Evaluation of the suppression ability of rice (Oryza sativa) on Monochoria vaginalis by measuring photosynthetic photon flux density below rice canopy

Field experiments involving eight cultivars were conducted in 1998 and 16 cultivars in 1999 to study the ability of rice (Oryza sativa L.) to suppress Monochoria vaginalis (Burm. f ) Kunth through light competition. Dry weights of M. vaginalis shoots in early season culture exceeded those in normal season culture of any rice cultivars. The relative photosynthetic photon flux density (R‐PPFD), which was calculated as the ratio of the photosynthetic photon flux density (PPFD) below the rice canopy to that measured above the rice canopy, varied according to rice cultivar. A strong linear correlation was observed between the mean R‐PPFD at 29–35 days after transplanting (DAT) (r² = 0.80; p < 0.01 in 1998; r² = 0.63, p < 0.001; and r² = 0.93, p < 0.001 in 1999), or 36–42 DAT (r² = 0.66, p < 0.05 in 1998; r² = 0.72, p < 0.001; and r² = 0.97, p < 0.001 in 1999), and the dry weight of M. vaginalis shoots at approximately 60 DAT. Data from the three experiments could be pooled into one regression line because intercepts and regression coefficients were not significantly different. The r² values of the combined regression were highest when R‐PPFD was expressed as the mean of measurements taken during 14 days (from 29 to 42 DAT; r² = 0.81, p < 0.001). The shortest period for measuring mean R‐PPFD in order to obtain a meaningful relationship with M. vaginalis shoot dry weight was 7 days (from 29 to 35 DAT; r² = 0.78, p < 0.001). For that same period, relationships between M. vaginalis shoot dry weight at 60 DAT and rice tiller number or leaf area index (LAI) at ground level were weak. However, there were negative relationships between M. vaginalis shoot dry weights at 60 DAT and rice LAI measured 20 cm above the ground, plant heights or rice shoot dry weight, but these coefficients of determination were smaller than those calculated by R‐PPFD for the same period. Thus, the ability of rice to suppress M. vaginalis can be evaluated more accurately by measuring mean R‐PPFD below the rice canopy for 7 days (from 29 to 35 DAT) than by measuring rice LAI, plant height and shoot dry weight.     

稻田杂草生物防治研究现状、问题及展望

本文对稻田主要杂草的生物防治,特别是稗草微生物防治的研究现状进行了综述、指出了存在的问题,以及今后应着重研究解决的技术难点提出了作者的观点。     

Effect of allelopathic rice varieties combined with cultural management options on paddy field weeds

BACKGROUND: A number of techniques, including cultural management, allelopathy and bioherbicide, have been considered as alternatives for synthetic herbicides, but successful weed control will require the careful integration of these multiple techniques. This study was conducted to assess the use of allelopathic rice varieties in combination with cultural management options on paddy weeds, in order to develop an allelopathy-based technique to reduce herbicide use in paddies. RESULTS: The weed-suppressive effects of the rice varieties tested varied highly with allelopathic trait, planting pattern and cultural management including planting density, flooding depth and duration and supply of nitrogen. Allelopathic rice varieties PI312777 and Huagan-1 demonstrated much stronger weed suppression than the non-allelopathic variety Huajianxian under the same planting pattern and cultural management. Their weed-suppressive effect was increased with cultural management options. In particular, if integrated cultural management options of allelopathic rice varieties included a low-dose (bensulfuron-methyl, 25 g AI ha(-1), a third of the recommended dose) herbicide application, the emergence and growth of most weeds found in paddy fields was completely controlled. No grain yield reduction for allelopathic varieties occurred under integrated cultural management options, whereas with the non-allelopathic variety a reduction of up to 45-60% was measurable even with the low-dose herbicide application. CONCLUSION: The allelopathic potential of rice varieties will likely have a great impact on paddy weed control if integrated with cultural management options and application of low doses of herbicides. Therefore, it is feasible to reduce herbicide input in paddies if allelopathic rice is grown under integrated cultural management practices.     

Effects of loosing Aigamo ducks on the growth of rice plants, weeds, and the number of arthropods in paddy fields

Aigamo duck farming has been noticed as one of the techniques of environmental conservation agriculture. This study was carried out to investigate the effects of loosing Aigamo ducks on the growth and production of rice plants, the quantity of weeds and arthropods, and the balance of nitrogen (N) in paddy fields by changing the density of the Aigamo ducks. A paddy field was divided into three test plots: a 10-Aigamo-duck plot, a five-Aigamo-duck plot, and a weeding plot. The results show that the height, number of culms, and yield crops of the rice plants increased more in the 10-Aigamo-duck plot and the five-Aigamo-duck plot than that of the weeding plot. Millet ( Echinochloa oryzicola ) remained in both the Aigamo duck plots. The weeding plot was covered with monochoria ( Monochoria vaginalis ). In both the Aigamo duck plots, the outbreak of total arthropods was lower than that of the weeding plot, but the number of rice plants damaged by grass leaf rollers ( Cnaphalocrocis medinalis ) was increased. The number of spiders, regarded as useful insects, did not differ that much between the experimental plots. The N content of the soil did not differ as an effect of loosing the Aigamo ducks. The rice plants in the 10-Aigamo-duck plot absorbed more N than the rice plants in the other plots.     

秸秆残茬对低温潜沼性稻田土壤还原性物质含量及稻谷产量的影响

采用盆栽实验的方法,研究了秸秆残茬对低温潜沼性稻田土壤氧化还原电位、土壤还原性物质总量、土壤Fe²⁺含量及其稻谷产量的影响。研究结果表明：(1) 在低温潜沼性稻田中,与无秸秆残茬田(T0)相比,随着秸秆残茬量的增加（2.5～10.0 t·hm^-2）,T1,T2和T3处理的土壤还原性物质总量增加2.2～4.8 cmol·kg^-1;土壤Fe²⁺含量增加10.8～40.8 mg·kg^-1,土壤氧化还原电位降低23.2～96.5 mV。其中,当秸秆残茬量超过5.0 t·hm^-2时,秧苗移栽-返青期土壤Fe²⁺含量增加88.2 mg·kg^-1,土壤氧化还原电位降低196 mv,不利于水稻生长。(2) 在低温潜沼性稻田中,与无秸秆残茬田(T0)相比,随着秸秆残茬量的增加（2.5～10.0 t·hm^-2）,T1,T2和T3处理的稻谷产量降低1 140～1 560 kg·hm^-2;当秸秆残茬量高于5.0 t·hm^-2时,稻谷千粒重降低0.2 g,结实率等显著降低4.2%。     

氮肥运筹对苏打盐碱地水稻养分积累、转运及产量的影响

于2017—2018年,以粳稻品种垦粳7号和垦粳8号为试验材料,设置5种氮肥运筹方式:不施氮肥(N0)、农民习惯施氮(N1)、平衡施氮(N2)、减氮施肥(N3)和氮肥后移(N4),研究氮肥运筹对苏打盐碱地水稻氮磷钾养分积累转运以及生产效率的影响.结果表明:与农民习惯施氮相比,平衡施氮和减氮施肥显著提高了齐穗期和成熟期植...     

喷雾参数对自走式喷杆喷雾机稻田喷雾农药利用率及雾滴沉积分布的影响

比较在不同喷雾压力和施药液量条件下,采用自走式喷杆喷雾机在水稻分蘖期、孕穗期、扬花期进行喷雾处理的农药利用率、沉积分布均匀性及水稻茎基部雾滴密度的差异,为建立自走式喷杆喷雾机在稻田的高效施药技术提供理论依据。以生物染料丽春红-G作为农药示踪剂,估测不同喷雾参数的农药利用率,并用变异系数、绝对份额比例值比较农药分布的均匀性。同时通过水敏纸收集水稻基部雾滴密度,分析不同喷雾参数下农药雾滴穿透水稻冠层的能力。结果表明:在水稻分蘖期,采用自走式喷杆喷雾机在喷雾压力为1.2 MPa、施药液量为375 L/hm^2条件下喷雾,每个采样点的丽春红-G的平均沉积量仅为0.11 mg,与喷雾压力为0.4 MPa、施药液量为300 L/hm^2条件下喷雾的沉积量相比减少了56.00%。在水稻孕穗期,当喷雾压力为1.2 MPa、施药液量为375 L/hm^2时进行喷雾处理,每个采样点的丽春红-G的平均沉积量达0.26 mg,显著高于其他4个处理。在水稻扬花期,不同喷雾参数间的沉积量差距减小。在合适的喷雾压力和施药液量时,自走式喷杆喷雾机在水稻分蘖期、孕穗期和扬花期进行喷雾处理,农药利用率分别达到40.57%、54.97%和55.50%。综合变异系数和绝对份额比例两个指标,采用自走式喷杆喷雾机在喷雾压力为0.8 MPa、施药液量为300 L/hm^2条件下喷雾,农药分布更均匀。喷雾压力对水稻基部雾滴密度有显著影响,在水稻生长中后期,当喷雾压力低于0.8 MPa、施药液量为225~375 L/hm^2时,水稻茎秆基部雾滴密度均小于30个/cm^2。研究结果表明,喷雾压力和施药液量对自走式喷杆喷雾机稻田喷雾的农药利用率、分布均匀性及水稻茎秆基部雾滴密度有显著影响。在水稻生长前期,不宜采用高压力大水量喷雾作业;在水稻生长中后期,为增加对水稻基部病虫害的防治效果,需提高喷雾压力。     

Effects of density and sowing pattern on weed suppression and grain yield in three varieties of maize under high weed pressure

We tested the hypothesis that improved weed suppression by maize can be achieved through increased crop density and spatial uniformity. Field experiments on three varieties of maize sown at three densities (5, 7 and 10.5 seeds m^?2) and in two spatial patterns (grid pattern and rows) under very high weed pressure from Brachiaria brizantha were performed in 2012 and 2013. We measured weed biomass 1 month after sowing and at harvest, and grain yield at harvest. Density, variety and sowing pattern all had strong and significant effects on both weed biomass and yield. On average, weed biomass was reduced (by 72% in the first year and 58% in the second year), and grain yield was increased (by 48% and 44%) at the highest density in the grid pattern compared with standard sowing practices (medium density, row pattern). There was a significant density × variety interaction, which is evidence for genetic differences in the response of the varieties to density in characteristics that influence weed suppression. The variety that suppressed weeds best at high density had the lowest variation in the angle of insertion of the oldest living leaf at harvest (leaf 6), supporting the hypothesis that reduced phenotypic plasticity may be advantageous for weed suppression under high density and spatial uniformity. Increased density and uniformity can contribute to weed management in maize in many cases, potentially reducing the need for herbicides or mechanical weed control.     

基于引力和场强模型的干旱内陆河流域城乡体系相互作用及空间表达

综合运用遥感数据和相关统计资料,在对石羊河流域城乡生态环境、人口分布、经济发展深入考察研究的基础上,结合环境生态学、物理学、数理统计学、城市规划学、区域分析及可持续发展理论,通过构建城乡规模评价指标反映城乡规模及辐射范围,结合流域内部相互辐射、引力及场强模型建立遥感与GIS模型。利用引力模型分析城乡间联系的疏密程度和城镇在流域体系中的集聚能力,利用场强模型分析城镇间的辐射作用强度。结果表明:对于干旱内陆河流域区域分析研究,能充分利用到遥感和GIS技术进行空间定位和空间表达,以此建立研究区城镇规模评价指标体系,对其相互作用及联系的紧密程度可以进行直观可视化表达,从而使评价指标体系更为完善。在上述研究成果的基础上深入探讨关于石羊河流域城乡体系协调发展的整合模式,从而为石羊河流域生态环境综合治理、城乡一体化发展及经济社会协调可持续发展提供参考依据。     

基于DNDC模型的不同水文年稻田水碳管理模式优化

为探究不同水文年型下稻田最优的水碳管理模式,基于2 a田间试验数据校正并验证了DNDC模型,选取了3种典型的水文年,模拟了不同灌溉模式和秸秆还田水平下稻田土壤有机碳(SOC)和水稻产量的变化,并对结果进行了比选。结果表明:DNDC模型可以较好地模拟节水灌溉条件下稻田SOC和水稻产量变化;灌溉模式影响了稻田SOC和水稻产量,相同秸秆还田水平下,控灌稻田0～10 cm土层SOC略低于淹灌处理,但水稻产量更高,控灌稻田的SOC和水稻产量分别较淹灌稻田降低了0.25%～1.92%和增加了0.32%～8.13%。随着秸秆还田水平的提高,不同水文年的稻田SOC均呈阶梯状上升趋势,但水稻产量和水分生产率的结果存在差异,平水年呈先升高后稳定的趋势,在6 500 kg·hm^-2秸秆还田水平下达到峰值,丰水年条件下秸秆还田的增产作用较枯水年更为明显。与1 000 kg·hm^-2的秸秆还田水平相比,8 000 kg·hm^-2秸秆还田水平下水稻产量和水分生产率在1964年(枯水年)分别增加了1.95%和2.27%,而在1977年(丰水年)分别增...