased WUE under GCRPS.

Ground cover rice production systems increase soil carbon and nitrogen stocks at regional scale

Abstract. Rice production is increasingly limited by water scarcity. Covering paddy rice soils with films (so-called ground cover rice production system: GCRPS) can significantly reduce water demand as well as overcome temperature limitations at the beginning of the growing season, which results in greater grain yields in relatively cold regions and also in those suffering from seasonal water shortages. However, it has been speculated that both increased soil aeration and temperature under GCRPS result in lower soil organic carbon and nitrogen stocks. Here we report on a regional-scale experiment conducted in Shiyan, a typical rice-producing mountainous area of China. We sampled paired adjacent paddy and GCRPS fields at 49 representative sites. Measured parameters included soil carbon (C) and nitrogen (N) stocks (to 1 m depth), soil physical and chemical properties, δ15N composition of plants and soils, potential C mineralization rates, and soil organic carbon (SOC) fractions at all sampling sites. Root biomass was also quantified at one intensively monitored site. The study showed that: (1) GCRPS increased SOC and N stocks 5–20 years following conversion from traditional paddy systems; (2) there were no differences between GCRPS and paddy systems in soil physical and chemical properties for the various soil depths, with the exception of soil bulk density; (3) GCRPS increased above-ground and root biomass in all soil layers down to a 40 cm depth; (4) δ15N values were lower in soils and plant leaves indicating lower NH3 volatilization losses from GCRPS than in paddy systems; and (5) GCRPS had lower C mineralization potential than that observed in paddy systems over a 200-day incubation period. Our results suggest that GCRPS is an innovative production technique that not only increases rice yields using less irrigation water, but that it also increases SOC and N stocks.