What Does Seedplaced Fertilizer Injury Look Like?

Submitted by John Heard, Soil Fertility Specialist, Manitoba Agriculture

Already we are hearing of spotty emergence with cereal crops in Manitoba.  Possible culprits may be dry seedbeds, poor quality seed, seed depth, herbicide residues, or seed placed fertilizer injury.Past Prairie studies suggested a 15% stand reduction was tolerable for cereals since surviving plants tillered and filled in the stand.  But maturity is less uniform and is delayed up to 4 days.
How might one confirm seedplaced fertilizer injury?  Close inspection can show a range of symptoms:
1.        Seeds that imbibed water but did not develop any root or shoot
2.       Seeds that developed shoots but no roots
3.       Seeds that developed root and shoot but leafed out below ground
4.       Those that did germinate and emerge (about 44%) were ½ to 1 full leaf stage behind normal seedlings in the low fertilizer strip.
In other crops injury can show as:
Canola – seeds just do not germinate and remain intact.   Fields simply appear to have very poor crop establishment.
Soybeans – stands may be injured, especially with wider row spacing and on sandy soils under dry conditions.
For more information, see the full .pdf document on Manitoba Agriculture Current Crop Topics – What Does Seedplaced Fertilizer Injury look like in Cereals
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Volatilization of surface applied urea/UAN

Submitted by: John Heard, Manitoba Agriculture, Soil Fertility Specialist
Surface broadcasting of nitrogen (N) fertilizers has become popular to increase operational efficiency – increasing the speed of seeding and reducing risk of seed injury.  But, in a dry spring with limited rain prospects, growers may choose not to till and avoid further drying out seedbeds.  Then growers must consider the risks of nitrogen volatilization loss and take precautions when risk is high.
Volatilization of ammonia (NH3) from urea or the urea portion of UAN (28-0-0) affected by several factors and can be increased under specific situations.
For more details on the risk factors and ways to minimize losses, see full .pdf 
More topics on soil fertility can be found on Manitoba Agriculture’s Soil Fertility webpages.
 
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Spring Preplant Banded nitrogen Too Hot for Corn in Dry Springs!

Submitted by: John Heard, Manitoba Agriculture, Soil Fertility Specialist
There is no single best way to fertilize corn in Manitoba.  The 4 most common N application methods are spring broadcast and incorporated, fall banded, banded at seeding and preplant banded.
In a dry spring like 2019 (similar to 2018),  broadcasting and incorporating fertilizer before seeding, risk drying out the seedbed.  Many farmers, especially on clay-textured soils prefer not to disturb their seedbed in the spring and so prefer to fall band their N.  And although spring preplant banding is a very efficient way to place nutrients for a corn crop, it comes with some particular cautions – thinning and seedling injury.  
More detailed information and analysis in full .pdf
More topics on soil fertility can be found on Manitoba Agriculture’s Soil Fertility webpages.
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Can Sidebanded Nitrogen Cause Injury in a Dry Year?

Submitted by: John Heard, Manitoba Agriculture, Soil Fertility Specialist

With a lack of seedbed moisture, there are justified concerns about seedplaced fertilizer injury to canola and other crops.  How safe is sidebanded nitrogen? Research studies by  Dr. Cindy Grant documented considerable canola stand thinning when high rates of sidebanded urea or UAN solution were applied.  Agrotain (AT) served to reduce stand injury, but is no longer supported for this use by the manufacturer. 

Points:
  • Stands were thinned at even modest N rates, on a clay loam soil.  At high rates stands were reduced to 50%
  • Crop growth compensated for reduced stands and generally produced as good a yield as the Agrotain protected stands, except at the highest rate.
For more detailed analysis and discussion on the issue see the full .pdf
More topics on soil fertility can be found on Manitoba Agriculture’s Soil Fertility webpages.
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Seed Placed Fertilizer Cautions for Canola

Submitted by: John Heard, Manitoba Agriculture, Soil Fertility Specialist

Spring 2019 (like 2018) has brought many questions about seedplaced fertilizer rates for canola.  Several factors are causing concern:

  • Drier soils – which increase the risk of seed toxicity
  • Desire to apply sufficient P to meet crop removal – since many fields have seen decreasing P levels due to high yield.  P removal is about 1 lb P2O5/bu, so high yield potential fields are looking at high P replacement rates.
  • Increased use in low disturbance, low seedbed utilization (SBU) drills.  Many new openers are arriving on the scene, which are “close-to-seed” sidebanding for which one may need to consider as seedplaced.
  • Desire by growers to reduce seeding rates for cost savings.  Most research studies investigating seedplaced fertilizer injury were seeded at some 150 seed/m2, about double what some farmers are now targeting.
For more detailed analysis on the issue, see the full text in .pdf format 
 
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Crop Germination – What Soil Temperatures are Needed?

Soil temperature drives germination and seedling emergence, so how cold is too cold?  What is your soil temperature at your targeted seeding depth….today? Finally, when should you be measuring the soil temperature?

The following are the minimum temperatures needed for germination to begin in various crops.  These values should be regarded as approximate, since germination depends on factors other than just temperature.  But, if soils are too cool, germination will be delayed and cause uneven or poor seedling emergence.

 

Crop Temperature     (°C)
Wheat 4
Barley 3
Oats 5
Corn 10
Canola 5
Flax 9
Sunflower 6
Edible Beans 10
Peas 4
Soybeans 10

Sources: North Dakota State University Extension Service, Alberta Agriculture & Rural Development and Canola Council of Canada

Getting an accurate measure on soil temperature

Determine how deep you will be seeding. Then place your soil thermometer at the targeted depth. Take two measurements throughout the day: one in the morning (8am) and one in the early evening (8pm).  Average the two readings to determine the average soil temperature. The recommendation is to take readings for two to three days to establish a multiple day average and to measure at a number of locations in the field, to account for field variability.

Still not sure and short on time?  See the soil temperature data for various locations across Manitoba from the MB Ag-Weather Program: https://www.gov.mb.ca/agriculture/weather/soil-temperature.html.  This can be used as a guideline for an area, but in-field measurements are going to tell you what is actually going on in your field!

 

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How Longer Can Winter Wheat Survive under Flooded Conditions?

Flooding tolerance of crops is impacted by a lot of things, but the main ones are: crop type, length of time under water and the temperature.

A couple of things that winter wheat has going for it is that is may not have yet broke dormancy when the water arrived and with relatively cool soil temperatures and cold water, things slow down for biological activities.  One report from North Dakota indicates that winter wheat could withstand flooded conditions for up to 3 weeks, but source is anecdotal https://www.ag.ndsu.edu/news/newsreleases/2009/april-20-2009/flooding-impacts-winter-wheat/

With all water-logged crops, once water has receded, inspect the crown to see if there are any signs of life. As weather warms and if soils remain saturated, there is still risk of oxygen deprivation in the plants and potential for seedling death.

 

General information on crop tolerance to flooding: https://www.gov.mb.ca/agriculture/crops/crop-management/seed-survival-flood-conditions.html

Impact of Flooding on Soil Fertility in Red River Valley: https://www.gov.mb.ca/agriculture/crops/crop-management/impact-of-flooding-soil-fertility.html

Forage Stands – Assessing Flooding Injury: https://www.gov.mb.ca/agriculture/crops/crop-management/forage-stands-assessing-flooding-injury.html

 

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How Much Nitrogen Do I Use to Fertilize my Fall Hybrid Rye?

Submitted by John Heard, Crop Nutrition Specialist, Manitoba Agriculture

Interest and acreage of fall rye has grown substantially in Manitoba. Hybrid rye has about a 20% yield advantage over traditional open pollinated (OP) varieties and are expanding onto more productive soils than rye’s historic range on the droughty sands.

With increased yield potential comes the question about nitrogen rates to sustain that higher yield. The hybrids are shorter and more lodging tolerant, so one might suspect they can tolerate more nitrogen, and hence respond to more nitrogen. Very few studies have looked at nitrogen rates of the open pollinated versus hybrid varieties. Three Saskatchewan studies provide the extent of the data. From this data we observe the substantial yield increase of the hybrids over the open pollinated variety but that similar rates of nitrogen are required to optimize yield of each.

Read the whole story here (PDF 325KB): hybrid-rye-fertilization-rates

 

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Impact of In-Season Sprayer Track Ruts on Corn Yield

Submitted by John Heard, Crop Nutrition Specialist

The concern that producers have is that compaction in the ruts would limit root growth and subsequently reduce nutrient and water uptake, therefore limiting yield.

University of Minnesota studies indicate a possible 17% yield loss when corn is planted into parts of fields badly rutted during the previous harvest. But yield loss data due to in-season wheel traffic ruts and compaction between rows is limited.

Most of Manitoba Agriculture’s applied corn nitrogen research is done in farmer’s fields, so sprayer traffic through plots does occur. Manitoba Agriculture Soil Fertility Specialist, John Head, is seldom concerned as compaction ruts are rarely visible. However in 2016, on one of the sandy loam sites, sprayer ruts were 3-4” deep and quite visible, so they were taken to yield.

Read the whole story here (PDF 600KB) wheel-ruts-corn-yields 

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What is the value of that corn stover?

With corn harvest nearing there may be some questions about harvesting corn stover for feeding beef cattle. There are some implications for the crop farmer with regard to nutrient removal, future nitrogen needs, organic matter and erosion control.

Grain yield is usually about 45-50% of the total dry matter yield of a corn field. It is estimated that a 140 bu/ac corn field leaves about 4 ton/ac of roughage (at 25-30% moisture).  Table 1 includes some nutrient content values from past Manitoba studies1 compared to those of the International Plant Nutrition Institute2.

Table 1. Crop nutrient removal with a 140-150 bu/ac corn crop.

  Stover amount Nitrogen (N) Phosphorus (P2O5) Potassium (K2O) Sulphur

(S)

    Lb nutrient/ton
IPNI average Per dry ton 19 5.7 32
MB Ag Per dry ton 12 4 34 1
    Lb nutrient /acre
All stover removed At 4 t/ac

(2.7 DM ton)

33 11 96 3
½ stover removed At 2 t/ac 17 5 48 2

 

What is the approximate value of fertilizer nutrients removed in stover?

Using the MB Ag values from table 1, the approximate value of nitrogen, phosphorus, potassium and sulphur per dry ton of harvested corn stover is $6, $2.40, $10.20 and $0.40, respectively (based on fertilizer prices of $0.50/lb N, $0.60/lb P2O5, $0.30/lb K2O and $0.40 /lb S) for a total nutrient value of $19/ton.  If harvested stover yields are 4 ton/ac (2.7 dry ton/ac), the total value of nutrients removed from the field would be $51.30/acre.  Since the full stover amount is seldom harvested, the removal would be reduced accordingly.  Note that over half the nutrient value removed is as potassium.

Implications:

One might conclude that all nutrients need to be replaced to sustain continued crop production. But this may not be the case:

  • clay textured soils in Manitoba tend to have high natural reserves of potassium.
  • Potassium is readily leached from mature crop residues, so rained on and delayed corn stover removal will leave much of the potassium in the field.
  • since stover harvest is done only occasionally, it will impact soil test levels slightly
  • nitrogen requirements may actually be less for the next crop (read on)

Nitrogen needs of the following crop may actually be reduced when some corn residue is removed. With the typically high residue loads of corn stover and the relatively high C:N ratio, inorganic soil N levels can be depressed during residue decomposition, called immobilization.  This temporary tie up of nitrogen by microbes to breakdown residue will be less if there is less stover. US studies with corn following corn have shown that optimum N rates may be 10-45 lb less N per acre when half the residue is removed.   We grow little corn following corn here so may not such large differences.

Now if corn stover was grazed by cattle, many of these fertilizer nutrients would simply remain in the field, but most crop farmers want cattle off the field so they can complete fall tillage operations to prepare for the 2019 crop season.

Erosion, organic matter levels and soil structure would be negatively affected by full and continuous removal of corn stover, but not likely by occasional removal. Mechanical harvesting (usually stover cutting with a rotary hay cutter, raking with a double rake, then baling) may only remove some 40% of the total stover biomass, generally leaving sufficient soil cover.  And since Manitoba corn stover is usually aggressively tilled, this reduced cover will require less than normal tillage to prepare a seedbed for springtime.

In summary, the occasional removal of a portion of the corn stover should have minimal effect on soil properties – other than nutrients. Soil testing is important to know if you have such nutrients to spare or how much to charge for such removal.

References:

1 Heard, J. 2004.  http://www.umanitoba.ca/faculties/afs/MAC_proceedings/proceedings/2004/heard_nutrient_uptake_corn.pdf

2Fixen, P. 2007. Better Crops/Vol 91, no.1) https://www.ipni.net/ppiweb/bcrops.nsf/$webindex/BD81AB2128ECC7D2852572DE005B4364/$file/07-2p12.pdf

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