The Effect of Bradyrhizobium Strains on Monocropped and Intercropped Soybean (Glycine max L. Merr.) Biomass and Protein

An experiment was conducted during rainy season (April-August) of 1994 and 1995 to assess the performance of rice, maize, sesame, greengram and blackgram grown in sole and intercropping system on Gangetic alluvial upland (Entisol) in West Bengal. India. All intercropping systems except sesame + rice had higher total productivity in terms of rice equivalent yield and net returns than all the sole crops. However, maximum advantage was obtained from paired row planted maize blackgram system followed by maize + sesame, maize + blackgram and paired row planted rice + blackgram. Paired row planted maize + blackgram increased land use efficiency (42%), rice equivalent yield (2955 kg ha⁻¹), monetary return (Rs. 7294 ha⁻¹), income equivalent ratio (1.22), monetary advantage (Rs. 3701 ha⁻¹) compared with other cropping systems, which proved to be the most efficient system. The same treatment also indicated a modest competitive ratio (4.65:0.21) and gave a good value for the product of crowding coefficient (8.28).     

Wheat and chickpea intercropping systems in an additive series experiment: Advantages and weed smothering

For increasing land use efficiency and weed suppression intercropping plays a pivotal role. A field experiment was carried out on wheat (Triticum aestivum L. emend. Fiori and Paol)–chickpea (Cicer arietinum L.) mono- and intercropping with various weeding (0, 1, or 2 hand-weeding operations) and row spacing (20- or 30-cm) treatments in the eastern plateau region of India over consecutive five winter seasons (1997/2001). The experimental design was a randomized complete block with eighteen treatments replicated thrice. Significant (P ≤ 0.05) differences were observed in yield and economics with and without weeding treatments. Chickpea yield was significantly reduced by wheat when intercropped. However, total productivity and land use efficiency were higher under the intercropping system as compared to monocrops of either species. There was a significant reduction in weed density and biomass for the intercropping system over both monocrops. Wheat facilitated an increase in nodule number and dry weight in chickpea under intercropping over monocrops, moreover, root length of chickpea was greater when intercropped. These findings suggest that intercropping wheat and chickpea increase total productivity per unit area, improve land use efficiency and suppress weeds, a menacing pest in crop production. Considering the experimental findings, wheat–chickpea (30 cm) with two weedings may be recommended for yield advantage, higher net income, more efficient utilization of resources, and weed suppression as a biological control in eastern plateau region of India.     

Effect of Intercropping Cereal, Pulse and Oilseed Crops in Redgram on Yield, Competition and Advantage

Results of a field experiment conducted in rainy season (June to December) of 1988 and 1989 at Deochanda Experiment Station, Bihar, India, indicated that intercropping cereals, pulses and oilseeds with normal planted base crop of redgram ( Cajanus cajan [L.] Mill sp.) increased land use efficiency and gave higher total yields compared to pure cropping of redgram under rainfed conditions on upland oxisols of Bihar plateau. Cereals like maize, rice and fingermillet were more aggressive in intercropping system and they tended to have depressing effect on redgram. Intercropping of short duration pulses like blackgram and greengram and legume-oilseed crops like peanut and soybean with redgram showed balanced competitive abilities and proved more efficient in the system. Intercropping system of redgram-peanut proved to be the most efficient and productive.     

Effect of Planting Geometry on the Growth and Yield Performance of Maize Intercropped with Rice

A field experiment with maize and rice planted under four planting configurations in an intercropping system was conducted to evaluate the plant competition effects on the performance of component crops. Intercropping substantially reduced grain yields of both rice and maize. Rice yield was generally low giving monocrop yield of 1,084 kg/ha. Intercropped rice ranged between 179 kg/ha and 615 kg/ha depending on maize planting arrangement. Monocrop maize yielded highest in square planting (3,617 kg/ha) and lowest in skip-row (2,600 kg/ha) planting, but planting geometry did not influence intercropped maize yield. Monocrop maize outyielded the combined yield of component crops suggesting no yield advantage through rice-maize intercropping.     

Suppressing Weeds in Direct-seeded Lowland Rice: Effects of Methods and Rates of Seeding

High weed infestation is a major constraint to widespread adoption of direct seeding of rice (Oryza sativa L.) The experiments were conducted in 1998 wet and 1999 dry seasons in the Philippines to examine the effects of seeding methods and rates on suppressing weeds in direct-seeded lowland rice. Treatments consisted of four seeding methods: conventional and modified broadcast seeding, drill seeding with east–west and north–south row orientations; three seeding rates: 40, 80 and 160 kg seed ha⁻¹ as well as two weed control levels: weed control with herbicide and no weed control. Among the seeding methods drill seeding with east–west row orientation had the lowest rice grain yield loss caused by weeds (38 % in the wet and 20 % in the dry season), whereas the highest losses because of weeds were observed with conventional broadcast seeding (59 % in the wet and 27 % in the dry season). Seeding rate was inversely correlated to weed interference. Severe rice yield reduction (71 %) caused by weeds was found at a seeding rate of 40 kg seed ha⁻¹ in the wet season. Using seeding rates of 80 and 160 kg seed ha⁻¹, respectively, lowered yield loss to 47 and 26 % in the wet season, 32 and 18 % in the dry season. Therefore suitable method and/or rate of seeding can significantly suppress weeds in direct-seeded lowland rice.     

三种栽植方式下不同株型和化感特性水稻对无芒稗的干扰控制作用

以直播、小苗移栽和大苗移栽3种栽植方式为主处理,接种和不接种稗草为裂区处理,17份不同株型和化感特性水稻材料为再裂区处理,设计了对无芒稗干扰控制田间试验。结果表明,直播和小苗移栽对无芒稗株高、分蘖和干重有较好的抑制作用,优势株型和化感特性水稻对无芒稗具有较好的干扰控制作用。在30株 m^-2无芒稗的竞争干扰下,3种栽植方式间水稻产量差异不显著,杂草竞争干扰使水稻减产21.73%,化感作用水稻吓一跳、IR644-1-63-1-1、谷梅2号对稗草竞争力强,仍具一定产量水平。无芒稗竞争干扰对直播水稻株高、分蘖和植株干重影响大,与移栽水稻的差异显著。杂草干扰对供试水稻材料的农艺性状产生不同影响,水稻化感种质吓一跳中期分蘖强、植株高、干重大。无芒稗竞争干扰对成熟水稻株高无影响,但对分蘖、植株茎秆和穗干重差异显著。杂草竞争对3种种植方式的水稻千粒重无显著影响,但单株谷粒重以大苗移栽显著大于直播,移栽水稻的穗型较大,每穗总颖花数、每穗实粒数和结实率显著大于直播水稻。化感作用水稻谷梅2号、IR644-1-63-1-1、TN1和PI312777每穗颖花数不高、每穗实粒数少,化感作用水稻吓一跳每穗颖花数不高,但结实率高。水稻材料中早27、早籼浙207、早籼浙101、中早22等拥有较高的千粒重,化感作用水稻谷梅2号的千粒重显著高于IR644-1-63-1-1、TN1和PI312777。早籼浙101、早籼浙207和中早22等拥有较高的单株谷粒重,化感作用水稻中156的单株谷粒重显著高于谷梅2号、吓一跳、IR644-1-63-1-1、TN1和PI312777。     

Effect of Intercropping on the Yield Components of Rice, Mungbean, Soybean, Peanut and Blackgram

An experiment with sixteen cropping systems (pure and intercroppings) was conducted during the kharif season of 1985 and 1986. The sixteen cropping systems were: sole rice, sole mungbean, sole soybean, sole peanut, sole blackgram, rice + mungbean (2:1), rice + mungbean (4:1), rice + mungbean deferred (2:1), rice + soybean (2:1), rice + soybean (4 : 1), rice + soybean deferred (2 : 1), rice + peanut (2:1), rice + peanut (4 : 1), rice + blackgram (2:1), rice + blackgram (4:1) and rice + blackgram deferred (2:1). Sole crop of rice always recorded higher number of effective tillers/m², however, it was observed that legumes had an influence on the number of filled grains per panicle and thousand grain weight of rice in rice + legume combinations. Among legumes, pure crops of soybean and peanut always gave rise to increased number of yield components than the other crops grown in association with rice. In case of mungbean, number of pods per plant and thousand seed weight was higher in pure crops though number of seeds per pod was more with rice + mungbean combination. Deferred sown blackgram in association with rice yielded greater number of seeds per pod and thousand seed weight though sole crop of blackgram significantly produced higher number of pods per plant.     

Growth and Development of Six Barley (Hordeum vulgare ssp. vulgare L.) Cultivars in Response to a Model Weed (Sinapis alba L.)

The aim was to study the growth and development of six spring barley (Hordeum vulgare ssp. vulgare L.) cultivars as a response to a model weed population of Sinapis alba L. The development of light interception profiles over time was characterized for each cultivar in weed‐free stands. The cultivars were chosen such that they represent a range of weed‐suppressive abilities based on previously performed trials. One field experiment each was conducted in 1996 and 1997 at a site SE of Uppsala, Sweden. The two cultivars with low competitive ability against weeds, Etna and Blenheim, allowed the highest weed biomass and the lowest crop biomass in competition with the weeds. These two cultivars transmitted more photosynthetic active radiation through the canopy down to 20 and 40 cm height than did the other cultivars. Although the biomass of cv. Etna was low, the grain yield was higher than that of the other cultivars when grown in competition with weeds. In 1997, cv. Svani with good competitive ability against weeds transmitted least light and had greater grain yield than most other cultivars. The absence of a relationship between high grain yield and low weed suppressive ability in the present study indicates that it should be possible for plant breeders to combine high grain yielding capacity with approved weed‐competitive ability.     

Mechanical control of clover improves nitrogen supply and growth of wheat in winter wheat/white clover intercropping

The major objective for clover in a winter wheat/white clover intercropping system is to supply nitrogen (N) for the wheat. A field experiment was repeated in 2 years on a loamy sand in Denmark to investigate the possibilities for increasing N supply to the winter wheat by cutting and mulching the clover between the wheat rows. The clover was cut with a weed brusher on three different dates in each year.Intercropped wheat with unbrushed clover had a lower grain yield than wheat as a sole crop. Brushing increased wheat N uptake and wheat grain yields. Intercropping with two or three brushing dates gave higher wheat yields than wheat as the sole crop. The largest increases in grain N uptake, 21–25 kg N ha⁻¹, were obtained for the brushings around wheat flag leaf emergence. The highest yield increases with a single brushing, 0.98–1.11 Mg DM ha⁻¹, were obtained when brushing was performed during the stem elongation phase. The largest grain yields for treatments with two brushings were obtained with a first brushing at start of stem elongation and a second around flag leaf emergence. The first brushing probably provided N to increase the wheat leaf area index and thus the light interception, while the second brushing provided N to sustain the leaf area during grain filling and reduced clover biomass and therefore competition for water. Intercropping wheat and clover increased grain N concentrations by 0.11–0.39%-point compared with wheat as a sole crop. Intercropping may thus offer possibilities for improving the bread-making quality of organically grown wheat.     

The Influence of Row Spacing and Seeding Rate on Seed Yield and Yield Components of Forage Turnip (Brassica rapa L.)

The effects of four row spacings (17.5, 35.0, 52.5 and 70.0 cm) and five seeding rates (50, 100, 200, 400 and 800 viable seeds m^?2) on seed yield and some yield components of forage turnip (Brassica rapa L.) were evaluated under rainfed conditions in Bursa, Turkey in the 1998–1999 and 1999–2000 growing seasons. Plant height, stem diameter, pods/terminal raceme, total pods/plant, seeds/pod and primary branches/plant were measured individually. The number of plants per unit area was counted and the lodging rate of the plots was scored. The seed yield and 1000‐seed weight were also determined. Row spacing and seeding rate significantly affected most yield components measured. The number of plants per unit area increased with increasing seeding rate and decreasing row spacing. Plant height was not greatly influenced by row spacing and seeding rate, but higher seeding rates reduced the number of primary branches and the stem diameter. The number of pods/main stem was affected by row spacing and but not by the seeding rate. Also, the number of seeds per pod was not affected by either the row spacing or the seeding rate. In contrast, the number of pods per plant clearly increased with increasing row spacing, but decreased with increasing seeding rate. The plots seeded at narrow row spacings and at high seeding rates were more sensitive to lodging. Seeding rate had no significant effect on seed yield in both years. Seed yield was similar at all seeding rates, averaging 1151 kg ha^?1. However, row spacing was associated with seed yield. The highest seed yield (1409 kg ha^?1) was obtained for the 35.0‐cm row spacing and 200 seeds m^?2 seeding rate combination without serious lodging problems.     

Effects of water limitation on yield advantage and water use in wheat (Triticum aestivum L.)/maize (Zea mays L.) strip intercropping

Wheat (Triticum aestivum L.)/maize (Zea mays L.) strip intercropping is widely practiced in arid regions of northwestern China because of its high land use efficiency. However, its sustainability has been questioned because it consumes much more water than sole cropped wheat or maize. The present study was conducted to investigate the effects of water limitation on the yield advantage and water use of this system. Three field experiments were conducted in the Hetao Irrigation District in Inner Mongolia during the growing seasons of 2012–2014. Each experiment comprised two water applications, in which one was full irrigation and the other was a period of water limitation during the co-growth period of intercropping.The interspecific competition in wheat/maize intercropping was intensified by water stress. For water limitation applied during the wheat booting/maize V5 stage (Exp. I, second irrigation was not applied), the yield advantage of intercropped wheat (IW) over sole wheat was enhanced, whereas that of intercropped maize (IM) over sole maize was reduced compared with full irrigated treatments; for water limitation applied during the wheat jointing/maize V2 stage (Exp. II, first irrigation was not applied), the yield advantages of both IW and IM were greatly reduced; for water limitation applied during the wheat grain filling/maize V9 stage (Exp. III, third irrigation was not applied), the yield advantage of IW was slightly improved, whereas that of IM was reduced. The yield advantage of intercropping under limited irrigation was 25%, 3%, and 18% in Exps. I–III, respectively, whereas that under full irrigation ranged between 22 and 24%.Under well-watered conditions, wheat/maize intercropping used 24–29% more water than the weighted means of sole crops with the water use efficiency equivalent to sole crops. After the application of water limitation, 60 mm irrigation water was saved by intercropping every year, whereas the reduction of water use ranged from 25.1 to 70.8 mm; the changes in water use of intercropping relative to sole crops was reduced to 18–24%; the changes in water use efficiency stayed at nearly zero in Exps. I and III but decreased to a value of −13% in Exp. II. These results indicated that water limitation could be applied during wheat booting or filling stage in wheat/maize intercropping to save irrigation water in our study area.     

Assessment of the benefits of frost-sensitive companion plants in winter rapeseed

The intercropping of rapeseed with frost-sensitive companion plants (CP) has recently been proposed as a way to mitigate the negative environmental impact of rapeseed crops. Using mixed-effect linear models, we compared the yield and weed amounts of rapeseed intercropped with different CP species with that of rapeseed as a sole crop in an unique dataset of 79 field experiments covering a wide range of climate, soil and practices conditions in the northwestern part of France, from 2009 to 2015. Bayesian model averaging procedure was used to determine the relative contributions of sites characteristics to the effects of intercropping.Before winter, field pea and faba bean had accumulated the largest amounts of dry mass, with more than 100 g m⁻². Rapeseed biomass was reduced by 56% by non-legume CPs and by only 18% by legume CPs, the largest decrease being caused by pea. Non-legumes decreased the nitrogen nutrition index of rapeseed by 7%, whereas pea and faba bean increased this index by 6% and 3%, respectively. Intercropping with non-legume and legume CPs reduced weed amounts by 52% and 38% respectively, with no difference between CP species. Non-legume CPs decreased rapeseed yield at harvest by 0.58 t ha⁻¹, whereas faba bean and faba bean + lentil increased yield by 0.16 and 0.12 t ha⁻¹ respectively, when fertilized at the recommended rate. Intercropping with faba bean, lentil or a mixture of both made it possible to reduce nitrogen applications by 30–40 kg ha⁻¹ with no significant decrease in rapeseed yield. Faba bean and faba bean + lentil mixtures had the best overall performance. This work suggests that intercropping rapeseed is promising, particularly in soils with low nitrogen content with an early sowing date in the late summer.     

Effects of Bean Population and Row Arrangement on the Productivity of Chilli/Dwarf Bean (Capsicum annuum/Phaseolus vulgaris L.) Intercropping in Sri Lanka

Intercropping of chilli ( Capsicum annuum ) and dwarf bean ( Phaseolus vulgaris ) is a recently adopted practice by farmers in Sri Lanka. As chilli fetches a higher market price, the bean population which could be incorporated into a 100% population of chilli has to be found. In the present experiment, effects of three bean populations (100, 75 and 50% of sole crop population 250 000 pl ha⁻¹) and four row arrangements (1:1, 1:2, 2:1 and 2:2) were tested at Kundasale, Sri Lanka. The land equivalent ratio (LER) of all intercrops were significantly greater than one, indicating a greater productivity per unit land area in intercropping than sole cropping. At 100% and 75% bean populations, LER and intercrop yields of bean were significantly greater than at 50%. Row arrangement did not have a significant effect on either LER or bean yield in intercrops. Intercrop bean yields were lower than sole bean yields indicating significant competition from chilli. Chilli yields were not affected by either bean population or row arrangement. Intercrop chilli yields were greater than the sole chilli yield indicating significant positive effects from bean. Greater radiation interception and lower weed growth and the absence of overlap between yield formation periods of the two component crops were probably responsible for the greater productivity (LER) of intercrops.     

Evaluation of Upland Rice (Oryza sativa L.) Genotypes for Intercropping with Pigeon Pea (Cajanus cajan [L.] (Mill sp.))

Eleven upland rice genotypes of varying growth duration and plant stature were evaluated in two cropping systems: monocrop and intercrop, with pigeon pea cv. U pas 120, in order to study the effects of intercropping on rice grain yield and its contributing characteristics during 1990 to 1992 wet seasons. Cropping system and cropping system × genotype interaction effects were significant for yield ha⁻¹, panicle weight, panicles m⁻² and spikelet fertility suggesting the need for evaluating and selecting genotypes suitable for intercropping. Rice grain yield reduction in the intercrop ranged from 24.5 % in genotype RR 203-16 to 54.5 % in genotype Aditya. Panicle weight, total dry matter at flowering as well as at harvest, and harvest index were also reduced. Plant height and panicle weight were positively associated with yield in both systems, however, the yield was positively and significantly correlated with spikelets per panicle and spikelet fertility with the intercropping system. The correlation between cropping systems indicated the possibility of simultaneous improvement for these characteristics in monocropping and intercropping.     

Competitive and allelopathic interference between soybean crop and annual wormwood (Artemisia annua L.) under field conditions

Annual wormwood interference on soybean crop growth and yield may result from competition and allelopathy, which are modulated by crop management. Allelochemicals released by annual wormwood (e.g. artemisinin) may affect the crop directly or indirectly through the effect on the nitrogen fixing symbiont, Bradyrhizobium japonicum. The objectives were (i) to quantify the crop response (i.e. biomass production, nodulation and yield) to weed interference and (ii) to determinate the relative change of competition and allelopathy interferences, when a sublethal dose of herbicide is applied. Two split plot field experiments with three replications were used. The experiment involved a factorial combination of five weed–crop density (soybean/annual wormwood, plants m^?2) levels: D1, pure soybean, 40/0 plants m^?2; D2, 40/2 plants m^?2; D3, 40/4 plants m^?2 and D4, 40/8 plants m^?2, and D5, pure annual wormwood, 0/8 plants m^?2, two activated carbon (allelopathy) levels: C?, with activated carbon (reduced allelopathy) and C+, non activated carbon applied (with allelopathy) and two herbicide levels: H?, untreated and H+, treated with a sub-lethal dose of glyphosate. Activated carbon to adsorb allelochemicals (with and without activated carbon) and glyphosate application (with and no herbicide) were assigned to sub-plots. Increasing weed density did not affect crop biomass at flowering, but changed nodule number and soybean yield with a different pattern depending on carbon and herbicide treatment. Relative crop yield decreased with increasing relative weed biomass. This decrease was particularly drastic when allelopathy was reduced by activated carbon and without herbicide application. The maximum yield losses of 33% in 2006 and 17% in 2007 were observed with the highest weed density (8 plants m^?2). In contrast, without carbon (high allelopathy level), soybean yield remained stable within the explored range of annual wormwood biomass, despite the fact that weed biomass at high densities (D4) was high enough to generate competition. The lack of response to increasing weed density could be related to the indirect effect of allelochemicals interacting with soil microorganisms (i.e. B. japonicum) that positively affected the nodulation (e.g. larger nodules in 2006 and increased nodules biomass due to higher number of roots in 2007 at high densities). With herbicide application, soybean yield of both carbon treatments remained stable when biomass of annual wormwood increased. This research provided strong evidence in support of the existence of positive effect of allelopathic and competitive interactions between annual wormwood and soybean crop under field conditions that may be overridden under herbicide application.     

The Impact of Underseeding Barley (Hordeum vulgare L.) on Timothy (Phleum pratense L.)-Clover (Trifolium pratense L.; Trifolium hybridum L.) Forage Production in a Cool Maritime Climate

Growing barley (Hordeum vulgare L.) in the year of forage establishment is a common agronomic practice in marginal growing regions, but is often not recommended to growers. We examined the effect of silage barley production over an establishing timothy (Phleum pratense L.)‐clover (Trifolium pratense L.; Trifolium hybridum L.) forage sward in a 4‐year study near St. John's, Newfoundland, Canada. The experiment compared two barley varieties differing in plant height (semidwarf Chapais and Leger), three barley seeding rates and the effect of a forage understorey on forage (barley) production in the establishment year and forage (timothy‐clover) production in the subsequent year. The taller Leger yielded similar forage biomass to Chapais in the year of forage establishment, which (when planted at 375 plants m^?2) was roughly twice that of a pure‐stand timothy‐clover mix. Increasing the barley seeding rate from 125 to 375 plants m^?2 resulted in a linear increase in forage yield in the year of planting. The production of barley forage in the establishment year resulted in reduced timothy‐clover forage yield in the year following barley planted at 125 and 375 seeds m^?2, but not for barley planted at 250 seeds m^?2. Companion planting also altered forage species composition in that higher barley seeding rates resulted in 12–18 % less timothy and 2–4 % lower fibre levels in the year following planting. Barley seeded at rates of 250–375 seeds m^?2 and undersown with a timothy‐clover mixture (harvested at mid‐milk) resulted in greater forage yield of poorer quality than pure‐stand timothy‐clover in the planting year, and a barley seeding rate of 250 seeds m^?2 did not impede forage production in the subsequent year.     

地下水位对油菜生长及产量的影响

长江流域油菜生产主要采用水稻油菜轮作种植模式,地下水位高,易产生湿害。本试验采用PVC筒,在油菜4个生育期分别进行0、30、60和90 cm的地下水位处理,然后恢复至60 cm水位,比较2个耐渍性不同的油菜品系在不同生育期、不同水位条件下的生长状况及产量,从而确定油菜各生育阶段的适宜地下水位,为南方稻茬油菜排水降湿管理提供依据。试验结果表明: (1)地下水位高低影响了油菜的根系发育、地上部生长及产量形成;(2)就产量而言,各生育期对水分的敏感性依次为蕾薹期、花期﹥苗期、角果发育成熟期;(3)油菜苗期适宜地下水位为30~90 cm,蕾薹期、花期为30~60 cm,角果发育成熟期为30~90 cm;(4)就全生育期而言,即使选用耐渍性较弱的品种,地下水位控制在30~60 cm时能满足油菜生长发育及产量形成需求。     

Assessing non-chemical weeding strategies through mechanistic modelling of blackgrass (Alopecurus myosuroides Huds.) dynamics

Because of environmental and health safety issues, it is necessary to develop strategies that do not rely on herbicides to manage weeds. Introducing temporary grassland into annual crop rotations and mechanical weeding are the two main features that are frequently used in integrated and organic cropping systems for this purpose. To evaluate the contribution of these two factors in interaction with other cropping system components and environmental conditions, the present study updated an existing biophysical model (i.e. AlomySys) that quantifies the effects of cropping system on weed dynamics. Based on previous experiments, new sub-models were built to describe the effects on plant survival and growth reduction of mechanical weeding resulting from weed seedling uprooting and covering by soil, and those of grassland mowing resulting from tiller destruction. Additional modifications described the effect of the multi-year crop canopy of grassland on weed survival, growth, development and seed return to the soil. The improved model was used to evaluate the weed dynamics over 27 years in the conventional herbicide-based cropping system most frequently observed in farm surveys (i.e. oilseed rape/winter wheat/winter barley rotation with superficial tillage) and then to test prospective non-chemical scenarios. Preliminary simulations tested a large range of mechanical weeding and mowing strategies, varying operation frequencies, dates and, in the case of mechanical weeding, characteristics (i.e. tool, working depth, tractor speed). For mechanical weeding soon after sowing, harrowing was better than hoeing for controlling weed seed production. The later the operation, the more efficient the hoeing and the less efficient the harrowing. Tractor speed had little influence. Increasing tilling depth increased plant mortality but increased weed seed production because of additional seed germination triggering by the weeding tool. Decreasing the interrow width for hoeing was nefarious for weed control. The best combinations were triple hoeing in oilseed rape and sextuple harrowing in cereals. The best mowing strategy was mowing thrice, every 4–6 weeks, starting in mid-May. The best individual options were combined, simulated over 27 years and compared to the herbicide-based reference system. If herbicide applications were replaced solely by mechanical weeding, blackgrass infestation could not be satisfactorily controlled. If a three-year lucerne was introduced into the rotation, weed infestations were divided by ten. Replacing chisel by mouldboard ploughing before winter wheat reduced weed infestations at short, medium and long term to a level comparable to the herbicide-based reference system.     

Yield and yield components of wheat and maize in wheat–maize intercropping in the Netherlands

Intercropping is widely used by smallholder farmers in developing countries, and attracting attention in the context of ecological intensification of agriculture in developed countries. There is little experience with intercropping of food crops in Western Europe. Yields in intercrops depend on planting patterns of the mixed species in interaction with local growing conditions. Here we present data of two years field experimentation on yield and yield components of a wheat–maize intercrop system in different planting configurations in the Netherlands. Treatments included sole crops of wheat (SW) and maize (SM), a replacement intercrop consisting of strips of six wheat rows alternating with two maize rows (6:2WM), as well as subtractive or additive designs, based on skip-row (6:0WM, 0:2WM) and add-row (8:2WM, 6:3WM) configurations. The land equivalent ratio (LER) of intercrops varied from 1.18 to 1.30 in 2013 and from 0.97 to 1.08 in 2014. Wheat grown in the border rows of wheat strips had higher ear number per meter row, greater kernel number per ear, and greater yield per meter row than wheat in inner rows and sole wheat, indicating reduced competition. Wheat in the border rows in the intercrops had, however, reduced thousand kernel weight and harvest index, indicating that competition in border rows intensified over time. Intercropping negatively affected maize biomass and thousand kernel weight, especially in add-row treatments. This study indicates that there is a potential yield benefit for the wheat–maize intercropping system under Western European growing conditions. However, the LER was affected by yearly variation in weather conditions and significantly greater than one in only one of the two years of the study.     

两种除草剂对云南秋播苦荞田除草效应及其产量的影响

为了探讨除草剂对云南秋播苦荞田的防除效果、苦荞的安全性和产量的影响,以‘云荞1号’为材料,对云南秋播苦荞田进行不除草、人工除草、化学除草(金都尔、乙草胺)苗前土壤喷雾4个处理。试验结果表明,金都尔和乙草胺除草剂对秋播荞麦田的杂草有较好的防除效果,并且金都尔除草剂对阔叶杂草的防除效果大于禾本科杂草的防除效果,而乙草胺除草剂对禾本科杂草的防除效果大于阔叶杂草的防除效果;但两种除草剂对苦荞的出苗和幼苗生长都有一定的抑制作用,并且严重影响苦荞产量。因此在生产中,以阔叶杂草为主的苦荞田建议使用金都尔除草剂、以禾本科杂草为主的苦荞田建议使用乙草胺除草剂,但尚需进一步研究防除效果好又不影响产量的适合苦荞田除草剂浓度的筛选。