Water-saving Ground Cover Rice Production Research Articles

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.

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.

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.

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.

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.

More rice with less water – evaluation of yield and resource use efficiency in ground cover rice production system with transplanting

Adoption of the innovative water-saving ground cover rice production system (GCRPS) based on transplanting of rice seedlings under high soil moisture conditions, resulted in an overall increase in grain yield compared to previous reports on GCRPS employing direct seeding. However, there is a lack of quantitative information on water and nitrogen use efficiency as affected by water and nitrogen management in GCRPS-transplanting. To close this knowledge gap, we conducted a two-year field experiment with traditional paddy rice (Paddy) and GCRPS-transplanting under two soil moisture conditions (GCRPSsat and GCRPS80%), combined with 3 nitrogen fertilizer management regimes (0, 150kg urea-N/ha as basal fertilizer for Paddy and GCRPS, 150kg urea-N/ha in 3 splits for Paddy or 75kg urea-N/ha plus 75kg N/ha as chicken manure for GCRPS). Grain yield, water and nitrogen use efficiency, stable isotope 13C of plant shoots and yield components were evaluated.The study showed: (1) compared to Paddy, both GCRPSsat and GCRPS80% produced significantly more grain yield, while no significant difference in grain yield was found between both GCRPS treatments. (2) Irrigation water use efficiency was increased by 140% in GCRPSsat and >500% in GCRPS80%, while total water use efficiency was improved by 52–96% as compared to Paddy. (3) δ13C of plant shoots was significantly higher in GCRPS than in Paddy, and showed significant positive correlations with total and irrigation water use efficiencies. (4) Compared to Paddy, agronomic N use efficiency was significantly higher in both forms of GCRPS. However, N recovery rates were only significantly higher in GCRPS than in Paddy when all urea nitrogen was applied as basal fertilizer before transplanting. With improved fertilizer N management, i.e., split N application in Paddy or combined application of urea and chicken manure in GCRPS, there were no significant differences. Overall, this quantitative evaluation of water use efficiency highlights that the use of GCRPS involving transplanting of seedlings has a great potential to reduce irrigation water input, increase grain yield and resource use efficiency.

Water-saving ground cover rice production system reduces net greenhouse gas fluxes in an annual rice-based cropping system

Abstract. To safeguard food security and preserve precious water resources, the technology of water-saving ground cover rice production system (GCRPS) is being increasingly adopted for rice cultivation. However, changes in soil water status and temperature under GCRPS may affect soil biogeochemical processes that control the biosphere–atmosphere exchanges of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2). The overall goal of this study is to better understand how net ecosystem greenhouse gas exchanges (NEGE) and grain yields are affected by GCRPS in an annual rice-based cropping system. Our evaluation was based on measurements of the CH4 and N2O fluxes and soil heterotrophic respiration (CO2 emissions) over a complete year, and the estimated soil carbon sequestration intensity for six different fertilizer treatments for conventional paddy and GCRPS. The fertilizer treatments included urea application and no N fertilization for both conventional paddy (CUN and CNN) and GCRPS (GUN and GNN), and solely chicken manure (GCM) and combined urea and chicken manure applications (GUM) for GCRPS. Averaging across all the fertilizer treatments, GCRPS increased annual N2O emission and grain yield by 40 and 9%, respectively, and decreased annual CH4 emission by 69%, while GCRPS did not affect soil CO2 emissions relative to the conventional paddy. The annual direct emission factors of N2O were 4.01, 0.09 and 0.50% for GUN, GCM and GUM, respectively, and 1.52% for the conventional paddy (CUN). The annual soil carbon sequestration intensity under GCRPS was estimated to be an average of −1.33 Mg C ha−1 yr−1, which is approximately 44% higher than the conventional paddy. The annual NEGE were 10.80–11.02 Mg CO2-eq ha−1 yr−1 for the conventional paddy and 3.05–9.37 Mg CO2-eq ha−1 yr−1 for the GCRPS, suggesting the potential feasibility of GCRPS in reducing net greenhouse effects from rice cultivation. Using organic fertilizers for GCRPS considerably reduced annual emissions of CH4 and N2O and increased soil carbon sequestration, resulting in the lowest NEGE (3.05–5.00 Mg CO2-eq ha−1 yr−1). Accordingly, water-saving GCRPS with organic fertilizer amendments was considered the most promising management regime for simultaneously achieving relatively high grain yield and reduced net greenhouse gas emission.

Ground cover rice production systems are more adaptable in cold regions with high content of soil organic matter

Water-saving ground cover rice production systems (GCRPS) can increase grain yield in mountainous regions with seasonal water shortages and cold, stress-inducing temperatures. For GCRPS the soil surface is covered with a plastic film which can effectively alleviate low-temperature stress in the early growth stage due to thermal insulation. Since topdressing is not possible in GCRPS, farmers usually apply all fertilizer as basal dressing before transplanting; this can lead to excessive growth during the vegetative period and low crop growth during the reproductive stage. However, we hypothesized that the technique might be well suited for marginal rice growing regions in the Northeast of China. These areas are characterized by a short vegetation period and soils rich in organic matter, delivering the required amounts of nitrogen (N) over the course of the season due to N mineralization. Here we report on a two year experiment, conducted in the Northeast of China, that compared grain yields between GCRPS and conventional paddy rice production (paddy) at three N fertilizer rates (0, 90 and 135kgNha−1). Furthermore, crop growth rate, apparent nitrogen recovery rate and nitrogen physiological use efficiency were calculated. Compared to paddy, GCRPS significantly increased grain yield by 31%, 14% and 10% at N fertilizer rate of 0, 90 and 135kgNha−1, respectively. Grain yield at 135kgNha−1 was significantly higher than 90kgNha−1 in paddy, but no difference was found between N fertilizer rates in GCRPS. However, grain yield at 90kgNha−1 in GCRPS was still higher than that at 135kgNha−1 in paddy. The considerably higher number of filled grains in GCRPS indicates that crop growth rate during the reproductive stage was improved, likely due to the positive effect of higher mineralization of organic N on crops with a low rate of N fertilization. Our study demonstrates that GCRPS is a very promising and highly suitable technique for rice production in cold regions in the North of China that possess high content of soil organic matter. Moreover, it shows that N fertilization can be minimized due to the autochthonous N supply from soil rich in organic matter. In regards to the decomposition of SOM in GCRPS over time, mutual feedback mechanisms located both above and below ground revealed that the potential loss of SOM stocks can be compensated by a greater input of root biomass in GCRPS.

Do water-saving ground cover rice production systems increase grain yields at regional scales?

“Ground cover rice production system” (GCRPS) is an innovative production technique that uses significantly less water than traditional paddy cultivation (Paddy). Consequently, this system may allow for expansion of rice crops to regions with limited water availability. Earlier studies have reported contradictory grain yields and yield performances of GCRPS versus Paddy systems in experimental plots. However, the actual effects of using GCRPS on yields under real farming practices on heterogeneous environments are still unknown. In this study, we compared grain yields and yield components between GCRPS and Paddy systems by sampling paired adjacent farmer fields at 36 representative sites in the region of Shiyan, central China, which is typical for many mountainous areas across China. Furthermore, we characterized soil physico-chemical properties, soil redox potential, stable carbon isotopic composition of plant leaves, and monitored soil temperature during the growing season.Our study revealed the following findings: (1) Across all sites GCRPS significantly increased grain yield by on average 18%. Statistical analysis allowed us to classify three different groups of yield performance within the 36 paired sites: (a) group of significant increase (SI; n=22) with increases in yields on average 32%, (b) group showing no significant increase (NI; n=9), here yields increased on average 6%, and (c) sites with grain yields showing a small (−8%), but non significant decrease (ND; n=5). (2) Shoot dry biomass, number of productive tillers, spikelets per square meter and percentage of filled grains were significantly larger for GCRPS as compared to Paddy systems. (3) No significant differences in soil physical and chemical properties were found for the 0–20cm layer between GCRPS and Paddy systems. (4) Significantly higher soil temperatures observed in GCRPS during the first month after transplanting were only found in the SI sites, which showed that higher temperature during this critical period was the decisive factor for GCRPS-induced yield enhancement. (5) The average δ13C of plant leaves and soil redox potential were significantly higher in GCRPS than Paddy for the SI group only. In-detail analyses of the 5 pairs showing decreases in yields (ND) between GCRPS and Paddy systems revealed the lack of significant effects observed in some key parameters such as soil temperatures during the first month, δ13C of plant leaves and soil redox potential. These facts strongly suggested that unnecessary excess water was used, thus hampering GCRPS-induced increases in soil temperature and grain yields, and unequivocally signaling that appropriate water management by farmers is crucial for the successful implementation of GCRPS. Our study demonstrates the large potential of GCRPS to increase grain yields in regions where rice growth is both limited by low temperatures and water scarcity.

Growth and yield formation of rice ( Oryza sativa L.) in the water-saving ground cover rice production system (GCRPS)

A new water-saving ‘Ground Cover Rice Production System’ (GCRPS) was evaluated in 2001 and 2002 near Beijing, North China. Using GCRPS, lowland rice was cultivated without a standing water layer during the entire growth period and plots were irrigated when soil water tension was below 15 kPa (approximately 90% water holding capacity). In order to prevent soil evaporation, the soil surface was covered with 14 μm thick plastic film (GCRPS Plastic) or mulched with straw (GCRPS Straw). In a third GCRPS treatment the soil was left uncovered (GCRPS Bare). These treatments were compared with lowland rice cultivated under traditional paddy conditions (Paddy control). In an additional treatment with bare soil, one aerobic rice variety was cultivated. Compared to Paddy control, only 32–54% of irrigation water was applied in GCRPS treatments. Plants in GCRPS were smaller, developed fewer panicles and had a smaller leaf area index compared to Paddy control. Yield was significantly less in GCRPS Bare and GCRPS Straw compared to Paddy control in both years, while yield in GCRPS Plastic was only 8% less than the Paddy control yield in 2002. Water-use efficiency (WUE, gram grain yield per litre water input) in GCRPS Plastic was higher (0.35) than in Paddy control (0.23). Grain yield was highly significantly correlated with maximum leaf area index and leaf area index duration. Among yield components, the number of productive tillers had the greatest positive effect on yield, while the number of grains per panicle, thousand-grain weight and harvest index remained almost unaffected. Under uncovered condition, the aerobic rice variety had a significantly higher harvest index (HI), yield, and WUE compared to the lowland rice variety (GCRPS Bare). The experiment demonstrates that GCRPS has potential to save substantial amounts of water at relatively minor yield penalties, if stress factors such as low soil temperature, water deficit, and nutrient deficiencies during the vegetative growth stage are avoided by suitable management practices.