Weed:spring barley competition for applied nitrogen in pig slurry

Summary The experiments were carried out in the two spring barley fields of the organic six-course cattle:crop rotation at Foulumgaard, Denmark. The weed density was 300 and 1800 plants m⁻² respectively. Pig slurry was applied by hand in microplots by four methods: broadcasting followed by incorporation, or injected in bands to depths of 5, 10 or 15 cm. Spring barley and weeds were sampled separately six times during the tillering and elongation phase of the spring barley. The effect of application method on dry-matter (d.m.) production, nitrogen uptake and recovery of applied nitrogen in the spring barley and the weeds is reported. Slurry banding halved the weed d.m. and weed N uptake compared with broadcasting, irrespective of weed density. Weeds recovered up to 12% of the applied nitrogen, which made them a significant competitor when the slurry was broadcast and incorporated. Banding by direct injection reduced the slurry:soil contact and the weed:crop competition balance for applied nitrogen moved in favour of the crop. Thus, the crop recovery of applied nitrogen at the end of the sampling period was increased from approximately 45% for broadcast and incorporated to approximately 50% for injected slurry, and coincidental weed recovery was reduced to a maximum of 5%. As the nitrogen supply normally affects plant d.m. production, banding of slurry might well improve crop competitiveness and its tolerance to mechanical weed control.     

我国近年来水稻重大病虫害可持续控制技术重要研究进展——非化学控害技术研究

针对水稻病虫害防治中长期存在控害保产与生产无公害稻米矛盾比较突出的问题,研究提出了几种效果显著的非化学控害增产技术。其中,利用水稻遗传背景、对病虫抗感水平等差异显著的水稻品种多样性种植,控制稻瘟病的效果达42.12％～76.68％,抑制白背飞虱若虫数量增长效果明显,增产糯稻或优质稻600～1050 kg／hm²,平均增收约1 500元／hm²;稻鱼共育控制稻飞虱的效果为63.77％～86.89％,对纹枯病病株抑制率70.52％,控制稻田杂草效果为89.57％,平收获鲜鱼319.5～1 177.5 kg／hm²,水稻产量比对照区增产7.05％～10.11％;稻鸭共育控制稻飞虱效果63.73％～77.18％,控制稻螟效果30.11％,控制纹枯病效果19.33％～67.03％,对稻田杂草控制效果91.96％,减少施肥30.6％、农药59.3％,减少投入1 987.05元／hm²。     

保护性耕作模式下非化学除草技术的研究

随着保护性耕作技术的发展,杂草问题逐渐成为影响保护性耕作效益的重要问题,大规模使用除草剂导致的抗药性和环境污染问题,日益受到重视。为此,综合分析了在保护性耕作技术模式下,国内外采用的各种非化学除草技术的特点和发展现状,从而为确定适合我国特色的除草技术提供技术指导。     

Potential use of abrasive air-propelled agricultural residues for weed control

A potential new post-emergence physical weed control tactic is described. It entails plant abrasion and death upon assault from abrasive grits propelled by compressed air. Grit derived from granulated walnut shells was delivered by a sand blaster at 517 kPa at distances of 300–600 mm from seedlings of Chenopodium album in glasshouse pots. Control was influenced by size of plants at time of treatment. Seedlings at the cotyledon to 2-leaf stages of growth were mostly destroyed by a single split-second blast of grit of <1 s duration, but were unaltered by compressed air alone. Plants at the 4- to 6-leaf growth stages required up to 10 blasts of grit to be killed. These results indicate that small weed seedlings of susceptible species might be physically controlled by abrasion from air-propelled grit derived from suitable agricultural residues.     

Competitive interactions between chick-pea genotypes and weeds

Growing chick‐pea in sustainable systems requires the use and development of more competitive genotypes which can complement the effects of reduced input weed control. A 2‐year study assessed the competitive ability of 13 genotypes grown in either the presence or absence of weeds, in a split‐plot design including the weeds in pure stands. Crop and weed density, phenology, relative biomass of crop (RB_c) and weeds (RB_w), crop yield characters, crop biometric traits in the absence of weeds, relative biomass total of mixtures (RBT) and crop competitive ability (C_b = ln RB_c/RB_w) were recorded. Lines C136, C120, C101 and C106, and cultivars Pascià, Visir and Sultano gave the best seed yield in the absence of weeds (1.8–2.0 t ha^?1 DM). Weeds reduced yield by 75% and 83% in C136 and C133 and by 87–97% in the other genotypes. Weed biomass in mixture (mainly Chenopodium album) averaged 4.42 t ha^?1 DM. Chick‐pea genotypes C136 and C133 were the most competitive, but weeds were more competitive than any of the chick‐peas. C_b was correlated directly to the height of first fertile pod (r² = 0.84) and inversely to the insertion angle of primary branches to the vertical (r² = 0.77). Intergenotypic variation for competitive ability could be exploited in integrated weed control using more competitive genotypes, or used in breeding programmes aimed to develop highly competitive cultivars on the basis of easily screenable characters.     

Thermal weed control technologies for conservation agriculture—a review

Research and development activities on non-chemical weed control methods to date have mainly focused on mechanical and thermal applications. Selectivity in mechanical weed control is obtained using dynamically actuated harrows. Selectivity in thermal weed control is obtained through a certain heat tolerance of the crop. In conservation agriculture (CA), weed emergence is partially suppressed by constant soil cover with crops or cover crops. Large amounts of plant residues therefore remain on the soil, which make mechanical methods inefficient or difficult to implement. And thermal methods need to prevent not only crop damage but also fire from situationally dry plant residues. In this review, technologies that can potentially be used for in-crop weed control in CA are discussed. The technologies reviewed include spot-flaming, electric resistance heating, electromagnetic irradiation and steam/hot water application. Their evaluation focuses on efficiency and specificity (spatial precision). This review indicates that existing equipment does not fulfil the spatial precision required in CA and that further research and development is required on this topic. In particular, the authors suggest further research on the use of laser diodes, micro-flames and capacitive coupling of electric fields. It seems that the use of automated imaging systems for weed/crop differentiation is a prerequisite in CA to enable automatisation of weed control.     

Weed suppression ability of three winter wheat varieties at different row spacing under organic farming conditions

For three seasons, six field trials were conducted in winter wheat ( Triticum aestivum ) at different sites in North Rhine-Westphalia, Germany. The aim was to evaluate the performance of three varieties, which differ in their shading behaviour, in suppressing weeds under organic farming (Ökologischer Landbau) conditions and grown at three row spacings. The experimental factors were cultivar, row width and row orientation. Key parameters of crop and weed development, including ground cover and biomass, were assessed at different growth stages and analysed with anova . Growth of the site-specific weed vegetation was significantly affected in five of six trials. Weed growth was reduced by cvs Astron and Pegassos compared with cv. Greif, and was lower at 12 cm compared with 24 cm row spacing. No effect of row orientation (East-West, North-South) on weed growth was observed. The more competitive cultivars Astron and Pegassos were taller than the less competitive cv. Greif and had higher ground cover and light interception, presumably induced by planophile leaf inclination and partly, in the case of cv. Astron, because of higher leaf area index (LAI). Narrow row spacing (12 cm), resulting in a more even spatial plant distribution, increased crop ground cover, LAI, dry matter and light interception. In two trials, the variety with planophile leaf inclination performed better at wider row spacing, suggesting that planophile wheat cultivars may be advantageous in wider row stands.     

Organic soil amendments in relation to nematode management with particular reference to India

The addition of organic materials to soil has been used in managing plant-parasitic nematodes and has resulted in increased crop yield. Research on the utilization of waste materials such as oilseed cakes, chitin, compost, livestock and poultry manures, and cellulosic wastes appears promising for reducing populations of plant-parasitic nematodes. Nitrogen based amendments, plant phenolics, nematotoxic chemicals, development of predators and parasites of nematodes and microorganism stimulation have been considered to be promising agents for nematode management. In addition, organic amendments change the physical as well as the trophic structure of soil, which affects the pathogen development and overall plant growth performance. Mechanisms of action of organic soil amendments in relation to nematode management are yet to be fully explored.Plant Protection Division, Institute of Agriculture     

Integrated crop management, the basis for environment friendly crop protection of potatoes

Relatively large amounts of pesticides are needed to control diseases and pests in modern, intensive potato production. Integrated crop management offers a way of reducing the need for pesticides. It aims to reduce costs and improve the quality of the product and of the production methods, while maintaining soil fertility and the quality of the environment. The components of integrated crop management are described. Prevention of diseases and pests has high priority. If diseases or pests are present, non-chemical control methods are preferred and chemical control is based on economic criteria and the monitoring of the soil and crops. The contribution of integrated crop management to the control of two important fungal diseases, late blight (Phytophthora infestans), and stem canker (Rhizoctonia solani) and of one pest, potato cyst nematode (Globodera spp..) is described. The prospects for further development of integrated crop protection are discussed.     

Weed suppression by soil steaming in combination with activating compounds

The aim of this study was to determine the weed suppression potential of soil steaming plus activating compounds (KOH or CaO) to boost soil temperature. Different combinations between the compounds and rates were tested in experiments carried out in the field and in a controlled environment. Treatment effects were assessed on field weed vegetation and on seedbank and seedling emergence of three winter ( Alopecurus myosuroides , Matricaria chamomilla and Raphanus raphanistrum ) and four spring annuals ( Amaranthus retroflexus , Echinochloa crus-galli , Fallopia convolvulus and Setaria viridis ), were assessed on field weed vegetation. Neither maximum soil temperature (from 72 to 85°C) nor duration of high temperature in the 3 h following application consistently affected weed suppression. In the field, no significant effects on total weed density were recorded, but there were some significant effects on individual species. The weed seedbank was clearly suppressed by activated steaming: total seedling emergence was inversely related to increasing KOH rates both in the 0–10 and 10–20 cm soil layers, while for CaO the relationship was significant only in the 0–10 cm layer. Winter annuals were more sensitive to KOH than CaO and spring annuals had a more pronounced species-specific response to treatments. There was a strong negative relationship between compound rate and seedling emergence for all species. Alopecurus myosuroides was the most sensitive to the steam-alone treatment (77% reduction), whereas M. chamomilla and E. crus-galli were the least sensitive. Results from this study indicate that the type and rates of activating compounds for soil steaming must be adjusted to the weed community composition.