**3.9 Yield variability and soil management zones**

A study was conducted to compare yield variability resulting from variability of soil ECa and other parameters for both the dry and wet seasons in the same 140 ha study area (Gholizadeh, 2011). Fig. 14 shows typical variability maps of the harvested yield compared to the variability in the bulk soil electrical conductivity, bulk soil density and soil texture. High yielding areas are associated with mid-range ECa, high clay and low sand, and low bulk density. Low yielding areas are associated with low ECa and high sand content. High yield is also associated with high pH, high EC and high OC, and vice versa. Hence water management that will allow increase in pH of the paddy soil is desirable.
