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Starter
Fertilizer
With warming temperatures
and fields drying nicely, the prospects of another early planting season
here in the north is a distinct possibility. If in fact this comes to
pass, will remain to be seen, however, with early planting the use of
starter is a good management choice. Cool soil temperatures reduce the
soil microbial activity and reduce the amount of mineralization and release
of organically bound nutrients. Starter helps fill that gap and improves
emergence, establishment, and early season plant nutrition and plant development.
In general the lower the soil test, especially phosphorus, the greater
the response.
There are many methods of applying starter that include both liquid and
granular types of fertilizer. In addition, these applications range from
a placement of 2 inches to the side and 2 inches below, to direct application
to the seed. Most problems associated with starter are in cases where
fertilizer is applied directly to the seed. In general the farther from
the seed the greater amounts of fertilizer can be delivered. The main
thing to keep in mind is the salt index. This is defined by the total
amount of nitrogen and potash in pounds applied. For dry fertilizer in
means multiplying the number of lbs. per acre times the analysis for N
and K and adding these number together. For example: 100 lbs. of 9-23-30
will have a salt index of 39 arrived at as follows;
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.09x100 = 9
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.30x100= 30
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39
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For liquids it's a similar
process however, you will need to know the weight of the product you are
using. For example; 7-21-7 weighs 11 lbs. Per gallon which means that
each gallon contains the following; .77 lbs. of N, 2.31 lbs. of phosphorous
and .77 lbs. of potash. (11x .07=.77; 11x.21=2.31; 11x.07=.77) Therefore
10 gals of 7-21-7 would have an salt index of 15.4. (10x.77 + 10x.77=15.4)
There are various recommendations for the total amounts of salt which
can be tolerated in various placement situations. In general, when fertilizer
is placed in direct contact with the seed, the total salt content should
not exceed 8 lbs. per acre on heavy textured soils. That amount should
be reduced to 5 lbs. on sandy or lighter soils. In a typical 2x2 placement
no more than 30lbs of total salt should be tolerated on light soils and
60 lbs. on heavy soils. (In general these higher rates are more than is
necessary to produce a starter effect.)
It should be noted that cool dry soil conditions will increase the possibility
of damage from starter fertilizer, especially when it is applied directly
to the seed. Drying of the soil after planting will increase the concentration
of salts. In some cases damage has occurred when soil moisture has been
adequate at planting but because of lack of additional rainfall following
planting, damage still occurred. With the possibility of early planting
this spring a certain amount of caution should be exercised. Emergence
complaints associated with early planting are sometimes the result of
improper amounts and placement of starter. It is advisable to check equipment
carefully prior to planting to assure proper rates and placement of starter.
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