How long have the trees been established? If they are young, say 2-5 yrs, it's unlikely they will be sufficiently established to produce a crop. However, water could be an issue - poorly drained soil in Winter would lead to root rots and subsequent incapacity to swell the kernels, insufficient water in Summer, especially on thin, rocky soils could also exert the same impact. That being said almonds are pretty tough, but they do prefer deep, well-drained soils. They grow very well here in commercial groves that are based on alkaline, somewhat sandy soils.