Insect pest damage increases faba bean (Vicia faba) yield components but only in the absence of insect pollination

Identifying and quantifying crop stressors interactions in agroecosystems is necessary to guide sustainable crop management strategies. Over the last 50 years, faba bean cropping area has been declining, partly due to yield instabilities associated with uneven insect pollination and herbivory. Yet, the effect of interactions between pollinators and a key pest, the broad bean beetle Bruchus rufimanus (florivorous and seed predating herbivore) on faba bean yield has not been investigated. Using a factorial cage experiment in the field, we investigated how interactions between two hypothesized stressors, lack of insect pollination by bumblebees and herbivory by the broad bean beetle, affect faba bean yield. Lack of bumblebee pollination reduced bean weight per plant by 15%. Effects of the broad bean beetle differed between the individual plant and the plant‐stand level (i.e., when averaging individual plant level responses at the cage level), likely due to high variation in the level of herbivory among individual plants. At the individual plant level, herbivory increased several yield components but only in the absence of pollinators, possibly due to plant overcompensation and/or pollination by the broad bean beetle. At the plant‐stand level, we found no effect of the broad bean beetle on yield. However, there was a tendency for heavier individual bean weight with bumblebee pollination, but only in the absence of broad bean beetle herbivory, possibly due to a negative effect of the broad bean beetle on the proportion of legitimate flower visits by bumblebees. This is the first experimental evidence of interactive effects between bumblebees and the broad bean beetle on faba bean yield. Our preliminary findings of negative and indirect associations between the broad bean beetle and individual bean weight call for a better acknowledgment of these interactions in the field in order to understand drivers of crop yield variability in faba bean.     

Control of nematode disease of egg plant (Solanum aethiopicum) using manure

Pot experiment was conducted in the year 2010 and repeated in 2011 to examine the effects of organic manure (poultry, cow dung and domestic waste) and inorganic manure (NPK 15:15:15) on the yield, soil and root population of Meloidogyne incognita-infected Ethiopian egg plant Solanum aethiopicum in a greenhouse at Kabba college of agriculture, Ahmadu Bello University, Kabba, Nigeria. Each of the organic manure was applied as soil amendment at the rate of 5t/ha and the inorganic fertiliser (NPK) was applied at the rate of 200?kg/ha, while there was an untreated control that acted as standard check. The experimental design was a completely randomised design comprising of five treatments including control and each of the treatments was replicated four times. The result of the experiment showed that all the organic manures considered and NPK fertilisers were effective in suppressing the nematode’s negative effects on the plant, as shown by the improved yield, reduced soil and root population as well as reduced gall index of the organic and inorganic manure-treated plant compared with the control. The mean fruit yield of the manure-treated plant was of the range 18?±?1 fruits and NPK fertiliser had an average of fruit number of 17, while the untreated control recorded an average fruit number of 6.5. The organic and inorganic manure-treated plants recorded bigger fruit size compared with control, and are significantly different from the control. The soil and root population as well as root gall index are reduced in all the manure treatments compared with the control and are significantly different from the control. The result of this experiment confirmed that organic manure can be utilised to manage nematode in soil endemic with root-knot nematode M. incognita.     

Landscape composition modifies pollinator densities,foraging behavior and yield formation in faba beans

Wildlife-friendly management practices promote pollinators and pollination services in agricultural landscapes. Wild bee densities are driven by landscape composition, as they benefit from an increased availability of nesting and foraging resources at landscape scale. However, effects of landscape composition on bee foraging decisions and consequences for crop pollination have rarely been studied. We investigated, how landscape composition affects bee densities and foraging behavior in faba bean (Vicia faba L.) fields and how this impacts faba bean yield. We recorded densities and nectar robbing behavior of honeybees, long- tongued and short-tongued bumblebees in faba bean fields in eleven landscapes with varying landscape composition (e.g. land cover of oilseed rape, faba bean and semi-natural habitats). Moreover, we assessed yield components of faba beans via pollinator exclusion experiments. Increasing covers of faba bean and semi-natural habitats positively influenced bumblebee densities, while high oilseed rape covers negatively affected short-tongued bumblebee densities in bean fields. Increased faba bean covers enhanced the proportion of nectar-robbing short-tongued bumblebees. The number of beans per pod was increased by insect pollination, while the number of pods was decreased; these effects however depended on variety. Landscape composition interacted with bee densities in shaping yield components in V. faba. Our study emphasizes the importance of considering landscape management to maximize crop yields, as shown for the case of faba beans. The composition of agricultural landscape can modulate bee densities in crop fields, bees foraging behavior and pollination services.     

Increased bumblebee abundance along the margins of a mass flowering crop: evidence for pollinator spill‐over

Although the practice of cultivating mass flowering crops (MFCs) is seen as a means of counteracting the widespread decline of insect pollinators, no study to‐date has evaluated whether the increased pollinator abundance associated with MFCs influences pollinator visits to assemblages of adjacent native, non‐crop plant species (pollinator ‘spill‐over’). In this study we quantified bumblebee abundance along hedgerow transects in MFC (field bean) vs non‐MFC (wheat) margins. Surveys were conducted on east and west‐facing margins twice daily (morning and afternoon) for three or four days during the main MFC flowering period (June) over four years involving paired bean and wheat fields in Devon and Cornwall, southwest England. Although no single bumblebee species showed any consistent change in relative frequency, when taken across all years and bumblebee species combined, we observed twice as many bumblebees visiting flowers adjacent to the MFC. However, when we compared bumblebee activity along hedgerow transects two weeks after bean flowering, there was no difference between crops. We thus conclude that although there is evidence for pollinator spill‐over from the bean MFC to nearby semi‐natural habitat, the effect is comparatively short lived and not specific to any single bumblebee species. We also suggest that while pollinator services to native plant species might be briefly enhanced by MFC cultivation, the possible repercussions of bumblebee spill‐over from MFCs to semi‐natural habitats and the other pollinator groups they support should be evaluated before MFC cultivation is considered as a means of conserving declining bumblebee populations.     

Effect of irrigation,plant density and fertilisers on yield and NPK uptake by groundnut

Summary Three levels of irrigation, three plant densities and three fertiliser schedules were tested in 3³ factorial confounded design with two replications in winter on sandy loam soils of Tirupati campus of Andhra Pradesh Agricultural University. Pod yield did not vary due to the plant densities and the fertiliser schedules when the crop was sown in optimum time during 1980. When the sowings were delayed, as in 1979, 444000 plants per ha and 60 kg N ha⁻¹, 40 kg P ha⁻¹ and 100 kg K ha⁻¹ was optimum. Scheduling irrigation at 25 or 50% DASM (depletion of available soil moisture) was optimum for the groundnut crop. There was no difference in the uptake of NPK due to irrigations at 25 and 50% DASM in both the years. Low plant density was as effective as high plant density for efficient use of fertilisers. Uptake of NPK by the crop was relatively high at higher fertiliser levels. However, this higher uptake did not contribute to high pod yield, probably due to utilisation of absorbed nutrients for rank vegetative growth.     

Irish faba beans (Fabales: Fabaceae) depend on wild bumblebee pollination for marketable yields

1. Quantifying the contributions of insect pollinators to crops provides insight into how pollination services should be managed and protected into the future.
2. Faba bean, Vicia faba var minor (Linneaus), is a widely grown crop globally that can benefit from pollinator visitation, but only from species that are morphologically compatible with the plant's long-corollae flowers. Here, we rank insect pollinators in terms of their potential importance to faba bean pollination and quantify the economic value of pollination for Irish faba beans.
3. Our findings demonstrate that bee pollination contributes significantly to the pod set of faba beans, and, consequently, the crop's production value. We find that pollination services account for almost half of Ireland's total faba bean market value, with the pollinator contribution estimated at almost €4,000,000 per year.
4. We estimate that, relative to other pollinators, wild bumblebees contribute to approximately 70% of the economic value of pollination services in faba bean fields, driven mainly by the contributions of a long-tongued bumblebee species, Bombus hortorum (Linneaus; Hymenoptera: Apidae).
5. Based on these results, we suggest that B. hortorum populations be encouraged on farmland through appropriate management to ensure the continued delivery of pollination services to Irish faba beans.

     

Fertilisation practice changes rhizosphere microbial community structure in the agroecosystem

Rhizosphere microbial community is important for the acquisition of soil nutrients and closely related to plant species. Fertilisation practice changed soil quality. With the hypothesis of stronger rhizosphere effect of plant on rhizosphere microbial community than fertilisation management, we designed this research based on a long‐term field experiment (1982–present). This study consists of no fertilisation (NF), mineral fertilisers (NPK), mineral fertilisers plus 7,500 kg/ha of wheat straw addition (WS) and mineral fertilisers plus 30,000 kg/ha of cow manure (CM). After analysing, we found that fertilisation management not only elevated crop yield but also affected crop rhizosphere microbial community structure. The influence of fertilisation practice on wheat rhizosphere microbial structure was stronger than that of wheat. For wheat rhizosphere bacterial community, it was significantly affected by soil water content (SWC), nitrogen (TN), phosphorus (TP), pH, available phosphorus (AVP) and nitrogen (AVN), dissolved organic nitrogen (DON) and carbon (DOC). Besides SWC, pH, AVP, AVN, TN, TP and DOC, the wheat rhizosphere fungi community was also significantly affected by soil organic matter (SOM) and available potassium (AVK). Moreover, compared to rhizosphere bacterial community, the influences of soil physiochemical properties on rhizosphere fungal community was stronger. In conclusion, fertilisation practice was the primary factor structuring rhizosphere microbial community by changing soil nutrients availabilities in the agroecosystem.     

Simulating trends in crop yield and soil carbon in a long-term experiment—effects of rising CO2, N deposition and improved cultivation

Measurements of crop yield and soil carbon in the Bad Lauchstädt long-term fertiliser experiment were analysed with the FASSET model. The model satisfactorily predicted yield and soil carbon development in four treatments: no fertiliser, mineral fertiliser, farmyard manure and farmyard manure plus mineral fertiliser. However, there was a residual between the observed and simulated yield, which was correlated with year. This could be attributed to an increase in observed yields during the last six decades. Scenario analysis showed that the most probable explanation for this yield increase was the use of new crop varieties and/or pesticides, while the increase in atmospheric CO₂ and changes in local N deposition were of lesser importance. The rise in CO₂ thus only explained 9–37% of the yield increase. The observed and simulated developments in soil carbon were quite different in the four treatments. However, the changes within each treatment for different scenarios were much smaller than the substantial difference between treatments. Thus, it was concluded that the type of nutrient applied was more important than development in CO₂ concentration or N deposition in determining soil carbon.     

Arbuscular mycorrhizal fungal community structure and diversity in response to long-term fertilization: a field case from China

The influences of different fertilizer treatments on spore community structure and diversity of arbuscular mycorrhizal (AM) fungi (AMF) were investigated in a long-term fertilization experiment with seven treatments: organic manure (OM), half organic manure N plus half fertilizer N (1/2 OMN), fertilizer NPK, fertilizer NP, fertilizer NK, fertilizer PK, and the control (without fertilization). Fertilization generally increased the nutrient contained in the fertilizer and treatments with NPK and 1/2 OMN produced the highest crop yields. Thirty-five species of AMF within 6 genera, including 8 previously undescribed species, were recovered. Similarly in all seven treatments, the most abundant genus was Glomus, and followed by Acaulospora. All the fertilization treatments changed AM species composition, and NK treatment had the slightest influence. Fertilization with fertilizers NP, PK and NPK markedly increased AM fungal spore density, while 1/2 OMN, OM and NK treatments showed no significant influences. All the fertilizer treatments, especially OM, significantly decreased species richness and species diversity (Shannon-Weiner index). There were no significant correlations between AM fungal parameters (spore density, species richness and species diversity) and soil properties. The findings indicate that long-term fertilization all can change AM fungal community structure and decrease species diversity, while balanced fertilization with NPK or 1/2 OMN is the most suitable fertilization regime if taking both crop yields and AM species diversity into account.     

Quantitative proteomics to study the response of potato to contrasting fertilisation regimes

There is concern over the sustainability and environmental impact of mineral fertilisers and crop protection inputs used in intensive arable crop production systems. However, replacing mineral with organic fertilisers (animal and green manures) and restricting the use of chemosynthetic crop protection may significantly reduce crop yields. The effects of (a) replacing mineral with composted cattle manure fertiliser input and (b) omitting pesticide-based crop protection on potato (Solanum tuberosum) tuber yield, leaf and tuber mineral nutrient content and leaf protein profiles were investigated. Switching to organic fertiliser had a greater effect on yield and protein profiles than the omission of chemosynthetic crop protection. Leaf N and P composition were significant drivers of protein expression, particularly proteins involved in photosynthesis such as the large subunit of RuBisCO, RuBisCO activase and the photosystem I reaction centre, which were at higher abundances in potato leaves grown under mineral fertiliser regimes. Proteins known to be induced in response to stress, such as dehydroascorbate reductase and Glutathione S-transferases, were also shown to be up-regulated under mineral fertilisation, possibly associated with higher Cd composition, whereas two proteins known to be involved in biotic stress (1,3-β-d-glucan glucanohydrolase; putative Kunitz-type tuber invertase inhibitor) were more abundant under compost fertilisation. Results showed that switching from mineral to organic fertilisers led to reduced N availability, a significant change in leaf protein expression and lower tuber yield. In contrast, omission of chemosynthetic crop protection inputs had limited effects on protein expression and no significant effect on tuber yield. This study provides information on the effects of changes in nutrient supply on protein expression patterns. It is a prerequisite for the development of functional molecular markers for a directed strategy to inform breeding programmes to improve potato nutrient use efficiency.     

Enhancing Soil Organic Matter as a Route to the Ecological Intensification of European Arable Systems

Soil organic matter (SOM) is declining in most agricultural ecosystems, impacting multiple ecosystem services including erosion and flood prevention, climate and greenhouse gas regulation as well as other services that underpin crop production, such as nutrient cycling and pest control. Ecological intensification aims to enhance crop productivity by including regulating and supporting ecosystem service management into agricultural practices. We investigate the potential for increased SOM to support the ecological intensification of arable systems by reducing the need for nitrogen fertiliser application and pest control. Using a large-scale European field trial implemented across 84 fields in 5 countries, we tested whether increased SOM (using soil organic carbon as a proxy) helps recover yield in the absence of conventional nitrogen fertiliser and whether this also supports crops less favourable to key aphid pests. Greater SOM increased yield by 10%, but did not offset nitrogen fertiliser application entirely, which improved yield by 30%. Crop pest responses depended on species: Metopolophium dirhodum were more abundant in fertilised plots with high crop biomass, and although population growth rates of Sitobion avenae were enhanced by nitrogen fertiliser application in a cage trial, field populations were not affected. We conclude that under increased SOM and reduced fertiliser application, pest pressure can be reduced, while partially compensating for yield deficits linked to fertiliser reduction. If the benefits of reduced fertiliser application and increased SOM are considered in a wider environmental context, then a yield cost may become acceptable. Maintaining or increasing SOM is critical for achieving ecological intensification of European cereal production.     

长期施肥对华北典型潮土N分配和N2O排放的影响

利用长期定位肥料试验研究化学肥料N、有机肥料N以及化学肥料N和有机肥料N混合施用对N分配和N2O排放影响。处理包括化学肥料N、P、K的不同组合NPK、NP、NK、PK、全部施用有机肥料N（OM）、一半化学肥料N＋一半有机肥料N（1／2OM）及不施肥（CK）7个处理。结果表明,等N条件下,处理间N2O排放的差异不显著,N2O排放主要发生在玉米生长期。均衡提供N、P和K显著提高土壤N储量,有机肥料N的效果显著高于化学N肥。施肥也影响N的利用效率和N在作物中的分配。均衡的养分供应有利于N在子粒中积累,而养分缺乏的处理,秸秆中N含量相对较高。进入环境的N量以NK最多,1／20M最少。总体而言,施P肥和有机肥可减少N2O的间接排放,提高土壤N素肥力并能获得较高的产量。     

Impact of Fertilizing Pattern on the Biodiversity of a Weed Community and Wheat Growth

Weeding and fertilization are important farming practices. Integrated weed management should protect or improve the biodiversity of farmland weed communities for a better ecological environment with not only increased crop yield, but also reduced use of herbicides. This study hypothesized that appropriate fertilization would benefit both crop growth and the biodiversity of farmland weed communities. To study the effects of different fertilizing patterns on the biodiversity of a farmland weed community and their adaptive mechanisms, indices of species diversity and responses of weed species and wheat were investigated in a 17-year field trial with a winter wheat-soybean rotation. This long term field trial includes six fertilizing treatments with different N, P and K application rates. The results indicated that wheat and the four prevalent weed species (Galium aparine, Vicia sativa, Veronica persica and Geranium carolinianum) showed different responses to fertilizer treatment in terms of density, plant height, shoot biomass, and nutrient accumulations. Each individual weed population exhibited its own adaptive mechanisms, such as increased internode length for growth advantages and increased light interception. The PK treatment had higher density, shoot biomass, Shannon-Wiener and Pielou Indices of weed community than N plus P fertilizer treatments. The N1/2PK treatment showed the same weed species number as the PK treatment. It also showed higher Shannon-Wiener and Pielou Indices of the weed community, although it had a lower wheat yield than the NPK treatment. The negative effects of the N1/2PK treatment on wheat yield could be balanced by the simultaneous positive effects on weed communities, which are intermediate in terms of the effects on wheat and weeds.     

Comparison of the effect of market crop wastes and chemical soil fertility amendments on insect pests, natural enemies and yield of Brassica oleracea

Field studies were conducted over three growing seasons during 2 years to assess the relative effect of market crop waste (MCW)‐derived soil fertility amendments and conventional fertiliser (NPK) on tritrophic relations as well as yield performance of white cabbage. A randomised complete block design with four treatments and a control replicated four times was used. Treatments were (a) MCW compost incorporated in the soil, (b) uncomposted MCW incorporated in the soil, (c) uncomposted MCW applied as surface mulch, (d) a conventional chemical fertiliser (NPK) incorporated in the soil and (e) the untreated control. Results indicated that relative to NPK‐amended plants, MCW‐amended cabbage performed better in plant growth parameters as well as yield, despite having sustained aphid and Plutella xylostella infestations that could be as much as double as those in the NPK treatment. Natural enemy occurrence followed the trend of host insect infestations. The average yield performance and net financial benefits from MCW‐compost‐amended plants were three‐fold as that of NPK‐amended plants. Soil analysis results indicated an advantage in soil quality accruing from the MCW amendments. This study, therefore, provides documentation for the utilisation of MCW, previously handled as garbage to be disposed of, as a key component in integrated management of insect pests and depleted soils in crop production in sub‐Saharan Africa and beyond.     

The response of pigeon pea (Cajanus cajan) to the application of fertilisers

The effects of fertilisers on the performance of three cultivars of pigeon pea, Cita-1, Cita-2 and Cita-4, were measured in a pot experiment and a field trial from February to August 1982. The fertilisers were either applied as complete NPK (15-15-15) to the soil at a rate of 50 kg/ha in single or split doses within 4 wk of sowing, or as solutions containing 100 mg/litre each of N, P and K sprayed on to the plants 4 wk after sowing or at anthesis. The growth of pigeon pea was only enhanced significantly by fertiliser application in the field experiment but yields and their components were changed by fertilisers in both experiments. The magnitudes of the effects on growth and yield were similar with both methods of application.     

Integrated crop pollination to buffer spatial and temporal variability in pollinator activity

Insect pollination improves the yield and quality of many crops, yet there is increasing evidence of insufficient insect pollinators limiting crop production. Effective Integrated Crop Pollination (ICP) involves adaptable, targeted and cost-effective management of crop pollination and encourages the use of both wild and managed pollinators where appropriate. In this study we investigate how the addition of honeybee hives affects the community of insects visiting oilseed rape, and if hive number and location affect pollinator foraging and oilseed rape pollination in order to provide evidence for effective ICP. We found that introducing hives increased overall flower visitor numbers and altered the pollinator community, which became dominated by honeybees. Furthermore a greater number of hives did not increase bee numbers significantly but did result in honeybees foraging further into fields. The timing of surveys and proximity to the field edge influenced different pollinators in different ways and represents an example of spatial and temporal complementarity. For example dipteran flower visitor numbers declined away from the field edge whereas honeybees peaked at intermediate distances into the field. Furthermore, no significant effects of survey round on wild bees overall was observed but honeybee numbers were relatively lower during peak flowering and dipteran abundance was greater in later survey rounds. Thus combining diverse wild pollinators and managed species for crop pollination buffers spatial and temporal variation in flower visitation. However we found no effect of insect pollination on seed set or yield of oilseed rape in our trial, highlighting the critical need to understand crop demand for insect pollination before investments are made in managing pollination services.     

Managed bumble bees increase flower visitation but not fruit weight in polytunnel strawberry crops

Animal-mediated pollination is essential for the production and quality of fruits and seeds of many crops consumed by humans. However, crop pollination services might be compromised when wild pollinators are scarce. Managed pollinators are commonly used in crops to supplement such services with the assumption that they will enhance crop yield. However, information on the spatiotemporal pollinator-dependence of crops is still limited. We assessed the contribution of commercial bumble bee colonies compared to the available pollinator community on strawberry (‘Fortuna’ variety) flower visitation and strawberry quality across a landscape gradient of agricultural intensification (i.e. polytunnel berry crop cover). We used colonies of bumble bees in winter and in spring, i.e. when few and most wild pollinators are in their flight period, respectively. The placement of colonies increased visits of bumble bees to strawberry flowers, especially in winter. The use of bumble bee colonies did not affect flower visitation by other insects, mainly honey bees, hoverflies and other Diptera. Flower visitation by both honey bees and wild insects did not vary between seasons and was unrelated to the landscape gradient of berry crop cover. Strawberries were of the highest quality (i.e. weight) when insect-mediated pollination was allowed, and their quality was positively related to wild flower visitors in winter but not in spring. However, increased visits to strawberry flowers by managed bumble bees and honey bees had no effect on strawberry weight. Our results suggest that the pollination services producing high quality strawberry fruits are provided by the flower visitor community present in the study region without the need to use managed bumble bees.     

长期施肥对作物产量的贡献

以中国科学院沈阳生态试验站16年定位试验为平台,研究了8种施肥制度的增产效应与稳产性能。结果表明:不同施肥处理对作物产量有明显影响,作物平均产量NPK>NP>NK>N>PK>P>K>CK,不施N肥时(即P、K、PK等处理)作物产量低;肥料对作物产量的年际贡献率在N、NP、NK、NPK处理中总体呈上升趋势,而在P、K、PK处理中则表现出下降的趋势;从化肥N、P、K的增产效果上看,总趋势是N>P>K;作物年际间产量的变异系数随化肥的均衡施用呈下降的趋势;玉米在NPK处理时的稳产性能最好,大豆在PK处理的稳产性最好。     

Soil fertility and its significance to crop productivity and sustainability in typical agroecosystem: a summary of long-term fertilizer experiments in China

Aims and background

Soil fertility quality index is a useful indicator that helps to improve sustainable land use management and achieve economical yield in agriculture production. The objectives of this study were to evaluate the changes of soil fertility quality between the 1980s and 2000s in different cropping systems and its significance to crop productivity and sustainability.

Methods

We collected all published data on crop yields and soil parameters from 58 long-term experiments in three typical double-cropping systems in China, including maize-wheat (M-W), rice-rice (R-R) and rice-wheat (R-W) cropping systems, and selected seven fertilizer treatments in each experiment, including inorganic fertilizer [nitrogen and phosphorus fertilizer (NP), nitrogen and potassium fertilizer (NK), phosphorus and potassium fertilizer (PK) and balanced mineral fertilizer (NPK)], combined NPK with farmyard manure (NPKM) or crop straw (NPKS), and no fertilizer application (served as control). For comparison, an integrated fertility quality index (IFQI) was used to estimate the variations in soil fertility in different cropping systems. Moreover, the mean production variability index (PVI, %) in each cropping system was calculated to evaluate the stability of crop production.

Results

Over cropping systems, the averaged relative yields of PK, NK and NP ranged from 38.0 to 97.4 %, while the mean yields can be increased by 2.4–5.1 % in NPKM, compared to NPK. The mean yields were similar between NPK and NPKS for maize and wheat crops, but the yield was increased by 4.3–10.0 % in NPKS. Among the different treatments, the highest variability of cereal productivity was obtained in NK, PK or Control, while the lowest value was mostly recorded in NPKM or NPKS in these three cropping systems. Relative to the control, the IFQIs in fertilization treatments were increased by 9.4–150.0 %, 6.2–41.5 % and 1.3–17.5 % in M-W, R-W and R-R systems, respectively (except for PK treatment in R-R system). However, changes of IFQI in topsoil differed among fertilizer treatments, and greater increases existed in the treatments receiving organic residues (NPKM and NPKS).

Conclusions

The increase in crop yield is exponentially correlated with the increased IFQI over treatments in three cropping systems. Over the treatments and systems, production variability among years is shown to be negatively, linearly related to IFQI (P?<?0.001). Therefore, the high grain yield and low production variability can be simultaneously achieved by increasing soil fertility in all three cropping systems.     

黄壤性稻田稗草发生特征及其对长期不同施肥的响应

研究长期不同施肥下黄壤性稻田稗草发生特征,明确稗草发生与长期不同施肥水稻产量和土壤性质变异的响应关系.基于农业部贵州耕地保育与农业环境科学观测试验站的一项连续23年不同施肥管理水稻试验,选取不施肥(CK)、单施氮肥(N)、磷钾肥(PK)、氮磷肥(NP)、氮钾肥(NK)、常量化肥(NPK)、1/4有机肥替代化肥(1/4MNP)、1/2有机肥替代化肥(1/2MNP)、单施有机肥(M)和常量有机肥化肥配施(MNPK)10个处理,采用田间调查法调查各处理稗草发生密度、单株穗数、总穗数、穗粒数、千粒重和穗粒重等植物学参数;采用方差分析明确不同处理稗草发生差异,采用直线拟合、相关分析和通径分析明确杂草发生特征对水稻产量和土壤性质的响应.结果表明: 长期不同施肥处理导致黄壤性稻田稗草发生特征显著变异,稗草的密度、单株穗数和总穗数均以MNPK处理最高,其次是1/4MNP处理.相较常量化肥处理,长期不施肥(CK)和不平衡施肥(N、PK、NK、NP)各处理稗草发生的密度显著降低,施用有机肥各处理(1/4MNP、1/2MNP、M、MNPK)稗草的单株穗数显著增加.稗草的发生密度和总穗数与水稻产量呈极显著的正相关性,拟合直线的决定系数分别为0.622和0.624.土壤有机质、全氮、全磷、碱解氮、有效磷和速效钾与稗草发生参数之间存在显著至极显著的相关性;通径分析表明,土壤全氮含量对稗草单株穗数发生有直接正效应,全磷含量是影响稗草密度和总穗数的主要因素,速效钾含量对穗粒数和穗粒重影响最大.长期不同施肥导致黄壤性稻田稗草发生特征变异,施用有机肥提高了稗草的发生密度、单株穗数和总穗数.土壤全磷含量是黄壤性稻田稗草密度和总穗数发生变异的直接影响因素.