Unfortunately foliar tissue analysis is NOT exact science. In other words just because you have high levels in the leaves and/or vice verse does not mean everything is ok. Rather it helps to track nutrient trends in the plants. Soil testing tells what nutrients are in the soil and tissue analysis tells what nutrients the plant actually took up. However, the nutrient levels change with the time of the year they are taken. The most consistent time to take samples is usually mid July for most plants. So if you take them earlier than that you might get an unusually high reading. This is all conversation to say that most of the time it is not necessary to do a tissue analysis. Rather, have a soil test performed before planting and then fertilize accordingly. Then if you experience plant growth problems, you may need to come in and take a leaf sample to see if you can pin point the area of concern.