Starter Fertilizer and Liquid P -

An agronomists hands holding a young plant with a cyber display of technological factors.

Karl Wyant, Ph.D.

A Great Team For a Strong Start to Your Season.

Whether you are looking ahead to fall planting or starting to plan for spring, a starter fertilizer is worth considering.

As yield goals rise, the phosphorus (P) needed also increases. Phosphorus plays a key role in a strong crop establishment, root development, and shoot growth to name only a few. Without it young plants are dwarfed and thin, leaves are dark, and yield is reduced.

Starter Fertilizer: A Proactive Kick-Start

Starter fertilizers, which include formulations that have a high phosphate analysis (P₂O₅ %), are applied with the specific purpose of helping the plants acquire more nutrients early in the season, and is in addition to the fertilizer used in the nutrient management program to correct issues in the soil. It is generally applied in relatively small amounts either with or near the seed.

The primary benefit of starter fertilizer may be an increase in early growth and crop uniformity but applying starter fertilizer when a soil test is already at or above the critical value for the applied nutrient may not benefit yields.

There are two main reasons to use a starter:

First, when soil tests indicate the field is deficient in one or more nutrients (e.g., phosphorus), and these nutrients are relatively easy to apply with the planter.
Second, when the field to be planted is covered with more than 70 per cent residue and/or you expect the soil to be cool and wet early in the season. Soils that are slow to warm and wet can struggle to supply P to the growing crop.

If starter is going to be placed near the seed, be sure the formulation and dose will not hurt germination and stand establishment. (See the NebGuide, Using Starter Fertilizers for Corn, Grain Sorghum, and Soybeans.)

Proper use of starter fertilizer is part of the management for achieving high yields on some soils, but starter fertilizer may benefit production most under reduced tillage, on irrigated sandy soil, and on high pH soil. (NebGuide)

Liquid or Dry fertilizer?

What type of fertilizer and when best to apply, are key questions in the nutrient management plan.

There are various options to how you’ll apply a starter fertilizer. While dry fertilizers are generally easy to find, easy to store and apply, and can supply bulk nutrients and variable application options, there are limited blending options and a higher risk of environmental loss if broadcasted, since the amount of nutrients supplied in the fertilizer does not line up with immediate crop demand. Surface broadcasted nutrients can be lost in runoff and erosion, as is the case with phosphate.

Liquid fertilizers are newer to the market, require more specialized storage and application, and deliver a smaller dose of nutrients per application, but can be blended easily with other liquid products. A significant benefit is the lower risk of loss and improved uptake efficiency of P relative to the applied dose of the nutrient.

Manage P for Demand

Soil testing is the best place to start any nutrient plan. Understanding not only the P levels but also the other nutrient levels and soil pH, may be critical to ensuring any P applied is available to the crop when needed. Use other resources such as agronomists, extension specialists, university researchers, and personal trial-and-error to develop a plan that is right for every field.

Understanding how the P applied reaches its target is also important. According to recent research, approximately 93 per cent of phosphorus reaches the plant through diffusion, rather than root interception or mass flow. Because P interacts with many other soil elements which reduce its efficiency, it can be challenging to manage.

Getting the timing right can sometimes feel like an art. At the beginning of the season, if the soil is cooler, early phosphorus applications should be considered to ensure adequate P available for the plants. If the soil is excessively wet or dry, when the plants have poor root structure, and there is reduced microbial activity in the soil, growers may want to get a starter application down as soon as field conditions allow. Phosphorus applications can be delayed when the soil is warmer, there is adequate soil moisture, and good root structure, soil pH levels and microbial activity.

Looking Ahead

There are some best management practices that will help with working on nutrient planning every year. Understand soil types and local geography, do regular soil and tissue tests, manage large soil deficiencies at pre-plant, and in-season demand with fertilizers and foliar applications. Phosphorus can be challenging to manage, so understanding timing and having a resource such as an agronomist or extension specialist on the team is essential.