Shading effects on spatial growth and biomass partitioning of Cynodon dactylon

Cynodon dactylon is a low-growing C4 weed that is highly sensitive to shading. This species shows severe biomass reductions and highly plastic morphological changes in response to resource availability. The objective of this study was to analyse the effect of shading on the spatial and biomass growth of C. dactylon . Two experiments were carried out exploring different environmental conditions. Six treatments were applied on C. dactylon patches. Daylight and 18%, 41%, 48%, 69% and 85% shading of daylight photosynthetic active radiation (PAR) were imposed in Expt 1 and 0%, 22%, 44%, 50%, 74% and 87% shading of daylight PAR in Expt 2. Patches were slightly elliptical in shape and grew 3.2 and 1.5 cm d⁻¹ with 0% shading, on average, during the whole studied periods in Expts 1 and 2 respectively. Biomass was significantly reduced from 41% shading onwards in Expt 1 and from 50% shading in Expt 2. However, patch extension rate was only significantly reduced from 85% and 74% shading in Expts 1 and 2 respectively. Biomass partitioning was modified by shading in both experiments. A functional analysis of C. dactylon patches showed that the patch extension rate diminished linearly when patch biomass growth rate was lower than 1.66 g d⁻¹; above this value, the extension rate remained constant.     

Establishment of Cynodon dactylon from stolon and rhizome fragments

Summary A field survey and two field experiments were carried out to compare the performance of rhizomes and stolons of Cynodon dactylon , in terms of their sprouting efficiency and the dynamics and growth characteristics of the established ramets. The survey examined the relationships between morphological characteristics of above- and below-ground structures of ramets naturally established from both types of fragments in a crop field. The first experiment compared the emergence and early growth of ramets from standardized stolon and rhizome fragments, grown under uniform field conditions without competition. It also comparatively analysed the predictive value of the maximum stolon length on dry matter partitioning. The second experiment investigated fragment type × size interactions on the establishment, dry matter accumulation and partitioning in stolon- and rhizome-originated ramets. Results showed that under normal cropping conditions, more ramets can be originated from rhizome than from equivalent stolon fragments. Higher sprouting efficiency and dry matter partitioning to aerial structures, and a higher size dependence of the effective ramet recruitment were observed for stolon than for rhizome fragments. The observed differences between fragment type are dicussed in relation to their implications for predictions of weed emergence, and the efficacy of control strategies used under different cropping tillage systems.     

外源脱落酸对抗寒性狗牙根抗氧化酶活性的影响

以寒敏感的普通狗牙根、海岸狗牙根和抗寒的新农1号狗牙根、喀什狗牙根为供试材料,研究外源脱落酸（0 mg•L^-1、5 mg•L^-1、15 mg•L^-1、25 mg•L^-1）在4 ℃低温处理下（处理时间24 h、72 h）对叶片相对电导率（EC）、丙二醛（MDA）含量、超氧化物歧化酶（SOD）活性、过氧化氢酶（CAT）活性、过氧化物酶（POD）活性的影响。结果表明：与CK2（喷水、常温培养）相比,4 ℃低温处理24 h、72 h,无论是否喷施外源脱落酸,狗牙根均表现为[WTBX]EC[WTBZ]增大,MDA含量增加;但与CK1（喷水、4 ℃低温处理）相比,喷施外源脱落酸可以诱导狗牙根细胞EC、MDA含量降低,促进SOD活性、POD活性、CAT活性的进一步增加,保护膜系统的完整性,增强其对低温的适应。综合分析认为,抗寒狗牙根的适宜外源脱落酸喷施浓度为15 mg•L-1,寒敏感狗牙根为5 mg•L^-1更有利于其对低温的适应。随着低温处理时间的延长,抗寒狗牙根SOD活性增加率、MDA含量降低率明显高于寒敏感狗牙根,说明SOD酶活性不同可能是狗牙根抗寒性差异的原因之一。     

Soil water availability affects green area and biomass growth of Cynodon dactylon

Bermuda grass ( Cynodon dactylon ) is a stoloniferous and rhizomatous prostrate weed displaying high growth rates under non-limiting conditions. Radiation has been considered the major factor affecting C. dactylon patch extension and biomass growth, but little is known about the influence of water availability on those processes. C. dactylon green area and biomass growth were analysed in response to different soil water conditions. Four experiments comprising eight drought treatments were carried out during 2 years at different dates, to generate a wide range of soil water and evaporative demand conditions. Significant reductions in weed green area and biomass growth were found between treatments when low soil water conditions were imposed. Reductions in green area were of greater magnitude than reductions in biomass, suggesting a higher effect of drought on green area increment. There were significant ( P  < 0.05) relationships between green area increment and cumulative incident radiation, although slopes [relative green area growth rates (RGAGR)] differed among treatments. A strong logistic relationship was found between RGAGR and the ratio of plant-available soil water to potential evapotranspiration. The approach and parameters generated in this work can be used to predict C. dactylon growth changes under rain-fed conditions.     

The effect of temperature on sprouting and early establishment of Cynodon dactylon

Bud-sprouting dynamics, sprouting base temperature and reserve mobilization of rhizomes and stolons of Cynodon dactylon (L.) Pers. were characterized in a laboratory experiment under dark conditions. In addition, the dynamics of sprout emergence were determined during 2 years under field conditions. In the laboratory experiment, buds from the vegetative structures did not sprout at temperatures below 7^C. The rate of sprouting increased with temperature within the range 11–33^C, and a base temperature of 7.71^C was determined for bud sprouting of rhizome and stolons of the weed. An exponential model is proposed relating the percentage of sprout emergence in the field to accumulated thermal units, calculated as the sum of the daily mean air temperature above the base temperature of bud sprouting. This model satisfactorily predicted the dynamics of C. dactylon sprout emergence in sunflower (Helianthus annuus L.) crop fields. The efficiency of carbohydrate reserve use during sprout growth was highly dependent on temperature and type of vegetative structure The efficiency was maximum at 20^C and was higher for rhizomes than for stolons. The main factors influencing bud sprouting and early weed establishment are discussed.     

Comparative performance of the highly invasive Mimosa invisa and its less invasive subspecies under different nutrient and light conditions

Invasive plants may be more plastic than non‐invasive plants and maintain high fitness under various environmental conditions. Previous studies mainly focused on the comparisons between invasive and native plants, and comparisons between highly invasive and less invasive exotic species are still relatively rare, especially for comparisons at the subspecies level. This study examined the effects of nutrient addition and shading on the performance of the highly invasive Mimosa invisa and its less invasive subspecies M. invisa var. inermis under either isolated or competitive conditions. Nutrient addition increased biomass and plant height and decreased root‐to‐shoot ratio (R/S). Shading decreased biomass and R/S and increased plant height. Under isolated conditions, the two invaders did not differ in R/S, plant height and plasticity of these traits in response to nutrient addition or shading, and the two invaders also did not differ in biomass production under each of the nutrient and light treatments. When the two invaders competed with each other, M. invisa outcompeted M. invisa var. inermis under high soil nutrient conditions, and the two invaders did not differ in performance under other growth conditions. Thus, only considering competition may we find out the difference between highly invasive species and their closely related, less invasive subspecies. Management of M. invisa should focus on habitats with high soil nutrient availability, in which M. invisa is more likely to dominate.     

辽宁中西部地区6种保护性耕作措施玉米生长发育状况比较

针对辽宁省中西部地区春旱频繁、土壤风蚀严重的特点,设置1:2轮耕、1:1轮耕、铁茬垄侧播种、铁茬茬间播种、铁茬茬间播种覆盖、保墒蓄水耕作及灭茬后原垄播种(对照)等不同耕作措施,研究其玉米生长发育的差异状况.结果表明:保护性耕作措施有利于玉米4叶期后植株的生长发育,铁茬茬间播种覆盖和铁茬茬间播种处理的效果明显优于其它耕作措施.     

Dispersal of Avena fatua and Avena sterilis patches by natural dissemination, soil tillage and combine harvesters

The dispersal of Avena spp. (A. fatua and A. sterilis) by natural dissemination and by agricultural operations was studied in four experiments conducted in Spain and Britain. Natural dispersal was very limited, with a maximum dispersal distance of 1.5 m. Dispersal was higher in the geographic direction that was downwind than in any of the other three geographic directions. Although plant movement was very small under no‐tillage, an annual patch displacement of 2–3 m in the tillage direction was observed under conventional soil tillage. Ploughing downhill resulted in much larger dispersal distances than ploughing uphill. In the crops studied, combine harvesters dispersed few Avena spp. seeds, because of the fact that the plants had shed most of their seeds (>90%) before harvest. The percentage of seeds available to be dispersed by the combine was dependent on the harvest time. Although combine harvesting may not contribute much to short‐distance dispersal, it may play an important role in long‐distance dispersal. In our studies, isolated plants were located up to 30 m from the original sources. This small proportion may have a significant effect on the distribution of the weed within a field, acting as foci for new patches.     

保护性耕作对小麦生长和水分利用效率的影响

采用对比试验法研究了紫色土丘陵区保护性耕作对小麦光合特性、干物质积累和水分利用效率的影响。结果表明:秸秆覆盖和秸秆覆盖+施用腐熟剂均能提高小麦生育后期叶面积指数,净光合速率比传统耕作分别提高了2.90%和5.74%;两种处理能在一定程度上控制株高,并在小麦抽穗~成熟期促进干物质积累,使麦穗分配指数提高238.46%和242.31%;秸秆覆盖+腐熟剂使小麦增产8.07%,水分利用效率和降水利用效率也分别提高了5.80%和8.02%。     

保护性耕作对北疆麦后复种青贮玉米田地温和作物生长的影响

2013年在新疆生产建设兵团第七师130团七连8号地段大田,小麦收获的同时,秸秆粉碎还田,然后采取免耕播种和铧式犁翻耕后播种两种耕作方式,对比研究保护性耕作对北疆复播田土壤温度及复播作物生长发育的影响规律。试验结果表明:保护性耕作条件下土壤温度具有明显的阶段性变化,在复播玉米LAI达到1之前秸秆覆盖具有降温效用,土壤温度低于翻耕处理,之后则具有保温作用。整个生育期免耕田土壤温度变化平缓,累积温度、累积温差及日平均温差均低于翻耕处理。免耕处理下作物生育期后移,干物质积累主要在生育后期,产量及干物质积累略低于翻耕处理。     

DSSAT模型对豫西冬小麦保护性耕作效应模拟效果验证

简要介绍了美国乔治亚大学组织开发的DSSATV4.5模型,并利用洛阳市孟津县2005~2006年冬小麦田间试验结果对模型的模拟结果进行验证及其适用性分析。通过对冬小麦叶面积指数、产量和农田土壤水分、水分利用效率的模拟与实测结果的对比分析,认为DSSAT模型的模拟效果较好。分析结果表明:模型对叶面积指数的模拟误差RMSE在0.034~0.076之间;模拟各处理的产量与水分利用效率也与实测值的关系基本一致;对各处理土壤体积含水量的RMSE误差在0.051~0.151之间。研究结果认为DSSAT模型在豫西应用的适宜性较好,可为该地区研究保护性耕作对冬小麦生长及土壤水分的影响提供理论支持。     

连续14年保护性耕作对土壤总有机碳和轻组有机碳的影响

依托于2001年布设在陇中黄土高原半干旱雨养农业区的保护性耕作定位试验,于2014年测定了5种保护性耕作(免耕+秸秆覆盖NTS、免耕NT、传统耕作+秸秆翻埋TS、传统耕作+地膜覆盖TP和免耕+地膜覆盖NTP)和传统耕作T处理下小麦-豌豆双序列轮作中表层土壤(0~5、5~10、10~30 cm)总有机碳(SOC)和轻组有机碳(LFOC)在作物生育期前后的变化。结果表明:土壤总有机碳和轻组有机碳在土壤剖面上均随着土层深度的增加而降低;相比传统耕作T,NTS和TS处理能显著提高0~30 cm土层中SOC、LFOC的含量,在作物播种前较T分别提高了19.51%、64.58%和13.36%、42.08%,在收获后分别提高了28.00%、85.37%和18.61%、77.82%,而SOC、LFOC含量NT和TP处理与T处理间差异不显著;从作物播种前至收获后,各处理下0~30 cm土层SOC含量均有减小趋势,其中NTS和TS处理变化量最小,NT和TP处理加大了作物生育期间SOC和LFOC的消耗;LFOC可以灵敏地反应出土壤有机碳的变化。因此,在该区推行以免耕、秸秆覆盖为主的保护性耕作措施更有利于碳的积累和土壤质量的改善,促进该区农业的可持续发展。     

翻耕深度对膜下滴灌棉花生长和冠层小气候的影响

为探究翻耕深度对覆膜滴灌农田小气候及棉花生长的影响机制,于2019年4—10月在新疆库尔勒地区开展田间试验,设置20、30、40 cm 3组翻耕深度处理(T20、T30、T40),以免耕处理(NT)作为对照,分析了翻耕深度对土壤孔隙率、农田耗水量、田间小气候、棉花生长状况及产量的影响。结果表明：翻耕深度的增加能够有效提高土壤孔隙率、增加膜内耕层土壤温度、促进植株耗水;棉株从膜内土壤中消耗的水分对冠层小气候的调控作用大于膜外土壤的水分蒸发对冠层小气候的调控作用,NT、T20、T30、T40处理膜内位置的农田耗水量分别是膜外位置农田耗水量的2.48、2.52、3.08、3.47倍;全生育期内,T20、T30、T40处理的农田耗水量分别是NT处理的1.30、1.42、1.52倍;深翻导致农田耗水量的增加能够有效提高冠层湿度,延长棉花生育期,使棉花增产。全生育期内,各翻耕处理(T20、T30、T40)的近地表平均冠层湿度分别比NT处理高12.83%、14.49%、17.55%,棉花全生育期分别比NT处理长10、16、23 d,籽棉产量分别比NT处理高670.68、1 252.67、1 584.02 kg·hm^-2。     

农田不同耕层构造对玉米生长发育及产量的影响

在公主岭市吉林省农科院长期定位试验田(1983年)4种耕层构造(上虚下实、全虚耕层、全实耕层和虚实并存)上,通过对玉米出苗率、株高、茎粗、叶片数、叶面积、根系及产量指标测定,探讨不同耕层构造对玉米生长发育及产量的影响。结果表明,虚实并存耕层玉米出苗率为94.90%,明显高于其他耕层,增加苗期玉米株高和茎粗,叶片数较全虚耕层和上虚下实耕层分别增加0.8和1.2片,但与全实耕层相比差异不明显。从玉米生育中后期来看,虚实并存耕层促进玉米生长发育,增加叶面积,改善根系性状,与上虚下实耕层比较,根条数增加16.80条,气生根和地下根干重分别增加4.60 g和20.50 g,且气生根层数增加0.80层。同时,虚实并存耕层玉米产量显著高于其他耕层,增产幅度为8.17%~15.02%,上虚下实耕层产量最低。可见,虚实并存耕层"既发小苗,又发老苗",稳产高产,是较为理想的耕层构造。     

The effect of tillage system and use of a paraplow on weed flora in a semiarid soil from central Spain

Field experiments were conducted to study weed population shifts in long‐term conservation tillage systems. The objectives of this study were to determine weed community abundance, diversity and composition on conventional tillage (CT), minimum tillage (MT), no‐tillage with paraplow (ZT) and no‐tillage (NT) systems, and to identify species that are associated with specific tillage systems. The paraplow is a subsoiling technique that results in a deep loosening of the soil, in order to alleviate compaction in certain soils where NT is practiced. The results showed significant differences in both the composition and the abundance of weeds, depending on the tillage systems. Weed diversity, species richness and Shannon's diversity and evenness indices were higher under the conservation tillage systems than in the CT system. In addition, various weed species were associated with reduced tillage systems. For instance, Anthemis arvensis, Hirschfeldia incana and Lolium rigidum became more prevalent in the NT system, whereas Chenopodium album and Filago pyramidata dominated in the ZT system. Therefore, the application of a paraplow treatment changed the weed community in the NT system. Other weed species, such as Capsella bursa‐pastoris and Torilis nodosa, dominated in all three conservation tillage systems, whereas soil disturbance by mouldboard ploughing favoured species such as Polygonum aviculare and Phalaris paradoxa.     

Long‐term effect of different tillage systems on the emergence and demography of Bromus diandrus in rainfed cereal fields

The adoption of no‐tillage systems in semi‐arid cereal fields in northern Europe has resulted in difficulties in controlling Bromus diandrus. However, in some fields, lower densities are observed in continuous long‐term no‐tillage management than in other reduced tillage systems. A cumulative effect on the seedbank could promote changes in the period of seedling emergence and in population demography. This study evaluated the effect of long‐term mouldboard plough (MbP), chisel plough (ChP), subsoiler (SS) and no‐tillage (NT) on the population dynamics of B. diandrus. The work was carried out in a barley (Hordeum vulgare)–wheat (Triticum aestivum)–barley rotation during three seasons where these soil management systems had been applied for the last 22 years. Cumulative emergence (CE) and densities of B. diandrus followed a gradient of ChP > SS > NT > MbP. This cumulative effect over time resulted in significant differences in population demography. A previous hydrothermal emergence model developed for this species estimated the percentage of emergence prior to the date of sowing to be: 71%, 92% and 53% for the seasons 2008–2009, 2009–2010 and 2010–2011 respectively. Furthermore, the reduction in CE observed was on average 53% in SS, 92% in NT and 98% in MbP in comparison with that recorded in ChP. The long‐term effect of different tillage systems tended to cause changes to soil characteristics (photo‐inhibition of germination, soil temperature, water availability) affecting B. diandrus demography, reaching equilibrium in weed densities over years, which were significantly lower in MbP and NT than in ChP or SS.     

不同灌水水平下少耕地膜覆盖对玉米农田土壤温度和水分利用效率的影响

以大田玉米为研究对象,在少耕地膜覆盖和不同灌水水平下,研究了一膜两年用地膜覆盖、秋免耕春覆膜和传统耕作覆膜对玉米农田土壤温度和水分利用效率(WUE)的影响。结果表明:与传统耕作覆膜和秋免耕春覆膜两种新膜覆盖处理相比,一膜两年用处理在玉米播种到拔节期的增温效果显著低于新膜覆盖,农田0~25 cm土壤平均温度较传统覆膜处理低13.35%,而对玉米拔节期到成熟期的土壤温度无明显影响,且农田0~25 cm土层土壤积温差异也不显著,相同覆膜方式下不同灌水水平间有显著差异,随着灌水水平的降低土壤积温增加;一膜两年用地膜覆盖方式下玉米籽粒产量和WUE与两种新膜覆盖方式相当,中灌水水平下WUE最高,达到17.89kg·mm-1,且在低灌水水平下获得籽粒产量显著高于传统覆膜处理,一膜两年用覆盖、灌溉定额5 700 m3·hm-2较传统耕作覆膜、灌水定额5 700 m3hm-2处理的玉米产量高出16.39%。说明,一膜两年用地膜覆盖在玉米播种到拔节期的增温效应低于新膜覆盖,但并不影响籽粒产量的形成,且在存在水分胁迫的低灌水水平下一膜两年用覆盖模式可减缓干旱胁迫,提高作物籽粒产量,是适于西北绿洲灌区的具有较好经济效益和生态效益的覆膜农田管理新技术。     

不同耕作方式对北疆夏大豆荚粒空间分布及产量的影响

采用大区试验设计,研究滴灌条件下翻耕覆膜(TP)、翻耕(T)、旋耕(RT)、免耕(NT)四种耕作方式对北疆复播大豆的农艺性状、单株荚数、粒数的空间垂直分布、每荚粒数及产量的影响。结果表明,夏大豆的主要农艺性状基本表现为土壤实施耕作处理均优于免耕,其中以翻耕覆膜的效果最好,翻耕次之;单株荚数和粒数的空间垂直分布因耕作方式而异,翻耕覆膜、翻耕、旋耕的主要分布于主茎的中层和上层,免耕的主要分布于主茎中层和下层;不同荚粒的数量均与单株产量呈正相关,其中2粒荚和3粒荚的数量是构成不同耕作方式单株产量的主体,相关系数分别为r=0.99**和r=0.98**;各类荚的数量均以翻耕覆膜的最多,使得其单株荚数和单株粒数的数量均最多,与其它各处理均达极显著差异水平(P0.01),其产量分别比翻耕、旋耕、免耕的增产7.43%、10.85%和16.05%。     

保护性耕作对坡耕地粮豆草等高带状种植作物生长与水土保持效果的影响

为有效防治坡耕地水土流失,提高坡耕地水分利用率,选用多年生作物苜蓿及小麦、鹰嘴豆、马铃薯 等一年生作物作为供试作物,设置不同带状系统研究了各种种植方式和耕作方式对作物生长、土壤水分、WUE及 水土流失的影响。结果表明,(1)各处理保持水分的能力依次为：免耕+秸秆覆盖(NTS)>免耕(NT)>传统(T);(2) 保护性耕作具有良好的防止土壤侵蚀能力,依次为：NTS>NT>T;(3)免耕+秸秆覆盖和免耕方式与传统耕作相比, 均能提高半干旱地区土壤水分和作物对水分的利用效率,减少土壤侵蚀量。从不同处理保持水土效应来看,从优 至劣的顺序为NTS_PL>T_PL>NTS_CL>T_CL>NTS_WL>T_WL。由此可见,免耕秸秆覆盖是提高水分利用效率及控制水土流失的有效措施,粮草豆隔带种植,结合保护性耕作措施不但具有蓄水保土,减免侵蚀的生态作用,而且还能提高土地利用的经济效益,宜结合生产推广利用。     

三种杀线虫剂对甘薯茎线虫扩散的Hormesis效应

在实验室条件下应用沙柱法及水琼脂平板法,测定了低剂量水平的涕灭威、甲氨基阿维菌素苯甲酸盐和丙溴磷对甘薯茎线虫Ditylenchus destructor扩散行为的影响。结果表明:在含5 μ g/mL 药剂的沙柱中,以及甘薯茎线虫经0.1 μ g/mL的药剂浸渍24 h后在不含药剂的沙柱中,其运动扩散能力均受到抑制;在含较低质量浓度(5×10－3 μ g/mL)药剂的沙柱中,以及线虫经较低质量浓度(10－2,10－3 μ g/mL)的涕灭威和(10－4,10－5 μ g/mL)甲氨基阿维菌素苯甲酸盐浸渍24 h后在不含药剂的沙柱中,其通过率均比空白对照高10%以上,差异显著,表现出Hormesis效应(兴奋效应);经较低质量浓度(10-1 μ g/mL)的丙溴磷浸渍后在不含药剂的沙柱中未表现出该效应。在水琼脂平板试验中,虽然在低剂量水平下药剂对线虫的扩散具有促进作用,但产生的Hormesis效应不如沙柱法的结果明显。