The year after, crops that require lower nutrient levels can be planted in that spot. The third year, the legume crop is rotated back in. The fourth year, heavy feeders are finally used again. Rotation is one way to vary the demands on the soil and protect crops from a build up of insects and pathogenic organisms. Synthetic fertilizers are an economic way to provide specific nutrients that can be applied at certain times of plant development or used in a slow release formula.
Synthetic fertilizers are less bulky than organic soil amendments.
They can be applied to large areas with greater ease. However, synthetic fertilizers do not improve the physical properties of the soil and can be leached out of the root zone and into the ground water. The plant response desired, the availability and how costly the fertilizer or amendment is, and the ease of application. The ratio is the relationship between the respective nutrients. This is a fertilizer that includes all of the macronutrients- N, P, and K. 11.