Corn - Soil, Nutrition and Fertilizers
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
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. |
- 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
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.
- 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
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. |
FIGURE 4 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.
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 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.
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
Corn performance and efficiency of applied fertilizer nitrogen, phosphorus and potassium is influenced greatly by fertilizer placement and timing.
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).
- 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
- Broadcast and incorporated with tillage
- Broadcast without incorporation
- Broadcast into the standing crop
- Fertigation in irrigation water
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.
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.
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).
Type of manure |
Number of samples |
Total N (avail)* |
Ammonium
N |
Organic N |
Phosphate
P2O5 (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. |
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.
- 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
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 |
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. |
- 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.
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: