Site Productivity, the Key to Crop Productivity

If we call a significant yield increase in single crops a ‘green revolution’, then the first green revolution took place about 10 000–12 000 years ago, when humans started to cultivate land. This was also the beginning of civilization. Since then, humans have increasingly transformed the land and natural vegetation and have risen to be the main creators of the biogeosphere. Today, there is hardly any ecosystem around the globe that has not been influenced by humans. It was only in 1930 that the world population reached 2 billion, and since then it has increased to 6 billion in the year 2000. Because of this rapid increase, the demand for food, feed and industrial crops has grown enormously. Half of the 1.5 billion ha of arable land – 18 % of the biologically productive land area of the earth – was first cultivated only in the 20th Century, and mostly forest was sacrificed to meet this requirement. The second green revolution started only in the late 1960s when high‐yielding varieties of wheat and rice were designed to overcome the predicted hunger crisis. Great achievements were made, especially in relation to irrigated agriculture, while rain‐fed farming was hardly affected by this revolution. World agriculture today faces two major constraints to which not enough attention is paid by scientists and decision makers. First, we increasingly restrict our food basis to a limited number of plant species. Today, 65 % of the world's arable land is reserved for only 21 annual crops. Even more worrying is the fact that 60 % of our food energy and protein comes from only three cereals – wheat, rice and corn. Designing ‘functional’ food using gene technology to improve food quality, for example in rice, will speed up this process of constriction since diversified ingestion is no longer necessary to meet the daily required balance of food types. Secondly, arable land resources are under‐utilized because of poor management. Yields of rice, for example, are below the world average of 3.8 t ha^?1 (1998) in 70 countries. If those countries achieved only the average level for their continent, for example 2.2 t ha^?1 in Africa, world rice production could be increased by 17 %. There is a need to invest in better management of arable land to prevent further loss in productivity and simultaneously to investigate under‐explored plants to broaden our future food basis.     

Influence of pH and sodium chloride on selected functional and physical properties of African breadfruit (Treculia africana Decne) kernel flour

African breadfruit seeds were cleaned, parboiled (98 ^°C) for 15min, drained and dehulled. The kernels were sun-dried, then milled andsieved into flour. Nitrogen solubility (NS), water absorption capacity(WAC), emulsion activity (EA), viscosity, foaming and emulsifyingproperties of the flour were determined as functions of pH and NaClconcentration. The NS was pH dependent with a minimum at pH 4 andmaximum at pH 10. The flour also exhibited minimum and maximum foamcapacity at pH 4 and 10, respectively. The minimum emulsion activity wasat pH 4, a value which increased from 7–16% at pH 12. The addition ofNaCl at concentrations of 0.2 to 0.4 M improved WAC, NS, foamingand emulsion properties of the flour. Sodium chloride enhanced NS of theflour at pH 4–6 and EA at pH 2–8.The EA at pH 2, 10 and 12 correlated negatively (r = –0.30) with NaClconcentration levels; however, the correlation was not significant (p> 0.05). The flour dispersions had lower viscosities at acid pH and in thepresence of NaCl than at neutral and alkaline pH values. Results indicatedthe flour could be used in food product supplementation.     

Proximate composition and selected functional properties of African Breadfruit and sweet potato flour blends

Full-fat African breadfruit flour was used to replace 30, 40, 50, 60 and 70% of sweet potato flour. The chemical composition and functional properties of composite flours showed that they contains more protein, fat, and ash and less carbohydrate than sweet potato flour. With increasing level of supplementation of breadfruit, ash, protein and fat contents increased while carbohydrate decreased. The composite flours possessed higher water absorption than sweet potato flour. The water absorption capacity increased from 20% for sweet potato flour to the range of 85–120% for composite flours. The oil absorption capacities for some composite flours were higher than that for sweet potato but less than that of breadfruit. Composite flours had good foaming capacity but lacked foaming stability. The bulk density of the composite flours was found to be low which will be an advantage in the preparation of weaning food formulations.     

面包果双螺杆挤压膨化的试验研究

面包果是一种淀粉含量较高的水果,为开发其加工产品,利用双螺杆挤压技术,对面包果在挤压膨化过程中物料的喂入量、含水量、挤压温度和螺杆转速等对产品性能指标(如体积密度、膨胀率、吸水性、水中溶解度)以及感官特性硬度、脆度、色差变化和比机械能等进行了试验研究。并利用SAS数据统计软件,对试验数据进行了回归分析,得到了较优的回归模型。利用回归模型,分析了挤压因素对产品物理化学特性的影响,为面包果挤压膨化食品的开发提供参考。     

基于盐胁迫条件下施用氮钾肥对面包果养分吸收及渗透物质积累的影响

为探究不同氮钾配比影响盐胁迫下面包果生长的营养生理机制,以面包果[Artocarpus altilis (Parkinson) Fosberg]为材料,研究不同氮钾配比对盐胁迫下面包果养分吸收及渗透物质的影响。结果表明：与阴性对照（N₀K₀+W）相比,单盐胁迫（N₀K₀+S）对面包果生长指标有一定抑制作用,对根系生长指标有一定促进作用,其中N₁K₁+S处理的面包果地下部干重较单盐胁迫处理呈增加趋势,根系生长指标呈下降趋势。所有盐胁迫处理均显著增加根茎叶中的Na⁺含量和Na⁺/K⁺。与阳性对照（N₀K₀+S）相比,N₁K₁+S处理显著增加根茎叶中K⁺含量,减少叶中Na⁺含量和Na⁺/K⁺。N₁K₂+S处理较N₁K₁+S处理显著减少根茎中的Na⁺含量,N₂K₂+S处理较N₂K₁+S处理显著增加根中的N、P、K⁺、Na⁺含量和Na⁺/K⁺,茎中的N和K⁺含量以及叶片中的Na⁺含量、Na⁺/K⁺和叶片可溶性糖含量。N₂K₁+S处理较N₁K₁+S处理显著减少根、茎中K⁺含量,增加叶片N、Na⁺含量和Na⁺/K⁺,降低叶片可溶性糖含量,增加脯氨酸含量。N₂K₂+S处理较N₁K₂+S处理显著增加根、茎、叶中的Na⁺含量和Na⁺/K⁺。综上所述,适量增施氮钾肥通过调节K⁺、Na⁺向各器官的运输缓解盐胁迫对面包果生长及养分吸收的抑制效应,可为盐碱地的面包果施肥提供参考。     

Studies on weaning diets in Nigeria: 2 protein sources

Protein isolates were extracted from melon, groundnut, and soybean cakes in an aqueous system that could potentially yield both oil and protein from oilseeds quantitatively. Protein isolates obtained were 91.2, 78.6 and 79.5% of the total protein content of melon, groundnut and soybean cakes respectively. Both cakes and isolates were assessed in a rat bioassay while breadfruit, cassava, and corn starch were also investigated as sources of carbohydrate. Results showed that there were no significant differences between feed intake, weight gain and PER of rats fed the cake and the protein isolates except in soybean. Weight gain, PER and NPR were highest in cassava-soybean protein isolate diet followed by cassavacasein diet (control) while performance was only moderate with melon- and groundnutcassava diets. With melon protein isolate, cassava and breadfruit were better carbohydrate sources than corn starch. In simulated weaning diets, cassava-sucrose-melon-soybean protein isolate based diet performed better (weight gain 33.4 g, PER 1.63, NPR 2.23) than a commercial weaning food (weight gain 30.6 g PER 1.57, NPR 2.18) while replacement of sucrose and cassava at 30% by breadfruit yielded a cost effective diet with good performance (weight gain 29.4 g, PER 1.51, NPR 2.12). Diets where soybean protein served as the sole source of protein or breadfruit, white and yellow maize ogi served as the main source of carbohydrate performed only moderately.     

Efficacy of Artocarpus altilis (Parkinson) Fosberg extracts on contact mortality,repellency, oviposition deterrency and fumigant toxicity of Callosobruchus maculatus (F.) (Coleoptera:Bruchidae)

Callosobruchus maculatus (F.), a major pest of grain legumes, causes considerable losses worldwide. C. maculatus management relies on synthetic insecticides with their adverse environmental and health concerns. The current study investigated the use of Artocarpus altilis (breadfruit) extracts on contact and fumigant toxicity, repellency and oviposition deterrency of C. maculatus as a management strategy. Fumigant mortality (LC₅₀) of the dry inflorescence extract of A. altilis was 126.65 µL L^?1 air at 53.4 h. Fruit extract gave 73.3% repellency at 1000 ppm after 24 h. Percent repellency was dose and time dependent. Green inflorescence extract of A. altilis reduced egg laying with 50% oviposition occurring after 37.78 h at 1000 ppm. We conclude that extracts of leaf, fruit, green and dried inflorescence of A. altilis displayed contact mortality, repellency, deterred oviposition and had fumigant activity toward C. maculatus.     

盐胁迫对2种菠萝蜜属植物幼苗生长及光合荧光特性的影响

【目的】 研究盐胁迫对2种菠萝蜜属植物幼苗生长和光合荧光特性的影响,为热带盐碱地开发利用,发展岛礁特色农业提供参考。【方法】 以两种菠萝蜜属植物菠萝蜜（Artocarpus heterophyllus Lam.）和面包果（Artocarpus altilis (Parkinson) Fosberg）为材料,采用沙培法,从3叶期开始进行盐胁迫（处理设为T0—T4,盐浓度分别为0、3.4、10.2、17.0和23.8 g?kg ^-1）,研究盐胁迫下菠萝蜜和面包果幼苗生长、光合及叶绿素荧光参数的变化。 【结果】 盐胁迫显著抑制菠萝蜜幼苗生长、叶绿素含量和生物量积累,对面包果的抑制作用小于菠萝蜜。盐胁迫使菠萝蜜叶片净光合速率（Pn）、气孔导度（Gs）、胞间CO₂浓度（Ci）和蒸腾速率（Tr）降低,气孔抑制率（Ls）增加,面包果的变化幅度较菠萝蜜小。高盐胁迫（盐浓度>17.0 g?kg ^-1）显著抑制菠萝蜜叶片光化学猝灭系数（qP）、光系统Ⅱ活性（Fv/Fo）、潜在最大光能转换效率（Fv/Fm）、实际光能转换效率（ΦPSⅡ）、相对电子传递效率（rETR）;使面包果叶片qP、非光化学猝灭系数（NPQ）、ΦPSⅡ和rETR显著下降。叶绿素含量与光合参数呈显著正相关关系。盐胁迫、叶绿素含量和净光合速率以及它们之间交互作用解释作物生物量变化的比例为35.6%。 【结论】 盐胁迫显著抑制菠萝蜜幼苗生长、叶绿素含量、光合参数和生物量积累;面包果的光合参数和生物量在高浓度盐胁迫下较敏感。盐胁迫、叶绿素含量和净光合速率的变化与两种菠萝蜜属植物生物量变化密切相关。