Fertilizer placement: A primer

Excerpt

HIGHER crop yields, regardless of tillage system, are not only a matter of fertilizer rates and methods of application but fertilizer placement as well. Proper fertilizer placement improves nutrient availability to plants, which means higher yields, particularly in conservation tillage systems.

Why placement?

Nutrient placement generally involves locating nutrients close to the plant at seeding. This improves the chances of root interception of nutrients early in the growing season (11). Use of starter fertilizers is a good example of this type of placement. Besides the close proximity to the developing plant, phosphorus (P) and potassium (K) use in particular is improved by reduced soil contact, slowing the rate of both P and K reactions (fixation), which lower availability (4).

Temperature is an important factor in the use of starter fertilizers. Nutrient absorption and diffusion to roots are slower at lower temperatures (3, 10). Soil temperatures with conservation tillage can easily be 5°F lower, maybe more, than with conventional tillage. High concentrations of nutrients close to the seedling help overcome the slow development of roots and the low level of energy production in the roots.

Soil compaction also reduces nutrient availability. When compacted, the soil has less oxygen; plant roots …