Relations between summer crops and ground cover legumes in a subtropical environment 2. Effects of sorghum and sunflower on the growth of Vigna trilobata and Medicago scutellata

Vigna trilobata (L.) Verdc. is a low growing legume with potential as a ground cover for controlling soil erosion in cropping lands of the subhumid/semi-arid subtropics of northern Australia. When it was grown beneath sorghum (Sorghum bicolor (L.) Moench) and sunflower (Helianthus annuus L.) crops under well-watered conditions on a vertisol in southern Queensland it decreased their yields by about 20% in the first season. This paper reports the effects of competition from crops sown at a normal dryland density or at half the normal density on its growth.V. trilobata sown in pure stand in October produced 531 g m⁻² of above-ground dry matter, and sown in January produced 323 g m⁻², by the time the grain crops sown at the same time were mature. Yields under mature sorghum sown at the normal density (10 plants m⁻²) in October and January were 38% and 35% respectively of those from pure stands of ground cover sown at the same time. Under sunflower at the normal density (5 plants m⁻²), corresponding values were 42% and 22%. The decrease in dry matter yield attributable to competition for water, nutrients and/or radiation from the main crops was proportional to the decrease in intercepted radiation.V. trilobata responded to shade in several ways, but a substantial increase in specific leaf area, together with some additional partitioning of dry matter to leaf, was sufficient to ensure that its leaf area index under crops was similar to that in pure stands.Seed yields of 116 and 84 g m⁻² were obtained from pure stands of V. trilobata sown in October and January respectively. However, seed yields under crops sown at the normal density were only 4–18% of those measured in pure stands. Seed size was not affected by treatment.We conclude that, under well-watered conditions in southern Queensland, V. trilobata grown as a ground cover under crops of sorghum and sunflower should be able to produce sufficient biomass to decrease soil erosion, and also produce sufficient seed for regeneration in successive seasons. Its growth and suitability are also briefly compared with those of an alternative ground cover legume, Medicago scutellata (L.) Mill. (snail medic).     

Relations between summer crops and ground cover legumes in a subtropical environment 3. Soil water use under sorghum and sunflower

Vigna trilobata (L.) Verdc. and Medicago scutellata L. are short herbaceous legumes that help to reduce soil erosion when grown in association with row crops in the sub-humid/semi-arid subtropics. Soil water use and root distribution beneath sorghum (Sorghum bicolor (L.) Moench) and sunflower (Helianthus annuus L.) with and without V. trilobata were measured on a vertisol in South East Queensland. Sorghum was sown in October and January at densities of 10 and 5 plants m⁻² and sunflower at densities of 5 and 2.5 plants m⁻². V. trilobata seed was broadcast at 150 seeds m⁻². Pure stands of V. trilobata and M. scutellata were also sown.Soil profiles were uniformly wet to at least 2 m depth at each sowing date and remained so for the first 40 days of each growth cycle. Thereafter profiles dried rapidly over the next 40 days, providing opportunities for assessing soil water use. Subsequent rain restored and sustained profile water content until crop maturity.Undersown V. trilobata hastened soil drying, resulting in the extraction of 21 mm more water by maturity of the October sown crops. In pure stands, V. trilobata extracted water at the same rate as sunflower from the top 1.0 m of the soil profile, but not from the deeper layers. However, pure stands of M. scutellata extracted much less soil water than V. trilobata, with negligible extraction from below 0.8 m. Sunflower extracted 48 mm more water than sorghum in the January sowing because it had more roots and extracted more water from below 1.4 m.The capacity of V. trilobata to grow deep roots allows it to compete strongly for soil water and decrease yield of the main crop. Thus, a shallow-rooting plant would be preferred as a ground cover.     

夏播条件下向日葵光合性能与杂交种产量的关系

夏播条件下，向日葵群体的叶面积指数因杂交种不同变幅较大，辽嗑杂1号最大叶面积指数为3．87，而辽葵杂3号最大叶面积指数仅为2．23。向日葵杂交种的平均净光合效率为8．97g/m^2.d，变幅为7.57-11.13g/m^2.d。各杂交种的光合势与生物产量和籽实产量呈显著正相关。     

The type of relationship between plant density and reproductive yield of cotton in a subtropical environment

The type of relationship between yield of seed-cotton and plant populations ranging from 1 to 21 plants per m², was investigated in several cultivars of theGossypium hirsutum L. andG. barbadense L. species, under irrigated and dryland conditions over several seasons, localities and dates of sowingThe simple and quadratic equations and the simplified exponential reciprocal expression, as proposed by Holliday and by Bleasdale, respectively, similarly and very adequately described the investigated relationship at the plant level over the whole range of populations tested. The -constant of Bleasdale's equation exhibited a high degree of cultivar specificity. In the dryland experiments its intercultivar values were linearly positively correlated with estimated maximum yields of seed-cotton per unit area.At the unit area level the estimated relationship was of two types: asymptotic and parabolic. It actually was dynamic in type and assumed transient forms throughout the boll-opening period, generally being parabolic at first and asymptotic at later stages. The ultimate response type exhibited a great intercultivar variability and cultivar constancy, being asymptotic in Acala 4–42 and Acala 1517 C and parabolic in Coker 100 W and in two Pima-type cultivars. Environmental growth factors enhancing prolific vegetative growth during the reproductive phase deviated from a specific asymptotic response pattern to a parabolic type.The estimated optimum plant density of the parabolic response types ranged between 4.0 and 5.7 plants per m². This range was extended by an average of 0.7 plants per m² when 5% of the maximum yield, estimated for asymptotic types, was discounted. The top estimated maximum yields were 1940 and 4600 kg seed-cotton per ha in the dryland and irrigated environments, respectively.

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Zusammenfassung Es wurde die Beziehung zwischen dem Ertrag bei Baumwolle und der Bestandsdichte — zwischen 1 bis 21 Pflanzen pro m² — an verschiedenen Sorten vonGossypium hirsu tum L. undG. barbadense L. in Trockengebieten mit und ohne Bewässerung über mehrere Vegetationszeiten, an verschiedenen Standorten und bei unterschiedlichen Aussaatterminen untersucht.Durch die einfache und quadratische sowie die vereinfachte exponentiel-reziproke Gleichung, wie von Holliday bzw. von Bleasdale vorgeschlagen, werden auf sehr einfache und ausreichende Weise die untersuchten Beziehungen im Bereich der Einzelpflanze innerhalb der geprüften Population beschrieben. Die -Konstante der Bleasdalschen Gleichung weist eine hohe Sortenspezifität auf. Bei den Dürre-Versuchen bestand bei den Werten zwischen den Sorten eine lineare positive Korrelation mit den errechneten Höchsterträgen der Baumwollsamen pro Flächeneinheit.Bezogen auf die Flächeneinheit waren die Beziehungen von zweierlei Typus: asymptotisch und parabolisch. Tatsächlich waren sie dynamischer Natur und lassen während der Kapselöffnungsperiode Übergangs-Formen vermuten; im allgemeinen waren sie zunächst parabolisch und in späteren Stadien asymptotisch. Im Endergebnis stellte sich zwischen den Sorten eine große Variabilität und innerhalb der Sorten eine Stabilität heraus. Diese war asymptotisch bei Acala 4–42 und Acala 1517 C und parabolisch bei Coker 100 W und bei zwei Pima-Typ-Sorten. Umweltbedingungen jedoch, die das vegetative Wachstum währed der reproduktiven Phase begünstigen, wandeln eine typisch asymptotische Beziehung in eine parabolische um.Der errechnete optimale Pflanzenbestand der parabolischen Beziehungstypen schwankte zwischen 4,0 und 5,7 Pflanzen pro m². Dieser Bereich erweitert sich um durchschnittlich 0.7 Pflanzen pro m², wenn 5% des errechneten Höchstertrages für die asymptotischen Beziehungstypen abgezogen werden. Der höchste errechnete Maximal ertrag von Baumwollsamenfasern war 1940 kg/ha für die Dürre- und 4600 kg/ha für die bewässerten Versuche.

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Résumé Le type de relation entre le rendement en coton-graine et la densité de population fut étudié pour des populations variant entre 1 et 21 plantes per m², sur plusieurs variétés de coton deGossypium hirsutum L. etG. barbadense L., en culture irriguée et en culture sèche, pendant plusieurs saisons en différentes localités et dates de semis.L'équation exponentielle simplifiée ainsi que l'équation reciproque simple et quadratique proposées par Bleasdale et par Holliday, respectivement, décrivent convenablement les relations étudiées pour l'ensemble des densités testées. La constante de l'équation de Bleasdale a montré une forte spécificité varietale. Dans les essais en culture sèche, il y avait une corrélation lineaire positive entre les valeurs intervariétales et les rendement maximum respectifs, éstimés en coton-graine par unité de surface.Au niveau de l'unité de surface, les relations estimées étaient de deux types: asymptotique et parabolique. En fait elles étaient de type dynamique et prenaient des formes transitoires pendant la période d'ouverture des capsules. En général, elles étaient de type parabolique au début et asymptotique plus tard. Le type final de réponse a montré une grande variabilité intervariétale et une stabilité variétale; il était asymptotique pour les variétés Acala 4–42 et Acala 1517C et parabolique pour Coker 100 W et deux variétés de type Pima. Les facteurs de croissance qui ont induit une végétation prolifique pendant le stade de reproduction, ont fait dévier un réponse de type asymptotique en type parabolique.La densité optimale de plantes éstimée pour les résponses de type parabolique variait entre 4.0 – 5.7 plantes par m². Ces valeurs étaient accrues de 0.7 plantes par m² lorsqu'on tenait compte des 5% du rendement maximum éstimé pour les types asymptotiques. Les estimations les plus élevées des rendements maximum en cotongraine se chiffraient a 1940 kg et 4600 kg par ha, pour la culture sèche et irriguée, respectivement.

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Contribution from the Agricultural Research Organization, The Volcany Center, Bet Dagan, Israel. 1972 Series, No. 2242-E.     

Effect of leguminous cover crops on the growth and yield of abaca (Musa textilis Nee)

This 6-year study was conducted to determine the effect of three leguminous cover crops on the growth and yield of abaca and measure the contribution of the cover crops in restoring and conserving the inherent fertility of the soil. In the later years of the experiment (2000–2002), cover cropping with Desmodium ovalifolium and Calopogonium muconoides significantly increased the stalk and leaf lengths, and stalk circumferences. Fiber yield also significantly increased in plots with C. muconoides as plant cover. Among the cover crops used, D. ovalifolium showed the highest biomass production of 8.9 and 8.6 tons/ha in the 1999 and 2000 data gathering, respectively. Highest N content in the tissues among the covercrops used was noted in C. muconoides. Accumulation of soil organic matter was observed in plots with D. ovalifolium while higher total N in the soil was found in plots cover cropped with C. mucunoides. Among the cover crops tested, Centrocema pubescens is not an effective companion crop for abaca. However, lower erosion rates were noted in plots planted with cover crops.     

Effects of temperature and photoperiod on flowering time of forage legumes in a Mediterranean environment

Flowering time plasticity is a commonly occurring adaptive characteristic of fodder crops, including legumes, in arid and semiarid environments of the Mediterranean regions. Time of flowering is mainly influenced by genotype, temperature and photoperiod. Field experiments were carried out at Foggia (southern Italy) during successive growing seasons (from 8 to 16 growing cycles according to species) to study the relation among air temperature, photoperiod and duration of the morphological development of flowering in eight forage legume species: sulla (Hedysarum coronarium L.), sainfoin (Onobrychis viciifolia Scop.), pea (Pisum sativun L.), berseem clover (Trifolium alexandrinum L.), Persian clover (Trifolium resupinatum L.), faba bean (Vicia faba L.), common vetch (Vicia sativa L.) and hairy vetch (Vicia villosa Roth). Time to reach 10% flowering (EF) and 100% flowering (FF) were recorded. Rate of progress to flowering, defined as the inverse of time from sowing to EF and FF, was related to mean daily temperature, or to both mean daily temperature and mean photoperiod. Using the linear equations, the thermal time requirements (T_t) and the base temperature (T_b) expressed as heat units were determined by the x-intercept method for both EF and FF stages. Evaluation of flowering time was also based on days after planting (DAP), day of year (DOY) and on a photothermal index (PTI). For all species, a significant negative correlation (P ≥ 0.01) was found between planting date (PD) and DAP whereas PTI showed a significant negative relationship (P ≥ 0.05) only for faba bean, pea, berseem clover and common vetch. In sainfoin, sulla and berseem clover, the rate of progress to flowering was affected significantly (P ≥ 0.05) by both mean temperature and photoperiod. The T_t requirements to reach the EF and the FF stage ranged from 871 to 1665 °C day and from 1043 to 1616 °C day, respectively, for the studied species. Both phenological stages considered depended upon accumulated thermal time above a species-specific base temperature. Furthermore, in all legumes the onset of flowering only occurred when dual thresholds of a minimum T_t and a minimum photoperiod were reached, which were specific to each species.     

Relationships between ground cover,intercepted solar radiation,leaf area index and infrared reflectance of potato crops

Summary In field trials with potato several methods determining the proportion of intercepted solar radiation by the crop were compared. Non-destructive measurement of the proportion of ground cover with the aid of a grid correlated well with the proportion of intercepted photosynthetically active radiation as measured with a tube solarimeter and with the leaf area index. Measurement of the infrared reflectance of the crop proved to be an efficient and objective method to show differences between treatments. Moreover, it showed a good correlation with ground cover and radiation interception until full closure of the canopy. Percentage ground cover is useful for assessing intercepted solar radiation and leads to fewer errors in calculation of efficiency of conversion into dry matter than the other methods.     

不同作物茬口对冬油菜养分积累和产量的影响

为探究关中平原地区不同作物茬口对冬油菜养分积累和产量的影响,通过两年田间试验,研究分析不同茬口,包括休闲茬口(FW)、大豆茬口(SW)、毛苕子茬口(HW)和玉米茬口(MW)对冬油菜土壤养分含量、地上部干物质积累、分配和氮磷养分吸收积累、产量构成因素以及产量的影响,筛选冬油菜生产适宜的前茬作物,为加强冬油菜生产,提高土地...     

大垄垄上行间覆膜对土壤水分、温度及大豆产量形成的影响

为探讨大豆大垄垄上行间覆膜的增产机制,以垦丰15、垦丰16两个大豆品种为材料,在田间进行大垄垄上行间覆膜和不覆膜处理,研究了覆膜阶段土壤水温状况及植株形态指标变化。结果表明,行间覆膜对土壤的增温作用在大豆生育前期内呈“U”型变化,在增加耕层含水量、改善根系生长环境方面起到重要作用,覆膜大豆产量明显高于对照。     

Effect of nitrogen supply on the comparative productivity of maize and sorghum in a semi-arid tropical environment III. Grain yield and nitrogen accumulation

Differences in grain yield and grain nitrogen content due to variable N supply in maize and sorghum, grown under irrigation in the semi-arid tropics, were associated with differences in their rates of accumulation and in the extent of mobilization of pre-anthesis dry matter and N. Increases in harvest index, nitrogen harvest index, and grain size during grain-filling were essentially linear, and the rates were constant under variable N supply. Differences in harvest index at maturity at different levels of applied N were small relative to differences in biomass and grain yield, and differences in grain size were small relative to differences in grain number. In effect, variation in harvest index and grain size at maturity was associated with variation in the length of the effective grain-filling period. Nitrogen supply had a greater effect on the effective duration of grain-filling in maize than in sorghum.Maximum grain yields at high levels of N uptake were greater in maize (10.0 t ha⁻¹ at 15.5% moisture) than in sorghum (7.2 t ha⁻¹ at 14% moisture). These differences were related to differences in biomass production, rate of increase in harvest index and the effective duration of grain-filling. The rate of increase in harvest index was greater, but biomass production was less and the duration of grain-filling was shorter, in sorghum than in maize.     

氮素用量对油葵氮磷钾养分吸收积累及产量的影响

为研究氮素对油葵植株氮磷钾养分积累和产量的影响,采用田间试验方法,在宁夏中部干旱带同心地区进行了油葵肥料试验。结果表明,在供试土壤条件下,氮磷钾养分积累均呈“S”型曲线,符合Logistic方程。施氮量在6～18kg/667m2之间时,均促进油葵对氮磷钾的吸收。其中,100kg籽粒所需N、P2O5、K2O范围分别是5.68～6.19kg、4.32～4.62kg、14.82～21.20kg,三要素（N:P2O5:K2O）平均比例为1:0.76:2.93。成熟期时,氮磷钾总积累量均是N2P2K2处理最高,分别达到47.99g/株、35.45g/株、152.30g/株。当施氮量为10.53kg/667m2时,产量达最高值221.02kg/667m2,最佳经济效应施氮量为9.54kg/667m2,最佳经济效益产量为220.48kg/667m2。     

Effects of planting date on sugar and ethanol yield of sweet sorghum grown in Arizona

Sweet sorghum (Sorghum bicolor (L.) Moench) is an annual crop currently being investigated for biofuel production in the arid southwest United States (U.S.). Sweet sorghum is an ideal candidate because it can be grown under reduced inputs (water, fertilizer) and responds more efficiently to stresses than traditional crops. Many varieties have been bred for high sugar, syrup, and forage production, but much biodiversity still remains to be utilized.Studies performed in 2006 and 2007 found that high biomass and percent juice extracted were the best predictors of potential ethanol yield per area. This investigation was undertaken to determine what effects planting dates have on overall sugar and predicted ethanol yields.Four varieties (Dale, M81E, Theis, and Topper) were planted in April, May, June, and July of 2008. They were harvested at physiological maturity, with dates ranging from August 26 to December 2. Biomass, juice weight, and Brix of the juice were recorded in the field. Samples were analyzed in the laboratory by High Performance Liquid Chromatography (HPLC) for fructose, glucose, and sucrose.Theoretical ethanol yields were calculated based on biomass, juice weight, and percent sugar. These were compared to actual yields obtained from laboratory-scale fermentations of the harvested juice, which ranged from 7.4% to 11.2% (58.1-88.6 g L⁻¹). Since our predictive model uses the maximum conversion rate of sugar to ethanol and this was not reached in the lab, the predicted yields were always higher than the actual yields. However, the model can be a useful tool for estimating ethanol yield per area.Total sugars and predicted ethanol production were influenced by planting date, but the degree of the effects depended on the cultivar planted. Overall a May planting date at this location is preferable due to consistently higher values for the yield components analyzed, and Theis is not recommended due to its high susceptibility to heat. Sweet sorghum juice has been successfully fermented into ethanol, which indicates this crop may be able to play a transitory role in the emerging biofuel market.     

Relationships between disease levels on seed tubers,on crops during growth and in stored potatoes. 1. Introduction and black scurf

Summary In the Introduction general methods are described to assess inocolum of several potato diseases on seed tubers; on the progeny tubers during growth, at harvest and after 4 different storage regimes. Assessments were made in up to 26 commercial King Edward crops in each of 5 years, and up to 13 crops from ‘healthier’ seed, derived from stem cuttings, in 4 years. Results are reported from the work on black scurf (Rhizoctonia solani). Stem canker incidence was more closely related to the incidence of sclerotia on seed tubers than was the frequency ofRhizoctonia hyphae on growing tuber surfaces. Incidence of sclerotia on stored tubers was better related to the amount of surface colonization during growth than that of stem canker. Assessments on harvested and stored progeny of ‘healthier’ seed were correlated with those on adjacent commercial crops, indicating spread or, more likely, a common source of inocolum.

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Zusammenfassung In einer Studie wurde das Auftreten verschiedener Krankheiten im Erntegut der Sorte King Edward untersucht, die zwischen 1971 und 1975 in dem Fenland-Gebiet von Ostengland gewachsen war. Jedes Jahr wurden zwischen 15 und 26 Proben von Marktware untersucht und zwischen 1972 und 1975 wurde ‘gesünderes’ Pflanzgut (das von Stecklingen abstammte) auf dem selben Feld wie einige der Proben der Marktware gepflanzt (Tab. 1). Die Feststellung des Inokulums oder der Krankheit wurde an Pflanzgutproben, an Pflanzen w?hrend des Wachstums und an Knollen der Nachkommenschaft zum Erntezeitpunkt genommen. Geerntete Knollen wurden auch einheitlich verletzt und bei 3°C und 10°C gelagert, mit oder ohne zweiw?chige Wundheilperiode bei 15°C. Nach 3–4 Monaten erfolgte die Feststellung des Krankheitsbefalls. Die Auswertung der Ergebnisse wurde durch Regression zwischen allen m?glichen Paaren der Ergebnisse für jede Krankheit durchgeführt, wobei jedes Jahr sowohl getrennt als auch alle Jahre kombiniert genommen wurden. Die Regressionen wurden auch für das ‘gesündere’ Erntegut, das mit der entsprechenden Marktware übereinstimmte, durchgeführt. Rhizoctonia solani wurde auf dem Pflanzgut und auf dem nachfolgenden Erntegut als Prozentbefall mit Sklerotien angegeben, der Myzelbelag auf der Knollenoberfl?che rund um die Augen wurde durch mikroskopische Untersuchung von Augenstücken festgestellt und das Auftreten von Weisshosigkeit wurde w?hrend des Wachstums gesch?tzt. Das durchschnittliche Auftreten von Inokulum oder Krankheitsbefall auf Marktware (Tab. 2) zeigte, dass 1975 der Befall der Augen am h?ufigsten war und dass 1971 und 1975 der Krankheitsbefall im Lager am gr?ssten war. ‘Gesünderes’ Pflanzgut hatte gew?hnlich weniger Pocken als der Durchschnitt der Marktware aber der Befall der Augen der Tochterknollen w?hrend des Wachstums und zur Ernte war gr?sser und auf gelagerten Knollen wurden mehr Pocken gefunden (Tab. 3). Unter den nassen Erntebedingungen 1974 traten mehr Pocken auf den bei 10°C gelagerten Knollen auf als auf den bei 3°C, aber es ergaben sich keine Unterschiede in anderen Jahren. Die Signifikanz der Regressionen zwischen den Erhebungen, die nach verschiedenen Methoden oder zu verschiedenen Zeitpunkten (Tab. 4) gemacht wurden und Diagramme der signifikanten Regressionen in einzelnen Jahren (Abb. 1) zeigten, dass makroskopische und mikroskopische Bestimmungen auf dem Pflanzgut (Abb. la) und Befall der Schale rund um die Augen und Weisshosigkeit w?hrend des Wachstums (Abb. 1d) in allen Jahren miteinander verbunden waren. Die Weisshosigkeit stand h?ufiger in Beziehung zum Ausmass des Pockenbesatzes des Pflanzgutes (Abb. 1b) als der Befall der Augen (Abb. 1c). Dies führt zu der Annahme, dass die meisten Stengelinfektionen vom Inokulum des Pflanzgutes ausgingen w?hrend der Befall der Schale rund um die Augen auch durch andere Inokulumquellen (z.B. den Boden) beeinflusst wurden. Der Befall der Augen zur Ernte stand in jedem Jahr in Beziehung zum Befall w?hrend des Wachstums (Abb. 1e) und in 4 Jahren stand das Ausmass des Pockenbesatzes auf gelagerten Knollen in Beziehung zum Augenbefall w?hrend des Wachstums und zur Ernte (Abb. 1f und 1g). Die mikroskopische Untersuchung w?hrend des Wachstums gibt daher eine vernünftige Sch?tzung des Krankheitsbefalls im Lager. Wenn die Erhebungen des ‘gesünderen’ Pflanzgutes mit denen gleichartiger Marktware verglichen wurden (Abb. 2), ergaben sich signifikante Verbindungen für den Augenbefall w?hrend des Wachstums und zur Ernte, für den Pockenbesatz auf gelagerten Knollen, aber nicht für die Weisshosigkeit. Dies weist auf eine Verbreitung des Inokulums, auf die Bedeutung der allgemeinen Bodenbeschaffenheit oder, wahrscheinlicher, eine gemeinsame Quelle des Inokulums, vielleicht im Boden hin.

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Résumé Une étude a été entreprise sur la variété King Edward, pour conna?tre l'incidence de différentes maladies. Cette étude s'est déroulée de 1971 à 1975 dans la région de Fenland en Angleterre Orientale. Chaque année, on a examiné entre 15 et 26 lots commerciaux; entre 1972 et 1975 des semences ‘plus saines’ (provenant de bouturage) ont été plantées dans le même champ que les lots commerciaux (tableau 1). Les estimations d'inoculum ou de maladie ont été faites sur des échantillons de tubercules de semence, sur des plantes en course de croissance, et sur les tubercules-fils à la récolte. Les tubercules-fils récoltés ont été également endommagés de manière uniforme et conservés à 3°C et 10°C, avec ou sans période initiale de cicatrisation des blessures de 2 semaines à 15°C. L'incidence de la maladie a été estimé après 3–4 mois. Les résultats ont été analysés par régressions entre toutes les paires possibles de données pour chaque maladie, en prenant séparément chaque année et toutes les années combinées. Les régressions ont aussi été faites à partir des estimations provenant des lots ‘plus sains’, et des estimations correspondantes provenant des lots commerciaux adjacents. L'estimation du rhizoctone a été faite par notation du pourcentage de sclérotes sur les tubercules de semence et sur les tubercules-fils en conservation. La colonisation de la peau, autour des yeux, par du mycelium deRhizoctonia solani a été déterminée par examen microscopique au niveau des yeux. L'incidence des nécroses sur tige a été estimée au cours de la croissance. L'incidence moyenne de l'inoculum ou de la maladie sur les lots commerciaux (tableau 2) a montré que la colonisation du tubercule au niveau des yeux a été plus fréquente en 1975, et que l'incidence de la maladie en cours de conservation a été plus forte en 1971 et 1975. Les tubercules de semence ‘plus saine’ ont eu moins de rhizoctone que la moyenne des lots commerciaux, mais la colonisation des tubercules-fils, au niveau des yeux pendant la période de croissance et à la récolte a été plus grande. On a également trouvé plus de sclérotes sur les tubercules conservés (tableau 3). En 1974, les conditions de récolte étant plus humides, il y avait plus de sclérotes sur les tubercules conservés à 10°C que sur ceux conservés à 3°C; mais, pour les autres années, il n'y avait aucune différence entre les traitements. La signification des régressions entre les estimations faites par différentes méthodes ou à différentes époques (tableau 4), et les graphiques relatifs aux régressions significatives pour chacune des années (Fig. 1) ont montré qu'il y avait toutes les années des relations entre les estimations macroscopiques et microscopiques sur la semence (Fig. 1 a), la colonisation de la peau autour des yeux et les nécroses des tiges en cours de végétation (Fig. 1d). Les nécroses sur tige étaient plus fréquemment en rapport avec les sclérotes portés par la semence (Fig. 1b) qu'ac la colonisation au niveau des yeux du tubercule (Fig. 1c). Les auteurs suggèrent donc que la plupart de la contamination de la tige provient de l'inoculum présent sur le tubercule de semence mais que la colonisation de la peau autour des yeux est également influencée par d'autres sources d'inoculum (par ex. le sol). Chaque année, la colonisation des yeux à la récolte était en relation avec celle en cours de croissance (Fig. 1c). Pour les 4 années, la quantité de sclérotes sur les tubercules conservés était en rapport avec l'incidence de la colonisation au niveau des yeux pendant la croissance et à la récolte (Figures 1f et 1g). Les estimations faites en cours de croissance donne donc une estimation correcte de l'incidence de la maladie en cours de conservation. Quand on compare les résultats des lots ‘plus sains’ et ceux des lots commerciaux adjacents, il y a des associations significatives pour la colonisation des yeux durant la croissance et à la récolte, pour les sclérotes sur les tubercules conservés, mais pas pour les nécroses sur tige. Ceci suggère la dispersion de l'inoculum, l'importance des conditions de sol ou plus vraisemblablement la présence d'une source commune d'inoculum au niveau du sol.

     

Genotype by environment interaction and indirect selection for yield in sunflower: I. Two-mode pattern analysis of oil and biomass yield across environments in Argentina

A reference set of 10 sunflower hybrids was evaluated in 21 subtropical (northern), temperate (central), and managed environments of Argentina, to identify patterns of genotype-by-environment interaction and opportunities for indirect selection. Pattern analyses showed that the average genotypic discrimination effects of the central and northern regions for oil yield are strongly orthogonal. Photoperiod and minimum temperature would be partially underlying the observed interactions. These patterns are repeatable over seasons, which suggests that central and northern regions are different mega-environments and that selection for specific adaptation to each region would result in a faster genetic progress than selecting for wide adaptation to both regions. Cluster analysis revealed three genotypic groups: northern, central and broadly adapted. All central environments discriminated among genotypes in a similar fashion; discrimination in northern environments was more divergent across years and locations. Late planting dates in a central location associated positively with the northern environments. This represents an opportunity for indirect selection for the northern region from the breeding program headquarters in central Argentina. When photoperiod was extended to 15.5 h in these trials, genotypes exhibited responses similar to those of normal planting dates in central environments, indicating that photoperiod could be a central factor underlying this association. Analysis of specific genotype responses to photoperiod in terms of oil yield showed that these involved traits or processes distinct from time to flowering. Pattern analyses of physiological determinants and components of yield revealed the existence of different specific genotype responses to specific environmental challenges within the same genotype group.     

Persistence of tall fescue in a subtropical environment: tiller survival over summer in response to flowering control and nitrogen supply

Enhancing pasture persistence is crucial to achieve more sustainable grass‐based animal production systems. Although it is known that persistence of perennial ryegrass is based on a high turnover of tillers during late spring and summer, little is known about other forage species, particularly in subtropical climates. To address this question, this study evaluated survival of grazed tall fescue tillers growing in a subtropical climate. We hypothesized that hard tactical grazing during winter to remove reproductive stems (designated as ‘flowering control’), and nitrogen fertilization in spring, would both improve tiller survival over summer, and thus enhance tiller density. This was assessed in two experiments. In both experiments, few tillers appeared during late spring and summer and so tiller density depended on the dynamics of vegetative tillers present in the sward in spring. In Experiment 2, flowering control and nitrogen fertilization both enhanced the survival of that critical tiller cohort, but the effects were not additive. Responses were similar but not statistically significant in Experiment 1, which had a warmer, drier summer and lower overall survival rates. Unlike grasses in temperate environments, persistence of tall fescue in this subtropical site appeared to follow a ‘vegetative pathway’; i.e., new tillers were produced largely in autumn, from vegetative tillers that survived the summer.     

Relation between seeding times and stem yield of sorghum in cold region in Japan

The seeding time is an important factor affecting the process of stem yield. Nevertheless, details related to the optimum seeding time to maximize the stem yield of sweet sorghum have not been studied. This study elucidated information necessary to ascertain the optimum seeding time to obtain the maximum stem yield. We conducted an examination with three seeding times at intervals of two weeks, ranging from late May to mid-June for four years during 2009–2012, and we analyzed the relation between seeding times and stem yield based on internode characteristics of stems using two sorghum cultivars with different maturity: ‘Kazetachi’ and ‘Wray’. Differences were observed in the respective relations between the seeding times and the stem yields. For Kazetachi, the dry matter yield increased with the earlier seeding time. Thus, to expand the growing period, an earlier seeding time with good establishment is better. For Wray, a cultivar that can grow to heading in the Tohoku region, the stem dry weight was greater by seeding in early June. For cultivars such as Wray with a sufficient growing period in a given region, the optimum seeding time to obtain stable higher stem yield existed and the cultivars should be seeded when they could grow under good weather conditions at the critical time strongly influences growth.     

Double cropping of potatoes in a semi-arid environment: the association of ground cover with tuber yields

Summary The association of ground cover and ground cover duration with fresh- and dry-weight potato tuber yields in a semi-arid Mediterranean climate, was investigated. Cultivars of different maturity classes were tested under the contrasting climatological conditions of the spring and autumn seasons. The correlation coefficients of ground cover (GC) and ground cover duration (GCD) with fresh- and dry-weight tuber yields were lower for the autumn than for the spring season. In both seasons, high yields were positively correlated with high GCD. However, variation in tuber yields was evident in cultivars with similar GCD, indicating the involvement of factors other than ground cover and light interception in tuber yield. This investigation was supported by a grant from the Ministry of Foreign Affairs, Technical Assistance Department, Netherlands.     

不同播期对夏大豆南豆12产量和品质的影响

不同播期对夏大豆产量和品质的影响很大,结果表明,夏大豆晚熟类型品种南豆12六月上旬为高产播期,产量达181．5kg／667m^2,6月上旬至6月下旬为适宜播种期;5月23日为优质播期,蛋白质含量最高,达51．78％;总品质最好,达69．58％。夏大豆在适宜的播种期范围内适当早播有利于获得高产优质。