Iron deficiency, usually induced by excessively high soil pH, can cause yellowing on new growth. This yellowing will be distinctly between veins. Iron becomes more available as soil pH decreases. Excessive liming may result in an iron deficiency. The yellowing occurs because the iron needed for chlorophyll synthesis is limited, and iron cannot travel from old tissues into new tissues.
Soil acidification is the most cost effective way to increase iron availability. Ammonium sources of nitrogen tend to decrease soil pH around the root zone, thereby increasing iron availability. Foliar applications of iron may be desirable to help alleviate the problem until desired soil pH levels are reached.
More strawberry nutrient deficiency information.