Page 215 - Nutrient Management Planning Guide

Spring application in this discussion refers to fertilization prior to or at seeding. The idea is to provide immediately available nutrients to the growing crop. There are several advantages of spring versus fall application including:

During spring application nutrients are applied close •

to when the crop requires them. Nutrients are not stored over the winter in the soil so •

they are not susceptible to early spring losses (e.g., runoff, denitriﬁcation). An exception is elemental S fertilizer, which has less opportunity to convert to crop available forms when applied in the fall. Spring application allows for more precise nutrient •

applications, since spring moisture conditions can be considered. Soil analysis results and changes in expected crop •

prices can be incorporated into planning. By applying fertilizer in the spring, high disturbance •

ﬁeld operations can be avoided in the fall, leaving more standing crop residue to trap snow and enhance moisture retention. Applying in the spring may allow the possibility of •

combining the seeding and fertilizer operations into one-pass, reducing ﬁeld operations.

The soil disturbance associated with spring •

application can dry out the seedbed thereby reducing germination and yield potential. The time required to complete seeding and related •

ﬁeld operations may increase. Regional weather conditions in the spring can have •

a large impact on demand for fertilizer, which can impact availability and cost.

Some producers purchase fertilizer in the fall and store it until spring. This requires suitable storage facilities, which can be a substantial cost. Storing fertilizer also has an environmental risk, since inappropriate storage can result in nutrient release to the environment.

Post-emergent fertilizer application refers to an application after crop emergence including: fertigation, broadcast, banded, and foliar applications. The major advantage of post emergent fertilizer application is that it permits adaptation to dramatic changes in growing conditions after seeding (e.g., moisture conditions or nutrient deﬁciencies). When moisture conditions are better than expected, additional fertilizer can help to take advantage of the increased yield potential. Alternatively, excessive precipitation can lead to conditions that promote nutrient loss and additional fertilizer could be applied to compensate for losses.

In some instances, post-emergent nutrient applications can result in crop damage. This is inﬂuenced by crop type and stage of development, as well as environmental conditions at the time of application. For each nutrient, there are limits on the form and amount that can be safely foliar-applied to the crop.

A major challenge with post emergent applications is that to be effective nutrients must be taken up by the plant before productivity is limited by deﬁciencies. There is a very narrow window of opportunity for this to happen successfully. In addition, multiple applications represent additional costs.