Starter fertilizer is defined as the placement of small amounts of nutrients in a concentrated zone close in proximity to the point of seed placement at the time of planting. This placement can be in a band over the row, in the furrow, below the seed, to the side of the seed or to the side and below the seed.

A disadvantage of placing starter fertilizer over the row is that the immobile nutrients are not in a position available to early root growth, although this is often of little agronomic importance.

Starter fertilizer is applied in addition to nutrients utilized to correct soil nutrient deficiencies. It should not be confused with fertilizer placed in a band near the row to correct a soil nutrient deficiency.

Band application of fertilizer is an effective way to correct nutrient deficiencies and can result in early growth response as well. Applied phosphorus recovery during the year of application is great- er with band application of phosphorus fertilizer on low phosphorus soils.

Placement of starter fertilizer in the seed furrow, commonly called "pop-up," requires care to prevent germination injury from fertilizer salts. Metering equipment must function properly to deliver uniform low rates of fertilizer in the seed furrow.

The amount that can be supplied safely is limited and depends on the fertilizer used and soil properties. Ammonium thiosulfate should never be placed in the furrow with the seed.

A starter fertilizer usually is composed of two or more nutrients. Under Nebraska conditions, a combination of nitrogen and phosphorus often constitutes an effective starter material. Liquid 10-34-0 is a popular starter fertilizer material. 7-21-7 also is commonly used; however, potassium application is not needed on most Nebraska soils.

The addition of zinc and/or sulfur may be desirable for some soil conditions.

Zinc should be included when the zinc level in the soil is marginally adequate. Sulfur should be added for sandy soils low in organic matter.

Nitrogen alone may give an early growth response where soil nitrogen is low at the time of planting, or with cooler soil temperatures under heavy crop residue where phosphorus, zinc and sulfur are adequate. This is most likely to occur after excessive spring rains, particularly on low organic matter and/or sandy soils. Such rains will leach nitrogen and can result in cooler soil conditions.

The primary benefit of starter fertilizer is an increase in early growth and crop uniformity. Corn and grain sorghum commonly respond to starter fertilizers with increased early growth. This early growth response results in larger plants of more uniform size, which may permit earlier lay-by cultivation and ditching for gravity irrigation.

Increased early growth in corn or grain sorghum can occur when starter fertilizer containing phosphorus is applied to soils that test as high as 45 parts per million phosphorus.

Growth response often occurs on sandy soils when proper rates of nitrogen and sulfur are used, even if the soils have high phosphorus levels.

Early growth response to starter fertilizer may result in slightly earlier flowering or crop maturity. Flowering or maturity a few days earlier can result in improved yield in years of early frost in the fall.

This effect of starter fertilizer is most often observed on grain sorghum in areas where nights are cooler. Also, earlier maturity may result in slightly drier grain at harvest.

However, increased growth and earlier flowering often does not translate to higher yield. Grain yield increase from starter fertilizer containing phosphorus is most likely on soils low on phosphorus. Grain yield increase on sandy soil is commonly due to nitrogen and/or sulfur in the starter fertilizer.

Soybeans seldom respond to nitrogen in starter fertilizer in Nebraska, although response of short-season varieties often occurs further north and west, such as the regions around Brookings, S.D., and Ogallala.

For soybeans, fertilizer containing phosphorus is suggested when the soil test level is 10 parts per million phosphorus or less. The fertilizer can be banded beside the row but not closer than one inch to the seed.

Tom Drudik is a Hall County Extension specialist in agriculture.