Soil salinity and sodicity effects of wastewater irrigation in South East Australia

Although ‘sewage farming’ or wastewater irrigation started in Australia in the latter parts of the 19th century, it was in the late 1960s that a considerable interest was revived in arid and semi-arid parts of the world due to scarcity of alternative water sources and the urgency to increase local food production. The practice has manifold benefits in the form of water conservation, nutrient recycling, surface and ground water pollution prevention. But for arid and semi-arid regions like many parts of Australia, while wastewater irrigation can be an attractive solution to irrigation water problems, it might not be the ideal solution for the common soil types encountered in these regions. Due to characteristic low rainfall, high evaporation and low leaching, these soils tend to have higher salt accumulations. This paper examines the soil salinity and sodicity effects of wastewater irrigation in soil types typical to South Eastern Australia and takes the soils of Western Treatment Plant (WTP) as a case study to highlight these issues.     

阿拉伯胶和香精油对香蕉及番木瓜贮藏过程中炭疽病及品质的控制效果

严格控制由刺盘孢属(Colletotrichum spp.)真菌引起的炭疽病对减少热带水果工业的经济损失十分重要。本文主要研究了阿拉伯胶(GA)(10%)、柠檬香草精油(LG)(0.05%)、肉桂精油(CM)(0.4%)及其复合组分在试验条件下对离体与活体香蕉和番木瓜炭疽病菌的抑制活性。结果表明,0.05%的LG和0.4%的CM对于引起香蕉和番木瓜炭疽病的两种病原菌Colletotrichum musae和Colletotrichum gloeosporioides分别具有抑制活性;单独GA处理并未表现出抑菌活性,但将0.05%LG、0.4%CM与10%GA混合处理则具有较大的抑菌活性;在各处理中,以PDA培养基中加入10%GA及0.4%CM的处理对C.musae和C.gloeosporioides这两种病原菌抑制活性最显著,对于两种病原菌菌丝生长抑制率分别为73.4%和70.0%,对孢子萌发抑制率分别为88%和85%。活体试验结果也表明,10%GA结合0.4%的CM处理具有最佳的作用效果,对C.musae和C.gloeosporioides的抑制方面表现出较强的增效作用,对人工接种的香蕉和番木瓜炭疽病导致的腐烂抑制率分别为80%和71%。品质评价的试验结果也表明,10%GA结合0.4%CM的涂膜处理具有良好效果,果实失重率、硬度、可溶性固形物和可滴定酸含量的变化均表明该处理可显著推迟果实的成熟。上述结果表明,10%阿拉伯胶结合0.4%肉桂精油处理可以作为控制诸如香蕉和番木瓜等常见热带水果采后炭疽病的生物杀菌剂。     

Allelopathy of buckwheat: Assessment of allelopathic potential of extract of aerial parts of buckwheat and identification of fagomine and other related alkaloids as allelochemicals

The allelopathic potential of buckwheat ( Fagopyrum esculentum ) was investigated. Field study showed that living buckwheat reduced weed biomass compared with plots without buckwheat. Laboratory study revealed that root exudates suppressed root and shoot growth of weeds and reduced weed dry weight. Sequential partitioning of the aqueous ethanolic extract of the aerial parts of buckwheat showed that the chloroform extract caused an 80% reduction in radicle elongation of lettuce seedlings at a concentration of less than 100 p.p.m. Fagomine, 4-piperidone and 2-piperidinemethanol were isolated and identified by ¹H and ¹³C nuclear magnetic resonance from the chloroform extract. These compounds caused a 50% inhibition of radicle elongation in lettuce seedlings at concentrations of less than 100 p.p.m. These results suggest that compounds 1, 2, and 3 might act as allelochemicals and affect the growth or germination of different plant species.