SOIL, NUTRITION AND FERTILIZERS Rotation

Transcription

1 SOIL, NUTRITION AND FERTILIZERS Rotation Fertility factors to consider when including corn in the crop rotation: Yield potential of corn following various crops N credits following crops P needs after different crops The ability of corn to retrieve N located below the rooting depths of other crops Corn yields vary depending on the previous crop according to Manitoba Agricultural Services Corporation (MASC). TABLE 2. Relative response of corn yield following various crops in Manitoba ( ) 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. Previous crop % of MB corn acreage following this crop Yield index compared to corn after corn Corn 16% 1 Factors other than pests can account for corn yield differences following various crops. Low residue crops tend to have warmer spring soil temperatures. igh water use crops may limit the water for corn and conversely low water use crops may leave stored soil moisture for corn use. Dry beans 11% 133 Cereals 28% 14 Potatoes irrigated Potatoes dryland 1% 73* 1% 133 Sunflowers 5 % 16 Pulse crops or heavily fertilized crops may leave residual N for used 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. 1

2 Soil Factors Important in Corn Production The major physical soil characteristics influencing corn production are drainage and water-holding capacity (WC). The relative affect of soil texture on both these 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, interrow 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 Coarse AWC* (in/4 ft depth) * 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 of 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. Salinity is measured using two methods. The commercial method of 1:1 (soil:water) produces values approximately two times greater than the official, but more time-consuming and expensive, saturated paste method. Ensure you are aware of the method of soil test reports of charts to ensure proper interpretation. Relative corn yield as a percentage of maximum yield potential drops rapidly with increasing salinity for example at ECs of 2, 4, 6, 8 and 1 ds/m using the saturated paste method, yields is 96, 72, 48, 24 and percent of the maximum yield potential (source Franzen 212. Managing Saline Soilds in North Dakota. See Table 6.) sand Water infiltration (in/hr) Limitation 4 in >1 in/hr Droughtiness Sand loam 9 in 2 in/hr Droughtiness Loam 11 in 1 in/hr Poor drainage on wet sands over clay Clay loam 12 in.5 in/hr Poor natural Clay 14 in.4 in/hr Poor natural drainage 11

3 lb nutrient/acre NUTRIENT REQUIREMENTS Adequate fertility is an essential step for profitable corn production. Sixteen essential plant nutrients are required for growth, and an insufficient supply of any of these essential nutrients can have a detrimental effect on plant growth and ultimately, crop yields. All but three of the essential nutrients (C,, O) are derived from the soil. 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 modest amounts by corn. Since Manitoba soils are largely derived from dolomitic limestone, these nutrients are well-supplied. Typical nutrient uptake and removal of a corn crop is illustrated in Figure Nitrogen (N) Phosphate (P25) Potassium (K2) Grain Sulphur (S) Stover Calcium (Ca) Magnesium (Mg) Chlorine (Cl) Boron (B) Copper (Cu) Iron (Fe) Manganese (Mn) Nutrient Stover Grain Zinc (Zn) FIGURE 6. Macro and secondary nutrient uptake and removal by a 1 bu/ac grain corn crop (Soil Fertility Guide) FIGURE 7. Micronutrient uptake and removal by a 1 bu/ac corn crop (Soil Fertility Guide) Other elements, including chlorine (Cl), boron (B), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu) and molybdenum (Mb) are called micronutrients and are required in smaller amounts (Figure 7). 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 high in p, low organic matter, sandy soils. Corn is sensitive to Zn deficiency, which may be found on highly calcareous (high lime content) soils and when subsoil has been exposed by erosion or land levelling. Soil testing, tissue sampling and visual deficiency symptoms are used to diagnose micronutrient deficiencies 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 Details on these principles are covered in Manitoba s Soil Fertility Guide Fertilizer Placement, Timing and Rates Corn performance and efficiency of applied fertilizer N, P and K is influenced greatly by fertilizer placement and timing. 12

4 Nitrogen (N) Nitrogen is required for proper growth and development. It is taken up continuously by the plants through to maturity. 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. See Figure 8 Nitrogen uptake and partitioning by a 146 bu/ac grain corn crop. Figure 8. Nitrogen uptake and partitioning in grain corn (Manitoba, 23, 146 bu/acre). Placement: Nitrogen fertilizer efficiency is increased via in-soil banding by minimizing potential losses due to immobilization, denitrification, leaching, volatilization and weed uptake. Band placement of N is generally 2% more efficient than broadcast application. 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 Using directed UAN solution 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. Safety is also determined by the depth of ammonia injection, which should be at least 4 below the depth of seeding. Side-banding is optimal placement for phosphorus fertilizer, but efficiency may be reduced if excessive rates of N and/ or K are applied in a typical 2 to the side and 2 below the seed in this band. igh rates may burn seedling roots, or inhibit root growth into the concentrated band to access critical early season P. For this reason, no more than 3 lb/ acre of total fertilizer product should be applied in a side band. 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 sidedressed N (placed between every second row) is as efficient as placing N between every row. With these skip-row applications, the same rate is maintained, but output per shank is doubled with half the amount of shanks applying fertilizer. 13

5 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 can be utilized pre-plant or post-planting. Surface applied N into corn is dependent on rainfall, or some kind of incorporation, to move it into the root zone, to reduce losses. 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 p, 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 applicationss of urea into growing corn may injure the growing point if granules fall into the whorl. Likewise, dribbled UAN solution should be directed between the corn rows if possible to reduce flow into the whorl. TIMING NITROGEN APPLICATION: N losses are expected to be higher for fall-applied than spring-applied, therefore spring-applied is considered to be 2% 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 depth are greater than 5 o 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 the 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. Wet conditions in May and June leaves N vulnerable to losses. Side-dressing in June is best applied as anhydrous ammonia or UAN, and should be completed by the time corn reaches 6 in height, if the fertilizer is placed in moist soil and if serious injury to the root system, through root pruning, is avoided. Splitting of nitrogen applications between preplant and post seeding may be desirable on soils that are particularly susceptible to leaching (eg. Irrigation of coarse sands). NITROGEN SOURCES: All sources of nitrogen fertilizer will perform well when applied at the right time and placement. Since corn has delayed N uptake compared to our cool season cereal and canola crops, the nitrogen is more vulnerable to loss in the spring. An option is to use a slow or controlled release nitrogen products, such as polymer coated urea ( eg. ESN 44--). Manitoba research has shown benefits to this controlled release nitrogen source in very wet springs, but no difference under typical or dry conditions DEFICIENCIES: Nitrogen deficiencies cause stunted, spindly, yellow plants, reduced yield and delayed maturity. Older leaves will show a V-shaped yellowing of the inner leaves with margins remaining green. Old leaves show deficiencies first. Excessive N can reduce yield, increase harvest moisture and N 3 accumulation in the stalk. See page 2 for images showing nitrogen deficiencies in corn plants. 14

6 Phosphorus (P) Phosphorus is required for plant growth and seed development. Considered immobile in the soil, P is taken up by the root by diffusion over short distances through the soil solution. Phosphorous 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 7% of the P in the plant is in the grain. Figure 9. Phosphorus uptake and partitioning in grain corn (Manitoba, 23, 146 bu/acre). 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. Banding a small amount of P 2 O 5 near the seed can result in more vigorous growth of the seedling, referred to as a pop-up or starter effect. 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. Phosphorus uptake is impaired following canola (brassica crops) or summerfallow due to low levels of vesicular arbuscular mycorrhizae, which aids in phosphorus uptake. Mycorrhizae are a naturally occurring beneficial fungus that assists many plants (excluding canola) to increase uptake of phosphorus. The hyphal threads or strands of the fungi act as an extension of the root system and increase interception and uptake of nutrients. Mycorrhizae may increase the effective rooting volume of young plants by up to tenfold. Research studies indicate that application of phosphate fertilizer to corn only partially overcomes this early season P uptake impairment. Phosphorus uptake may be greater under zero tillage systems, which do not disturb established hyphal strands. DEFICIENCIES: Deficient seedlings appear stunted and weakened. Leaves and stems will often show purpling or reddening. Ears may have irregular rows and twisted ends with underdeveloped kernels and grain will have higher moisture content at harvest. See page 2 for images showing phosphorus deficiencies in corn plants. 15

7 Potassium (K) Most Manitoba soils contain sufficient potassium for crop uptake, however, soils that are likely to be low in K are frequently those same lighter-textured soils that are suited to corn production, so 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 potassium 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. Figure 1. Potassium uptake and partitioning in grain corn (Manitoba, 23, 146 bu/acre). Considered immobile in the soil, K is taken up by the root by diffusion over short distances through the soil solution. Efficiency of band applications of potassium is greater than broadcast application, especially when requirements are low. Band options include preplant banding or side-banded at seeding. The N and K content of fertilizer restrict the quantity of fertilizer that can be safely seed-placed. DEFICIENCIES: Yellowing and drying of leaf margins, especially on older leaves; stunted plants with short internodes; delayed maturity and plants may frequently lodge or blow down late in the season. See page 21 for images showing potassium deficiencies in corn plants Sulphur (S) Sulphur is a key component of several important amino acids that are required for the development of proteins and enzymes, and taken up by the roots in the form of sulphate. Elemental sulphur fertilizer must be oxidized by soil microorganisms to the sulphate form. Sulphate-S may leach in coarse soils, and levels within the field often vary, depending upon soil type and slope position. It is not uncommon for low lying, heavy soils to contain many times more sulphatesulphur as light-textured hilltops. Figure 11. Sulphur uptake and partitioning in grain corn (Manitoba, 23, 146 bu/acre). DEFICIENCIES: General stunting, delayed maturity, and yellowing of new foliage. Deficiencies are most likely to occur in well-drained soils, and soils with low organic matter. See page 21 for images showing sulphur deficiencies in corn plants. 16

8 Micronutrient Deficiencies Calcium (Ca) Deficiency results in a ladder-like effect with leaf tips stuck to the next lower leaf. (Not seen in Manitoba soils.) Magnesium (Mg) Deficiency results in yellowing of upper leaves and intervenal chlorosis of older leaves. (Not seen in Manitoba soils.) Zinc (Zn) Deficiency results in intervenal chlorosis on new corn leaves. Pale white bands between the leaf margin and mid-vein in the basal part of leaf, and under severe deficiencies, new leaves may be completely white. Deficiency occurs most frequently on high p, low OM soils in years with cold wet springs. Iron (Fe) Deficiency causes pale, yellowish-green plants with distinct stripping the full length of leaf. Symptoms are similar to zinc, occurring on the same types of soils. Copper (Cu) Deficiency causes youngest emerging leaves to be yellow and the tips may die. Boron (B) and Molybdenum (Mo) Unlikely to be deficient in MB soils Manure Corn has a high demand for nutrients and is a very suitable crop for manure application. Table 4, from the Soil Fertility Guide, illustrates the opportunity for manure to supply nutrient needs of the corn crop. As with fertilizer nutrients, manure N is optimized through 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 LIQUID Number of samples Total N (avail)* Lb./1 gallons Ammon- ium N Organic N Phosphate P 2 O 5 (avail)* Potassium K 2 O Sulphur S Dry matter og (18) (7.5) Dairy 7 26 (18) (6.5) SOLID Lb./ton og 3 14 (6) (7.5) Poultry 2 34 (12) (15) Beef 33 9 (3) (2) content Manitoba Agriculture, Food and Rural Initiatives, Soil Fertility Guide, amount available for following crop use; for nitrogen = % 17

9 Fertilizer Recommendations TABLE 5. Nitrogen recommendations for corn (based on a spring banded application) Target Yield Nitrogen Recommendation (lb/ac) Grain Yield bu/ac Silage Yield 7% moisture Fall Soil NO 3 -N lb/ac in -24 in Rating L M M V V V+ TABLE 6. Phosphorus, potassium and sulphur recommendations for corn Soil phosphorus (sodium bicarbonate P test) P 2 O 5 lb/ac Soil potassium (ammonium acetate K test) K 2 O lb/ac Soil Sulphate-Sulphur in -24 in. S lb/ac ppm lb/ac Rating SB * ppm lb/ac Rating SB* PPI** lb/ac Rating L L L M M L 2 25 M M M V V V V V+ 4+ V+ *SB = based on side band applications for row crops ** PPI = based on broadcast and preplant incorporated Fertilizer recommendations have been developed and 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. 18

10 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 the 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 1 15% to this average for a target yield. ybrid 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 the use of in-season soil testing, early tissue analysis or use of the SPAD chlorophyll meter. Consult your crop advisor for details. 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: Pre-plant incorporate 1-15 lb/ac zinc as zinc sulphate or 2-3 lb/ac zinc as zinc EDTA chelate. Pre-plant incorporate 5-1 lb/ac copper as a 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. TABLE 7. Soil test criteria for micro-nutrients Producers neglecting to soil test, must resort to using general recommendations as follows: Micronutrient Extractant Critical level Marginal Copper (Cu) DTPA.2 ppm.2-.4 ppm TABLE 8. Fertilizer requirements for corn lacking a soil test 5. ppm for peat soil Iron (Fe) DTPA 4.5 ppm 5-12 ppm on peat soil Previous crop Fallow/ or forage legumes Stubble Phosphate Potassium* Sulphur Manganese (Mn) DTPA 1. ppm Zinc (Zn) DTPA 1. ppm Lb N/ac Lb P 2 O 5 /ac Lb K 2 O/ac Lb S/ac Yield response to applied micronutrient is more likely when soils test in the critical and marginal range *On sandy-textured or organic soils 19

11 Figure 12. Nitrogen deficient corn (L) versus non-deficient corn (R ). Photo by John eard MAFRI. Figure 13. Phosphorus deficient corn (L) versus nondeficient corn (R ). Photo by John eard MAFRI. Figure 14. (L, below) Phosphorus deficient corn as a result of corn on canola syndrome. Photo by Morgan Cott MCGA. Figure 15. (R, below): Phosphorus deficient corn as a result of corn on canola syndrome, close-up. Photo by Morgan Cott MCGA. 2

12 Figure 16. Potassium deficient corn. Photo by John eard MAFRI. Figure 17. Nondeficient corn (L) versus sulphur deficient corn (R ). Photo by John eard MAFRI. 21

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