Chapter 7: Evaluating a soil's fertility

Deciding how much and what kind of fertilizer a farmer needs for her crops is a twostage process:

1. The soil's present fertility level should be evaluated, ideally by soil testing.

2. Once the soil's present state of fertility is known, the most appropriate kinds and amounts of fertilizers can be determined, considering the following factors:

• Type of crop

• Feasible yield goal as determined by:

•• Yield-limiting factors such as available moisture, soil characteristics, weather, pests, and diseases.

•• Farmer management level

•• Available capital for needed inputs

• Expected cost/return based on likely yield and market value (more difficult to predict with vegetable crops than field crops).

In this chapter, we'll focus on stage 1 and cover the following methods of evaluating a soil's fertility:

• Soil testing

• Plant tissue testing

• Fertilizer trials

• Spotting visual "hunger signs"