Effects of Two Underseed Species, Medicago polymorpha L. and Scorpiurus muricatus L., on the Yield of Main Crop (Durum Wheat) and Subsequent Crop (Teff) Under Humid Moisture Regimes in Ethiopia

Mixed cropping of leguminous underseed species and cereal crops may increase productivity and serve some additional purposes. Two leguminous weed species which are widely distributed in annual crops of the Ethiopian highlands have been studied with varying coverage in greenhouse trials in Ethiopia with regard to their suitability as underseeds and with wheat ( Triticum turgidum [L.] Thell. var. durum [Desf.] MacKey) as a main crop. The competitive effects of Scorpiurus muricatus L. on the grain yield of wheat were smaller than those of Medicago polymorpha L. (-14.1 % and -23.6 % respectively, compared with the underseed free control) which is mainly ascribed to differences in their speed of development and shoot height. The residual effects of the underseed's root masses on the grain yield of the successive teff crop (Eragrostis tef [Zucc] Trotter) were significantly higher with Scorpiurus muricatus (+99.3 %) than with Medicago polymorpha (+63.6 %). The results are discussed with regard to the specific site conditions in the cereal-dominated cropping systems of the Ethiopian highlands.     

The Effect of Intercropping Lablab purpureus L. with Sorghum on Yield and Chemical Composition of Fodder

In two years the growth and composition of mixtures of sorghum with Lablab purpureus as strips, paired rows and alternate rows were compared with those of sorghum and lablab monocrops. In the first year, when sowing did not occur until 7 August, the sorghum yields were low in the monocrop and even less in the mixed crops. Lablab yield was also reduced in mixtures compared with the monocrop, but total forage yield was greater for the mixed crops compared with sorghum alone. Of the mixed cropping systems, a reduction in the yield of lablab plants and in the phosphorus and potassium content of shed lablab leaves in paired rows suggested that there was more competition for nutrients between lablab plants grown in this treatment. In the second year, earlier sowing increased sorghum growth at the expense of lablab yield in the mixed cropping systems, with the result that total forage yield was not increased when sorghum was intercropped with lablab. However, the crude protein content of sorghum stems and leaf yield were increased in mixed crops, particularly in paired and alternate rows rather than strips, demonstrating that close configuration of the legume and cereal are necessary for the cereal to obtain most benefit from nitrogen fixed by the legume. It is concluded that, when conditions are favourable for rapid sorghum and lablab growth, the sorghum will benefit more when it is grown in paired rows with lablab rather than in strips. However, the close spacing normally adopted for paired rows may encourage competition between lablab plants and increase the requirements for phosphorus and potassium fertilizer.     

Crop Rotation to Improve Agricultural Production in Sub-Saharan Africa

A three years' trial was conducted in a farmers' field in northern Ghana to evaluate the effect of sole crops (cotton, cowpea, groundnut, soybean, and sunflower) planted once or twice on yield of the staple foods of the region, maize and sorghum. Sole cropping for only one year already resulted in significant yield increases for maize and partly for sorghum compared to the conventional cropping of mixed stands of maize–sorghum or maize–groundnut and natural fallow. Lowest yield of maize and sorghum was obtained where these cereals followed maize–sorghum (monoculture). Intercropping of maize with groundnut led to subsequent maize and sorghum yields which were similar to those obtained after maize–sorghum. After growing legumes and sunflower for one year the grain and straw yield of maize and sorghum was significantly higher in the two consecutive years than after cereal (maize–sorghum) monoculture. In this trial maize and sorghum were found to be not as tolerant to the disadvantages of monoculture or preceding cereals–legumes mixture. The results suggest that continuous intercropping with cereals under the given conditions has negative effects on soil fertility and can lead to an increase in soil-borne pests and troublesome weeds like Striga comparable to monocropped cereals.     

Impact of the Cropping Systems of a Minor Dry Season on the Growth, Yields and Nitrogen Uptake of Maize (Zea mays L) Grown in the Humid Tropics during the Major Rainy Season

A field study evaluated the residual effect of a cropping system in two minor (dry) seasons on the productivity pattern and nitrogen utilization of a maize crop grown in the subsequent major (wet) seasons. The cropping systems established in the minor seasons, where evaporation exceeds rainfall, were either monocultures of maize (Zea mays L), or maize intercropped with either common bean (Phaseolus vulgaris L) or sunhemp (Crotolaria juncea L). In addition, monocultures of two green manures, namely sunhemp (Crotolaria juncea) or Tithonia (Tithonia diversifolia), were established. The residues of maize and beans and the green manures were incorporated at the end of the minor season; at the onset of rains in the major season, maize crops were established on the same plots. Germination of maize was not affected by the previous cropping system. In contrast, crop growth and yields of maize and nitrogen utilization were affected by the previous cropping system. Optimum growth and highest yields were procured in maize that was grown after a green manure crop. Similarly, although the yields were high, the planting of a green manure crop reduced nitrogen utilization by maize in the major season, thereby indicating its potential contribution to sustainability, due to its lower mining of soil nitrogen. On the basis of the results of this two‐year study, the impact of cropping systems in minor seasons on the productivity of maize, a very important highland cereal in the tropics, grown under rain‐fed conditions in a major season, is presented.     

Results of Long-term Experiments with Growing Flue-cured Tobacco (Nicotiana tabacum L.) in Monoculture and Different Types of Crop Rotations

In broadly conceived long-term experiments, tobacco was grown in monoculture and with different crop rotations. This paper presents results in terms of the yields achieved and the major yield components for the crops grown, and the proportion of particular tobacco quality classes obtained. In addition to tobacco monoculture (initially only fertilized and later also unfertilized) as the key crop, different types of crop rotations included, besides tobacco, the following crops: winter wheat, maize, soybean, oil-seed rape, and red clover. Experiments involved two 2-year and two 4-year crop rotations, and a 3-year, a 5-year, and a 6-year crop rotation. Experiments were set up on luvic semigley on multilayered Pleistocene sands. Average 10-year results suggest that there is an advantage of crop rotation over monoculture for tobacco leaf yields. The influence of different crop rotation types on yields of other crops was variable, tending towards higher values as the number of crops in rotation was increased. Values obtained for yield components should be considered from two angles: some of the values were primarily influenced by genetic factors, while others were influenced by ecological factors, including crop rotation as an overall biological buffer. With regard to quality classes (IB-III), the growing of flue-cured tobacco in crop rotation represents a great advancement relative to its growth in monoculture, even in a narrower crop rotation.     

Evolution in crop–livestock integration systems that improve farm productivity and environmental performance in Australia

Australian farming systems have an enduring history of crop–livestock integration which emerged in the face of high climate variability, infertile soils and variable landscapes. Ley farming systems with phases of shorter annual legume pasture phases with cereal crops predominate but, emerging sustainability issues and the need to manage risk is driving ongoing innovation in crop–livestock integration. We discuss the recent evolution of selected innovations that integrate crop and livestock production and their impacts on farm productivity, sustainability and business risk. Dual-purpose use of cereals and canola (Brassica napus) for forage during the vegetative stage while still harvesting for grain is now practiced throughout southern Australia's cropping zone. This practice provides risk management benefits, diversifies crop rotations, reduces pressure on other feed resources and can significantly increase both livestock and crop productivity from farms by 25–75% with little increase in inputs. Sacrificially grazing crops when expected grain yield is low and/or livestock prices are attractive relative to grain provides further flexibility in crop–livestock management systems vital for business risk management in a variable climate. Replacing annual pastures with perennial pasture phases in rotation with crops can provide a range of benefits including improved hydrological balance to reduce dryland salinity, subsoil acidification and water-logging, provide a management tool for herbicide-resistant or problem weeds, improved soil nutrient and carbon stocks as well as increased livestock productivity by filling feed gaps. In some environments, integration of perennial forages in mixtures with cropping, such as alley cropping and inter-cropping, also provide options for improving environmental outcomes. These practices are all innovations that provide flexibility and enable tactical decisions about the mix of enterprises and allocation of land and forage resources to be adjusted in response to climate and price. We discuss these innovations in the context of the emerging constraints to crop–livestock integration in Australia including the continuing decline in labour availability on farms and increasing management skill required to optimise enterprise profitability.     

华北寒旱区作物轮作的生产效应

To understand mechanisms of crop adaptability to various previous crop croppings, evaluate crop performance on the croppings, and identify suitable crop combinations for rotation of major crops in the cold and arid region of Northern China. A five-year field experiment was conducted using five crops from 2015 to 2019, including potato (Solanum tuberosum), faba bean (Vicia faba), forage maize (Zea mays), oat (Avena sativa), and beet (Beta vulgarwas). Yields of potato, oat, and beet in rotation were 1.30-1.68, 1.28-1.48, and 1.25-1.48 times of those in continuous cropping of single crops, respectively. Yield of faba bean on beet cropping was 10.58% lower than that of continuous faba bean while yield of forage maize on oat or beet stubble was 9.10%-15.42% lower than that of continuous forage maize. The LERr of 10 crop combinations was 1.09-1.68, indicating positive effects of rotation. Combinations of oat → potato, beet → potato, forage maize → potato and faba bean → potato had higher LERr, indicating faba bean and forage maize might be more durable of continuous cropping. In terms of productivity, suitable crop combinations for rotation in the area were oat → potato, beet → potato, forage maize → potato, faba bean → potato and oat → beet.     

Forage and Food Legumes in a Multi‐Year,Wheat‐Based Rotation Under Drought‐Stressed Conditions in Northern Syria’s Medium Rainfall Zone

Long‐term crop rotation trials were designed to assess sustainability of alternatives to traditional fallow and monocropping. The trial described here (6 years) involved wheat (Triticum aestivum L.) in rotation with lentil (Lens culinaris L.), forage vetch (Vicia sativa), pasture medic (Medicago spp.), fallow and watermelon (Citrullus vulgaris). Barley (Hordeum vulgare L.) was compared with wheat for an additional 2 years. Cereal grain and straw yields were highest with fallow and watermelon followed by vetch, lentil and medic; the latter showed no differential effect of variable grazing intensity. Fertilizer N increased yields except in the low‐rainfall years (less than 250 mm). Barley out‐yielded wheat in terms of grain, but not straw. Medic yielded highest in dry matter, whereas lentil produced highest seed yield. Despite the difficulty of assessing crop and animal‐oriented rotations because of non‐commonality of outputs, economic considerations are foremost, but other benefits of rotations (soil quality, water‐use relations) are also relevant to the overall assessment of cereal‐based Mediterranean rotations. The study suggested barley rather than wheat as the desired cereal in rotation with legumes in this marginal‐rainfall (350 mm) environment and provided support for the viability of vetch and lentil in the cropping system. Given the importance of sheep in the region’s farming system, vetch is likely to have a major role in crop rotations.     

克服蔬菜作物连作障碍问题之研究进展

蔬菜作物连作障碍是蔬菜生产持续发展所面临的一个重要问题,通过查阅有关克服蔬菜连作障碍的研究报告,结合作者从事相关研究的结论和进展,就蔬菜作物连作障碍产生的原因和克服的途径进行综述,以便为相关研究和类似技术的实际应用提供借鉴。大量的研究表明,引起蔬菜作物连作障碍的主要原因有土壤中有害微生物的积累、土壤的次生盐渍化、蔬菜作物的自毒作用等。通过轮作、间作套种、生物防治、选育抗重茬品种、嫁接栽培、增施有机肥等措施可以部分或全部解决蔬菜作物的连作障碍问题。     

Reduced inter-row distance improves yield and competition against weeds in a semi-dwarf durum wheat variety

Weed and nutrient management in cropping systems of semi-arid areas is a major constraint to cereal yield. Where the use of herbicides is banned or discouraged, the competitive ability of a crop is crucial to reduce weed growth and diffusion. Genotypic differences in the competitive abilities of crops are an important trait to reduce weeds, especially for plant height. However, there is contrasting information about the interactions of other management practices and genotypic traits on wheat yield and competitive ability against weeds and weed growth. The present study investigated yield and quality of durum wheat (Triticum durum Desf.) and weed growth and composition for two wheat cultivars with contrasting competitive abilities against weeds. Wheat was grown under three spatial arrangements (5-cm, 15-cm, 25-cm inter-row distance) and three sowing densities, and broadleaf weeds were either removed or not. The sowing rate did not affect the yield of these wheat cultivars or the weed growth. Reduced inter-row distance dramatically reduced weed biomass for both wheat cultivars, and increased wheat yield and nitrogen uptake in the low-competitive, high-yielding, semi-dwarf cv. ‘PR22D89’, when both weed free and with weeds. These results have direct implications for weed and nutrient management in low-input and organic cropping systems.     

连作和轮作对谷子叶片构型和叶绿素、氮素含量的影响

研究旨在提升谷子连作障碍认知度,为谷子轮作制度和可持续生产提供理论依据和技术支持。采用周年单序轮作处理和连作处理相比较的方法,研究其对旱地谷子叶片构型、叶绿素和氮素含量的影响。结果表明,连作处理降低谷子个体的叶面积和群体的叶面积指数,严重影响谷子叶片的生长发育;降低谷子叶片的叶绿素和氮素含量,影响谷子叶绿体的发育。谷子连作种植是不科学的田间生产方式,应选择合理的年际轮作制度,以实现谷子高产稳产。     

轮作种植制度的生态经济效益分析及发展建议

在集约化种植和经济效益的驱动下,连作在中国已经成了较为普遍的种植模式,即年复一年地在田间种植单一作物。长期的连作导致了病虫害严重、产量低下、土壤健康状况降低等诸多问题。轮作是有效解决连作障碍的方法之一,在国家粮食安全、生态环境发展以及乡村振兴等战略实施中有着至关重要的作用。本研究通过文献检索,利用对比分析法,进行文献综述,阐述相比于连作,轮作所带来的经济效益与生态效益,并且通过国内外相关轮作制度的对比,为中国轮作产业的发展提供建议。结果显示,相比于连作,轮作在经济与生态方面都有着很高的效益。同时通过对比发现,中国目前的轮作体系与国外在指导思路、推广机制、补贴方式与监管措施上均有差异,在轮作发展过程中,中国仍存在诸多问题。结合国外的相关轮作经验,中国应该着手于制定科学的轮作计划、发展轮作的配套技术（如保护性耕作、覆盖作物、节水灌溉等）、加强轮作相关的宣传与推广、精准落实轮作政策同时按时进行轮作的合理评估与政策调整,进而完善中国的轮作体系,这对于在国内大规模开展轮作种植具有一定的指导意义。     

Relay-intercropped forage legumes help to control weeds in organic grain production

In organic grain production, weeds are one of the major limiting factors along with crop nitrogen deficiency. Relay intercropping of forage legume cover crops in an established winter cereal crop might be a viable option but is still not well documented, especially under organic conditions.Four species of forage legumes (Medicago lupulina, Medicago sativa, Trifolium pratense and Trifolium repens) were undersown in six organic wheat fields. The density and aerial dry matter of wheat, relay-intercropped legumes and weeds were monitored during wheat-legume relay intercropping and after wheat harvest until late autumn, before the ploughing of cover crops.Our results showed a large diversity of aerial growth of weeds depending on soil, climate and wheat development. The dynamics of the legume cover crops were highly different between species and cropping periods (during relay intercropping and after wheat harvest). For instance, T. repens was two times less developed than the other species during relay intercropping while obtaining the highest aerial dry matter in late autumn. During the relay intercropping period, forage legume cover crops were only efficient in controlling weed density in comparison with wheat sole crop. The control of the aerial dry matter of weeds at the end of the relay intercropping period was better explained considering both legumes and wheat biomasses instead of legumes alone. In late autumn, 24 weeks after wheat harvest, weed biomass was largely reduced by the cover crops. Weed density and biomass reductions were correlated with cover crop biomass at wheat harvest and in late autumn. The presence of a cover crop also exhibited another positive effect by decreasing the density of spring-germinating annual weeds during the relay intercropping period.     

不同种植模式对河北低平原区域地下水平衡和水分经济利用效率等的影响

河北低平原区是全世界地下水超采的主要地区,同时又是中国主要的粮食主产区。不同的种植模式对水资源利用和粮食安全生产起着非常重要的作用。为了探清河北低平原区不同种植模式对区域地下水平衡及水分经济利用效率等方面的影响,以河北低平原区沧州市为研究区域,通过利用实验结果及统计数据,对该区主要存在的一年两作、一年一作和两年三作的12种不同种植模式下的耗水、产量及对地下水的影响等进行了分析。结果表明：冬小麦—夏玉米一年两作的传统种植模式2年的产量最高(30000 kg/hm²),需水量也最大,达到1683 mm,但效益和水分利用经济效益最低[2.61元/(mm·hm²)],并且对地下水的影响最大;棉花—冬小麦—夏玉米的两年三作模式经济效益和水分利用经济效率最高,分别为15750元/hm²和12.2元/(mm·hm²);一年一作的种植模式对地下水的影响最小。因此,从该区域农业水资源可持续发展和粮食安全角度考虑,应该发展棉花—冬小麦—夏玉米的两年三作种植模式。     

蔬菜种植模式对涂地土壤性状及蔬菜连作障碍的影响

为探讨蔬菜种植模式和种植年限对蔬菜地土壤性状及蔬菜生长障碍发生的影响,在浙东滨海涂地区按蔬菜种植年限（5~10年和10~20年）和种植模式（水稻 蔬菜年内连作、露天蔬菜-水稻轮作、露天蔬菜、冬季大棚蔬菜 夏季露天蔬菜和常年大棚蔬菜）分组鉴定土壤质量与蔬菜地连作障碍,并与长期种植水稻等粮食作物的农田进行比较。结果表明：种植蔬菜后,土壤容重呈增加的趋势;与长期种植水稻的用地相比,露天蔬菜、露天蔬菜-水稻轮作和水稻 蔬菜年内连作有利于土壤结构的改善,但长期种植大棚蔬菜则可导致土壤结构的恶化。种植蔬菜后,土壤酸度增加,有机碳下降,磷素、氮素、有效钾和盐分明显增加,对大棚蔬菜地的影响比露天蔬菜地更为明显。土壤中磷素、氮素、有效钾的积累和土壤酸化随着蔬菜种植年限的增加而呈现增加的趋势;种植蔬菜也显著增加了土壤过氧化氢酶、磷酸酶、脲酶和脱氢酶活性。研究区内蔬菜地连作障碍类型主要有病害、地下虫害、土壤理化性质恶化和缺素等,其发生比例随蔬菜种植年限明显增加,由低至高依次为：水稻 蔬菜年内连作地<露天蔬菜-水稻轮作地<露天蔬菜地<冬季大棚蔬菜 夏季露天蔬菜地<常年大棚蔬菜地。研究认为,蔬菜与水稻轮作可减少蔬菜连作障碍的发生。     

秸秆还田对豆-稻-菜循环耕作模式下作物产量和土壤肥力的影响

豆-稻-菜循环耕作模式是中国南方地区最重要的轮作模式之一,但秸秆还田对该耕作制度下作物产量和土壤肥力的影响尚不明确。通过连续7年的田间定位试验（2009—2015年）,研究秸秆还田对豆-稻-菜循环耕作模式下作物产量和土壤养分状况的影响。结果表明：秸秆还田对浙江省豆-稻-菜轮作模式下作物产量的影响显著：与单施化肥相比,秸秆还田有效提高了水稻和小萝卜的产量,且水稻和小萝卜年均增产10%以上;此外,秸秆还田对豆-稻-菜循环种植区域土壤肥力也有较大影响：提高了土壤有机质、全氮、有效磷、速效钾含量和土壤pH值,此外,秸秆还田区域土壤全氮、有效磷和速效钾含量呈逐年增加趋势。由此可见,多熟制耕作制度下秸秆还田仍具有作物增产和土壤培肥作用,可作为耕地质量提升的有效手段长期实施。     

长期轮作连作对不同作物土壤磷组分的影响

对长期轮作连作条件下的大豆、玉米、小麦土壤磷组分进行研究,试验结果表明,供试土壤在不施肥情况下,土壤全磷以轮作区降幅最大,而土壤有效磷以小麦连作区降幅最大,土壤磷组分以大豆连作区土壤中的Ca2-P降幅最大;在施有机肥的情况下,土壤全磷以大豆连作区增幅最大,而土壤有效磷以轮作区增幅最小,土壤磷组分以轮作土壤中的Ca2-P增幅最大。     

Nutritional and mineral content of prickly pear cactus: A highly water‐use efficient forage,fodder and food species

Increased demand for food requires us to investigate livestock forage and fodder crops that can be grown over a wide range of locations where their cultivation will not compete with that of the food supply. A large portion of the southwestern United States consists of underutilized semi‐arid land. Crops typically used for livestock fodder or forage have high‐water demands that make them uneconomical or unsustainable for semi‐arid and arid regions. The growth rate and low‐input requirements of prickly pear cactus (Opuntia ficus‐indica) make it an excellent candidate for forage or fodder supplementation or replacement in these regions. Previous reports about forage quality data on Opuntia have been scattered across multiple locations, growing conditions and cultivars. Here, we report on the forage quality and mineral content of Opuntia ficus‐indica grown under both field and greenhouse conditions. Crude protein was 71 and 264 g/kg of dry mass for field and greenhouse conditions, respectively. Field‐grown plants showed higher acid and neutral detergent fibre content than greenhouse‐grown plants reflecting higher cellulose, hemicellulose and lignin accumulation. Nutritional values were also compared to requirements of cattle to determine what deficiencies might need to be addressed through supplementation. These data suggest that Opuntia can be used in combination with other feed sources to reduce the demand of resource‐intensive forage crops for raising livestock in dryland areas.     

Linkage analysis among loci for RAPDs, isozymes and some agronomic traits in Brassica campestris L.

Common bean, Phaseolus vulgaris L. is intercropped or relay cropped with maize in many Andean highlands of Colombia and Peru. Breeding beans for the target multiple cropping systems is essential for the development of productive and sustainable agriculture for the Andean smallholders. Outline of the breeding programme should follow the farming system approach with the establishment of on-farm trials and early farmers involvement. Bean breeding is oriented to minimize intercrop competition and to stabilize complementarity with maize. Genetic traits needed for improved varieties are divided as follows : traits not interacting with the cropping systems, traits specific to intercrops and traits related with socioeconomic and seed quality aspects. Screening, prebreeding and recombination nursery are better made under sole cropping while varietal improvement and on-farm trials are conducted under the target multiple cropping systems. Breeding schemes may involve recurrent, pedigree and bulk hybrid selection. The given application concerns the genetic improvement of P. coccineus, P. polyanthus and interspecific hybrids of P. vulgaris for both simultaneous and relay intercropping in Colombia and Peru. Earliness, cold tolerance, resistance to fungus diseases (mainly Ascochyta leaf blight and anthracnosis) and seed yield potential were the major objectives of the bean improvement programme. Priority has been given to the exploitation of the large diversity available in the secondary gene pool of common bean. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relay Cropping of Sorghum and Legume Shrubs for Crop Yield Improvement and Striga Control in the Subsistence Agriculture Region of Tigray (Northern Ethiopia)

Striga hermonthica is a major constraint in the subsistence agriculture regions of northern Ethiopia. Low soil fertility and overall environmental degradation has contributed to the build up of the parasitic weed infestation. Improved cropping systems have to be introduced to address the interrelated problems of Striga and soil fertility decline. Thus, relay cropping of sorghum with legume shrubs was investigated at two locations representing different environments. Results showed that the output of the improved cropping system was dependent on ecological endowments. Relay cropping led to significant improvement in yield at Sheraro, at the site with relatively better weather and soil conditions. The legume shrubs resulted in significantly lower sorghum yield in a dryland location (Adibakel). Overall Striga infestation declined over the 3‐year period; however, treatment differences were not apparent. Among the two legume shrubs, Sesbania sesban was better adapted to the dryland areas. Relay cropping could provide a viable option for farmers in both types of environments that are characterized by accelerated decline in natural resource base. However, it could mean compromising the yield of non‐fertilized sorghum in the interest of long‐term benefits of low incidence of Striga and more rewarding crop enterprise in dry areas.