Corn - Soil, Nutrition and Fertilizers

Rotation
Crop rotation is as important for corn as with other Manitoba grown crops. Crop rotation is primarily practiced to manage diseases and insects.
  • Fertility factors to consider when including corn in the crop rotation:
  • Yield potential of corn following various crops
  • Nitrogen credits following crops
  • Phosphorus needs after different crops
  • The ability of corn to retrieve nitrogen located below the rooting depths of other crops
 
Corn yields vary depending on the previous crop according to Manitoba Crop Insurance Corporation (MCIC) records.
 
TABLE 2: Relative response of corn yield following various crops in Manitoba (1997-2001)
Previous Crop
% of MB Corn Acreage
 Following This Crop
Yield Index Compared To
Corn After Corn
Corn
16%
100
Dry Beans
11%
133
Cereals
28%
104
Potatoes - irrigated
10%
73*
Potatoes - dryland
1%
100
Sunflowers
5%
106
* Note: Irrigated potatoes are likely grown on coarse sands dependent on supplemental irrigation, When such irrigation is not supplied, corn yields would expect to be limited also.
 
Factors other than pests can account for corn yield differences following various crops.
  • Low residue crops tend to have warmer spring soil temperatures
  •  High water use crops may limit the water for corn and conversely low water use crops may leave stored soil moisture for corn use
  •  Pulse crops or heavily fertilized crops may leave residual N for use by corn. Corn may root 4-5’ deep under Manitoba conditions and retrieve nitrogen leached below the root zone of other crops
  •  Residues from herbicides used in previous crops may impair corn growth
  •  Soil compaction or soil erosion associated with previous cropping activity 
  •  Phosphorus uptake is impaired following canola or summerfallow due to low levels of the beneficial fungi, mycorrhizae
 
Soil Factors Important in Corn Production
The major physical soil characteristics influencing corn production are drainage and water-holding capacity. The relative affect of soil texture on both theses soil properties is reported in Table 3.
 
Well-drained soils with a sandy loam or silty clay loam texture are best suited to corn production. These soils have good internal drainage, which allows the soil to dry out and warm up early in the spring yet store moderate amounts of moisture for crop use.
 
Excessively wet soils impact corn growth and production in several ways:
  • Wet soils remain cooler in the spring, which delays emergence and growth
  • Corn is more susceptive to injury or death. Seedlings can only tolerate flooding for 3-4 days whereas corn at 24” will suffer after only 24 hours of flooding
  • Reduced oxygen levels in wet soils restricts root growth and nutrient uptake
  • Nitrogen loss due to leaching and denitrification can be substantial
  • May prevent timely field operations, such as seeding, inter-row cultivation and herbicide spraying, side-dressing N fertilizer and harvest
 
A combination of tile and surface drainage may be needed on poorly drained soils.
 
TABLE 3: Soil suitability for corn according to texture in Manitoba
Texture
AWHC* (in/4 ft depth)
Water infiltration (in/hr)
Limitation
Coarse sand
4 in
> 10 in/hr
Droughtiness
Sand loam
9 in
2 in/hr
Droughtiness
Pour drainage on "wet sands" over clay
Loam
11 in
1 in/hr
Clay loam
12 in
0.5 in/hr
Poor natural drainage
Clay
14 in
0.04 in/hr
Poor natural drainage
* Available water holding capacity in 4 foot rooting zone = the amount of water a soil can hold at field capacity that is available for crop uptake and growth.
 
Soils coarser in texture than sandy loams have low water holding capacity, but will produce satisfactory corn yields if adequate moisture can be provided by frequent rainfall or irrigation. These soils are more prone to periods of drought. During pollination corn transpires up to 1/3” water per day, and moisture stress has greatest impact on yield at this time. Coarse soils are also vulnerable to leaching losses of nitrate-nitrogen in periods when the crop is not aggressively using soil water.
 
Soils heavier in texture than clay loams can be satisfactory for corn production if they are naturally well-drained or surface and sub-surface drainage is provided.
 
Salinity causes germination problems and poor corn growth. One of the main effects of salinity is to limit water uptake and any slight moisture stress will aggravate the problem. Therefore, soils having electrical conductivity (EC) greater than 4 ms/cm must be avoided and those with EC of 2-4 ms/cm must be managed properly.

 

 


FIGURE 4
Macro and secondary nutrient uptake and removal by a 100 bu/ac grain corn crop
(Soil Fertility Guide)

 
 
 
 


 
FIGURE 5
Micronutrient uptake and removal by
a 100 bu/ac corn crop
(Soil Fertility Guide)
Nutrient Requirements
 
Adequate fertility is an essential step for profitable corn production. 16 essential plant nutrients are required for growth. An insufficient supply of any these essential nutrients can have a detrimental effect on plant growth and ultimately crop yields. All but three of the essential nutrients (carbon, hydrogen and oxygen) are derived from the soil. Four nutrients-nitrogen, phosphorus, and to a lesser degree potassium and sulphur, are likely to be of concern for Manitoba crop production. Calcium and magnesium are used in higher amounts by corn than other crops, but Manitoba soils generally have sufficient levels available for successful corn production. Typical nutrient uptake and removal of a corn crop is illustrated in Figure 4.
 
Other elements, including chlorine (Cl), boron (B), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and molybdenum (Mo) are called micronutrients and are required in smaller amounts (Figure 5). Most soils in Manitoba are adequately supplied with micronutrients. Copper and zinc are the two micronutrients most likely to be deficient in Manitoba soils. Copper availability may be low in peat soils and in high pH, low organic matter, sandy soils. Corn is sensitive to Zn deficiency, which may be found on highly calcareous (high lime content) soils. Soil testing, tissue sampling and visual deficiency symptoms are used to diagnose micronutrient deficiencies.
 
Nitrogen
Nitrogen is required for proper growth and development. A lack of nitrogen results in stunted and yellow plants, reduced yield and delayed maturity. Excessive N can result in reduced yield, higher harvest moisture and nitrate accumulation in the stalk. Therefore it is important that nitrogen application rates be appropriate for the soil type and the expected yield.
 
Nitrogen is taken up continuously by the plants through to maturity. The rate of uptake after silking is slower than just before tasselling. A large part of the N accumulated in the leaves and stem is translocated to the grain as it matures and about 2/3 of the N in the plant will be found in the grain at maturity.
 
Phosphorus
Phosphorus is required for plant growth and seed development. Banding a small amount of P2O5 near the seed can result in more vigourous growth of the seedling. This is referred to as a pop-up’ or ‘starter’ effect. 
 

Mycorrhizae are a naturally occurring beneficial fungus that assists many plants to increase uptake of phosphorus. The hyphal threads or strands of the fungi act as an extension of the plant root system and increase interception and uptake of nutrients. Mycorrhizae may increase the effective rooting volume of young plants by up to 10 fold. Mycorrhizal populations are not supported under summerfallow or Brassica crops such as canola. When corn follows such cropping systems P uptake may be impaired. Research studies indicate application of phosphate fertilizer to corn only partially overcome this early season P uptake impairment. Phosphorus uptake may be greater under zero tillage systems which do not disturb established hyphal strands.

 
Phosphorus is taken up continuously during the growing season. Large amounts of P are required after tasseling and during the ripening period. Most of the P accumulated in the leaves, stalks, and husks is translocated to the grain at maturity when about 70% of the P in the plant is in the grain.
 
Potassium
Most Manitoba soils contain sufficient potassium for crop production. Soils likely to be low in K are frequently those same lighter-textured soils most suited to corn production, thus soil testing is recommended. Rapid uptake of K starts at about the same time as the start of rapid plant growth and is maintained only until the grain starts to be formed, at which time the uptake of K is complete. Most of the K taken up by the plant remains in the leaves and stalk. Large quantities of potassium can “leak” from the plant during the grain drydown stage.
 
Sulphur
Sulphur is a key component of several important amino acids that are required for the development of proteins and enzymes. Sulphur is taken up by the roots in the sulphate form. Elemental sulphur fertilizer must be oxidized by soil micro-organisms to the sulphate form. Sulphate-S may leach in coarse soils, and levels within a field can vary, depending upon soil type and slope position. It is not uncommon for low lying, heavy soils to contain many times more sulphate-sulphur as light-textured hilltops. Sulphur deficiencies are most likely to occur in well drained soils, and soils with low organic matter.
 
Fertilizer Application
Soil and tissue testing are two ways to determine the available nutrient status of a field. Reliable test results and recommendations depend upon:
  • Proper soil and tissue sampling
  • Proper analysis techniques
  • Sound fertilizer recommendation guidelines
 
 
Fertilizer Placement, Timing and Rates 
Corn performance and efficiency of applied fertilizer nitrogen, phosphorus and potassium is influenced greatly by fertilizer placement and timing.
 
Nitrogen Placement
Nitrogen fertilizer efficiency is increased by in-soil banding by minimizing potential losses due to immobilization, denitrification, leaching, volatilization and weed uptake. Band placement of nitrogen is generally 20% more efficient ‘than broadcast application’ (i.e. similar yield would be expected from 100 lb N/ac banded as from 120 lb N/ac broadcast).
 
There are several options for band placement of N in corn:
  • sub-surface banded into soil prior to seeding (in spring or previous fall)
  • side banded at seeding
  • mid-row banded at seeding
  • sub-surface banded or side-dressed between the rows after emergence
  • surface banded after seeding
 
The type of seeder will influence placement options. Those seeding with row-crop equipment and wider rows have the option of side-dressing N after seeding, sometimes at the same time as inter-row cultivation. Those seeding with air-seeders in narrow rows may choose to mid-row band N at seeding.
 
Preplant application of anhydrous ammonia should be on an angle to the direction of planting to minimize any fertilizer injury of seeds placed above injection zones.
 
Side-banding is optimal placement for phosphorus fertilizer, but efficiency may be reduced if excessive rates of N and/or K are applied in this band. High rates may burn seedling roots, or inhibit root growth into the concentrated band to access critical early season P.
 
Side-dressing should be completed by the time corn reaches the 6” height. Further delaying application risks root pruning and wet weather that may thwart field operations. Cornbelt studies indicate that “skip-row” application of side-dressed N (placed between every second row) is as efficient as placing N between every row.
 
There are several options for broadcast applications of nitrogen for corn:
  • Broadcast and incorporated with tillage
  •  Broadcast without incorporation
  •  Broadcast into the standing crop
  •  Fertigation in irrigation water
 
 
Broadcast and incorporated applications provide some flexibility in allowing simultaneous application with some soil-applied herbicides.
 
Surface applied nitrogen into corn is dependant on rainfall to move it into the root zone. When rainfall is delayed, surface applications of urea-based fertilizer (including UAN solutions) are vulnerable to loss due to volatilization, particularly under conditions of high temperatures, drying winds and low organic matter, high pH, light-textured soils.
 
Surface banded N after seeding is usually done by dribble banding UAN solutions, and although volatilization losses are not eliminated, they are minimized compared to broadcast application.
 
Broadcast applications of urea into growing corn may injure the growing point if granules fall into the whorl.
 
N Timing
N losses due to leaching, denitrification, immobilization and weed growth are expected to be higher for fall-applied than for spring-applied nitrogen. Hence, spring-applied nitrogen is often considered to be 20% more efficient. These losses may be greater if the nitrogen is applied too early in the fall (prior to mid-September) or when soil temperatures at the 4 inch depth are greater than 5°C. Loss of N accounts for much of the difference in efficiency. Ideally, fall nitrogen would be applied in a band into cool soils using ammonia N forms (eg. urea, anhydrous ammonia). Under dry soil conditions, the efficiency of nitrogen banded in late fall can approach that of spring banded. Efficiency of fall-applied N can be substantially lower than those indicated under excessive moisture conditions in spring or fall, and/or an early fall application before soils have cooled to 5°C.
 
In a practical sense, time and method of application should be based not only on the needs of the crop and potential losses from the soil, but also on co-ordination of the soil fertility program with an efficient overall farm management system. Select a time and method of N application that permits preparation of a good seedbed, conserves soil moisture, aids in prevention of soil erosion, allows for timeliness of operations and is consistent with maximization of net returns.
 
Splitting nitrogen applications between preplant and post seeding may be desirable on soils that are particularly susceptible to leaching (eg. irrigation of coarse sands).
 
Phosphorus and Potassium
Early season uptake of P and K is essential to the successful establishment of corn. These “immobile” soil nutrients do not move far in the soil and are taken up by the root by diffusion over short distances through the soil solution.
 
Placement is dually important; to create a high probability that plant roots will come into contact with these applied nutrients, and that minimizing soil contact will result in more availability.
 
Band applications of P are superior to broadcast applications under conditions frequently observed in Manitoba; low soil test P levels, cold and wet soil conditions at seeding and calcareous soils that fix substantial quantities of P. Broadcast applications may need to be 2-4 times greater in order to equal growth and yield achieved by band placement.
 
Similarly, efficiency of band application of potassium (K) is greater than broadcast application, especially when requirements are low. Band options are: pre-plant banding, side-banded and seed-placed. The N and K content of fertilizer restrict the quantity of fertilizer that can be safely seed-placed.
 
Manure
Corn has a high demand for nutrients and is a very s from the Soil Fertility Guide illustrates the opportunity for manure to supply nutrient needs of the corn crop (Table 4).
 
As with fertilizer nutrients, manure N use is optimized though sub-surface banding. In order to maintain timely planting and to minimize soil compaction, manure should be applied to dry soils in the fall prior to seeding. Unlike cereals, corn will tolerate areas of inadvertent excessive manure application without lodging.
 
TABLE 4: Average nutrient analysis of manure and the amount available for crop use the year applied
Type of manure
Number of
samples
Total N (avail)*< 
Ammonium N
Organic
N
Phosphate P2
O5 (avail)*
Potassium
K2O
Sulphur
S
Dry matter
content %
LIQUID                                Lb/1000 gallons
Hog
36
23 (18)
16
7
15 (7.5)
13
1.4
2
Dairy
7
26 (18)
14
12
13 (6.5)
29
2.4
6
SOLID Lb/ton
Hog
3
14 (6)
2
12
15 (7.5)
16
2.5
35
Poultry
2
34 (12)
2.3
32
30 (15)
28
6.5
57
Beef
33
9 (3)
0.3
9
4 (2)
11
1.4
30
*Manitoba Agriculture, Food and Rural Initiatives, Soil Fertility Guide, amount available for following crop use; for nitrogen = ammonium-N + 30% of organic-N, for phosphorus = 50% of total phosphate.
 
TABLE 5: Nitrogen recommendations for corn (based on a spring banded application)
Target Yield
Nitrogen Recommendation (lb/ac)
Grain Yield bu/ac
130
115
100
85
Silage Yield t/ac @ 70% moisture
19.4
17.1
14.9
12.6
Fall Soil NO3-N (lb/ac in 0-24 in)
Rating
20
VL
260
205
150
95
30
L
225
170
115
60
40
M
200
145
90
35
50
M
170
115
60
5
60
H
140
85
30
0
70
H
110
55
0
0
80
VH
80
25
0
0
90
VH
55
0
0
0
100
VH+
25
0
0
0

 
Fertilizer Recommendations
Fertilizer recommendations have been developed and recently verified for corn in Manitoba (see Tables 5 & 6). Recommendations are based on soil testing and on target or expected corn yield for nitrogen. Proper soil sampling strategies and procedures are outlined in Manitoba’s Soil Fertility Guide.

 

Selection of an appropriate expected yield is critical to developing a nitrogen recommendation. The yield goal should be challenging, yet realistic and achievable in a good year.
 
Consider the following:
  • Past yields on that same field
  •  Discounts for soil limitations – eg salinity and drainage
  • Assess your management level - from farm yields for the past 5 years, drop the low and the high yield and determine the average. Add 10-15% to this average for a target yield.
  •  Hybrid maturity and yield potential
  •  Previous crop effect
  •  Stored soil moisture and anticipated rainfall
  
There is an opportunity to fine-tune nitrogen applications in corn since the final N application can be done in-crop. Techniques can be used in-season to assess crop nutrient sufficiency and to determine the need to apply additional N or to hold back applications. These include use of in-season soil testing, early tissue analysis or use of the SPAD chlorophyll meter. Consult your crop adviser for details.
 
TABLE 6: Phosphorus, potassium and sulphur recommendations for corn
  
Soil Phosphorus
(sodium bicarbonate P test)
P2
O5
Soil Potassium
(ammonium acetate K test)
K2O lb/ac
Soil Sulphate-Sulphur
in 0-24 in.
S lb/ac
ppm
lb/ac
Rating
SB*
ppm
lb/ac
Rating
SB*
PPI**
lb/ac
Rating
0
0
VL
40
0
0
VL
100
200
0
VL
20
5
VL
40
25
50
VL
90
180
5
VL
20
5
10
VL
40
50
100
VL
80
160
10
VL
20
15
L
35
75
150
L
75
150
15
L
20
10
20
M
30
100
200
M
65
130
20
L
20
25
M
20
125
250
M
55
110
25
M
20
15
30
H
15
150
300
H
50
100
30
H
0
35
H
10
175
350
H
40
80
35
H
0
20
40
VH
10
200
400
VH
30
60
40
VH
0
20+
40+
VH+
10
200+
400+
VH+
0
0
40+
VH+
0
* SB = based on side band applications for row crops
**PPI = based on broadcast and preplant incorporated
 
TABLE 7: Soil test criteria for micronutrients
 
Micronutrient
Extractant
Critical Level
Marginal Range
Copper (Cu)
DTPA
0.2 ppm
5.0 ppm
for peat soil
0.2-0.4 ppm
5-12 ppm
on peat soil
Iron (Fe)
DTPA
4.5 ppm
Manganese (Mn)
DTPA
1.0 ppm
Zinc (Zn)
DTPA
0.5 ppm
0.5 to 1.0 ppm
Yield response to applied micronutrient is more likely when soils test in the critical and marginal range.
 
Corn is most likely to respond to the micronutrients zinc and copper in Manitoba soils. There are several options for source, timing and application method of micronutrient fertilizers. Application options are broadcast and incorporated, soil banded or foliar. Broadcast and thoroughly incorporated application generally maximizes, nutrient uptake by increasing opportunity for root interception. Broadcast and incorporated micronutrient fertilizers are recommended as follows:
  • Preplant incorporate 10-15 lb/ac zinc as zinc sulphate or 2-3 lb/ac zinc as zinc EDTA chelate.
  • Preplant incorporate 5-10 lb/ac copper as copper sulphate or 1-2 lb/ac copper as EDTA copper chelate.
  • On peat, incorporate 5-15 lb/ac copper as copper sulphate or 1-3 lb/ac copper as EDTA copper chelate.
  
Banded micronutrients at lower rates have been observed to be effective but residual effect will be shorter. Likewise, foliar applications may also be effective to correct deficiencies diagnosed early in the growing crop.
 
Producers neglecting to soil test must resort to using general recommendations as follows:
 
TABLE 8: Fertilizer requirements for corn lacking a soil test
 
Previous Crop
Fallow/or forage legumes
Stubble
Phosphate
Potassium*
Sulphur
Lb N/ac
Lb P2O5/ac
Lb K2O/ac
Lb S/ac
0-30
65-135
30-40
30-100
20
*On sandy-textured or organic soils
 

More information: