الفهرس 
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Abstract
An ecological studies were conducted to record the distribution of weeds in some crops, i.e, barley and maize grown in Sharkia Governorate, Egypt. The highest value of fine sand was recorded in soil of Elsalheia; meanwhile the lowest value was recorded in soil of Zagazig. On the other hand the silt and clay fractions attained the highest values at Belbees and Zagazig. The obtained data revealed the correlation between the increase of fine soil particles and cation contents. Forty weed species were in barley fields at winter season and fifty-six in maize fields at summer in the six studied localities. Barley fields have 40 weed species out of which only, Avena fatua , Avena sterilis , Chenopodium album, Convolvulus arvensis and Senecio desfontainei are the major weeds. Maize fields have 56 weed species out of which Amaranthus viridus , Avena sativa, Chenopodium album , C. murale , Convolvulus arvensis , Cynodon dactylon , Echinochloa crusgalli , Lathyrus aphaca , Launea nudicalus, Malva parviflora , Medicago intertexta , Panicum repense , Polypogon monspeliensis, P. semiverticillatus, , Senecio desfontainei and Xanthium strumarium, are the major weeds. Finally, it is clear that fine particles play an important role in weeds distribution by its character and through its effect on other soil properties such as organic matter, cation exchange capacity , CaCO3 content and its effect on aggregate formation. Nitrogen is often the most limiting factor in crops production. Hence, the increase of soil nitrogen results in higher biomass yields , protein yield and its concentration in plant tissue. In cereals, abundant supplies of nitrogen change the relative proportion of crop quality. Increasing nitrogen supply generally improves kernel integrity and strength, resulting in better milling properties of the grains of barley and corn.