Chinese Double Rice Cropping System Research Articles

Differences in uptake, utilization and loss of nitrogen and phosphorus in a Chinese double rice cropping system under different irrigation and fertilization managements

In order to optimize water and fertilizer use in the double-cropping rice in eastern Fujian Province, a field runoff plot experiment was conducted to investigate rice yield, nutrient uptake, and runoff losses of N (nitrogen) and P (phosphorus) in the T0(no chemical fertilization with traditional flooding irrigation), T1(common chemical fertilizer of 273 kg N·hm-2, 59 kg P·hm-2, and 112 kg K·hm-2 combined with traditional flooding irrigation), T2(chemical fertilizer of 240 kg N·hm-2, 52 kg P·hm-2, and 198 kg K·hm-2 combined with traditional flooding irrigation) and T3(chemical fertilizer combined with shallow intermittent irrigation) treatments. Results showed that early rice grain yield in the T1, T2 and T3 treatments significantly increased by 0.7, 1.0, 1.1 times, late rice grain yield significantly increased by 0.9, 1.1, 1.0 times compared to that in the T0 treatment, respectively. The T1, T2 and T3 treatments significantly increased the uptake of N and P in aboveground parts of the plants, especially in grains. The T1, T2 and T3 treatments significantly increased N uptake by 1.1, 1.2, 1.2 times, increased P uptake by 0.9, 1.4, 1.6 times in early-season grains, and significantly increased N uptake by 0.8, 1.0, 1.0 times, increased P uptake by 0.7, 0.9, 0.9 times in late-season grains, compared to T0, respectively. Furthermore, T3 increased agronomic N use efficiency (AEN) and agronomic P use efficiency (AEP) by 71.1% and 69.2% in early rice plants, increased AEN and AEP by 26.4% and 25.0% in late rice plants, whereas T3 decreased total dissolved N (DN) by 16.0% in comparison with T1. Dissolved inorganic N loss in surface runoff occurred mainly in the form of NO3--N (nitrate N) under different water and fertilizer regimes. However, there were no significant differences in AEN and AEP between T2 and T3 treatments. These findings suggested that optimal applications of water and fertilizers (T3) might increase N and P uptake in rice plants, maintain yield, and reduce N loss, especially in the form of NO3--N in surface water from early rice field. In general, this study could provide theoretical support for the optimization of irrigation and fertilization and for the control of N and P non-point source pollution from the double cropping rice paddy fields in eastern Fujian Province.

Net global warming potential, greenhouse gas intensity and carbon footprint as affected by different tillage systems from Chinese double-cropping paddy fields

Conservation tillage may be an alternative system for rice production in China, yet differences in net global warming potential (NGWP), greenhouse gas intensity (GHGI) and carbon footprint (CF) among different tillage methods are poorly documented. Accordingly, a 3-year field experiment was conducted to simultaneously measure methane (CH4) and nitrous oxide (N2O) emissions and changes in soil organic carbon (SOC) under conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) methods in Chinese double-rice cropping systems. There was no difference in SOC content among the tillage treatments, but SOC sequestration under NT reduced obviously with the increase of soil depth at 0∼20 cm. CH4 emissions were conspicuously correlated with SOC content at soil depth below 5 cm. Tillage methods had no significant effect on N2O emission, except for the substantial N2O emission under NT during non-rice season. Compared with the NT plots, the annual CH4 emission and NGWP were significantly increased in the CT and RT plots over the three years. There were no significant differences among the tillage methods with respect to GHGI and CF, whereas the grain yields were greatly increased in the RT plot. We conclude that RT practice are promising in rice production for higher grain yield with similar GHGI and CF, while increasing productivity of the NT system is a high priority since the CH4 emission and NGWP can be dramatically reduced.

Responses of net assimilation rate to elevated atmospheric CO2and temperature at different growth stages in a double rice cropping system

Effects of elevated atmospheric CO2 concentration and temperature on rice dry matter accumulation vary in planting regions and cropping systems. It remains unclear how dry matter productivity responds to factorial combination of elevated CO2 and temperature in the double rice cropping system of China. Field experiments were conducted using open-top chambers (OTC) to simulate different scenarios of elevated CO2 and/or temperature for three rotations of double rice in Jingzhou, Hubei Province. Liangyou 287 and Xiangfengyou 9 were used as rice cultivar for early rice and late rice, respectively. There were five treatments: UC, paddy field without OTC covering; CK, OTC with the similar temperature and CO2 concentration to field environment; ET, OTC with 2 ℃ temperature elevation; EC, OTC with 60 μmol·mol-1 CO2 elevation; ETEC, OTC with simu-ltaneous 2 ℃ temperature elevation and 60 μmol·mol-1 CO2 elevation. We measured aboveground biomass, leaf area index (LAI) and net assimilation rate (NAR) of dry matter under different treatments. Our results showed that elevated CO2 and/or temperature had no significant effects on NAR from transplanting to jointing, increased NAR from jointing to heading, but decreased NAR from heading to maturity (except for EC treatment in early rice). Elevated CO2 and/or temperature promoted leaf area development at all growth stages, with ETEC showing the highest increase in LAI except at maturity. Warming and CO2 enrichment jointly promoted dry matter accumulation at heading, with ETEC increasing aboveground biomass by 10.3%-39.8% and 23.6%-34.4% compared with CK in early rice and late rice, respectively. At maturity of early rice, elevated temperature partly offset the positive effects of elevated CO2 on aboveground biomass, as shown by a reduction of 3.2%-14.1% under ETEC compared with EC. Contrarily at maturity of late rice, co-elevation of CO2 and temperature further increased aboveground biomass, showing a synergistic interaction. Results from regression analysis showed that warming and CO2 enrichment had positive effects on NAR at vegetative stages of double rice, while warming showed negative effects on NAR at reproductive stages. Considering the dissimilarities in growth characteristics, growing periods and ambient temperature, elevated CO2 and temperature might increase dry matter production in the Chinese double rice cropping system.

Integrated soil fertility and yield trend in response to long-term fertilisation under the Chinese double rice-cropping systems

Soil fertility is fundamental in determining crop productivity and sustainability in farming systems. A long-term fertiliser experiment in Chinese double rice-cropping systems initiated in 2011 was used in this study to gain an insight into a complete estimating of soil fertility. The six fertiliser treatments included mineral fertiliser (NP, NK, and NPK), combined NPK with farmyard manure (NPKM) or crop straw (NPKS), and no fertiliser application as a control. Results showed that grain yield averaged 5.5–13.0 t/ha/year, and significant increasing trends were observed in the phosphorus-applied plots (NP, NPK, NPKM, and NPKS), but the treatments without phosphorus applied (control and NK) resulted in declining trends in both early- and late-rice yields. After long-term rice cultivation, the contents of total and available phosphorus significantly declined in phosphorus-deficient plots compared to other treatments. Regression analysis showed that the improvement in grain yields was positively correlated with the increased soil fertility over treatments. Relative to the NPK treatment, the NPKM treatment greatly enhanced soil fertility from 0.50 to 0.78, and particularly dramatically increased the content of available soil phosphorus. Therefore, the high grain yield and soil fertility can be simultaneously achieved by long-term balanced fertiliser applications in Chinese double rice-cropping systems.

Leaf photosynthesis and stomatal conductance acclimate to elevated [CO2] and temperature thus increasing dry matter productivity in a double rice cropping system

Changes in atmospheric CO2 concentration ([CO2]) and temperature have impacts on leaf photosynthesis (Anet) and stomatal conductance (Gs) of rice, which strongly affect dry matter productivity. Understanding of the acclimation responses of Anet and Gs under elevated [CO2] and/or temperature is limited. A field experiment of double rice (early rice-late rice rotation) was conducted using open-top chambers from 2013 to 2016 in Hubei Province, Central China, with two levels of [CO2] (ambient, ambient + 60 μmol mol−1) and two levels of temperature (ambient, ambient + 2°C). Averaging across the four-year experiment, elevated [CO2] and elevated temperature increased Anet by 2.4 %–9.4 % and 2.4 %–10.7 %, respectively at pre-heading stages. A positive interaction was observed between elevated [CO2] and temperature in early rice which further increased Anet, while the interaction was not additive in late rice. Elevated [CO2] caused lower Gs and partly offset the stimulation of elevated temperature on Gs at tillering and jointing. At post-heading stages, photosynthetic acclimation to elevated [CO2] was observed as the stimulation of Anet was not continued. Elevated temperature decreased Anet by 1.7 %–16.6 % and further accelerated photosynthetic down-regulation by elevated [CO2]. Warming reduced Gs at milking and maturity in early rice because of high ambient temperature, which resulted in stomatal limitation to photosynthesis, but its effects on Gs in late rice were positive because the ambient temperature was low. Generally, Gs acclimated to warming and CO2 enrichment in parallel with Anet when there were no environmental constraints. Earlier leaf senescence, decreased leaf SPAD, lower seed-setting rate or larger sink capacity caused by elevated [CO2] and/or temperature might directly or indirectly explain the down-regulation on photosynthesis after heading. Our results show that warming alters the acclimation of leaf photosynthesis and stomatal conductance to CO2 enrichment and the combined effects differ between growth stages, and indicate that co-elevation of [CO2] and temperature may increase dry matter productivity in the Chinese double rice cropping system.

Air warming and CO2 enrichment increase N use efficiency and decrease N surplus in a Chinese double rice cropping system

Effectiveness of N might be modified in rice cultivation under future climate change with elevated atmospheric CO2 concentration ([CO2]). At present, limited information is available to understand how plant N uptake and N use efficiency respond to elevated [CO2] and/or temperature in Chinese double rice cropping systems. A four-year field experiment was therefore conducted using open-top chambers with varying [CO2] (ambient, ambient +60 μmol mol−1) and varying temperature (ambient, ambient +2 °C) in Hubei Province, Central China. Compared with ambient conditions, elevated [CO2] increased plant N uptake and N use efficiency, as measured by fertilizer N recovery efficiency (NRE), N agronomic efficiency (NAE), N physiological efficiency (NPE) and apparent system N use efficiency (NUEsys), in both early rice and late rice. CO2 enrichment tended to decrease soil mineral N concentration since more N was assimilated by plants. Elevated temperature led to lower plant N uptake and decreased NRE and NAE in early rice, due to a reduction in grain yield induced by heat injury. In contrast, warming increased plant N uptake and N use efficiency in late rice as no heat stress existed. Warming tended to increase soil mineral N concentration in early rice but had negligible effects in late rice. When elevated [CO2] and temperature were combined, the positive effects of CO2 enrichment for N utilization were able to compensate for the negative effects of warming in early rice, while the interaction was synergetic in late rice. Hence, co-elevation of [CO2] and temperature led to higher N use efficiency (64.6% for NUEsys across four years) and decreased annual N surplus by 28.6–36.5 kg N ha−1 compared with ambient conditions. Our findings confirm that CO2 enrichment and air warming can improve N use efficiency at both crop level and system level in Chinese double rice cultivation.

Variable effects of 2°C air warming on yield formation under elevated [CO2] in a Chinese double rice cropping system

Elevated atmospheric CO2 concentration ([CO2]) and temperature can strongly affect rice (Oryza sativa L.) production. However, the impact of warming is variable depending on ambient temperature and cropping system. Little is known about the effect of elevated temperature and its interaction with elevated [CO2] in the Chinese double rice cropping system. To study this issue, field experiments were conducted using open-top chambers (OTC) with varying [CO2] (ambient, ambient+60 μmol mol−1) and varying temperature (ambient, ambient+2 °C) for 4 rotations of double rice from 2013 to 2016. Elevated [CO2] significantly increased grain yield in both early rice and late rice. This could be attributed to greater aboveground biomass, higher panicle number (m-2), spikelet number (per panicle) and 1000-grain weight. Elevated temperature decreased yield in early rice (except for 2016) due to decreases in % filled grains and 1000-grain weight. Elevated temperature increased yield in late rice due to increases in aboveground biomass, number of panicles and spikelets, although % filled grains decreased. We found that warming had positive effects on tiller development and dry matter accumulation during the pre-heading period both in early and late rice, which contributed to yield formation. When elevated temperature and [CO2] were combined, yield changed by −1.9–23.7% in early rice compared with ambient condition as warming partly offset the benefits of CO2 enrichment, while yield increased by 14.3–18.8% in late rice due to a synergy between warming and CO2 enrichment. The benefits of CO2 enrichment for fertile spikelets (m-2) and aboveground biomass could reduce or eliminate the negative impacts of warming. However, there were no significant interactions between elevated temperature and [CO2] in most rice seasons. Our findings indicate that warming by 2 °C is not detrimental to yield formation under CO2 enrichment, and suggest that grain yield may not decrease under future climate change in the Chinese double rice cropping system.

Mitigating net global warming potential and greenhouse gas intensity by intermittent irrigation under straw incorporation in Chinese double-rice cropping systems

To clarify the effect of water management on global warming potential and crop yield with rice straw returning in typical double-rice cropping systems, a field experiment was conducted in 2013–2016. The three strategies of water management included continuous flooding (F), flooding during the rice season but with drainage during the midseason and harvest time (F–D–F), and flooding during transplanting and tillering stages, drainage during the midseason and intermittent irrigation after midseason drainage (F–D–F–M). Compared with F plots, annual topsoil organic carbon sequestration rates were reduced by 10–45% and 49–66% for F–D–F and F–D–F–M plots, respectively. However, the annual CH4 emissions were significantly decreased by 33–52% and 46–69% for the F–D–F and F–D–F–M plots. As a result, the net annual global warming potential was reduced by 34–57% for F–D–F plots and 38–63% for F–D–F–M plots, respectively. Similarly, the greenhouse gas intensity was reduced 38–60% and 39–64% for F–D–F and F–D–F–M plots, respectively. These results suggested that intermittent irrigation has the potential to mitigate GHG emissions without sacrificing grain yield under rice straw returning in Chinese rice cropping systems.

Response of chalkiness in high-quality rice (Oryza sativa L.) to temperature across different ecological regions

Field experiments were conducted to determine the relationship between chalkiness of high-quality rice and temperature during grain filling period in 2016–2017. Significant differences in chalkiness and response to temperature during grain filling period were observed among the cultivars and years of production. A positive correlation between chalkiness and temperature that includes daily minimum temperature (T-min), daily mean temperature (T-mean) and daily maximum temperature (T-max) during grain filling period was observed. The correlation between chalkiness and T-min during 7 days after heading was lower than that of other stages, while the correlation between chalkiness and T-mean during the ripening stage was the highest than other stages. The chalkiness values of some varieties such as Jiuxiangzhan, Zhendao18 and Yongyou1538 were sensitive to temperature, however, it might be reached optimum level through suitable ecological regions. Other varieties such as Huanghuazhan, Wangxiangyouhuazhan and Ganchangjing1 could maintain lower level of chalkiness regardless of different ecological regions in southern China. These high-quality rice varieties with low and relatively stable chalkiness could be moderately planted in Chinese double-rice cropping systems, and could be used as breeding materials to cope with the adverse effects of future global temperature increase (mainly night temperature) on the appearance quality of rice.

Net global warming potential and greenhouse gas intensity as affected by different water management strategies in Chinese double rice-cropping systems

This study provides a complete account of global warming potential (GWP) and greenhouse gas intensity (GHGI) in relation to a long-term water management experiment in Chinese double-rice cropping systems. The three strategies of water management comprised continuous (year-round) flooding (CF), flooding during the rice season but with drainage during the midseason and harvest time (F-D-F), and irrigation only for flooding during transplanting and the tillering stage (F-RF). The CH4 and N2O fluxes were measured with the static chamber method. Soil organic carbon (SOC) sequestration rates were estimated based on the changes in the carbon stocks during 1998–2014. Longer periods of soil flooding led to increased CH4 emissions, reduced N2O emissions, and enhanced SOC sequestration. The net GWPs were 22,497, 8,895, and 1,646 kg CO2-equivalent ha−1 yr−1 for the CF, F-D-F, and F-RF, respectively. The annual rice grain yields were comparable between the F-D-F and CF, but were reduced significantly (by 13%) in the F-RF. The GHGIs were 2.07, 0.87, and 0.18 kg CO2-equivalent kg−1 grain yr−1 for the CF, F-D-F, and F-RF, respectively. These results suggest that F-D-F could be used to maintain the grain yields and simultaneously mitigate the climatic impact of double rice-cropping systems.

Modifying nitrogen fertilizer practices can reduce greenhouse gas emissions from a Chinese double rice cropping system

Practical nitrogen fertilizers are required that simultaneously increase yield and reduce greenhouse gas (GHG) emissions from rice (Oryza sativa L.) paddies. A field experiment was conducted to measure methane (CH4) and nitrous oxide (N2O) fluxes in situ during two double rice-winter fallow rotations (2012–2014) under five different nitrogen fertilizer treatments: traditional urea (CK), polymer-coated controlled release urea (CRU), urea with N-Sever nitrapyrin (NU), urea with 3,4-dimethylpyrazole phosphate (DMPP), and urea with effective microorganisms (EM). The results revealed that GHG emissions ranged between 77.2 and 178.2kg CH4ha−1 and 4.18 and 10.11kg N2Oha−1 averagely over the whole rotation, and significant differences (P<0.05) among treatments and seasons were found. N2O emissions accounted for 26.6–36.9% of total GWP, and significant N2O emissions were observed during the winter fallow period, ranging from 3.1 to 3.88kg N2Oha−1. Compared to the GWP (7.66 and 8.85MgCO2ha−1) and GHGI (0.52 and 0.63MgCO2Mg−1 grain) from CK in 2012 and 2013 rotation, respectively, CRU achieved the highest reduction (48.5% for GWP and 55.4% for GHGI) in 2012, NU achieved the highest reduction (37.6% for GWP and 43.1% for GHGI) in 2013, and other treatments also realized different levels of decrease. Thus, controlled release urea, nitrification inhibitor or effective microorganisms might be effective fertilization options for low-carbon rice production with high yield.

Effects of biochar amendment on the net greenhouse gas emission and greenhouse gas intensity in a Chinese double rice cropping system

The impacts of biochar amendment on the net greenhouse gas emission (NGHGE) and greenhouse gas intensity (GHGI) of double rice cropping systems are not well examined. In this study, a field experiment was carried out to investigate the effects of biochar amendment on NGHGE and GHGI emissions in a subtropical double rice cropping system managed with intermittent flooding during two rice-growing seasons and drainage during a fallow season from April 2012 to April 2013. Three biochar treatments were studied, with application rates of 0, 24 and 48 t ha−1 (named CK, LC and HC, respectively). In each treatment, the fluxes of methane (CH4), nitrous oxide (N2O) and soil heterotrophic respiration (Rh) were measured using a static chamber/gas chromatography method. Key soil properties related to greenhouse gas (GHG) emissions were also determined throughout an entire double rice cycle. The results showed that biochar amendment significantly reduced annual CH4 emissions by up to 40% compared with the CK treatment, possibly due to the soil pH increase after biochar amendment other than increased soil aeration. In contrast, annual N2O emissions significantly increased by 150% and 190% in the two biochar treatments, compared with the CK treatment, which may be related to the increase of soil dissolvable organic C or NH4+ in the biochar treatments. The cumulative Rh significantly increased by 19% in the HC treatment possibly due to the additional carbon dioxide (CO2) emissions from decomposition of the labile C within biochar, but showed no increase and even a decrease in the LC treatment throughout the study period. Annually, the global warming potential for CH4 and N2O emissions, NGHGEs, and GHGIs in the biochar amendment treatments were reduced by 31–36%, 1551–2936% and 1452–2894%, respectively (p < 0.05). Our collective data may suggest that as the rice grain yield was improved by the biochar amendment found in this study, the biochar application in paddy fields may be an effective measure for GHG emission mitigation in the subtropics.

Ammonia volatilization in Chinese double rice-cropping systems: a 3-year field measurement in long-term fertilizer experiments

The impact of long-term fertilizer on ammonia (NH3) volatilization in a double rice-cropping system is not well documented. A long-term fertilizer experiment in Chinese double rice-cropping systems initiated in 1990 was used in this study to evaluate the NH3 volatilization. Six fertilizer treatments were designed, including inorganic fertilizer [nitrogen and phosphorus fertilizer (NP), nitrogen and potassium fertilizer (NK), and balanced mineral fertilizer (NPK)], combined inorganic/organic fertilizers at full and reduced rate (FOM and ROM), and no fertilizer application (served as control). Ammonia volatilization fluxes were measured using a continuous airflow enclosure method during double rice growing seasons from 2007 to 2009. Results showed that the cumulative NH3 volatilizations in the fertilizer plots ranged from 12.8 to 27.3 kg N ha−1 for the early rice season and from 17.3 to 32.7 kg N ha−1 for the late rice season, which accounted for 9.2–33.6 % and 17.8–32.2 % of the applied N, respectively. The NH4 + concentration in floodwater is a predominant factor to NH3 losses in the double rice-cropping systems. Compared with the NPK, the cumulative NH3 volatilizations during double rice growing seasons were respectively increased by 9.7, 50.6, and 37.6 % for the NP, NK, and FOM plots, respectively, while they were decreased by 24.6 % for the ROM plots. Compared with the NPK, N uptakes by rice were decreased by 7.2–49.7 % with imbalanced fertilizer application (NP and NK), while they were increased by 9.6–41.0 % with combined inorganic/organic fertilizers application (ROM and FOM). Grain yields were comparable among the NPK, ROM, and FOM treatments, but they were declined by the treatments with imbalanced fertilizer application. These results suggested that agricultural economic viability and NH3 volatilization mitigation can be simultaneously achieved by balanced inorganic and organic fertilizers application.

Net annual global warming potential and greenhouse gas intensity in Chinese double rice-cropping systems: a 3-year field measurement in long-term fertilizer experiments

The impact of agricultural management on global warming potential (GWP) and greenhouse gas intensity (GHGI) is not well documented. A long-term fertilizer experiment in Chinese double rice-cropping systems initiated in 1990 was used in this study to gain an insight into a complete greenhouse gas accounting of GWP and GHGI. The six fertilizer treatments included inorganic fertilizer [nitrogen and phosphorus fertilizer (NP), nitrogen and potassium fertilizer (NK), and balanced inorganic fertilizer (NPK)], combined inorganic/organic fertilizers at full and reduced rate (FOM and ROM), and no fertilizer application as a control. Methane (CH4) and nitrous oxide (N2O) fluxes were measured using static chamber method from November 2006 through October 2009, and the net ecosystem carbon balance was estimated by the changes in topsoil (0–20 cm) organic carbon (SOC) density over the 10-year period 1999–2009. Long-term fertilizer application significantly increased grain yields, except for no difference between the NK and control plots. Annual topsoil SOC sequestration rate was estimated to be 0.96 t C ha−1 yr−1 for the control and 1.01–1.43 t C ha−1 yr−1 for the fertilizer plots. Long-term inorganic fertilizer application tended to increase CH4 emissions during the flooded rice season and significantly increased N2O emissions from drained soils during the nonrice season. Annual mean CH4 emissions ranged from 621 kg CH4 ha−1 for the control to 1175 kg CH4 ha−1 for the FOM plots, 63–83% of which derived from the late-rice season. Annual N2O emission averaged 1.15–4.11 kg N2O–N ha−1 in the double rice-cropping systems. Compared with the control, inorganic fertilizer application slightly increased the net annual GWPs, while they were remarkably increased by combined inorganic/organic fertilizer application. The GHGI was lowest for the NP and NPK plots and highest for the FOM and ROM plots. The results of this study suggest that agricultural economic viability and GHGs mitigation can be simultaneously achieved by balanced fertilizer application.