Soybeans are a crop that can remove significant amounts of nutrients per bushel of grain harvested. For this reason, soybeans may respond to starter fertilizer applications on low test soils, especially phosphorus.
State K guidelines for soybeans include a soil test for phosphorus (P), potassium (K), sulfur (S), zinc (Zn), and boron (B). If the fertilizer is recommended by soil test results, the fertilizer should be applied either directly to the soybeans or indirectly by increasing the fertilizer rates on another crop in the rotation by the amount needed for the soybeans.
The most consistent response to starter fertilizer with soybeans would be on soils very deficient in any of the nutrients listed above, or in very high yield potential situations where soils have low fertility levels. or means. Additionally, starter fertilizer in soybeans can be a good way to supplement nutrients that may have been lost by high-yielding crops in the rotation, such as corn, and help maintain optimal levels of analysis. of the ground.
Spreading fertilizer to the side and under the seed at planting is an effective application method for soybeans. This method is especially useful in low-tillage or no-till soybeans because P and K have only limited mobility in the soil from broadcast surface applications.
However, with narrow-row soybeans, it may not be possible to install deep-strip fertilizer units. In this situation, growers can top apply the fertilizer. Fertilizer should not be placed in-furrow in direct contact with soybeans, as the seed is very susceptible to salt damage.
Soybeans rarely respond to nitrogen (N) in starter fertilizer. However, some research in high yield irrigated environments with sandy soils suggests a potential benefit of small amounts of N in starter fertilizer.
Kansas Soybean Row Spacing
There are still many questions about row spacing for soybean production. A summary of recent research from K-State, 2015-17, a series of six on-farm experiments conducted in eastern and central Kansas. Compared to conventional row spacing of 30 inches, soybeans in narrow rows (15 inches or less) in these tests were likely to show equal or slightly higher yields (2-12%), especially when the environment yield was less than 50 bushels. per acre (regardless of planting date, seeding rate or maturity). Above this yield threshold, soybeans showed no yield response to changing row spacing. Overall, the common denominator of response to row spacing is inconsistency, denoted by large response error and variability between sites and years.
Final considerations – some of the benefits of narrow row spacing:
• Early canopy closure promotes better light interception,
• Improved weed control and reduced potential for soil erosion.
On the other hand, some of the disadvantages of narrow rows:
• Potential reductions in final stand at a given seeding rate, related to equipment and row compaction.
• In very dry years, narrow row spacing may consume limited soil water earlier in the growing season, reducing the amount of water available for the critical period around pod formation and seedling. seed filling.
• In humid years, too narrow a spacing (less than 15 inches) can reduce air circulation in the canopy and promote the appearance of certain diseases, such as white mould.
Stacy Campbell is the Agriculture and Natural Resources Officer for the Cottonwood Extension District. Email him at firstname.lastname@example.org or call Hays’ office at 785-628-9430.