Assessment the Impact of Shallow Groundwater on Soil Salinity and Biomass Yield of Plants Grown in North Nile Delta Using Remote Sensing and GIS Techniques

This study was conducted to evaluate soil salinity distribution and biomass yield as affected by shallow groundwater (GW) in North Delta by employing a geographical information system (GIS) and remote sensing technologies. These techniques permit to evaluate wide area in relative short time and low costs.
The GW in the investigated area is mainly affected by the drainage system status and more efficient the drainage system, the deeper is the GW. The ground water depth (GWD) in this area ranged between 80 and 130 cm based on the performance status of the tile drainage collectors in different parts. The drawdown rate (DDR) of GW was decreased rapidly by time, due to poor structured soil which influences its water entry to the soil. DDR was 18.5-45.1 cm/day through the 1st 24 hr after irrigation, then decreased to 14.6-31.2 cm/day through the 1st48 hr, while it recorded 6.2 -10.1 cm/day through the duration time (DT) which is the time for GW to reach the deepest level after irrigation. The deep GW with long DT may have negative effect on plant and soil more than the shallow GW with short DT. The DT is inversely proportioned to the DDR and their values are related mainly to the efficiency of the subsurface drainage system and soil properties. Consequently, the shallowest GW was recorded with the relative long DT, with relative slow DDR and vice versa.A negative but significant correlation was found between the GWD and soil salinity (R2 =0.576, r =- 0.483, P < 0.05). Consequently, the soils of the part in the studied area suffers from shallow GW (81cm), in sequence, have salinity higher than that in other parts (6.8 dS/m). On the other hand, the lowest salinity level (4.6 dS/m) was found in part which has relatively deep GW (125 cm).
2A positive weak correlation was observed between biomass yield and GWD (R2 = 0.55, r=0.71, P < 0.05), whereas its correlation with root zone ECe was significant and negative (R2 =0.68, r = -0.80, P > 0.05). The yield potential in the parts with relative low EC soils (4.6-4.9 dS/m) was about 10 % higher than that in parts with relatively high salinity (6.8 dS/m).
The obtained data showed also that the integration of satellite imagery and GIS has enabled new evaluation possibilities in agricultural areas in relative short time and low cost