Biochar application is a promising sustainable strategy for enhancing soil properties thus
crop production. However, biochar application to soil certainly alters its biological and physical
properties, and could require extra costs. Therefore, biochar suitability to agroecosystems must
be proactively estimated. The advantage of biochar addition to poor fertile or weathered soils has
been well studies, however, its feasibility to fertile soil under low quality (saline) irrigation water
was not frequently studied. Consequently, this work investigates the hypothesis of whether the
application of biochar at a rate of 4.8 tons/ha to fertile soil (Nile Valley, Giza, Egypt) would ameliorate
the negative effects of saline irrigation regime (3000 ppm) on tomato crop and soil. The results
of two seasons experiments showed that saline irrigation significantly reduced tomato crop yield
by an average reduction ratio of 51%, and biochar addition could not compensate such reduction.
Furthermore, biochar did not reduce accumulated Na+ in fruits or roots. Tomato fruits produced
from biochar-added soil were lower in TSS levels (41.7% reduction ratio) yet larger in diameter by
approximately 1.5-fold increase. Interestingly, biochar addition into soil greatly promotes the length
of stem-borne lateral roots and elevates the expression of LeNR (encodes nitrate reductase enzyme)
in leaves yet under fresh irrigation regime. For soil properties, biochar application enhanced the
soil properties under either saline or fresh water irrigation conditions. Collectively, it is assumed
that biochar application to fertile soil in Nile Valley of Egypt could not alleviate tomato fruits yield
reduction affected by applied saline irrigation regime.