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 (F int 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 F int 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 highproductivity site. Our results indicate that intercropping could be useful for weed suppression in organic row-crops such as maize and cotton.

Field experiments were conducted to determine the effects of tillage systems and varieties on growth, yield and quality of wheat crop (Triticum aestivum L.). The experiments conducted at two sites were laid out in a split-plot design with four replicates, three main plots [conventional tillage (CT), no-tillage (NT) and minimum tillage (MT)] and four sub-plots (‘Siette’, ‘Panifor’, ‘Myrto’, ‘Estero’). The soil porosity and total nitrogen were higher in soils subjected to conservation tillage systems (NT and MT) than under conventional tillage. There were no differences in root growth neither between the tillage systems nor among the varieties. Yield was influenced by the tillage system and variety. The highest grain yield (421-459 kg ha-1) was found under the CT system with ‘Siette’, ‘Myrto’ and ‘Estero’ varieties. In contrast, the highest grain yield was observed under conservation tillage (NT and MT) with ‘Panifor’ variety. There were no significant differences between the tillage systems concerning the protein content and Zeleny value. In contrast, the highest Hagberg falling number was found with MT. Zeleny value was positively and significantly correlated with protein content. High flour quality, as demonstrated by high protein content and Zeleny value, and low Hagberg falling number, was produced in the ‘Estero’ variety.

Organic cotton is a new industrial crop product. Field experiments were conducted to determine the effects of cultural systems and varieties on the growth, fiber quality and yield components of cotton crop (Gossypium hirsutum L.). The experiments, conducted during 2006 and 2007, were laid out in a split plot design with four replicates, two main plots (organic and conventional system) and two sub-plots (cotton varieties: Athena and Campo). There were no significant differences between the organic and conventional system for cotton growth, yield and fiber quality. The results suggest that the soil N released from both the inorganic (80 : 40 : 40 kg ha -1 N : P 2 O 5 : K 2 O) and organic pool (green manure) were sufficient to maintain good growth. Inferior-quality fiber was produced in the variety. Campo, which had the lowest fiber fineness (micronaire), strength, length and reflection. In addition, this variety had the highest fiber elongation and yellowness. There were no significant differences between varieties as far as uniformity and leaf trash ratio are concerned. A positive correlation was observed between fiber strength and length. However, a negative correlation was found between lint yield and fiber strength.

Laboratory experiments were conducted to determine the effects of soil aluminum levels and moisture content on aluminum (Al) bioaccumulation and protein content in the earthworm (Octodrilus complanatus). The experimental design was a completely randomized block with 2 factors (aluminum content [C-0: 0 mg kg -1 , C-1: 1000 mg kg -1 , C-2: 2000 mg kg -1 , C-3: 3000 mg kg -1 ] and moisture level [M1: 100% of soil water capacity, M2: 60% of soil water capacity] and 3 replications. The lowest pH was noted in the C-0 treatment. There were no significant differences in the electrical conductivity, cation exchange capacity or total nitrogen in soil between the aluminum treatments. Moreover, there were no significant differences in soil properties between the moisture treatments. The highest soil Al content was noted in the C-3 treatment. No earthworm mortality was observed in soil contaminated with Al. Moreover, the highest aluminum content in earthworms was observed in the C-3 treatment. The aluminum content in the earthworms was significantly positively correlated with the aluminum content in the soil (r=0.984***, p<0.001). Our results indicated that the growth of earthworms was affected by the Al level. Lastly, Al caused a reduction in earthworm protein content.

Markets for organically produced high quality cotton (Gossypium hirsutum L.) are projected to increase. Field experiments were conducted to compare the effects of two cropping systems on seed and lint yield and fiber quality of three cotton cultivars. The experiments, conducted during 2008, 2009, and 2010, were laid out in a split plot design with four replicates, two main plots (organic and conventional system) and three subplots (cotton cultivars: Athena, Alexander, and Fandom). The organic system resulted to a seed cotton yield at greater or same levels than the conventional system. Micronaire values and maturity for all the cultivars at 2009 and 2010 were satisfactory, while fiber length did not differ between cropping systems, except in 2009. Elongation of the fiber differed among cropping systems only in 2010 and Fandom had the highest rate of fiber elongation. For the organic and conventional systems, fiber strength reached values of 34.47 and 32.5 g tex -1 , respectively. Short fiber index declined throughout the 3-yr period in the organic system. This study confirmed that organic cultivation does not negatively affect lint yield or fiber quality, while in the same time it also produced high seed yield. Findings suggest that despite the significant role of genotype, the interactions of year with cultivar and cropping system have a decisive impact on fiber quality.