Weed management in soybean with a special focus on the control of purple nutsedge (Cyperus rotundus)

Purple nutsedge (Cyperus rotundus L.) is globally an important perennial weed. Infestations from this species lead to significant losses in yield and quality of crop production. A field study was conducted at Kopaida region in Greece, to evaluate the efficacy of different herbicides for the weed management in soybean. The evaluation of the herbicides was based on the efficacy against purple nutsedge and the effect on soybean biomass production and crop seed yield. Treatments included an untreated control, two pre-emergence applications (with S-metolachlor and pendimethalin), as well as three post-emergence applications (with trifloxysulfuron, bentazone and pyrithiobac sodium). A single application of S-metolachlor maintained the density of purple nutsedge at 15 plants per m2 in soybean and allowed the crop to compete adequately with the weed. S-metolachlor also resulted in a seed yield of 3.26 tn ha-1 , a value 52% higher than the untreated control and 38–45% higher than the other herbicides. The results from this study demonstrated that a combination of high seed density in soybean and effective application of herbicides like S-metolachlor can lead to economically acceptable yields

Sex differences in self-construal and in depressive symptoms: predictors of cross-national variation

Sex differences in aspects of independent versus interdependent self-construal and depressive symptoms were surveyed among 5,320 students from 24 nations. Men were found to perceive themselves as more self-contained whereas women perceived themselves as more connected to others. No significant sex differences were found on two further dimensions of self-construal, or on a measure of depressive symptoms. Multilevel modeling was used to test the ability of a series of predictors derived from a social identity perspective and from evolutionary theory to moderate sex differences. Contrary to most prior studies of personality, sex differences in self-construal were larger in samples from nations scoring lower on the Gender Gap Index, and the Human Development Index. Sex differences were also greater in nations with higher pathogen prevalence, higher self-reported religiosity, and in nations with high reported avoidance of settings with strong norms. The findings are discussed in terms of the interrelatedness of self-construals and the cultural contexts in which they are elicited and the distinctiveness of student samples

Weed-suppressive effects of maize-legume intercropping in organic farming

In organic agriculture, intercropping is receiving increasing attention as it offers potential advantages for increasing sustainability in crop production. However, intercropping can increase competition between crops and weeds. In this study, we analyzed the effects of maize-legume intercrops on the weed community in an organic cropping system. We were concerned only with competition between crops and weeds for light. We recorded a statistically significant negative correlation between the fraction of photosynthetically active radiation (Fint PAR) intercepted by the canopy, and both weed density and weed dry matter. Maize-legume intercropping led to a higher soil canopy cover (leaf area index) than sole crops. The lowest values for Fint PAR were received in sole crops. Thus, in maize-legume intercrops the decrease in available light for weeds led to a reduction of weed density and dry matter, compared to sole crops. Intercropping maize and legumes considerably reduced the weed density in the intercrop compared with the maize pure stand. Weed suppression by crops was also greater on a low-productivity site than on a high-productivity site. Our results indicate that intercropping could be useful for weed suppression in organic row-crops such as maize and cotton. © 2010 Taylor & Francis