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Soybean seeding rates affect input costs

April 10, 2009
From Wayne Schoper Brown/Nicollet Extension Educator

As you know, we have seen a lot of volatility in the corn and soybean markets over the past year or so. Not quite a year has passed since we saw record high corn and soybean prices. Around the end of June 2008, corn reached just over $7 per bushel and soybeans were over $16 per bushel for a short period of time. That being said, the high prices were short lived and very few farmers actually sold much crop at those prices.

However, we are still feeling the repercussions of those high commodity prices through increased input costs and high land rental costs. Speaking of land rent, I still feel that a fair land rent, taking everything into consideration, should be around $155-$160 for 2009 production. This figure would be for good, average farm ground that is well-drained and with few other complications.

As for other input costs, we have seen fertilizer prices come down somewhat during the past few months. Some fertilizer products such as 0-0-60 (potash) have not budged too much. But Anhydrous Ammonia (82-0-0) has come down significantly. Part of this is that Anhydrous Ammonia consumes petroleum products in its manufacture and oil prices are less than half of what they were a year ago. So we have seen some inputs come down.

One input that has received some attention this last year is the cost of seed. This is because weed control costs have been shifted more heavily onto the seed in the form of technology fees related to glyphosate resistance. Seth Naeve is an extension soybean agronomist with the University of Minnesota. He had the following comments regarding soybean seeding rates. Before having this discussion, it is important to focus on some of the underlying principles of populations and yield. Soybean plant populations do not create yield, yet, maximum yields require sufficient populations. Soybean stands must be large enough to maximize light interception throughout the growing season and provide an abundance of fruiting sites (leaf axils) so that pod set can be maximized. More plants allow more potential places for seed to set and mature. For this reason, the minimum plant stand at harvest to maximize yield is the critical number to strive for. Initial seeding rates help to determine spring-time emergence stands. The initial stand then helps determine the number of plants that will ultimately bear seed and produce yield.

Under ideal conditions, soybeans in southern Minnesota should be planted at about 140,000 live seeds per acre. It appears that soybeans grown in central and northwestern Minnesota require harvest stands of 125,000 to 150,000 plants per acre to maximize yields. This is likely due to shorter-stature soybeans with fewer total nodes that are often produced in these regions. Increased seeding rates are required in central and northwestern Minnesota. Therefore a system based on soybean maturities has been developed to point producers toward reasonable soybean seeding rates.

- Maturity Group II soybeans: 140,000 live seeds per acre

- Maturity Group I soybeans: 150,000 live seeds per acre

- Maturity Group 0 soybeans: 160,000 live seeds per acre

- Maturity Group 00 soybeans: 170,000 live seeds per acre

Some cautions:

A. Recommendations are independent of row spacing

B. Recommendations are based on live seed. Take a look at germ rates provided on seed tags.

C. Seeding rate suggestions are based on excellent to ideal planting conditions. Planting early or into cold and/or wet soils may require increased seeding rates.

D. Soybeans planted into high pH areas that are prone to iron deficiency chlorosis (IDC) may benefit from higher seeding rates. This benefit is amplified when soybeans are planted in wider rows (22 - 30")

One final comment, there are many variables affecting final stands. A good strategy might be to utilize liberal seeding rates until you understand how your planting equipment, planting date, soil type, and spring conditions affect your actual plant populations.



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