<Emphasis Type="Italic">Kuth</Emphasis> (<Emphasis Type="Italic">Saussurea lappa</Emphasis>) cultivation in the cold desert environment of the Lahaul valley,northwestern Himalaya,India: arising threats and need to revive socio-economic values

Surveys were conducted in the cold desert environment of the Lahaul valley in the northwestern Himalaya for assessing the past and present status of Kuth (Saussurea lappa) cultivation. The findings reveal that this age-old practice now is in bottleneck. Main factors responsible for this setback to the species were the lengthy cultivation cycle, small land holdings, and even fluctuating and relatively low market prices. Owing to these constraints farmers have now started replacing cultivation of this threatened herb with pea (Pisum sativum L.), potato (Solanum tuberosum L.) and hop (Humulus lupulus L.). These crops obtained popularity due to comparatively more economic returns as well as their easy adaptability to the short growth season of the cold desert environment. Kuth cultivation in this region is among the interesting examples of domesticating wild medicinal herb by some innovative farmers during the 1920s. However, in the recent past farmers have been less interested to continue this practice due to its larger cultivation cycle, more profits with cash crops like pea and potato, and permit formalities at the time of export from the valley. In addition to being the oldest cash crop in the cold desert environment, Kuth is an endangered medicinal herb that has to be conserved on a priority basis. This study attempts to find out potential measures such as regular revision of market rates, development of existing uncultivable land under medicinal plant cultivation and strengthening the marketing network through establishment of federations of farmers at village level to revive cultivation of this important species.     

Outcrossing potential between 11 important genetically modified crops and the Chilean vascular flora

The potential impact of genetically modified (GM) crops on biodiversity is one of the main concerns in an environmental risk assessment (ERA). The likelihood of outcrossing and pollen‐mediated gene flow from GM crops and non‐GM crops are explained by the same principles and depend primarily on the biology of the species. We conducted a national‐scale study of the likelihood of outcrossing between 11 GM crops and vascular plants in Chile by use of a systematized database that included cultivated, introduced and native plant species in Chile. The database included geographical distributions and key biological and agronomical characteristics for 3505 introduced, 4993 native and 257 cultivated (of which 11 were native and 246 were introduced) plant species. Out of the considered GM crops (cotton, soya bean, maize, grape, wheat, rice, sugar beet, alfalfa, canola, tomato and potato), only potato and tomato presented native relatives (66 species total). Introduced relative species showed that three GM groups were formed having: a) up to one introduced relative (cotton and soya bean), b) up to two (rice, grape, maize and wheat) and c) from two to seven (sugar beet, alfalfa, canola, tomato and potato). In particular, GM crops presenting introduced noncultivated relative species were canola (1 relative species), alfalfa (up to 4), rice (1), tomato (up to 2) and potato (up to 2). The outcrossing potential between species [OP; scaled from ‘very low’ (1) to ‘very high’ (5)] was developed, showing medium OPs (3) for GM–native relative interactions when they occurred, low (2) for GMs and introduced noncultivated and high (4) for the grape‐Vitis vinifera GM–introduced cultivated interaction. This analytical tool might be useful for future ERA for unconfined GM crop release in Chile.     

Effect of deep and shallow root systems on the dynamics of soil inorganic N during 3-year crop rotations

Unused inorganic nitrogen (N_inorg) left in agricultural soils will typically leach to deeper soil layers. If it moves below the root zone it will be lost from the system, but the depth of the root zone depends on the crop species grown. In this experiment we studied the effect of 3-year crop sequences, with different combinations of deep-rooted and shallow-rooted crops, on soil N_inorg dynamics to 2.5 m soil depth and the possibility of crop utilization of N leached to deep soil layers. We grew ten different crop sequences for 3 years. The crops and catch crops grown were selected to allow different sequences of deep-rooted and shallow-rooted crops. Very different rooting depths were obtained, from only 0.5 m (leek), to ∼1.0 m (ryegrass and barley), 1.5 m (red beet), 2.0 m (fodder radish and white cabbage) and more than 2.5 m by the chicory catch crop. The results showed a significant retention of N_inorg within the 2.5 m soil profile from one year to the next, but the retained N had leached to deeper parts of the profile during the winter season. Only little N_inorg was retained over two winter seasons. The retention in the deeper soil layers allowed N_inorg to be taken up by succeeding deep-rooted main crops or catch crops. The effects of crop rooting depth on N_inorg in the subsoil layers from 1.0 to 2.5 m were striking. White cabbage reduced N_inorg below 1.0 m with up to 113 kg N ha^-1 during its growth. Grown after catch crops, leek and red beet left on average 60 kg N ha⁻¹ less below 1.0 m than leek and red beet grown without a preceding catch crop. We conclude that it is possible to design crop rotations with improved nitrogen use efficiency by using the differences in crop rooting patterns; deep-rooted crops or catch crops can be used to recover N_inorg leached after previous crops, and catch crops can be grown before shallow-rooted crops to lift the deep N_inorg up to layers where these crops have their roots.     

A genetic discontinuity in root-nodulating bacteria of cultivated pea in the Indian trans-Himalayas

Evolutionary relationships of 120 root‐nodulating bacteria isolated from the nodules of Pisum sativum cultivated at 22 different locations of the trans‐Himalayan valleys of Lahaul and Spiti in the state of Himachal Pradesh of India were studied using 16S rRNA gene PCR‐RFLP, ERIC‐PCR, sequencing of 16S rRNA, atpD, recA, nodC and nifH genes, carbon‐source utilization pattern (BIOLOG?), and whole‐cell fatty acid profiling. The results demonstrated that all isolates belonged to Rhizobium leguminosarum symbiovar viciae (Rlv). Isolates from the two valleys were clearly separated on the basis of ERIC fingerprints, carbon‐source utilization pattern, and whole‐cell fatty acid methyl esters. Phylogenetic analysis of atpD, recA, nodC and nifH genes revealed a common Rlv sublineage in Spiti valley. Lahaul valley isolates were represented by three sequence types of atpD and recA genes, and four sequence types of nodC and nifH genes. Genotypes from the two valleys were completely distinct, except for two Lahaul isolates that shared nodC and nifH sequences with Spiti isolates but were otherwise more similar to other Lahaul isolates. Isolates from the two highest Spiti valley sites (above 4000 m) had a distinctive whole‐cell fatty acid profile. Spiti valley isolates are closely related to Rlv sublineages from Xinjiang and Shanxi provinces in China, while Lahaul valley isolates resemble cosmopolitan strains of the western world. The high mountain pass between these valleys represents a boundary between two distinct microbial populations.     

黄土高原-青藏高原过渡带农户生产系统的能值分析——以通渭-渭源-夏河样带为例

通渭-渭源-夏河样带位于黄土高原向青藏高原过渡的生态区,是我国典型农牧交错带。长期以来,不合理的农业生产结构带来生态、经济等一系列问题,制约了该地区草地农业的持续发展。为此,从能值角度分析区域农业生产结构,可为农(牧)户决策提供理论依据,为优化区域农业生产结构提供科学依据。收集研究区农户作物和家畜生产的投入-产出数据,用能值方法分析农户生产系统结构特征、农户生产决策行为及生产系统耦合作用,用结构方程模型(SEM)分析农户生产系统能量的组分间流动。研究发现,随海拔增高,农户作物生产活动减少,作物总产出能值递减;尽管作物生产主要投入和产出要素相同,但同一作物不同地点的同一要素投入、产出能值和能值收益率均存在显著差异(P0.05);同一地点不同作物的同一要素投入、产出能值和能值收益率均差异显著(P0.05);作物生产投入要素中,有机肥能值在通渭和渭源均有较高贡献;作物投入和产出能值的农户生产决策阈值自东向西递减,在能值投入初始增加时,夏河农户作物生产规模扩增最为迅速。家畜养殖规模、能值投入和产出自东向西递增;通渭和渭源,小麦秸秆和苜蓿作为中间投入,能值贡献率达到80%;夏河家畜生产投入要素中,补饲粮食能值贡献率高达90%;家畜投入和产出能值的农户生产决策阈值点自东向西递增;能值收益率随耦合度的增加呈指数上升,通渭和渭源能值收益率的增加速度,随耦合度的增加趋于缓慢,而夏河能值收益率增速随耦合度的增加而上升。调整作物生产内部粮、经、饲产品比例结构,加强作物生产与家畜生产耦合作用,优化天然草地利用方式,实现生态效益最大化;阈值点调控农户生产决策行为,实现该区域农业生产结构优化。     

Farmers' perspectives for the development of a bioenergy industry in Ireland

A survey of Irish farmers was conducted to identify farmers’ opinions on energy crop production and to characterize potential adopters of energy crop cultivation in Ireland. One hundred and seventy‐two surveys were completed from 25 counties in Ireland. Miscanthus (48%) and grass (30%) were the preferred crops for adoption of energy crop production. Potential adopters described themselves as having a significantly greater level of knowledge of energy crop production compared with other respondents. The results indicate that lack of interest in adopting energy crop production may be due to lack of knowledge regarding the economic benefits of adoption and the variety of energy crops available for cultivation in Ireland. The establishment of long‐term contracts and government schemes were identified as important requirements for the development of bioenergy crop production in Ireland. Energy crop adoption was not limited to farmers undertaking specific farm enterprises. Farmers were motivated to adopt energy crop production for both economic and environmental benefits. These results are the first to provide valuable information on the perspectives of potential adopters of bioenergy crop production in Ireland for the promotion and implementation of a national bioenergy industry. Policy requirements and outreach strategies to encourage adoption of energy crops by agricultural producers are suggested.     

Breaking the Cycle of Xanthomonas campestris pv. musacearum in Infected Fields through the Cultivation of Annual Crops and Disease Control in Adjacent Fields

Cultivation of non‐host crops after uprooting Xanthomonas campestris pv. musacearum (Xcm)‐infected banana plants has been advocated for breaking Xanthomonas wilt disease (XW) cycle in fields. Knowledge on the interaction of these crops with Xcm is limited. Maize, beans and sweet potato were planted after uprooting Xcm‐infected banana plants in Rwanda and eastern Democratic Republic of Congo (DR Congo). A weed fallow (mixed species) served as the control. After one, two and/or four break‐crop or fallow seasons, healthy plantlets were replanted and monitored for XW for 12–24 months. XW status in adjacent fields was monitored, and diseased stems within 100–300 m radius of the two‐ and four‐season experiments were uprooted. In Rwanda, soil and plant parts from the one‐season experiments were sampled for Xcm isolation and Xcm‐like colonies confirmed with Xcm‐specific primers using PCR. Pathogenicity tests were performed to confirm the ability of the PCR‐positive isolates to infect healthy banana plantlets. XW was observed in all the one‐season experiments, with higher cumulative incidences in maize and bean plots. However, no similar trends were observed in the two‐season experiments, with a 6–8% incidence observed only in bean and potato plots in DR Congo. Lengthening time under break crops to two and four seasons, respectively, reduced the incidence to 3% and zero in Rwanda and 0–8% in the two‐season experiments in DR Congo. Incidence in the first‐season experiments highly correlated (R = 88) to that in the adjacent fields, suggesting possible re‐infections from these fields. Two season with break crop plus collective XW control are recommended in these agro‐ecosystems. PCR‐positive Xcm‐like colonies from break crops only induced localized cell death on banana, while PCR‐positive isolates from symptomatic banana plants caused full XW symptoms. Cross‐infection/inoculation studies under controlled conditions are still needed to conclusively elucidate Xcm interaction with these crops.     

Living with a large predator: Assessing the root causes of Human–brown bear conflict and their spatial patterns in Lahaul valley,Himachal Pradesh

Brown bear‐mediated conflicts have caused immense economic loss to the local people living across the distribution range. In India, limited knowledge is available on the Himalayan brown bear (HBB), making human–brown bear conflict (HBC) mitigation more challenging. In this study, we studied HBC in the Lahaul valley using a semi‐structured questionnaire survey by interviewing 398 respondents from 37 villages. About 64.8% of respondents reported conflict in two major groups—crop damage (30.6%) and livestock depredations (6.2%), while 28% reported both. Conflict incidences were relatively high in summer and frequently occurred in areas closer to the forest (<500 m) and between the elevations range of 2700 m to 3000 m above sea level (asl). The dependency of locals on forest resources (70%) for their livelihood makes them vulnerable to HBC. The “upper lower” class respondents were most impacted among the various socioeconomic classes. Two of the four clusters were identified as HBC hot spots in Lahaul valley using SaTscan analysis. We also obtained high HBC in cluster II with a 14.35 km radius. We found that anthropogenic food provisioning for HBB, livestock grazing in bear habitats, and poor knowledge of animal behavior among the communities were the major causes of HBC. We suggest horticulture crop waste management, controlled and supervised grazing, ecotourism, the constitution of community watch groups, and others to mitigate HBC. We also recommend notifying a few HBB abundant sites in the valley as protected areas for the long‐term viability of the HBB in the landscape.     

Identifying multiple wildlife species-crop interactions using network analysis

Managing crop damage by wildlife is a complex challenge in agrarian-wildlife landscapes. Losses to farmers and their negative attitude towards crop-raiding wildlife, compromise wildlife conservation and farmer-wildlife coexistence. Priority crop types, crop-raiding wildlife and socio-ecological factors are highly integrated. Here we use cross-sectional network analysis as a conservation planning tool to simultaneously identify the crop types used by crop-raiding wildlife, and evaluate the importance of these crop-wildlife interactions relative to the socio-ecological factors that affect these interactions. The most vulnerable crops were maize, millet and fruit trees, while the most problematic crop-raiding wildlife were African elephant, bushpig, hippo, warthog and red-billed quelea. Crop damage declined with countermeasure effectiveness, farm size, and distance from river to farm, but increased with richness of attractive crops. Undamaged crops included cash crops, such as chili, onion, ginger, lemon grass and garlic. Applying network analysis to different crops and damage scenarios enables identification of the most important and influential crops, crop-raiding wildlife and socio-ecological factors needed to develop effective crop protection strategies.     

Soil profile gravel concentration and its effect on rainfed crop yields

Summary Soil characteristics in the crop root zone are critical to soil water and nutrient availability to rainfed crops and determine crop production in coarse textured soils. A four-year field study was conducted in the foot-hills of North Himalayas near Chandigarh (India) on a coarse textured soil (Gravelly udic ustocrepts) to evaluate the effect of varying soil profile gravel concentration on the yield of rainfed crops of Taramira (Eruca sativa Mill.) in winter followed by maize (Zea mays L.), sorghum (Sorghum vulgare Pers.), cowpea (Vigna unguiculata L.) and sesamum (Sesamum indicum L.) in summer. Taramira gave a mean grain yield of 683, 410 and 275 kg ha^–1 at gravel concentration (GC) of 18, 28 and 40 percent by volume in the surface one metre soil depth. The grain and forage yield of summer crops decreased with the increasing GC. The gross monetary returns decreased in the order: Sorghum fodder, cowpea, sesamum and maize. The dilution of soil mass with increasing GC and corresponding decrease in nutrient and water holding capacity of the soil appears to have depressed the crop yields. The results indicated that the legume which can also conserve rainwater with dense canopy like cowpea or crops having vigorous fibrous root system and are relatively drought tolerant like sorghum may provide better economic returns in light textured soil containing gravel upto 40 percent.     

Field observations on nitrogen catch crops. III. Transfer of nitrogen to the succeeding main crop

In temperate climates with a precipitation surplus during autumn and winter, nitrogen (N) catch crops can help to reduce nitrogen losses from cropping systems by absorbing nitrogen from the soil and transfer it to a following main crop. In two field experiments the catch crop species winter rye (Secale cereale) and forage rape (Brassica napus ssp. oleifera (Metzg.) Sinsk) or oil radish (Raphanus sativus spp. oleiferus (DC.) Metzg.) were planted end of August and 3 weeks later with a non-limiting supply of N and zero-N controls. In the next spring catch crops were incorporated into the soil. In Expt 1, N transfer was measured as (i) the N uptake of a potato test crop, grown with zero and 12.5 g m^–2 N applied, and (ii) the increase in soil mineral N (0–30 cm) in uncropped soil covered with polythene film. In Expt 2, N transfer was measured as the increase in soil mineral N in covered cylinders placed in uncropped soil (in situ incubation). Subsidiary laboratory incubations were performed in Expt 2. In Expt 1, the apparent recovery in potato of fertilizer N (R _f) was 0.56. The recovery in potato of N mineralized from 'native' N pools other than catch crop material (R _n) ranged from 0.43 to 0.51, depending on the value assumed for the depth of N extraction by potato roots. The average recovery in potato of incorporated catch crop N (R _c) was 0.34. Expressed as `fertilizer N replacement factor' (F _r) the latter was 0.61 (i.e. 1 kg of N in catch crop material counts for 0.61 kg fertilizer N). Under the film in Expt 1 the fraction net mineralization of incorporated catch crop N (M _n) was 0.36 on August 11 and 0.43 on October 18. In Expt 2, the average value of M _n was 0.31, which was lower than in Expt 1 and probably associated with the drier soil in Expt 2. In the laboratory incubations (20°C) M _n showed values up to 0.54 after 84 days with the largest rates of change in mineralization occuring early after the start of the incubation. In conjunction with literature data it is concluded that cultivation of nitrogen catch crops shows promise as a means to reduce N input and N losses in temperate climates with wet winters.     

Assessing the performance of pea and lentil at different seeding densities as trap crops for the management of wireworms in spring wheat

Wireworms, the larvae of click beetles (Elateridae), are difficult to manage due to their habitats and behaviour. Wireworms pose a major threat to the wheat crop in the north‐western USA. Seed treatment with neonicotinoids, biological control management and some cultural controls are recommended to manage these pests. Trap cropping is an emerging way to manage wireworms. In strawberry and potato crops, trap cropping has been found effective at attracting wireworms away from the principal crop. An earlier study in the Golden Triangle area of Montana found that pea and lentil could be effective trap crops for managing wireworms in spring wheat. In the present study, experiments were conducted at two locations. The effectiveness of peas and lentils as trap crops with wheat at different seeding densities was assessed [pea at 0, 4, 8, 16 seeds/sq.ft. or 0, 43, 86, 172 seeds/sq.m.; lentil at 0, 6, 12, 18 OR 0, 65, 130, 194 seeds/sq.m.; both with wheat at 0, 11, 22, or 28 seeds/sq.ft. or 0, 120, 230, 300 seeds/sq.m.] in a randomized design where all three crops were intercropped. Both trap crops were found to be effective in protecting wheat at standard seeding rates of 8 seeds/sq.ft. for pea and 12 seeds/sq.ft. for lentils. At these seeding rates, higher numbers of wireworms were found to be attracted to the trap crop, resulting in higher yield (7%–10%) of the associated spring wheat plant stands at 22 seeds/sq.ft. To develop an effective trap crop strategy, the pea–wheat and lentil–wheat spatial patterns that are possible need to be assessed in further field trials. Proper design and evaluation of the cost–benefit ratio of pea and lentil as trap crops are likely to produce good results for wheat crops in Montana.     

Tracking disease resistance deployment in potato breeding by enrichment sequencing

Following the molecular characterisation of functional disease resistance genes in recent years, methods to track and verify the integrity of multiple genes in varieties are needed for crop improvement through resistance stacking. Diagnostic resistance gene enrichment sequencing (dRenSeq) enables the high‐confidence identification and complete sequence validation of known functional resistance genes in crops. As demonstrated for tetraploid potato varieties, the methodology is more robust and cost‐effective in monitoring resistances than whole‐genome sequencing and can be used to appraise (trans) gene integrity efficiently. All currently known NB‐LRRs effective against viruses, nematodes and the late blight pathogen Phytophthora infestans can be tracked with dRenSeq in potato and hitherto unknown polymorphisms have been identified. The methodology provides a means to improve the speed and efficiency of future disease resistance breeding in crops by directing parental and progeny selection towards effective combinations of resistance genes.     

Seventeenth century organic agriculture in China: I. Cropping systems in Jiaxing region

The cropping systems of seventeenth century traditional organic agriculture in the Jiaxing region of eastern China required about 2000 hr of labor per hectare for rice production. Rice and related grain crops were produced employing only human power. The input was about 200 times that for most mechanized grain production today. The charcoal or fossil energy input to produce simple hand tools accounted for only 1–2% total energy in the crop systems. Organic wastes including manures, pond sediments, and green manure crops supplied most of the nutrients. Rice yields, ranging as high as 6700–8400 kg/ha, were similar to some of the highest yields today. The energy output/input ratio ranged from 9 for compost-fertilized rice to 12 for green manure-fertilized rice production. These ratios were 2–10 times higher than most mechanized rice production systems of today. Knowledge of the crop and soil system enabled the early Chinese farms to maintain high crop yields and sustain highly productive soils.     

Evaluation of the different <Emphasis Type="Italic">Alternaria</Emphasis> prediction models on a potato crop in A Limia (NW of Spain)

The main crop of the A Limia region is the potato, with an average production of 5 million kilos per year, under the protected geographic indication (IGP) Pataca de Galicia (Galician potato) label recognized by the European Community. Alternaria represents an important part of the pathogenic fungus spectra on this crop, representing an average of 1.9–3.1% of the spores collected. It represents the fourth and third most common type, respectively, in the years of study, after the Cladosporium type (which represented 80% and 64% respectively in each year of study), the Basidia type (5.5% and 1.4%), Botrytis (3.5% and 1.3%), and Fusarium (2.7% and 25.2%). A Lanzoni VPPS 2000 Hirst volumetric sampler was placed in Damil, in the region of A Limia in order to determine the airborne concentration of Alternaria conidium over a potato crop and finally to try to establish the most suitable prediction models for Alternaria attacks and how they might be controlled. We applied different models based on temperature, such as the model of propitious days (P-Days), the model of accumulation of disfavourable days (DD), and the relative humidity model of interrupted wet periods (IWP). The most efficient model was found to be the interrupted wet periods (IWP) method as it could predict several days of attack during the development of the crop. It is efficient in A Limia even when the features described in this model are fulfilled during five consecutive days. In the first year of study the efficiency of this method was lower as alternariosis did not proliferate to the same degree due to the adverse meteorological conditions registered for the development of the fungus. This study is the first step towards prediction of infection by Alternaria in potato crops. We need more years of study in order to adjust these models to the conditions of the sampling area, and thus be able to confirm the necessary values and their suitability with the aim of developing possible alternatives to reduce the negative consequences of this pathogen.     

Environmental costs and benefits of growing Miscanthus for bioenergy in the UK

Planting the perennial biomass crop Miscanthus in the UK could offset 2–13 Mt oil eq. yr^?1, contributing up to 10% of current energy use. Policymakers need assurance that upscaling Miscanthus production can be performed sustainably without negatively impacting essential food production or the wider environment. This study reviews a large body of Miscanthus relevant literature into concise summary statements. Perennial Miscanthus has energy output/input ratios 10 times higher (47.3 ± 2.2) than annual crops used for energy (4.7 ± 0.2 to 5.5 ± 0.2), and the total carbon cost of energy production (1.12 g CO₂‐C eq. MJ^?1) is 20–30 times lower than fossil fuels. Planting on former arable land generally increases soil organic carbon (SOC) with Miscanthus sequestering 0.7–2.2 Mg C4‐C ha^?1 yr^?1. Cultivation on grassland can cause a disturbance loss of SOC which is likely to be recovered during the lifetime of the crop and is potentially mitigated by fossil fuel offset. N₂O emissions can be five times lower under unfertilized Miscanthus than annual crops and up to 100 times lower than intensive pasture. Nitrogen fertilizer is generally unnecessary except in low fertility soils. Herbicide is essential during the establishment years after which natural weed suppression by shading is sufficient. Pesticides are unnecessary. Water‐use efficiency is high (e.g. 5.5–9.2 g aerial DM (kg H₂O)^?1, but high biomass productivity means increased water demand compared to cereal crops. The perennial nature and belowground biomass improves soil structure, increases water‐holding capacity (up by 100–150 mm), and reduces run‐off and erosion. Overwinter ripening increases landscape structural resources for wildlife. Reduced management intensity promotes earthworm diversity and abundance although poor litter palatability may reduce individual biomass. Chemical leaching into field boundaries is lower than comparable agriculture, improving soil and water habitat quality.     

Mating frequency in dispersing potato tuber moth, Phthorimaea operculella, and its influence on the design of refugia to manage resistance in Bt transgenic crops

Mating of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was investigated in relation to the dispersal of males in laboratory and field trials. The effect of stimulating the flight of males to light sources in a large cage on their mating ability was estimated for three age groups, and compared with similar estimates for confined moths. Although the mating of males declined with ages of up to 15 days, simulated dispersal had no effect on subsequent mating when the males were paired with virgin females. The dispersal of male moths was also categorised by the initial flight activity of untethered moths to a light source. Scores for poor, moderate, and good flight provided a repeatable measure of initial male flight activity, but the degree of activity was not related to their subsequent mating ability. In the field, virgin female potato tuber moths were tethered at various distances from the edge of isolated potato crops and then dissected to determine their mating status. Female mating frequency averaged 75% at the crop margin, remained above 50% up to 200 m, and then declined to 19% at 360 m from the margin. Derivation of the mating probability for an individual male potato tuber moth confirmed earlier work by other researchers that has indicated a tendency for dispersal prior to mating, and that males retain their ability to mate as they disperse from a crop. The influence of dispersal and mating on gene flow between crops, and its potential effects on refuge size required to minimise the development of resistance to Bt transgenic potato crops was examined.     

中国主要农作物种植农药施用温室气体排放估算

过去30年来我国农作物的播种面积并未产生太大变化,但病虫害的发生和防治次数却不断增加。根据6种中国主要农作物的病虫害发生情况,收集了相应的农药用量及其制造的温室气体排放量数据,估算了中国主要农作物在种植过程中,因对病虫害使用杀虫剂和杀菌剂而产生的温室气体排放量现状。结果表明,我国主要农作物小麦、水稻、玉米、马铃薯、油菜和棉花的每公顷病虫害防治时使用农药所产生的温室气体排放量分别是9.19(1.86—23.24)、20.54(2.03—50.95)、10.38(3.45—19.32)、5.91(2.15—18.34)、10.84(8.10—13.62)、19.51(5.11—49.01)kg CE hm~(-2)a~(-1),即水稻和棉花最高;但论单产农药温室气体排放量,则油菜和棉花远高于其余4种粮食作物。每年小麦、水稻、玉米、马铃薯、油菜和棉花的病虫害防治使用农药所产生的总温室气体排放量分别是220.8(44.7—558.4)、606.7(60.0—1505.1)、336.4(112.0—606.3)、30.9(11.2—96.0)、79.5(59.4—99.8)、96.4(25.2—242.2)Gg CE,总计1.37(0.31—3.13)Tg CE。将以上6种作物的病虫害防治情况外推到全国农作物,则我国一年因为农作物病虫害防治而产生的温室气体排放量为2.13(0.48—4.85)Tg CE。另外由于缺乏草害面次数据而没有包括除草剂本分,所以以上数字仍是低估。病虫害防治由于作物本身、防治对象、防治方法以及药剂用量的固有差异,导致农作物病虫害防治的温室气体排放量计算结果存在着较大的不确定性,目前基于自下而上农户调查的估算方法无法克服这些问题,更精确的估算需要自上而下的企业级调查数据。     

中国四川旱坡地植物篱农作系统能流特征

关于农业生态系统能流特征的研究很多,但关于植物篱农作系统能流特征的研究很少。在四川盆地雨养丘陵农区,2/3的耕地土壤侵蚀严重,为了控制土壤侵蚀和提高耕地生产力,该区域大量栽种了植物篱。该研究通过了解作物与植物篱之间的能流交付作用,通过系统能量投入水平提高与结构优化,建立环境友好的农作系统,最终实现坡地农业的可持续。通过两年田间小区试验,详细记录所有劳力投入、化肥投入、农药投入、农事管理活动以及落叶的数量并折算为标准能量单位。作物收获后所有生物产量的能量根据其各部分的转换值折算为标准能量。系统能流特征及效率通过统计分析完成。通过研究主要获得了以下3个结论:1)“作物-植物篱”系统产出能和输入能的数量和结构变化主要受植物篱子系统类型的影响。与大面积旱坡地传统农作物生产系统比较,植物篱农作系统能有效提高系统光能利用率、人工输入能效率,耕地单位面积总产出能也会增加,坡度越大,相对增幅亦越大;由于能极显著减少无机能施入量,这有利于降低化肥农药使用量,减少对环境的污染和破坏。2)“作物-果树类植物篱”系统输入能总量和有机能输入量大幅度增加,因此有利于优化输入能结构,促进坡地生态系统良性循环和集约高效农业发展。3)“作物-草本植物篱”系统人工辅助能的输入量大幅度下降,由于它所需投入能少,有机能耗和无机能耗均低,人工输入能效率很高而生物产量也较高,并且它们提高了与其间作的其它作物的能量产投比,因此提升了整个系统能量产投比率;由于保水固土的生态功能显著,使它能在四川广大山地、丘陵区退耕还林还草工程中发挥重要作用。     

Modelling the carbon and nitrogen balances of direct land use changes from energy crops in Denmark: a consequential life cycle inventory

This paper addresses the conversion of Danish agricultural land from food/feed crops to energy crops. To this end, a life cycle inventory, which relates the input and output flows from and to the environment of 528 different crop systems, is built and described. This includes seven crops (annuals and perennials), two soil types (sandy loam and sand), two climate types (wet and dry), three initial soil carbon level (high, average, low), two time horizons for soil carbon changes (20 and 100 years), two residues management practices (removal and incorporation into soil) as well as three soil carbon turnover rate reductions in response to the absence of tillage for some perennial crops (0%, 25%, 50%). For all crop systems, nutrient balances, balances between above‐ and below‐ground residues, soil carbon changes, biogenic carbon dioxide flows, emissions of nitrogen compounds and losses of macro‐ and micronutrients are presented. The inventory results highlight Miscanthus as a promising energy crop, indicating it presents the lowest emissions of nitrogen compounds, the highest amount of carbon dioxide sequestrated from the atmosphere, a relatively high carbon turnover efficiency and allows to increase soil organic carbon. Results also show that the magnitude of these benefits depends on the harvest season, soil types and climatic conditions. Inventory results further highlight winter wheat as the only annual crop where straw removal for bioenergy may be sustainable, being the only annual crop not involving losses of soil organic carbon as a result of harvesting the straw. This, however, is conditional to manure application, and is only true on sandy soils.