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osunpk

osunpk

Since 2008 I have served as the Precision Nutrient Management Extension Specialist for Oklahoma State University. I work in Wheat, Corn, Sorghum, Cotton, Soybean, Canola, Sweet Sorghum, Sesame, Pasture/Hay. My work focuses on providing information and tools to producers that will lead to improved nutrient management practices and increased profitability of Oklahoma production agriculture

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In-furrow fertilizers for wheat

From Guest Author, Dr. Dorivar Ruiz Diaz, Nutrient Management Specialist, Kansas State University

Wheat is considered a highly responsive crop to band-applied fertilizers, particularly phosphorus (P). Application of P as starter fertilizer can be an effective method for part or all the P needs. Wheat plants typically show a significant increase in fall tillers (Figure 1) and better root development with the use of starter fertilizer (P and N). Winterkill can also be reduced with the use of starter fertilizers, particularly in low P testing soils.

Figure 1. Effects on wheat tillering and early growth with in-furrow P fertilizer on soil testing low in P. Photo taken in 2020 in Manhattan, KS. Photo by Chris Weber, K-State Research and Extension.

In-furrow fertilizer application

Phosphorus fertilizer application can be done through the drill with the seed. In-furrow fertilizer can be applied, depending on the soil test and recommended application rate, either in addition to or instead of, any pre-plant P applications. The use of dry fertilizer sources with air seeders is a very popular and practical option. However, other P sources (including liquid) are agronomically equivalent and decisions should be based on cost and adaptability for each operation.

When applying fertilizer with the seed, rates should be limited to avoid potential toxicity to the seedling. When placing fertilizer in direct contact with wheat seed, producers should use the guidelines in Table 1.

Table 1. Suggested maximum rates of fertilizer to apply directly with the wheat seed

 Pounds N + K2O (No urea containing fertilizers)
Row spacing
(inches)
Medium-to-fine
soil textures
Course textures or dry soils
 
151611
102417
6-83021

Air seeders that place the starter fertilizer and seed in a 1- to 2-inch band, rather than a narrow seed slot, provide some margin of safety because the concentration of the fertilizer and seed is lower in these diffuse bands. In this scenario, adding a little extra N fertilizer to the starter is less likely to injure the seed – but it is still a risk.

What about blending dry 18-46-0 (DAP) or 11-52-0 (MAP) directly with the seed in the hopper? Will the N in these products hurt the seed?

The N in these fertilizer products is in the ammonium-N form (NH4+), not the urea-N form, and is much less likely to injure the wheat seed, even though it is in direct seed contact. As for rates, guidelines provided in the table above should be used. If DAP or MAP is mixed with the seed, the mixture can safely be left in the seed hopper overnight without injuring the seed or gumming up the works.  However, it is important to keep the wheat mixed with MAP or DAP in a lower relative humidity.  A humidity greater than 70% will result in the fertilizer taking up moisture and will cause gumming or caking within the mixture.  

How long can you allow this mixture of seed and fertilizer to set together without seeing any negative effects to crop establishment and yield?

The effects of leaving DAP fertilizer left mixed with wheat seed for various amounts of time is shown in Figure 2. Little to no negative effect was observed (up to 12 days in the K-State study).

Figure 2. Effects on wheat yield from mixing P fertilizer with the seed. Study conducted in 2019 and 2020 at four sites. Graph by Chris Weber, K-State Research and Extension.

Although the wheat response to these in-furrow fertilizer products is primarily from the P, the small amount of N that is present in DAP, MAP, or 10-34-0 may also be important in some cases. If no pre-plant N was applied, and the soil has little or no carryover N from the previous crop, the N from these fertilizer products could benefit the wheat.

Dorivar Ruiz Diaz, Nutrient Management Specialist
ruizdiaz@ksu.edu

Chris Weber, former Graduate Research Assistant, Soil Fertility

Canola fertilizer rates when skip row seeding.

When drilling canola a common strategy to improve seeding rate accuracy is to only use every other row which effectively doubles the rate of seed going through each meter.  There are also many producers who utilize air seeders and just prefer the wider spacing.  Every season I get several questions about determining total fertilizer rates if the seed is dropped every other row but fertilizer is dropped every row. Regardless of whether or not fertilizer goes down every row it is important that the amount of salts placed with seed does not exceed the limit.  The table below provide the limits in terms of lbs of salt per acre.  If using 18-46-0 (DAP) or 11-52-0 (MAP) this is equivalent to pounds of N per acre. However if the fertilizer you use contains potassium (K) or sulfur (S), those have to be considered. An easy rule of thumb for determining total salt level of a fertilizer is pounds of N + K + 1/2 S.

Maximum amount of salt that can be applied in furrow with canola seed. Application rate should be at or below this value.

Maximum amount of salt that can be applied in furrow with canola seed. Application rate should be at or below this value.

In a scenario in which canola is seeded in skip rows but every row will get fertilizer the total amount of fertilizer can be doubled.  For example on a 15″ row spacing the max salt rate is 5 lbs per acre. If you were using DAP as your starter that maximum rate to place in furrow would be 28 lbs of DAP per acre.  If using a drill set of 7.5″ spacing and putting fertilizer down every row the max rate would increase up to 56 lbs DAP per acre.

 

Seed, colored blue, is placed in every other row but an equal amount of fertilizer, dark grey circles, is placed in every row.

Seed, colored blue, is placed in every other row while an equal amount of fertilizer, dark grey circles, is placed in every row.

Some producers may have the capability of applying different rate in every other row.  In this scenario it is important to maintain that safe rate in the seed furrow. In the opposite row, fertilizer rate can go as high as you wish or the equipment can handle.

Seed, colored blue, is placed in every other row but an fertilizer, dark grey circles, is placed in every row. In this scenario a high rate is placed in the row without seed.

Seed, colored blue, is placed in every other row  while fertilizer, dark grey circles, is placed in every row. In this scenario a high rate is placed in the row without seed.

Now the big question is, “Is between row fertilization a good idea?” While we do not have results on this style of application (trials will be going out this year)  we can draw upon upon similar work in other crops. For me the best win would be the second scenario in which a higher rate could be place between the rows.  In this row I would use a urea and DAP blend.  Any time we can put urea below the soil surface its a win and in fields with very soil soil test phosphorus (P) it would create something similar to the deep P bands  once popular in corn production. Now if the field had adequate soil test P, I would focus on urea between rows. Keep in mind it is never a good to place urea in furrow with canola seed. For the average producer who is using a box drill the first scenario is the only option.  In this case the rate of the between row bands will be reduced however I still believe on fields with very low soil test P this is potentially a great way to get the rest of it on. Remember if on 15″ and using DAP max rate only gets 12.9 lbs of P2O5 down.  If fertilizer is dropped down every tube that number increases to about 26 lbs P2O5, which is still not enough for fields with low soil test P, but is better.  With hope we will have some good results to share from the 2015-2016 canola crop.

Phosphorus Fertilizer recommendations based upon Mehlich 3 P test reported as STP index (ppm * 2)

Phosphorus fertilizer recommendations based upon Mehlich 3 P test, reported as STP index (ppm * 2)