Competition between lupin (Lupinus angustifolius L.) and great brome (Bromus diandrus Roth.): development of leaf area, light interception and yields

Great brome (Bromus diandrus) is a common weed in wheat and can be expected as a weed in lupin crops (Lupinus angustifolius L.), particularly those in rotation with wheat. Although chemical control of brome in lupin is available, those plants escaping control compete with the lupin. This competition has been investigated by comparing the growth of lupin (cv. Yandee) in monoculture with its growth in the presence of 2 densities of brome, and with the growth of brome in monoculture. Each of the 4 treatments was grown with high and low fertiliser applications, to see how the competition was modified by nutrient availability. Water was not limiting. Daily measurements were made of lupin growth rates and the development of leaf area, and light interception and radiation use efficiencies were calculated (g DM assimilated per MJ intercepted photosynthetically active radiation). Radiation use efficiency changed with the phase of development of lupin, increasing to over 3 g/MJ at 95 days after sowing. It was higher in the high fertiliser treatments and in the presence of brome, particularly before 95 days after sowing. Changes in unit leaf rate (i.e. net assimilation rate) of lupin due to brome were small, but these, and changes in radiation use efficiencies, may have played a minor role in the depression of crop growth rates, more important during early lupin growth than later when leaf area indices had reached >15% of their maximum values. Depressions of the crop growth rate of lupin caused by the presence of brome were linearly related to changes in leaf area indices of lupin. The decrease in lupin seed yield per plant was due to a decrease in pod number per plant, not to a change in the number of seeds per pod or single seed weight. The number of pods was linearly related to the number of axes per plant (i.e. branches plus main stem)

A model to predict growth and yield of sunflower

We have developed further a preliminary model (2) which simulates the growth, development and yield of sunflower cv. Hysun 30. The inputs needed are maximum and minimum daily temperatures, daily irradiance, plant population density, and date and latitude of sowing. The developmental phases of the crop (emergence, completion of floret initiation, first anthesis and physiological maturity) are calculated from daylength and temperature (1,6). Estimates of the areas of individual leaves are generated (5). These are modified by leaf N concentration at floret initiation and population density (affecting the rate of leaf expansion) and leaf position (affecting the duration and rate of leaf expansion). Leaf area per plant is also modified by temperature (affecting leaf number). The progress of leaf senescence in sunflower needs more investigation but in the model it starts at full anthesis with the rate being constant over time and scaled according to leaf N status and population density. The accumulation of shoot dry matter is derived as a function of incident radiation, canopy light interception and the efficiency of conversion of energy to dry matter. The latter is temperature dependent (7)..

A model to simulate the development, growth and yield of irrigated sunflower

A simulation model of the development, growth and yield of sunflower cv. Hysun 30 is presented. In the model, crop growth rate is a function of radiation use efficiency, incident radiation, the canopy extinction coefficient and leaf area index. The radiation use efficiency of a sunflower canopy was measured and found to change during the growth of the crop. It is higher after floret initiation than before, and reaches a maximum at anthesis. The changing radiation use efficiency has been incorporated into the model. The leaf area index each day is a function of the number of leaves produced and the rate and duration of expansion of each leaf. A nitrogen and plant population factor modulates crop growth through its effect on the expansion rate of each leaf and the rate of leaf senescence after anthesis. In this way the nitrogen concentration in leaves at floret initiation and population density affect the dry-matter accumulation by the crop. Crop dry matter at the end of floret initiation and at physiological maturity are used to calculate the components of yield from relationships previously demonstrated in greenhouse experiments. The mean daily temperature affects the rate of leaf production and the radiation use efficiency, as well as determining the time of phenological stages through thermal time. Although the model was developed for the hybrid Hysun 30, it has been extended to some other hybrids by changing the size and activity of the generative area producing florets in the floral meristem. The simulated yields of four hybrids are close to the measured yields of irrigated crops

Selection for bulb maturity in onion Seleção para maturidade de bulbos em cebola

It is possible to produce onions (Allium cepa) all over the year in Brazil, but most of the Brazilian cultivars have poor quality bulbs, a fact that favours onion imports from Argentina, a producer of Valenciana type cultivars that does not bulb in Brazil, but please Brazilian consumers. To study the effect of selection for bulb maturity, seventeen half sib progenies selected for early maturity and twenty five for late maturity, from the intervarietal triple cross [Crioula x (Pira Ouro x Valenciana Sintetica 14)] were grown, along with the triple cross itself and the cultivars Pira Ouro (short-day), Crioula (intermediate-day) and Armada (long-day). A total of forty six treatments were tested in a randomized block design with three replications of 32 plants per plot. The progenies selected for earliness had cycles from 67 to 83 days, whereas those selected for lateness had cycles of 85 to 103 days. This difference was evident when comparisons were made for the percent thick neck bulbs, which varied from 0 to 6.2% and from 8.1 to 59.8% for the early and late progenies, respectively. High heritability estimates were obtained for all characters and they varied from 0.65 (thick neck percentage, in the late selection) to 0.80 (average bulb weight, in the early selection). Progenies of higher bulb weight and maturity similar to the standard cultivars were obtained. Selection for maturity was highly efficient and the population selected for early maturity has potential to originate adapted cultivars, with bulb yield and quality superior to the available cultivars.<br>Embora seja possível produzir cebola (Allium cepa) o ano inteiro no Brasil, a maioria dos cultivares nacionais apresentam bulbos com baixa qualidade, o que proporcionou grande importação de cebola da Argentina, do tipo Valenciana, que não bulbifica no Brasil, mas que agradou os consumidores brasileiros. Para estudar o efeito da seleção para maturidade de bulbos baseada em progênies de meios irmãos obtidas do híbrido triplo intervarietal [Crioula x (Pira Ouro x Valenciana Sintética 14)] foram semeadas 17 progênies selecionadas para maturidade precoce e 25 para tardia, além da geração F1 e dos cultivares Pira Ouro (dias curtos), Crioula (intermediários) e Armada (dias longos), totalizando 46 tratamentos. O delineamento foi em blocos ao acaso, com três repetições de 32 plantas por parcela, cultivadas em bandejas de isopor. As progênies precoces apresentaram ciclo médio variando de 67 a 83 dias e as tardias de 85 a 103 dias. Na comparação da porcentagem de plantas improdutivas esta diferença também foi evidente, variando de 0,0% a 6,2% nas precoces e de 8,1% a 59,5% nas tardias. Os coeficientes de herdabilidades obtidos foram elevados, variando de 0,65 (porcentagem de plantas improdutivas, na seleção tardia) a 0,80 (peso médio de bulbo, na seleção precoce), sendo, em média, superiores na população selecionada para maturidade precoce. Foram obtidas progênies com peso de bulbo superior às testemunhas 'Pira Ouro' e 'Crioula' e com ciclo que não diferia destas. A seleção para maturidade foi altamente eficiente e a população selecionada para maturidade precoce apresenta grande potencial de originar cultivares adaptados, com produção e qualidade de bulbos superiores às disponíveis no mercado brasileiro