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1.
While the application rate of nitrogen fertilizer is believed to dramatically influence rice fields and improve the soil conditions in paddy fields, fertilization with low use efficiency and nitrogen loss may cause environmental pollution. In this paper, 15N-labeled urea was used to trace the fate of nitrogen at four rates (0, 75, 225 and 375 kg N/ha) of urea fertilizer over three split applications in Hangzhou, Zhejiang, in 2014. Plant biomass, the soil nitrogen content of different layers, NH3 volatilization and N2O emissions were determined using the 15N abundance to calculate the portion from nitrogen fertilizer. The results indicated that rice yields increased with the application rate of nitrogen fertilizer. NH3 volatilization is the main nitrogen loss pathway, and N2O emissions were significantly associated with nitrogen application rates in the paddy. The percent of nitrogen loss by NH3 volatilization and N2O emissions increased with the nitrogen application rate. This study showed that the suitable N fertilizer in a loam clay paddy, considering the yield requirements and environmental issues, is approximately 225 kg N/ha in Hangzhou, with a distribution of 50.06% of the residual in the rice and soil and 48.77% loss as NH3 volatilization and N2O emissions. The nitrate from fertilization mainly remained in the 0–20 cm level of the topsoil.  相似文献   

2.
前氮后移对杂交中稻及其再生稻产量的影响   总被引：2，自引：0，他引：2  
以20个杂交中稻组合为材料,在前氮后移与重底早追两种施氮方式下,研究了前氮后移对头季稻及再生稻产量的影响。结果表明,前氮后移有助于提高杂交中稻组合头季稻及再生稻产量,且高于重底早追施氮方式,但各杂交组合间表现各异。其中,内5优306、蓉18优447、德香4103、内5优317和川谷优7329这5个组合前氮后移处理头季稻比重底早追处理显著或极显著增产,乐优198、宜香优800、蓉优1808、冈比优99、冈优725、德香4103、炳优900、F优498、内5优317这9个组合的再生稻产量前氮后移处理比重底早追处理高。综合考虑头季稻产量和再生力,两季总产较高的组合为宜香优800、内5优317和蓉18优447。  相似文献   

3.
Vietnam is one of the world’s top two rice exporting countries. However, rice cultivation is the primary source of agriculture’s greenhouse gas (GHG) emissions in Vietnam. In particular, strategies are required to reduce GHG emissions associated with the application of organic and inorganic fertilisers. The objective of this study was to assess the effects of various combinations of biochar (BIOC), compost (COMP) and slow-release urea (SRU) on methane (CH4) and nitrous oxide (N2O) emissions. In total, 1170 gas samples were collected from closed gas chambers in rice paddies at Thinh Long commune and Rang Dong farm in northern Vietnam between June and October 2014. The gas samples were analysed for CH4-C and N2O-N fluxes using gas chromatography. The application of BIOC alone resulted in the lowest CH4 emissions (4.8–59 mg C m?2 h?1) and lowest N2O emissions (0.15–0.26 µg N m?2 h?1). The combined application of nitrogen–phosphorus–potassium (NPK) + COMP emitted the highest CH4 (14–72 mg C m?2 h?1), while ½NPK + BIOC emitted the highest N2O (1.03 µg N m?2 h?1 in the TL commune), but it was the second lowest (0.495 µg N m?2 h?1) in the RD farm. Green urea and orange urea reduced N2O emissions significantly (p < 0.05) compared to white urea, but no significant differences were observed with respect to CH4 emissions. SRU fertilisers and BIOC alone measured the lowest greenhouse gas intensity, i.e. <2.5 and 3 kg CO2 eq. kg?1 rice grain, respectively. Based on these results, application of fertilisers in the form of BIOC and/or orange or green urea could be a viable option to reduce both CH4 and N2O emissions from rice paddy soils.  相似文献   

4.
杂交稻再生稻经济性状试验研究   总被引：4，自引：0，他引：4  
围绕我省当前再生稻发展需要，在大田生产中，采用１２个杂优组合对影响再生稻产量的因素进行研究，结果表明：再生穗和实粒数对产量的影响呈显著正相关；通过提高栽培水平，可显著增加再生穗从而达到再生稻增产的目的  相似文献   

5.

With the aim of assessing differentiation of greenhouse gas emissions as manipulated by plastic film mulching (PFM) from paddy field from a year-round perspective, we determined net ecosystem CO2 exchange (NEE, CO2 flux), CH4 and N2O fluxes from a rice–rapeseed rotation field. PFM and non-mulching (NM) treatments were set from 2014 to 2017 (May 2014 to April 2015, May 2015 to April 2016 and May 2016 to April 2017 were set as Annual 1, Annual 2 and Annual 3, respectively) in Southwest China. Compared with NM, CH4 emissions were increased by 60.00% (P?<?0.05), 111.54% (P?<?0.05) and 62.07% (P?<?0.05) under PFM in Annual 1, 2 and 3, respectively. Additionally, PFM delayed the peaks of CH4 fluxes by 5–10 days during rice season. However, PFM did not affect N2O emissions on the annual basis. PFM reduced the net carbon loss from soil during rice season while had insignificant influence on soil carbon sequestration capacity during fallow and rapeseed seasons. Overall, the mean annual net ecosystem greenhouse gas exchange among three annuals was 32.11% lower under PFM than under NM. Moreover, PFM slightly increased crop yields of both rice and rapeseed. Accordingly, PFM recommended the suitable agricultural management in the rice–rapeseed rotation field for simultaneously alleviating global warming and maintaining crop yields.

  相似文献   

6.
【Objective】 The combination of mid-season rice+ratoon rice is a new pattern of rice planting in southern Henan Province. However, the changes in grain yield and quality between the main and ratoon seasons remain unclear. Clarifying the changing law of grain yield and rice quality can lay a theoretical and practical basis for the screening of ratoon rice varieties with higher grain yield and better rice quality in southern Henan Province. 【Method】 In this study, 12 hybrid indica rice combinations suitable for single-cropping rice were used as materials under local high-yield cultivation conditions. The tested combinations were divided into four types according to their yields in main and ratoon seasons: BH, both high grain yields in main and ratoon season; HL, high grain yield in main season and low grain yield in ratoon season; LH, low grain yield in main season and high yield in ratoon season; BL, both low grain yields in main and ratoon seasons. The difference in rice quality was also analyzed. 【Result】 1) The processing quality and appearance quality in ratoon season were significantly improved, however, the protein contents decreased, and the eating quality of rice was improved to different extents as compared with those in main season; 2) Except for BL type (only one combination, Shenliangyou 11), the processing quality of BH and HL was better, and HL has better appearance quality and cooking and eating quality. There was no significant difference in protein contents among different yield types in main season, while in ratoon season, the protein contents in BH were 10.7 % higher than those in HL, and 1.75% lower than those in LH. 3) The effect of daily average temperature after full heading on grain quality was far greater than the sunshine hours, and the relatively low average daily temperature after full heading in ratoon season was the main reason for its better grain quality. 【Conclusion】 Based on higher grain yield and better rice quality, Liangyou 6326, Tianliangyou 616, Guangliangyou 476 and Fengliangyouxiang 1 were suitable varieties for ratoon cultivation in southern Henan Province.  相似文献   

7.
豫南地区头季和再生季水稻产量与品质差异分析   总被引：1，自引：0，他引：1  
【目的】 “中稻+再生稻”组合是豫南稻区新的水稻种植模式,但是头季与再生季水稻产量和稻米品质变化尚不清楚。明确其产量和米质变化规律可为豫南地区高产优质再生稻品种选择提供理论与实践依据。【方法】以两优6326等12个适于单季种植的杂交籼稻为材料,在当地高产栽培条件下,依据头季和再生季两季产量将其划分为两季产量均高(双高)、头季稻产量高再生季产量低(头高再低)、头季稻产量低再生季产量高(头低再高)和两季产量均低(双低)等四种类型,并分析了米质的差异。【结果】 1)与头季稻相比,12个组合的再生季稻米加工品质和外观品质显著改善,蛋白质含量降低,稻米食味品质不同程度变优。2)两季不同产量类型之间比较,除双低类型(仅深两优11号一个品种)外,双高类型和头高再低类型加工品质较优,而头高再低类型的外观品质和蒸煮食味品质较优。蛋白质含量在各产量类型头季稻之间无显著差异,而再生季双高类型较头高再低类型高10.7 %,比头低再高类型低1.75 %。3)齐穗后日平均温度对稻米品质的影响远大于日照时数,再生季齐穗后日平均温度较低是其稻米品质优于头季稻的重要原因。【结论】综合产量及品质,两优6326、天两优616、广两优476和丰两优香1号是适于豫南地区的高产优质再生水稻品种。  相似文献   

8.
甬优4949和超优1000在华中地区再生稻种植的氮肥运筹研究   总被引：3，自引：1，他引：2  
【目的】研究不同氮肥运筹处理下,超优1000、甬优4949作再生稻种植时的产量、氮肥偏生产力以及再生力的表现,以期为超优1000和甬优4949引入再生稻系统提供理论依据。【方法】试验为裂区设计,主区为氮肥处理,共设置了6个不同的氮肥处理,分别为N_1(120main150ratoon)、N_2(120main225ratoon)、N_3(185main150ratoon)、N_4(185main225ratoon)、N_5(250main150ratoon)、N_6(250main225ratoon);品种为副区(甬优4949、超优1000,两优6326作为再生稻大面积种植的对照品种)。测定不同品种在不同氮肥运筹下株高、分蘖数、叶面积指数、地上部生物量、产量、产量构成因子和成熟籽粒氮含量。【结果】试验结果表明,在头季,两优6326、超优1000、甬优4949最高产量分别为9.16 t/hm^2、9.08 t/hm^2和11.15 t/hm^2,其对应的施氮量分别为185 kg/hm^2、120 kg/hm^2和185 kg/hm^2。三个品种在高施氮量下(225 kg/hm^2)的平均再生季产量分别为5.41 t/hm^2、4.98 t/hm^2、6.02 t/hm^2,在低施氮量下(150kg/hm^2)的平均再生季产量分别为5.78 t/hm^2、5.41 t/hm^2、6.49 t/hm^2。然而,三个品种在低氮处理下的氮肥偏生产力均显著高于高氮处理。综合产量和氮肥偏生产力,甬优4949的最优氮肥运筹应与两优6326保持一致(185main150ratoon),而超优1000在目前的产量水平下的头季施氮量低于两优6326(120 kg/hm^2),而再生季可与两优6326保持一致。【结论】甬优4949可在华中地区作再生稻种植并且氮肥运筹模式可与两优6326保持一致,而超优1000由于生育期太长,再生季不能完全成熟,不适合在华中地区作再生稻种植。  相似文献   

9.
A field experiment was conducted at the farm of Yangzhou University, Yangzhou, China, to study the effects of organic fertilizers made from maize straw on rice grain yield and the emission of greenhouse gases. Four organic fertilizer treatments were as follows： maize straw （MS）, compost made from maize straw （MC）, methane-generating maize residue （MR）, and black carbon made from maize straw （BC）. These organic fertilizers were applied separately to paddy fields before rice transplanting. No organic fertilizer was applied to the control （CK）. The effects of each organic fertilizer on rice grain yield and emission of greenhouse gases were investigated under two conditions, namely, no nitrogen （N） application （ON） and site-specific N management （SSNM）. Rice grain yields were significantly higher in the MS, MC and MR treatments than those in CK under either ON or SSNM. The MS treatment resulted in the highest grain yield and agronomic N use efficiency. However, no significant difference was observed for these parameters between the BC treatment and CK. The changes in the emissions of methane （CH4） carbon dioxide （CO2）, or nitrous oxide （N20） from the fields were similar among all organic fertilizer treatments during the entire rice growing season. The application of each organic fertilizer significantly increased the emission of each greenhouse gas （except N20 emission in the BC treatment） and global warming potential （GWP）. Emissions of all the greenhouse gases and GWP increased under the same organic fertilizer treatment in the presence of N fertilizer, whereas GWP per unit grain yield decreased. The results indicate that the application of organic fertilizer （MS, MC or MR） could increase grain yield, but also could enhance the emissions of greenhouse gases from paddy fields. High grain yield and environmental efficiency could be achieved by applying SSNM with MR.  相似文献   

10.
Deep placement of controlled-release fertilizer increases nitrogen(N) use efficiency in rice planting but is expensive. Few studies on direct-seeded rice have examined the effects of deep placement of conventional fertilizer. With prilled urea serving as N fertilizer, a two-year field experiment with two N rates(120 and 195 kg/hm~2) and four basal N application treatments(B50, all fertilizer was broadcast with 50% as basal N; D50, D70 and D100 corresponded to 50%, 70% and 100% of N deeply placed as basal N, respectively) were conducted in direct-seeded rice in 2013 and 2014. Soil N distribution and plant N uptake were analyzed. The results showed that deep placement of basal N significantly increased total N concentrations in soil. Significantly greater soil N concentrations were observed in D100 compared with B50 at 0, 6 and 12 cm(lateral distance) from the fertilizer application point both at mid-tillering and heading stages. D100 presented the highest values of dry matter and N accumulation from seeding to mid-tillering stages, but it presented the lowest values from heading to maturity stages and the lowest grain yield for no sufficient N supply at the reproductive stage. The grain yield of D50 was the highest, however, no significant difference was observed in grain yield, N agronomic efficiency or N recovery efficiency between D70 and D50, or between D70 and B50, while D70 was more labor saving than D50 for only one topdressing was applied in D70 compared with twice in other treatments. The above results indicated that 70% of fertilizer-N deeply placed as a basal fertilizer and 30% of fertilizer-N topdressed as a panicle fertilizer constituted an ideal approach for direct-seeded rice. This recommendation was further verified through on-farm demonstration experiments in 2015, in which D70 produced in similar grain yields as B50 did.  相似文献   

11.
淹涝胁迫对杂交中稻生长特性及产量形成的影响   总被引：1，自引：0，他引：1  
以近年审定的20个杂交中稻品种为材料,研究了分蘖期和抽穗期淹涝胁迫对杂交中稻的某些生理指标、生长发育、产量及干物质生产的影响。结果表明:(1)淹没胁迫对杂交中稻的生育期有显著影响。分蘖期受淹没胁迫,头季稻和再生稻的抽穗期分别平均延长了3.25 d和3.95 d,成熟期分别平均延长了1.85 d和2.75 d;而抽穗期受淹没胁迫,成熟期会提前,平均提前1.60 d,且品种间差异较大。(2)淹没胁迫对杂交中稻的产量有显著影响。与对照相比,分蘖期受淹没胁迫,分蘖期叶干重、有效穗数、每穗粒数降低,使其平均减产59.0%;齐穗期受淹没胁迫,每穗粒数和结实率显著降低,使其平均减产57.6%。(3)分蘖期受淹没48 h后,不宜割苗蓄留再生稻,应以加强田间管理保留头季稻为主,耐淹性较强的品种有川谷优6684、冈优169和乐优198;抽穗期受淹没48 h后,则以割苗蓄留再生稻较佳,其中冈优169、内5优317、蓉优22和川谷优6684的产量较高。(4)分蘖期和抽穗期耐淹组合间没有相关性,生产上应分别在各时期筛选相应耐淹能力较强的品种。  相似文献   

12.
Nitrous oxide (N2O) emission from croplands in China is a serious environmental concern. Water management is an important factor in regulating N2O emissions from croplands. In China, controlled irrigation (CI) is one mode of the water-saving irrigation for rice and is widely used. This study aims to assess the lasting effects of CI on N2O emissions from winter wheat croplands in Southeast China, with traditional irrigation (TI) as the control. CI performed during the rice-growing season had obvious lasting effects on N2O emissions of the subsequent winter wheat-growing season. Compared with TI, CI significantly increased the cumulative N2O emission by 129.1 % during the rice-growing season (p < 0.05), but significantly decreased it by 47.7 % during the wheat season (p < 0.05). Continuous flooding of the TI during most of the rice-growing season resulted in an increase in N2O emissions during the winter wheat-growing season. Over the whole annual cycle, the cumulative N2O emission from the plots under CI during the rice-growing season was 5.3 kg N2O–N ha?1, which was 103.2 % of that under TI (p > 0.05). The results suggest that CI does not significantly increase the cumulative N2O emission from the rice–winter wheat rotation systems while insuring rice and wheat yields. This study focuses on the lasting effects of water-saving irrigation mode during rice-growing season on N2O emissions during the following wheat-growing season. Thus, it is a development and complement of the previous researches on the effects of water-saving irrigation on N2O emissions from rice–winter wheat rotation croplands.  相似文献   

13.
Burning of rice straw is a common practice in northwest India, where rice–wheat cropping system is extensively followed. The practice results in loss of nutrients, atmospheric pollution and emission of greenhouse gases. A field experiment was conducted at Indian Agricultural Research Institute, New Delhi, India during the rabi season (November to April) of 2002–2003 to evaluate the efficacy of the various modes of rice straw recycling in soil in improving yield and soil fertility and reducing not only carbon dioxide emission but also nitrous oxide (N2O) emission. The treatment with no rice straw incorporation and application of recommended doses of fertilizer (120, 26 and 50 kg N, P and K ha−1, respectively), gave the highest yield of wheat. Treatments with the incorporation of rice straw at 5 Mg ha−1 with additional amount of inorganic N (60 kg N ha−1) or inoculation of microbial culture had similar grain yields to that of the treatment with no straw incorporation. The lowest yield was recorded in the plots where rice straw was incorporated in soil without additional inorganic N and with manure application. All the treatments with rice straw incorporation had larger soil organic C despite the effect on the mineralisation of soil organic matter. Emission of N2O was more when additional N was added with rice straw and secondary when straw was added to the soil because of higher microbial activity. The study showed that burning of rice straw could be avoided without affecting yield of wheat crop by incorporating rice straw in soil with an additional dose of inorganic N or microbial inoculation. However, the reduction of N2O emission due to avoiding burning is in part counterbalanced by an increase in emission during the subsequent wheat cultivation.  相似文献   

14.
赣东北地区光热充足,非常适宜发展再生稻。为明确合理的促芽肥施用时期和留茬高度,本研究于2011年在江西省余江县设置了不同的促芽肥用量(170 N kg/hm2和125 N kg/hm2以及不施肥)、收割方式和留茬高度(留茬高度为60 cm和30 cm),探讨了不同处理对再生稻籽粒产量和产量构成、再生芽萌发能力的影响。结果表明,与不施促芽肥相比,施促芽肥的再生稻产量显著提高,平均增幅为48.9%和36.9%;其再生稻的每丛穗数、每穗粒数也显著提高。与机械收割相比,人工收割处理的产量显著提高,其再生芽萌发率、每丛穗数和每穗粒数比机械收割分别增加7.7%、27.9%和11.6%。在人工收割方式下,留高茬处理的再生稻产量、再生芽萌发率、每丛穗数和每穗粒数均明显高于留低茬处理。这说明,在赣东北地区,要保障再生稻高产,施促芽肥170 N kg/hm2、人工收割、留高茬是较好的再生稻管理模式。  相似文献   

15.
杂交中稻培育再生稻施用赤霉素两季增产的机理和技术   总被引：10，自引：1，他引：10  
头季稻齐穗后１５天施用赤霉素既可增加头季稻产量，又可增加再生稻产量，增产的原因是头季稻的穗粒数、千粒重和再生稻的有效穗的提高。外源赤霉素改变了内源激素的含量和相互间的平衡，延缓了根叶衰老。  相似文献   

16.
Water shortage in the Huai River Basin prompts farmers to adopt water-saving technologies such as direct-seeded nonflooded or aerobic rice. Different cultivation practices impact on tiller growth and development. Improved insight into tiller dynamics is needed to increase yield in these production systems. We conducted field experiments with four direct-seeded rice varieties under flooded and nonflooded conditions in Mengcheng county, Anhui province, in 2005–2006. The soil water content in the nonflooded treatment varied between saturation and field capacity. Yields in nonflooded soil ranged from 3.6 to 4.7 t ha−1, and did not differ significantly from yields in flooded soil that ranged from 3.6 to 5.1 t ha−1. Variety had a significant effect on biomass, yield, panicle number, spikelet number, grain weight, and grain filling percentage. Panicle number was the main factor limiting yield, resulting from a low tiller emergence frequency and a low fraction of productive tillers in both the flooded and the nonflooded soils. On average, the panicle number was 159–232 m−2, including 34–167 productive tillers per m2 for all the varieties under the two water regimes. The contribution of productive tillers to yield varied between 7% and 47%. There were two peaks of tillers that contributed to yield, one at the low (4th or 5th) and one at the high (10th or 11th) phytomer orders. Frequencies of tiller emergence at most phytomer orders were higher in the flooded soil than in the nonflooded soil. There were no significant differences in frequencies of productive tiller emergence and contributions to yield from tillers between the soil water regimes for three of the four tested varieties. To increase yield in direct-seeded nonflooded rice production systems, both the tiller emergence frequency and the fraction of productive tillers should increase through breeding, improved crop management, or a combination.  相似文献   

17.
Rice is cultivated through transplanting of seedling in submerged field which is a cumbersome, labour intensive and water-guzzling practice. A field experiment was conducted to study the effect of crop establishment methods and irrigation schedules on water productivity, economics and energetics of aerobic direct-seeded rice at Punjab Agricultural University, Ludhiana, India, during Kharif 2012–2013. The experiment was laid out in split plot design, keeping combinations of two tillage system (no-tillage and conventional tillage) and two methods of sowing (uni-directional and bi-directional) in main plots and four irrigation schedule [(30, 45, 60 and 75 mm CPE (cumulative pan evaporation)] in sub plots. Aerobic direct-seeded rice sown after conventional tillage gave significantly higher grain yield than no-till with 15.4 % higher water expense efficiency. The energy gain and net monetary returns were 13.2 and 21.2 % higher in conventional sown crop than no-till, respectively. Bi-directional sowing resulted in 26.5 % higher grain yield than uni-directional with no effect on quality traits of grains. The net energy gain and net monetary returns were 26.5 thousands MJ/ha and 125.3 $/ha higher from bi-directional sown crop than uni-directional sown crop. Crop irrigated at 30 mm CPE schedule resulted in significantly higher grain yield than that irrigated at 45, 60 and 75 mm CPE. The energy gain, energy use efficiency and net returns were also maximum at 30 CPE schedule than at 45, 60 or 75 CPE. However, brown, milled and head rice recoveries were statistically at par between irrigation scheduling at 30 and 45 mm CPE but significantly better than 60 and 75 mm CPE. Bi-directional sowing with conventional tillage and irrigation at 30 CPE is an energy efficient and economical viable technique for direct-seeded rice.  相似文献   

18.
The contribution of rice production to the three major greenhouse gases CO2, CH4 and N2O in 1990, the base year of the Kyoto protocol is investigated for Japan. For the CO2 assessment, we use a top-down life cycle approach, CH4 is assessed using the Japanese GHG emission inventory and N2O is assessed according to the ratio of rice area divided by the total area of agricultural soils. In total, 1.6% of greenhouse gas (GHG) emissions in 1990 originated from rice production. Next, we assess regional variations in nine rice-producing regions, based on the CO2 data of 1990. General trends in rice production from 1960 to 2000 and data from the Japanese GHG emission inventory since 1990 are used to assess variations in time. The rice-related GHG emissions decreased to 1.05% of the total GHG emissions in 2001 and will be less than half the 1990 level in 2012, mainly due to the decrease in rice production. Contrary to the trend in GHG emissions of rice, overall GHG emissions increased as rice production fulfils important roles, in mitigating global warming and in adapting to changing climates. The protection of rice production is required to counter the increase of GHG emissions in transportation, waste and domestic sectors and to minimize problems related to landscape, water and natural hazard management.  相似文献   

19.
Nitrogen fertilizer practices affect nitrous oxide (N2O) emissions from agricultural soils. The “4R” nutrient stewardship framework of using N fertilizer at the right rate, right source, right placement and right time can reduce N2O emissions while maintaining or improving yield of field crops, but understanding of how the various factors affect N2O emissions from irrigated processing potato is lacking. We examined the effects of selected 4R practices on emissions, using results from two irrigated processing potato studies each conducted in 2011 and 2012 in Manitoba, Canada. Experiment 1 examined combinations of source (urea, ESN), placement (pre-plant incorporation [PPI], banding), and rate (100 and 200 kg N ha-1) on a clay loam soil. Experiment 2 examined timing and source treatment combinations (urea PPI, ESN PPI, urea split, urea split/fertigation) on a loamy fine sandy soil. For Experiment 1, use of ESN at 200 kg ha-1 did not reduce area-, yield- and applied fertilizer N- based N2O emissions compared to urea at 200 kg ha-1, irrespective of placement. Emissions from pre-plant banding ESN at 200 kg ha?1, however, were 32% lower than from PPI ESN. For Experiment 2, compared to single pre-plant urea application, fertigation simulated by in-season application of urea ammonium nitrate (UAN) gave lower area-, yield- and applied fertilizer N- based emissions. Split urea ( \( \raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right. \) pre-plant, \( \raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right. \) hilling) also reduced area- and yield- based N2O emissions compared to single pre-plant urea application. Emissions were generally lower at the site with loamy fine sandy soil than the site with clay loam soil. These results demonstrate that combinations of “4R” practices rather than source alone are best to achieve reductions in N2O emissions from irrigated potato production.  相似文献   

20.
Rice (Oryza sativa L.) ratooning is the production of a second rice crop from the stubble left behind after the main-crop harvest. Lowering the main-crop stubble height by harvesting the main crop at a lower than traditional height is believed to alter growth parameters and increase ratoon yields. The objectives of this study were to evaluate the effect of main-crop stubble height on ratoon grain yield, agronomics, and cumulative/weekly panicle growth parameters (density, point of origin, and weight). Main-crop ‘Cocodrie’ and ‘Trenasse’ rice cultivars were harvested to leave either a 40- or 20-cm stubble height. When the main-crop stubble was harvested at 20 cm, ratoon rice grain yield in 2007 was increased by 375 and 190 kg ha−1 for Cocodrie and Trenasse, respectively. Yield was not improved in 2006 using the low (20 cm) harvest height. The yield advantage in 2007 was associated with the increased weight of the basal panicles when the main crop was harvested at 20 cm. When the main-crop stubble was 20 cm, basal and axial panicle points of origin were numerically similar 5 weeks after main-crop harvest (WAH), while panicles originating from basal nodes were predominant 6 WAH and beyond. In contrast, when the main-crop stubble was 40 cm, approximately 75% of the emerged panicles originated from axial nodes 5 WAH, panicles from both axial and basal points of origin were nearly identical 6 WAH, and basal panicles were dominant thereafter. Results from this study indicate that when the initial stubble height is reduced from 40 to 20 cm the growth of the ratoon crop is altered by shifting panicle point of origin during the early growth period and delaying maturity.  相似文献   

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