Langzeit-Systemvergleiche in Kenia und Indien: Konventionelle und biologische Erträge aus dem ersten Umstellungsjahr

Organic agriculture is more and more perceived as a promising approach to increase food security in developing countries. However, only few attempts have been made so far to assess agronomic and economic performance of organic agriculture in these^regions in a systematic way. This article reports the first year’s results of two long-term farming systems comparison field trials in Kenya and India. In sub-humid Central Kenya, on a high potential site in Meru South District (Chuka), there were no differences between yields of conventional and organic systems for the first maize and brassica crops. In contrast, organic yields were 14 to 60% lower than conventional yields on a trial site in a medium potential zone in Maragua District (Thika). It is assumed that the organic crops in Chuka could benefit from N and P mobilisation from the soil. In Thika, where N and P were less available, the crop depended on the easily soluble nutrients applied in the conventional treatments. In the semi-arid cotton belt of^Central India, biodynamic, organic, conventional and genetically modified (GM) cotton are compared. Soya and wheat are also part of the crop rotation under study. Biodynamic and organic cotton and wheat yields were 30% lower than conventional and GM yields. Soya yields did not differ between the treatments. It is suggested that yield in organic farming systems in conversion depends on initial inherent soil fertility and crop

Influence of temperature on the development, reproduction and longevity of Ceratothripoides claratris (Thysanoptera: Thripidae) on tomatoes

Ceratothripoides claratris (Shumsher) is a serious pest attacking tomatoes in Thailand. Temperature-dependent development of C. claratris was studied at seven constant temperatures, i.e. 22, 25, 27, 30, 34, 35 and 40°C. Pre-adult survivorship was greatest (95%) at 25 and 30°C and shortest at 22°C. Egg-to-adult time decreased within the range of 20 to 30°C and at 34°C it started to increase. The lower thermal threshold for egg-to-adult development was estimated at 16 and 18°C by linear regression and the modified Logan model, respectively. The optimum temperature for egg-to-adult development was estimated at 32-33°C by the modified Logan model. The influence of temperature on reproduction and longevity of C. claratris was determined at 25, 30 and 35 and 40°C. Both inseminated and virgin females failed to reproduce at 40°C. Virgin females produced only male offspring, confirming arrhenotoky. The sex ratio of the offspring of fertilized females was strongly female-biased, except at 25°C. Mean total fecundity per female and mean daily total fecundity per female were highest for both virgin and inseminated females at 30°C. Female longevity was longest at 25°C and shortest at 40°C. Male longevity was longest at 30°C and shortest at 40°C. The net reproductive rate (R0) and intrinsic rate of natural increase (rm) was greatest at 30°C while, mean generation time (G) and the doubling time (f) were highest at 25°C. The finite rate of increase (λ) was fairly constant (1.1-1.5 days) over the three temperatures tested. The pest potential of C. claratris for tropical Asia is discussed