A moderately long-term field trial was carried out at East North Delta of Egypt
(EI Serw Res.Station) since 1996/1997 season up to 2003/2004 season to study
sustainability of soil fertility status under differer t resource managements, i.e. 4 levels
of NP (0, low, recommended and high), water quality (fresh and drainage) and 3 crop
rotations;Rot.1 (wet), Rot.2(very wet) and Rot. 3ldry) . The collected data of the first 3-
years crop rotation showed that: l-The available N&P residuals were significantly increased with increasing fertilizer
rates while that of K was not affected. 2- The residual N was increased under drainage water application by about 31 % over
fresh water, which may be due to the leached N03 anions in drainage water. while
the residuals P and K were not affected by water quality. 3-The micronutrient residuals were decreased wilh increasing NP fertilizer levels.
4·Drainage water application caused significant (eduction in the residual Fe, whereas
those of Mn and Zn were slightly increased with drainage water application. 5-Crop rotation 2(very wet) and 3(dry) caused s,gnificant increase in Zn residual only
by about 42% and 31% respectively, while Fe and Mn were not affected. 6- Crop rotation 2 recorded also significant increase in organiC matter content
compared to rotations 1 (wet) and 3(dry), which may be due to that winter crop was
berseem(Egyptian clover) during the 3-years crop rotation. 7-The highest relative contribution(R C%) of water quality was for Fe residual
(79.22%) followed by N residual (25.55%) , while the highest RC% of crop rotation
were 24.76% and 21.24% for OM and P respectively. 8-The added N recorded remarkable RC% for N residual (47%) followed by Zn
(10.38%), and the RC%of the added P wa s 69% for residual P and 22.99% for
residual Zn. 9-The total RC% of all tested factors were pronounced for the available P (90.29%),
Fe (81.07) and N (79.98%) and to some extent for Zn (33.37%), Mn (41.97%) and
organic matter (24.76%) whereas, it was the least for K (7.82%). which may be due
to the heavy clay soils with high K content at this location.