Fertilizer Recommendations for Growing Soybean

Soybeans high yields are possible only when the crop meets its nutritional requirements. In many cases, mismanagement of nitrogen application prevents the soybeans grower from achieving the yield potential.

WHEN AND HOW TO FERTILIZE SOYBEANS?

Increasing soybeans yield

Soybeans do not require high fertilizer application rates, yet, an accurate nutritional plan is necessary for increasing yields.

The crop classified as moderately sensitive to saline, with a salinity threshold of 2.0 dS/m. Soil pH of 6 – 6.8 is ideal.
Banding fertilizers and foliar feeding are common application methods but should be considered only when conventional methods are not satisfying.

Soybeans grains have a nitrogen content of 40%, therefore an adequate fertilization of nitrogen is a key factor in achieving high quality yields.

NITROGEN DEFICIENCY AND FIXATION

Whenever nitrogen is in deficient, symptoms such as yellowing or chlorosis will appear. Since nitrogen is mobile, the element will translocate to new growing tissues and thus the symptoms will first appear in the lower parts of the canopy.

Nitrogen comes from two main sources:

•   The soil solution
•   The nitrogen fixation process

Nitrogen fixation takes place in the root system, in small oval structures called nodules. The roots associate with a bacteria (Bradyrhizobia japonicum) that transforms atmospheric nitrogen (N2) into available ammonia (NH₃).

TIMING OF NITROGEN APPLICATION

Many studies we’re conducted in order to determine the ideal time for nitrogen application. Extension services tends to disagree on the importance of fertilizing in the early season or in the pod filling stage.

Understanding the soybeans nutrient uptake can lead to the correct timing of nitrogen application. The translocation of nitrogen is at its peak in around 8 weeks after the planting. In any case, the fertilizer program has to be based on a reliable yield estimation and on soil and water tests, whenever available.

Sampling leaves for plant tissues analysis is vital for precise Fertilizer Software. Sampling the first fully develop leaf at first flowering in highly recommended.

Table 2. Soybeans tissue analysis – recently matured leaf adequate element level

There is no benefit in fertilizing the crop incorrectly. Mismanagement of fertilizer applications can have a negative effect as nutrient deficiencies can.

Creating an optimal fertilizer schedule will support the plant throughout its life cycle and thus maximize the yield and avoid waste.

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