Diversity of Arbuscular Mycorrhizal Fungi Associated with Six Rice Cultivars in Italian Agricultural Ecosystem Managed with Alternate Wetting and Drying

Alternate wetting and drying(AWD)system,in which water has been reduced by approximately 35%with an increased occurrence of beneficial arbuscular mycorrhizal(AM)symbiosis and no negative impact on rice yield,was proposed to utilize water and nutrients more sustainable.In this study,we selected six rice cultivars(Centauro,Loto,Selenio,Vialone nano,JSendra and Puntal)grown under AWD conditions,and investigated their responsiveness to AM colonization and how they select diverse AM taxa.In order to investigate root-associated AM fungus communities,molecular cloning-Sanger sequencing on small subunit rDNA data were obtained from five out of the six rice cultivars and compared with Next Generation Sequencing(NGS)data,which were previously obtained in Vialone nano.The results showed that all the cultivars were responsive to AM colonization with the development of AM symbiotic structures,even if with differences in the colonization and arbuscule abundance in the root systems.We identified 16 virtual taxa(VT)in the soil compartment and 7 VT in the root apparatus.We emphasized that the NGS analysis gives additional value to the results thanks to a more in-depth reading of the less represented AM fungus taxa.

Wetting alternating with partial drying during grain filling increases lysine biosynthesis in inferior rice grain

Lysine content is a criterion of the nutritional quality of rice.Understanding the process of lysine biosynthesis in early-flowering superior grain(SG)and late-flowering inferior grain(IG)of rice would advance breeding and cultivation to improve nutritional quality.However,little information is available on differences in lysine anabolism between SG and IG and the underlying mechanism,and whether and how irrigation regimes affect lysine anabolism in these grains.A japonica rice cultivar was grown in the field and two irrigation regimes,continuous flooding(CF)and wetting alternating with partial drying(WAPD),were imposed from heading to the mature stage.Lysine content and activities of key enzymes of lysine biosynthesis,and levels of brassinosteroids(BRs)were lower in the IG than in the SG at the early grainfilling stage but higher at middle and late grain-filling stages.WAPD increased activities of these key enzymes,BR levels,and contents of lysine and total amino acids in IG,but not SG relative to CF.Application of 2,4-epibrassinolide to rice panicles in CF during early grain filling reproduced the effects of WAPD,but neither treatment altered the activities of enzymes responsible for lysine catabolism in either SG or IG.WAPD and elevated BR levels during grain filling increased lysine biosynthesis in IG.Improvement in lysine biosynthesis in rice should focus on IG.

Grain yield and water use efficiency of super rice under soil water deficit and alternate wetting and drying irrigation

This study investigated if super rice could better cope with soil water deficit and if it could have better yield performance and water use efficiency （WUE） under alternate wetting and drying （AWD） irrigation than check rice. Two super rice cultivars and two elite check rice cultivars were grown in pots with three soil moisture levels, well watered （WW）, moderate water deficit （MWD） and severe water deficit （SWD）. Two cultivars, each for super rice and check rice, were grown in field with three irrigation regimes, alternate wetting and moderate drying （AWMD）, alternate wetting and severe drying （AWSD） and conventional irrigation （CI）. Compared with that under WW, grain yield was significantly decreased under MWD and SWD treatments, with less reduction for super rice than for check rice. Super rice had higher percentage of productive tillers, deeper root distribution, higher root oxidation activity, and greater aboveground biomass production at mid and late growth stages than check rice, especially under WMD and WSD. Compared with CI,AWMD increased, whereasAWSD decreased grain yield, with more increase or less decrease for super rice than for check rice. Both MWD and SWD treatments and eitherAWMD orAWSD regime significantly increased WUE compared with WW treatment or CI regime, with more increase for super rice than for check rice. The results suggest that super rice has a stronger ability to cope with soil water deficit and holds greater promising to increase both grain yield and WUE by adoption of moderate AWD irrigation.

Agronomic performance of drought-resistance rice cultivars grown under alternate wetting and drying irrigation management in southeast China

Compared to drought-susceptible rice cultivars(DSRs),drought-resistance rice cultivars(DRRs)could drastically reduce the amount of irrigation water input and simultaneously result in higher grain yield under water-saving irrigation conditions.However,the mechanisms underlying these properties are unclear.We investigated how improved agronomic traits contribute to higher yield and higher water use efficiency(WUE)in DRRs than in DSRs under alternate wetting and drying(AWD).Two DRRs and two DSRs were field-grown in 2015 and 2016 using two different irrigation regimes:continuous flooding(CF)and AWD.Under CF,no statistical differences in grain yield and WUE were observed between DRRs and DSRs.Irrigation water under the AWD regime was 275–349 mm,an amount 49.8%–56.2% of that(552–620 mm)applied under the CF regime.Compared to CF,AWD significantly decreased grain yield in both DRRs and DSRs,with a more significant reduction in DSRs,and WUE was increased in DRRs,but not in DSRs,by 9.9%–23.0% under AWD.Under AWD,DRRs showed a 20.2%–26.2% increase in grain yield and an 18.6%–24.5% increase in WUE compared to DSRs.Compared to DSRs,DRRs showed less redundant vegetative growth,greater sink capacity,higher grain filling efficiency,larger root biomass,and deeper root distribution under AWD.We conclude that these improved agronomic traits exert positive influences on WUE in DRRs under AWD.

Moderate wetting and drying increases rice yield and reduces water use, grain arsenic level, and methane emission

To meet the major challenge of increasing rice production to feed a growing population under increasing water scarcity,many water-saving regimes have been introduced in irrigated rice,such as an aerobic rice system,non-flooded mulching cultivation,and alternate wetting and drying(AWD).These regimes could substantially enhance water use efficiency(WUE) by reducing irrigation water.However,such enhancements greatly compromise grain yield.Recent work has shown that moderate AWD,in which photosynthesis is not severely inhibited and plants can rehydrate overnight during the soil drying period,or plants are rewatered at a soil water potential of-10 to-15 k Pa,or midday leaf potential is approximately-0.60 to-0.80 MPa,or the water table is maintained at 10 to 15 cm below the soil surface,could increase not only WUE but also grain yield.Increases in grain yield WUE under moderate AWD are due mainly to reduced redundant vegetative growth;improved canopy structure and root growth;elevated hormonal levels,in particular increases in abscisic acid levels during soil drying and cytokinin levels during rewatering;and enhanced carbon remobilization from vegetative tissues to grain.Moderate AWD could also improve rice quality,including reductions in grain arsenic accumulation,and reduce methane emissions from paddies.Adoption of moderate AWD with an appropriate nitrogen application rate may exert a synergistic effect on grain yield and result in higher WUE and nitrogen use efficiency.Further research is needed to understand root–soil interaction and evaluate the long-term effects of moderate AWD on sustainable agriculture.

Influence of Seed Priming on Performance and Water Productivity of Direct Seeded Rice in Alternating Wetting and Drying

Direct seeded rice is promising alternative to traditional transplanting, but requires appropriate crop and water management to maintain yield performance and achieve high water productivity. Present study evaluated the effect of seed priming and irrigation on crop establishment, tillering, agronomic traits, paddy yield, grain quality and water productivity of direct seeded rice in alternate wetting and drying （DSR-AWD） in comparison with direct seeded rice at field capacity （DSR- FC）. Seed priming treatments were osmo-priming with KCI （2.2%）, CaCI2 （2.2%） and moringa leaf extracts （MLE, 3.3%） including hydro-priming as control. Among the treatments, seed osmo-primed with MLE emerged earlier and had higher final emergence, followed by osmo-priming with CaCI2. Tillering emergence rate and number of tillers per plant were the highest for seed priming with CaCI2 in DSR- AWD. Total productive and non-productive tillers, panicle length, biological and grain yields, harvest index were highest for seed priming with MLE or CaCI2 in DSR-AWD. Similarly, grain quality, estimated in terms of normal grains, abortive and chalky grains, was also the highest in DSR-AWD with MLE osmo-priming. Benefit cost ratio and water productivity was also the highest in DSR-AWD for seed priming with MLE. In conclusion, seed priming with MLE or CaCI2 can be successfully employed to improve the direct seeded rice performance when practiced with alternate wetting and drying irrigation.

Growth,yield and water productivity of dry direct seeded rice and transplanted aromatic rice under different irrigation management regimes

Sustainability of traditionally cultivated rice in the rice-wheat cropping zone(RWCZ)of Pakistan is dwindling due to the high cost of production,declining water resources and escalating labour availability.Thus,farmers and researchers are compelled to find promising alternatives to traditional transplanted rice(TPR).A field study was conducted in Punjab,Pakistan,in 2017 and 2018 to explore the trade-offs between water saving and paddy yield,water productivity and economics of two aromatic rice varieties under dry direct seeded rice(DDSR)and TPR.The experiment was comprised of three irrigation regimes on the basis of soil moisture tension(SMT)viz.,continuous flooded(>–10 kPa SMT),alternate wetting and drying(AWD)(–20 kPa SMT)and aerobic rice(–40 kPa SMT),maintained under TPR and DDSR systems.Two aromatic rice verities:Basmati-515 and Chenab Basmati-2016 were used during both years of study.In both years,DDSR produced higher yields(13–18%)and reduced the total water inputs(8–12%)in comparison to TPR.In comparison to traditional continuous flooded(CF),AWD under DDSR reduced total water input by 27–29%and improved the leaf area index(LAI),tillering,yield(7–9%),and water productivity(44–50%).The performance of AWD with regard to water savings and increased productivity was much higher in DDSR system as compared to AWD in TPR system.Cultivation of DDSR with aerobic irrigation improved water savings(49–55%)and water productivity(22–30%)at the expense of paddy yield reduction(36–39%)and spikelet sterility.With regard to variety,the highest paddy yield(6.6 and 6.7 t ha–1)was recorded in DDSR using Chenab Basmati-2016 under AWD irrigation threshold that attributed to high tiller density and LAI.The economic analysis showed DDSR as more beneficial rice establishment method than TPR with a high benefit-cost ratio(BCR)when the crop was irrigated with AWD irrigation threshold.Our results highlighted that with the use of short duration varieties,DDSR cultivation in conjunction with AWD irrigation can be more beneficial for higher productivity and crop yield.

Effects of zeolite application on grain yield,water use and nitrogen uptake of rice under alternate wetting and drying irrigation

With the increasing scarcity of water resources and growing population,the dual goal of saving irrigation water and increasing grain yield has become a major challenge in rice production around the world.A two-year lysimetric experiment was conducted to assess the effects of zeolite application(Z_(0):0 and Z1:15 t/hm^(2) and water regimes(W_(0):continuous flooding irrigation,W1:energy-controlled irrigation,W2:alternate wetting and drying irrigation)on grain yield,water use and total nitrogen uptake of rice.Zeolite addition to paddy field significantly increased grain yield,total N uptake,and water use efficiency(WUE),despite a negligible effect on amount of irrigation water used.Compared with W_(0),the separate use of W_(1) and W_(2) each considerably decreased irrigation water.However,W2-grown rice showed a significant decline in grain yield.In contrast,W1 showed comparable grain yield with W_(0),and achieved the highest WUE.Correlation analysis revealed that grain yield was significantly and positively correlated with effective panicles,spikelets per panicle,water consumption,and total N uptake.It is concluded that the combination of zeolite application at the rate of 15 t/hm^(2) and energy-controlled irrigation could be recommended to benefit farmers by reducing irrigation water while improving grain yield on a clay loam soil.

Determination of the Effect of the System of Rice Intensification (SRI) on Rice Yields and Water Saving in Mwea Irrigation Scheme, Kenya

Irrigated rice cultivation has long been associated with large amounts of water. Currently convectional rice production is faced with major challenges of water shortage as a result of increasing population sharing the same water resources, as well as global environmental changes. The System of Rice Intensification (SRI), as opposed to conventional rice production, involves alternate wetting and drying (AWD) of rice fields. The objective of this study was to determine the optimum drying days period of paddy fields that has a positive effect on rice yields and the corresponding water saving. The experimental design used was randomized complete block design (RCBD). Four treatments and the conventional rice irrigation method were used. The treatments were the dry days allowed after draining the paddy under SRI before flooding again. These were set as 0, 4, 8, 12 and 16 day-intervals. Yield parameters were monitored during the growth period of the crop where a number of tillers, panicles, panicle length and panicle filling were monitored. Amount of water utilized for crop growth for each treatment was measured. Average yield and corresponding water saving were determined for each treatment. The results obtained show that the 8 days drying period gave the highest yield of 7.13 tons/ha compared with the conventional method of growing rice which gave a yield of 4.87 tons/ha. This was an increase of 46.4% above the conventional method of growing rice. Water saving associated with this drying regime was 32.4%. This was taken as evidence that SRI improved yields with reduction in water use.

Effect of Nitrogen and Water Management on Methane Emission of Boro Rice Cultivation in Bangladesh

Water and nitrogen are two key elements required for successful rice cultivation. We examined the responses of nitrogen and water management on methane emission of Boro rice in the field laboratory of Bangladesh Agricultural University research farm, Mymensingh. Three treatments were studied in the field experiment viz, T1: Control plot (no nitrogen fertilizer), T2: Urea super granule (78 kg N/ha), T3: Prilled urea (104 kg N/ha) with three replications under two water management of Continuous Standing Water (CSW) and Alternate Wetting and Drying (AWD). Air samples were collected by the closed-chamber method and methane gas was determined by gas chromatography. The highest CH4 emission was found from CSW plots and the lowest from AWD plots. Under CSW condition, the effects of urea treatments on CH4 emission were not significant. In case of urea treatments, the highest CH4 emission was observed from treatment T3 under CSW condition and T2 under AWD condition and the lowest emission was from the control treatment. The overall results suggest that prilled urea and urea super granule should be applied under AWD and CSW condition, respectively to keep less CH4 emission from irrigated rice agriculture.

节灌条件缓释肥对水稻株高、分蘖、叶绿素及产量的影响

为研究水稻节水灌溉条件施用缓释肥的适宜性,于2014年水稻种植期开展了不同水肥处理水稻种植的桶栽试验。结果表明,缓释肥对植株叶绿素SPAD值、分蘖数的最终促进作用均明显强于常规肥,对株高的促进也并不比常规肥弱。淹灌缓释肥处理产量最高达15542kg/hm^2,间歇灌溉常规肥次之为11408kg/hm^2,间歇灌溉缓释肥最低仅为6074kg/hm^2。施用缓释肥水稻总干物质积累量平均高出常规肥处理164.7%。水稻传统间歇灌溉模式可能并不适用于缓释肥。

干湿交替诱导水稻根表铁膜形成的基因表达谱分析

【目的】干湿交替(AWD)是水稻种植过程中最重要的管理方式,能够提高水稻根系活力、增强抗逆性。研究发现,AWD能明显促进水稻根表铁膜的形成。然而,AWD诱导水稻根表铁膜形成的基因表达谱尚未见报道。【方法】采用砂培试验,研究了长期淹水(CK)、干湿交替(AWD)、长期淹水加Fe2+(CK+Fe)和干湿交替加Fe2+(AWD+Fe)四个处理下水稻根系基因的差异表达谱。【结果】AWD处理与CK处理相比,水稻根系有506个差异表达基因(DEG)上调表达,有687个DEG下调表达;AWD+Fe处理与CK+Fe处理相比,有308个DEG上调表达和179个DEG下调表达;CK+Fe处理与CK处理相比,有728个DEG上调表达和1175个DEG下调表达;AWD+Fe处理与AWD处理相比,有1252个DEG上调表达和1189个DEG下调表达。维恩图分析发现,共计有3822个DEG参与了AWD诱导水稻根表铁膜形成过程。基因功能(GO)分析表明,在生物过程中共有270个DEG参与了氧化还原反应过程,分子功能中共有165个DEG与氧化还原酶功能有关。生物通路富集分析(KEGG)结果表明,细胞器类、信号刺激类、光合作用类、生物合成类和代谢类等生物通路参与了AWD诱导水稻根表铁膜的形成过程。AWD和根表铁膜形成过程发现有38个共享DEG,这些基因的蛋白注释与水稻抗病性、抗旱性、细胞壁和细胞膜、氧化还原、蛋白激酶和转运、新陈代谢过程有关。与CK处理相比,AWD处理诱导了氧化还原反应过程相关的基因达102个,占总DEG数的8.25%。AWD处理促进了水稻根系过氧化物酶、脂肪酸氧化酶和乙醇酸氧化酶等相关基因的上调表达。与CK处理相比,AWD处理提高了水稻根系活力和根表铁膜数量,分别为22.9%和45.7%。实时荧光定量PCR验证结果与转录组分析结果基本一致,其相关系数达到0.90。【结论】综上所述,AWD明显诱导了氧化还原反应过程中的相关基因大量表达,增加了根系氧化力,促进根表铁膜的形成;过氧化物酶、脂肪酸氧化酶和乙醇酸氧化酶等相关的基因可能是AWD诱导水稻根表铁膜形成的重要基因。

农户自愿联合灌溉对干湿交替节水技术运用的影响——以湖北漳河灌区为例

本文基于湖北漳河灌区2006-2007年农户调查的数据,分析农户自愿联合灌溉小组形成的影响因素及其对干湿交替(AWD)节水技术运用的影响效应。本研究发现:当村民组社会资本高,农户就不倾向形成联合灌溉小组,因为高社会资本能规避农户过度用水行为。相反,当村民组社会资本低,农户愿意形成联合灌溉小组以规避过度用水行为。然而,水源丰富的客观条件又阻碍了这些联合小组的形成。因此,低社会资本和水源丰富的村民组,农户过度用水会导致AWD节水技术运用的减少。

干湿交替灌溉模式在湖南稻区适用性及其甲烷减排潜力评估

减排技术适用性评估的缺失,限制了区域水稻生产精准减碳政策的制定和中国双碳战略相关体系的完善。该研究通过对湖南水稻生产现状分析和干湿交替灌溉甲烷(CH4)减排技术区域适用性评估,力求为湖南水稻主产区提供精准的丰产减排水分管理措施。收集2016-2019年湖南水稻生产数据及各地市多年(1960-2017年)气象数据,利用基于稻田水分平衡模型的干湿交替灌溉技术适用性评估方法并结合地理信息系统工具,评估了该方法在湖南稻区的适用性及其加权CH4减排潜力。结果表明:2016—2019年湖南水稻播种面积略有下降,其中早、晚稻播种面积且单季稻播种面积逐年增加;而水稻单产稳步增加,单季稻4 a内年均单产为7259 kg/hm^(2),比双季早、晚稻分别高21.68%、13.19%。在湖南省地市和县区两级层面上,干湿交替灌溉适用性均具有显著的时间和空间差异,市、县两级层面上,相比早稻和中稻,晚稻更适宜实施干湿交替灌溉。针对水稻生育期,早稻季生长后期干湿交替灌溉适宜性较高,单季稻生长中、后期适宜性更好,而晚稻除分蘖期,其余生育期均适合执行干湿交替灌溉技术。干湿交替灌溉技术在湖南稻区有较大的减排潜力(51.16%),考虑适用性情景的干湿交替灌溉(Alternate Wetting and Drying,AWD)加权减排量达49.36万t,占全国稻田CH4排放的5.54%。在确保稻谷供应的基础上,因时因地制宜的实施动态的干湿交替灌溉精准调控技术,是湖南水稻生产低碳转型高质量发展的关键举措。

Adopting the system of rice intensification (SRI) in Tanzania: A review

The demand of water for irrigation purposes in Tanzania outstrips the amount of water available for irrigation and other demands. On the other hand, the demand for more food to feed the growing population is increasing, calling for the need to have technologies and farming practices that ensure more food production while minimizing water uses. Rice is among cereal crops grown in Tanzania, and it can assist in meeting the food demand for the nation. Majority of rice producers in Tanzania and Sub-Saharan Africa(SSA) are subsistence farmers and they practice continuous flooding, a technique that requires much water. In addition to using large amounts of water, the conventional practices of growing paddy using local varieties transplanting process are implemented when seedlings are more than 21 days old, and 3-4 seedlings are transplanted in one hole. This practice results in low yields, and low water productivity and water use efficiency. The system of rice intensification (SRI) on the other hand, is a promising new practice of growing paddy rice that has proven to be very effective in saving water and increasing rice yields in many parts of the world. SRI practice is spreading fast and it has been adopted in many countries. The SRI practice has been introduced in Tanzania during the last 3 years as such it is not widely practiced. This paper reviews SRI practice at global, regional and country (Tanzania) level, and evaluates the challenges, opportunities and implications for its adoption in Tanzania. Knowledge gaps at each level have been identified and discussed as well as suggestions for researchable areas.

Effects of Different Irrigation Management on the Textural Properties of Double-Cropping Late Indica Rice in South China

In order to investigate the effects of different irrigation management on the textural properties of two different double-cropping late indica rice,the effects of three irrigation management including conventional irrigation(CK),constant irrigation(CI)and alternate wetting and drying(AWD)on textural properties has been researched under field conditions of two years.The results indicated that the firmness,cohesiveness and chewiness were decreased under AWD treatment,and the stickiness was increased compared with CK,while the textural properties under CI treatment showed the opposite trend with AWD treatment.Additionally,AWD treatment signifi-cantly improved the springiness of TY871 compared with CK and CI treatment,but had no significant effect in RYHZ,suggesting improvement of the cooking and eating quality of TY871 under AWD treatment.Correlation analysis showed that the chewiness was positively correlated with the firmness and cohesiveness,and the cohesiveness was positively correlated with the firmness.AWD could promote the textural properties of high-quality late indica rice in South China whereas CI treatment has shown the disadvantage of the textural properties,which will provide useful information for the improvement of cooking and eating quality of rice.

Corrosion Behavior of Weathering Test Steel for Bridge Under the Neutral Wet/Dry Alternate Condition

The corrosion behaviors of the high-performance weathering test steel for bridge and the reference (09CuPCrNi-A) were symmetrically studied under 3.5% NaCl neutral wet/dry alternate condition,revealing their dynamics line tendency of primary corrosion and the rusting flow in the simulative marine atmosphere environment.By observing the corrosion evolution of surface microstructures and composition by the scanning electronic microscope (SEM) and the energy dispersive spectrometer (EDS) at the different stages,the corrosion mechanism was further discussed in details.