Vertical distribution, size and composition of the weed seedbank under various tillage and herbicide treatments in a sequence of industrial crops

Investigations were conducted during the 2003, 2004 and 2005 growing seasons in northern Greece to evaluate effects of tillage regime (mouldboard plough, chisel plough and rotary tiller), cropping sequence (continuous cotton, cotton–sugar beet rotation and continuous tobacco) and herbicide treatment on weed seedbank dynamics. Amaranthus spp. and Portulaca oleracea were the most abundant species, ranging from 76% to 89% of total weed seeds found in 0–15 and 15–30 cm soil depths during the 3 years. With the mouldboard plough, 48% and 52% of the weed seedbank was found in the 0–15 and 15–30 cm soil horizons, while approximately 60% was concentrated in the upper 15 cm soil horizon for chisel plough and rotary tillage. Mouldboard ploughing significantly buried more Echinochloa crus‐galli seeds in the 15–30 cm soil horizon compared with the other tillage regimes. Total seedbank (0–30 cm) of P. oleracea was significantly reduced in cotton–sugar beet rotation compared with cotton and tobacco monocultures, while the opposite occurred for E. crus‐galli. Total seed densities of most annual broad‐leaved weed species (Amaranthus spp., P. oleracea, Solanum nigrum) and E. crus‐galli were lower in herbicide treated than in untreated plots. The results suggest that in light textured soils, conventional tillage with herbicide use gradually reduces seed density of small seeded weed species in the top 15 cm over several years. In contrast, crop rotation with the early established sugar beet favours spring‐germinating grass weed species, but also prevents establishment of summer‐germinating weed species by the early developing crop canopy.     

Minimal soil disturbance combined with spring cropping can halt soil seedbank accumulation of Alopecurus myosuroides

The basic mechanism of soil inversion tillage for control of annual weeds is based on the vertical translocation of weed seeds from the soil surface to deeper soil layers. Buried weed seeds either remain dormant in the soil seedbank and are exposed to biological and chemical decay mechanisms, or they germinate but the seedlings cannot reach the soil surface (fatal germination). However, depending on the seed biology of the respective target species, frequent inversion tillage can lead to a build-up of the soil seedbank. For soil seedbank depletion based on available knowledge of the biology of Alopecurus myosuroides seeds, soil inversion tillage is suggested to be reduced to every third or fourth year with reduced or even no-tillage (direct seeding) in between (rotational inversion tillage systems). Including spring crops in the crop rotation could further help dampening the population growth and hence the seed return into the seedbank. This study investigated the effect of rotational inversion tillage in combination with reduced tillage or direct seeding on the soil seedbank and population development of A. myosuroides. In a long-term field trial, set up in 2012, these tillage strategies were compared with continuous inversion tillage in a 3-year crop rotation with two consecutive years of winter wheat (Triticum aestivum) followed by spring barley (Hordeum vulgare). The results showed a significant decline in the soil seedbank following the spring crop, irrespective of the tillage system. The continuous inversion tillage system and inversion tillage before spring cropping with reduced tillage (shallow tillage with a disc harrow) before winter wheat both led to accumulation of seeds in the soil seedbank. In contrast, inversion tillage before spring cropping with direct seeding of winter wheat depleted the soil seedbank significantly after only one crop rotation. Although only covering one intensively studied field site, these findings highlight the need for diversified cropping systems and indicate potential avenues for reducing soil tillage while controlling economically important weeds.     

免耕与传统耕作的投入产出比较分析

针对沙尘天气和土地荒漠化,北京及其周边地区开展了免耕治沙行动。在试验基地调研及农户访问等基础上,系统地对免耕与传统耕作的投入产出进行了比较分析,评价分析了北京全面实施免耕后的经济效益。结果表明:与传统耕作相比,北京市玉米实施免耕投入可减少1 016元/hm2,小麦实施免耕投入可减少921元/hm2;可以增加玉米产量846 kg/hm2,增加小麦产量209 kg/hm2;玉米免耕可提高效益2 030元/hm2,小麦免耕可提高效益1 215元/hm2;免耕实施的投入产出效益还具有一定的区域差异,在一年一熟的春玉米区的比较效益最好。该研究可为北京及其周边地区免耕实施的推广以及农业经济相关研究提供理论参考。     

Thrips (Thysanoptera: Thripidae) mitigation in seedling cotton using strip tillage and winter cover crops

BACKGROUND: Thrips are the most consistent insect pests of seedling cotton in the southeastern United States, where symptoms can range from leaf curling to stand loss. In a 2 year study, thrips adults and immatures were sampled at 14, 21 and 28 days after planting on cotton planted with a thiamethoxam seed treatment in concert with crimson clover, wheat or rye winter cover crops and conventional or strip tillage to investigate potential differences in thrips infestations. RESULTS: Densities of adult thrips, primarily Frankliniella fusca (Hinds), peaked on the first sampling date, whereas immature densities peaked on the second sampling date. Regardless of winter cover crop, plots that received strip tillage experienced significantly fewer thrips at each sampling interval. In addition, assessment of percentage ground cover 42 days after planting showed that there was more than twice as much ground cover in the strip‐tilled plots compared with conventionally tilled plots. Correlation analyses showed that increased ground cover was inversely related to thrips densities that occurred on all three sampling dates in 2008 and the final sampling date in 2009. CONCLUSIONS: Growers who utilize strip tillage and a winter cover crop can utilize seed treatments for mitigation of early‐season thrips infestation. Copyright © 2010 Society of Chemical Industry     

The effect of DD and dazomet treatments on nematode populations at various depths in the soil and on the transmission of soil-borne tobacco rattle virus to gladiolus

The relation between log dosage of DD injected at 15 cm depth or of dazomet applied to the soil surface (all in November 1971) and probit mortality ofRotylenchus and trichodorids in the top 20 cm of a field on sandy soil was found to be linear. Dosage increase efficiencies of both chemicals against both nematode species were medium to high. Superficial application of dazomet was very effective against the nematodes that would have survived if only a low dosage of DD had been injected at 15 cm depth. Injection of 40 ml or 80 ml DD per m² at 15 cm depth killed all nematodes between 20 cm and 60 cm deep. Gladiolus planted in the spring of 1972 grew better, flowered earlier and produced more weight of corms on treated than on untreated plots. The poor growth on the untreated plots cannot be ascribed to direct damage by nematodes or to the effect of TRV transmitted to the plants by the viruliferous trichodorids occurring in these plots in high densities. Symptoms of TRV infection in plants grown in 1973 from the corms harvested in the 1972 experimental field showed that only DD treatments had reduced the rate of TRV transmission considerably. However, even the highest dosages of DD had only reduced it from 26% (on untreated plots) to about 8%. Most probably, this residual TRV infection was due to transmission by trichodorids that had survived in soil layers below 60 cm depth. Therefore, soil treatment with nematicides, cannot prevent TRV transmission to gladiolus sufficiently where viruliferous trichodorids occur at great depths, as is the case in many sandy soils having a low water table.     

Effects of fenamiphos and biocontrol agents on cotton growing in nematode-infested soil

Efficacy of a chemical nematicide, fenamiphos and three microorganisms in controllingRotylenchulus reniformis andTylenchorhynchus latus on cotton planted in field plots was investigated. Monthly records of the nematode population levels showed that fenamiphos had the highest (p0.05) levels of their control which resulted in the top cotton yield. Plots receiving the bacteriumBacillus sp. had various degrees of nematode control though their cotton yield was comparable (P0.05) to the fenamiphos-treated plots. Plots inoculated with a fungusChaetomium spirale recorded the least effect for controlling the two nematode species and their cotton yield was not significantly different from the untreated plots. Plots treated with an actinomycete,Streptomyces sp., had an intermediate effect on both nematode population densities and cotton yield. At harvest,T. latus population densities were equally suppresed (P0.05) in all treatments which should be reflected on the subsequent crop.With 2 tables     

Long-term tillage and crop rotation effects on weed seedbank size and composition

Size and composition of the weed seedbank was assessed after 12 years of application of four tillage systems in two crop rotations. Mouldboard and chisel ploughing at 45 cm, minimum tillage at 15 cm and no tillage were compared in continuous winter wheat and a pigeon bean/winter wheat 2-year rotation. Weed control was based upon post-emergence herbicide application. Weed seedling emergence from soil samples taken at 0–15, 15–30 and 30–45 cm depths was assessed in a non-heated glasshouse for 12 months. The tillage system influenced weed seedbank size and composition to a much greater extent than crop rotation. Total weed seedling density was higher in no tillage, minimum tillage and chisel ploughing plots in the 0–15, 15–30 and 30–45 cm layers respectively. Density in the whole (0–45 cm) layer did not differ significantly among tillage systems. With no tillage, more than 60% of the total seedlings emerged from the surface layer, compared with an average 43% in the other tillage systems. Crop rotation did not influence either weed seedbank size or seedling distribution among soil layers, and only had a small influence on major species abundance. The weed seedbank was dominated (>66%) by Conyza canadensis (L.) Cronq. and Amaranthus retroflexus (L.), which thrived in chisel ploughing and no tillage respectively. Results suggested that crop rotation and substitution of mouldboard ploughing by non-inversion tillage (especially by minimum tillage) would not result in increased weed problems, whereas use of no tillage might increase weed infestations because of higher seedling recruitment from the topsoil.     

不同耕作方式对黑土农田土壤水分及 利用效率的影响

在土壤耕作长期定位试验的基础上,研究了免耕秸秆覆盖(NT)和少耕(RT)对东北黑土区农田土壤水分及利用效率、玉米产量及特性的影响。结果表明:在作物生长季3种耕作措施土壤剖面含水量整体上呈先降低后增加的变化趋势,各时期20～40 cm土层含水量均较低。免耕可显著提高0～90 cm土层土壤含水量,90 cm土层以下三种措施土壤含水量差异逐渐降低,到190 cm土层差异不明显。土体储水量主要受降雨及不同耕作措施的影响,在干旱的春季以及降水量较少的秋季土体储水量较低,表现为:免耕>传统>少耕,而在降水量较大时土体储水量相应增加,表现为:少耕>免耕>传统。3种耕作措施下玉米叶面积指数变化趋势一致,总体表现为:传统>少耕>免耕,其中传统和少耕最高分别比免耕高0.22和0.26。在生长季少耕蒸散量最高。传统耕作玉米籽粒产量和水分利用效率分别较免耕和少耕高30%和17%,29%和11%,籽粒产量均存在显著性差异(P<0.05),表现为:传统>少耕>免耕,所以对于玉米而言,在该区不适宜实施免耕秸秆覆盖和少耕这两种保护性耕作体系。     

不同保护性耕作措施对黄土高原旱作农田土壤物理结构的影响

选取黄土高原半干旱区连续4年进行保护性耕作的玉米样地,定位试验,研究了不同耕作方式对耕层土壤理化性质的影响。结果表明:免耕秸秆覆盖(NTS)可显著降低0~5 cm表层土壤容重,传统耕作秸秆粉粹还田(TS)和NTS处理可显著降低5~10 cm、10~30 cm土层的土壤容重;NTS处理可显著增大0~5 cm表层土壤孔隙度,TS和NTS处理可显著提高5~10 cm1、0~30 cm土层的土壤孔隙度;NTS处理可显著降低各层土壤的坚实度,其它处理对表层0~5 cm无显著影响,免耕无秸秆覆盖(NT)处理显著增加了5 cm以下的土壤坚实度;NTS处理0~5 cm表层土壤水分入渗率显著加强,而NT处理则显著减弱;土壤水稳性大团聚体含量均为:NTSNTTS传统耕作(T)。本试验中NT处理对土壤结构的改良效应不明显,NTS处理对于黄土高原土壤结构改良效果最佳。     

The effect of different tillage systems on the composition of the seedbank

The soil seedbank of a wheat crop grown with four tillage systems (mouldboard plough, disk, chisel and no-tillage) for 3 years was analysed. Density and composition of seedbanks varied according to tillage system and depth. The mouidboard plough crop had seedbanks with the lowest seed density and there was no difference in density or composition at 0-5 cm and 5-10 cm depth whereas no—tillage had a more dense seed bank, especially in the upper part of the soil profile. Diversity of seedbanks also increased from mouidboard plough, to disk, to chisel, to no-titlage, which had the most diverse bank. Therefore, the data strongly support the hypothesis that the systems causing less disturbance allow the build-up of a larger and more diverse soil seed bank.     

Suppression of weeds and weed seeds in the soil by stubbles and no-tillage in an arid maize-winter wheat-common vetch rotation on the Loess Plateau of China

Reduced tillage provides ecological and economic benefits to arable land on the Loess Plateau of China, where soil erosion has long been a serious problem and soil water availability is largely restricted. However, high abundances of weeds in reduced tillage systems cause significant yield losses. In this study, we explored the effects of no-tillage and stubble retention on the number and density of weeds and weed seeds in a 12-year maize-winter wheat-common vetch rotation on the Loess Plateau. Four treatments including conventional tillage, no-tillage, conventional tillage+stubble retention and no-tillage+stubble retention were designed and applied. We found that no-tillage increased the number of weed species and weed density in most of the crops, while stubble retention decreased weed density in maize and tended to suppress weeds in both no-tillage treatments(no-tillage and no-tillage+stubble retention). No-tillage led to an increase in the number of weed species in the weed seedbank and tended to increase seed density during the spring growth of winter wheat, but it decreased seed density during post-vetch fallow. Stubble retention tended to reduce seed density during the spring growth of winter wheat and post-vetch fallow. We concluded that no-tillage can promote weeds in the experimental crop rotation, while stubble retention suppresses weeds in untilled fields. The combined effects of stubble retention and no-tillage on weed suppression varied among the three crops. Based on these results, we recommend stubble retention in untilled legume-crop rotations on the Loess Plateau to improve the control of weeds.     

Isolation, Selection, and Efficacy of Pochonia chlamydosporia for Control of Rotylenchulus reniformis on Cotton

ABSTRACT The reniform nematode, Rotylenchulus reniformis, is a serious threat to cotton (Gossypium hirsutum) production in the United States, causing an annual loss of about $80 million. The objective of this study was to isolate fungi from eggs of R. reniformis and select potential biocontrol agents for R. reniformis on cotton. We focused on the fungus Pochonia chlamydosporia because it suppresses root-knot and cyst nematodes and because preliminary data indicated that it was present in Arkansas cotton fields. Soil samples were collected from six cotton fields in Jefferson County, Arkansas. A total of 117 isolates of the nematophagous fungus P. chlamydosporia were obtained. In an in vitro test, 105 of the 117 isolates parasitized fewer than 15% of R. reniformis eggs, but 12 isolates parasitized between 16 and 35% of the eggs. These 12 isolates produced from 6.8 x 10(4) to 6.9 x 10(5) chlamydospores per gram of medium in vitro, and chlamydospore production was similar on rice grain and corn grain media. In two greenhouse experiments, a single application of isolate 37 (5,000 chlamydospores per gram of soil) significantly reduced the numbers of R. reniformis on cotton roots and in soil. The three isolates (37, 26, and 14) that parasitized the most eggs in vitro were also the most effective in suppressing numbers of R. reniformis and in increasing cotton growth in the greenhouse.     

Relationships Between Tillage and Spatial Patterns of Heterodera glycines

ABSTRACT The dynamics of Heterodera glycines spatial patterns were studied under different tillage systems in two naturally infested soybean fields in Iowa from 1994 to 1997. At each location, there were four different tillage treatments (conventional tillage, reduced tillage, ridge tillage, and no tillage). Soil samples were taken from 98 contiguous quadrats (5.2 m(2)) per plot in the fall of 1994, before any tillage was performed, and in the spring of the following 3 years shortly after planting. Cysts were extracted from soil samples by elutriation and counted, and eggs were extracted from cysts and enumerated. Spatial patterns of H. glycines populations were characterized by geostatistical analysis and variance-to-mean (VM) ratios. Semivariance values were calculated for cyst and egg densities and semivariograms were constructed. In general, there was greater spatial dependence among cyst populations than egg populations. In one field with a strongly aggregated initial H. glycines population, tillage practices resulted in changes in spatial patterns of H. glycines populations, characterized by spherical-model semivariogram parameters (sill, nugget effect, and range of spatial dependence). These parameters indicated increasing aggregation over time in no tillage and ridge tillage treatments, but decreasing aggregation in reduced and conventional tillage treatments. There was an increase of 350% in sill values (maximum semivariance) for cyst populations after 3 years of no tillage, but in the conventional tillage treatment, sill values remained unchanged or decreased over time as tillage was implemented. Semivariograms for cyst and egg population densities revealed strong anisotropy (directional spatial dependence) along soybean rows, coincident with the direction of tillage practices. VM ratios for cyst counts increased each year in the no tillage and ridge tillage treatments, but decreased for 2 years in reduced tillage and conventional tillage treatments. Final VM ratios for cyst and egg counts were highest in the no tillage treatment. In a second field, with low initial aggregation of H. glycines populations, there was little measurable change in semivariogram parameters after 3 years of no tillage, but in the conventional tillage treatment, populations became less aggregated, as the range, sill, and the proportion of the sill explained by spatial dependence decreased for cyst population densities. Our results indicated that in soybean fields with initially aggregated populations of H. glycines, no tillage and ridge tillage systems promoted aggregation of the nematode population, whereas conventional and reduced tillage systems resulted in a less aggregated spatial pattern.     

耕作与施肥模式对渭北旱塬春玉米田蓄水保墒与玉米产量的影响

为揭示渭北旱塬春玉米田休闲期不同保护性耕作模式的蓄水保墒与增产增收效应,寻找适合渭北旱塬春玉米田水肥高效利用的耕作方式和施肥水平,于2013—2014年度在陕西省合阳县甘井镇春玉米田分别设置传统农户模式(翻耕+低肥,S1)、现有高效模式(免耕+高肥,S2)、创新高效模式(深松+平衡施肥,S3)等模式处理,研究各类耕作与施肥相结合保护性耕作模式下春玉米水分利用率、产量和经济效益差异。结果表明,创新模式S3和现有模式S2较农户模式S1播前增加了土壤贮水量;创新模式S3和现有模式S2处理在玉米主要生育期0~200 cm土层平均土壤贮水量分别比农户模式S1增加23.3 mm和18.1 mm,水分利用效率分别提高12.3%和10%,产量增加11.1%、9.2%。创新模式和现有模式均较农户模式能够增加土壤贮水量,提高水分利用效率,增加产量和经济效益,但创新模式蓄水保墒,增产增收优势明显,是适合渭北旱塬地区春玉米生产的水肥管理模式。     

不同灌水水平下一膜两年覆盖的玉米农田土壤水分和经济效益分析

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水分和产量的影响,以期为灌区玉米生产优化耕作措施、地膜再利用、提高水分利用效率提供理论依据。结果表明,一膜两年覆盖可显著提高播前农田0~60 cm土层土壤含水量和土壤贮水量(0~120 cm),一膜两年覆盖农田贮水量较传统耕作覆膜提高13.31%,且处理间差异显著;在玉米生育期一膜两年用地膜覆盖可明显提高0~30 cm土层土壤含水量,一膜两年用较传统覆膜处理0~30 cm土层土壤含水量提高7.67%,而不同处理对30~120 cm土层土壤含水量影响较小。高灌水水平下,一膜两年覆盖方式可达到与传统耕作覆膜方式相当的产量,在中、低灌水水平下高于传统覆膜处理,分别增产2.40%和16.39%,且在低灌水水平下WUE在不同覆膜方式处理间存在显著差异,一膜两年覆盖的WUE分别较秋免耕春覆膜和传统耕作覆膜高出5.25%和20.26%;此外,一膜两年覆盖方式可显著减少成本投入,产投比分别较秋免耕春覆膜和传统耕作覆膜提高7.27%和15.69%。说明一膜两年用地膜覆盖可显著提高播前和生育期0~30 cm的土壤含水量,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,提高作物子粒产量和水分利用效率,降低成本投入,提高产投比,是适于西北绿洲灌区的覆膜农田管理新技术。     

New weed management strategy using subterranean clover reseeding under different tillage systems: Numerical experiments with the subterranean clover-tillage dynamics model

Subterranean clover ( Trifolium subterraneum L.) appears to be a suitable winter legume cover crop for Japan because the subterranean clover stands maintain themselves by reseeding in autumn and the large seeds facilitate establishment and enable early fall production. However, there is little information on the relationship between reseeding and tillage systems for subterranean clover under Japanese climatic conditions. A weed-tillage population dynamics model was developed to investigate the effects of the tillage method and timing on the reseeding of subterranean clover. The field experiments were conducted in a silage corn and subterranean clover rotation system. The life cycle of subterranean clover was modeled to describe the seed production competing with weed growth, seasonal changes in the buried seeds' viability, and the movement of seeds by tillage treatments. In the numerical simulation, the effect of the tillage method on the seedling population of reseeded subterranean clover was investigated and the simulation results showed good agreement with the experimental results. Rotary tilling immediately after subterranean clover seed maturation successfully produced a good subterranean clover stand the following spring. However, rotary tillage conducted 2 months after seed maturation killed the emerging subterranean clover seedlings and the field was dominated by winter weeds. These simulation results suggest that a suitable tillage system can maintain successful subterranean clover re-establishment from year to year.     

Green manures and crop sequences influence potato diseases and pathogen inhibitory activity of indigenous streptomycetes

ABSTRACT A 2-year field trial was conducted to determine the effects of green manures and crop sequences on potato scab and Verticillium wilt. In addition, indigenous streptomycete densities and in vitro pathogen inhibitory activity were measured and their relationships to plant disease were determined. Green manures (buckwheat, canola, or fallow controls) were tested in conjunction with three crop sequences (alfalfa-potato, cornpotato, and potato-potato). Compared with fallow controls, tubers grown in buckwheat-treated soil had significantly lower Verticillium wilt ratings, and tubers grown in buckwheat- or canola-treated soil had greater yields. Potatoes grown in soil planted to corn or alfalfa the previous year had significantly lower Verticillium wilt and potato scab ratings as well as higher yields than potatoes grown in soil previously planted to potato. Streptomycetes from soils collected from green manure-treated plots tended to have greater in vitro pathogen inhibitory activity than streptomycetes from fallow-treated plots. Furthermore, streptomycete pathogen inhibitory activity was frequently negatively correlated with plant disease and positively correlated with potato yield. These results indicate that green manure treatments may contribute to active management of the pathogen inhibitory activity of the streptomycete community to achieve plant disease control.     

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。     

Effects of tillage, application time and rate on metribuzin dissipation

Metribuzin efficacy and dissipation were determined in two silty clay loam soils following preplant (PP), pre-emergence (PRE) and split (PP+PRE) application to tilled and no-till soybeans in rotation with corn at Clay Center and Lincoln, Nebraska. A similar experiment was conducted in tilled and no-till soybeans in rotation with wheat at Lincoln. Corn and wheat residue in no-till plots reduced the amount of metribuzin that reached the soil by approximately 54 and 89%, respectively. No differences in weed control or soybean yield were observed between tillage treatments or time of metribuzin application in the corn-soybean rotation. However, both weed control and yield were reduced in the wheat-soybean rotation. Most of the metribuzin remained at the 0–5 cm depth, and dissipation was exponential. The mean metribuzin half-life at the 0–5 cm depth across locations, tillage treatments, application time and rates was 11 days. The metribuzin half-life was 4–19 days following PP application and 3–17 days following PRE application. The metribuzin concentration did not exceed 65 μg kg_?1 at the 5–10 cm or 10–20 cm depths in any treatment, indicating that little metribuzin had leached from the surface soil after PP or PRE application. The finding of a higher metribuzin concentration at 5-20 cm depth in tilled plots than in no-till could be attributed to higher initial soil concentrations in the absence of crop residue.     

Seed survival and predation of Anoda cristata in soyabean crops

Anoda cristata is a troublesome annual broad-leaved weed in summer crops in the rolling Pampa in Argentina; seeds are the only source of regeneration of this species. Seed persistence or depletion is the result of survival and loss processes, including predation. The objective of this study was to determine survival at two burial depths in undisturbed soil and predation rates of A. cristata seeds in soyabean crops in different rotations and tillage systems. Survival was discontinuous and decreased to 25% after 35 months, after which no further reduction in survival was observed to the end of the experiment at 96 months. No differences in seed survival between seeds placed on the soil surface and buried 5 cm below the soil surface were found at 80 months, but at later times survival was lower for seeds placed on the soil surface. Predation rates ranged between 0.3% day⁻¹ and 6.7% day⁻¹. Of the models tested, a polynomial regression of the rate of predation with time gave the best representation of seed predation. From January to July, predation was higher in non-tillage plots in the wheat/soyabean rotation. There was no significant difference in predation rates between tillage systems in the soyabean monoculture and no difference between planting densities. Higher crop residue levels in non-tillage plots in the wheat/soyabean rotation was the dominant factor influencing seed predation, probably because such habitat favours the presence of seed predators.