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Oat Grower Manual: Fertility

Work done by Richard Engel, University of Montana, concluded that it takes approximately 10-12.5 cm (4 to 5 in.) of water to produce the first 36 kg/ha (1 bushel) of oat, and thereafter yield increases 500-575 kg/ha (12 to 14 bu/acre) with each 2.5 cm (1 inch) of additional water.

Soil testing should be used for determining fertilizer applications on specific fields. Where soil tests are not available, general recommendations may be followed.  However, field history, cultural practices and inherent fertility of the field must be considered when using general recommendations.
  
Oats utilize nutrients at a fairly predictable level. This level of crop nutrient  uptake and removal is summarized here.

Nitrogen (N)
In most fields in western Canada, nitrogen is the most yield limiting nutrient. Nitrogen is an essential component of amino acids and therefore, of proteins which include nucleic acids, enzymes and chlorophyll.  Deficient crops will grow poorly and produce low yields of low quality.
 
Nitrogen requirements are closely tied to moisture.  The more moisture that is received, the higher the yield potential and the higher the requirement is for nitrogen to achieve that yield. A 3584 kg/ha (100 bushel/acre) crop of oats will require 110-131 kg/ha (97-117 lbs/acre). 

Work done by Ramona Mohr and Cynthia Grant, AAFC Brandon,  and William May, AAFC Indian Head,  confirmed these values, concluding that optimum yields were achieved when soil + fertilizer N level were approximately 100 kg N ha (89 lbs/acre).  Optimum yields were usually achieved at 40-80 kg/ha (36-71 lbs/acre) applied N.

Rates above optimum levels caused yield decreases and crop lodging.  Increasing Nitrogen rates also resulted in statistically significant declines in test weight, kernel weight and the percentage of plump kernels, all detrimental crop quality measurements.

Nitrogen for organic production can be added to the soil by producing crops that are able to “fix” their own nitrogen (legume crops such as alfalfa, clovers or pulses) and working the crop residue into the soil (plow-down).  Livestock manure is also a good source of nitrogen.

Phosphate (P2O5)
Phosphate is involved in the formation of all oils, sugars, starches, etc. It helps with the transformation of solar energy into chemical energy, proper plant maturation and withstanding of stress. It also effects rapid growth and root development.  Response to phosphate in oats is inconsistent and often does not respond to soil test levels.

Situations that may respond to phosphate fertilizers include:

  • Fields that have not received  phosphate fertilizers in past 5 years
  • Fields newly broken or broken from legume forage production
  • Crops grown on fallow
  • Fields seeded during the first 25% of seeding dates for your area
  • Cold, wet soils
  • Sandy or gravelly soils
  • Fields that respond to phosphate fertilizer

Normally, an application of 20-30 kg/ha (18-28 lbs/acre) with half this amount applied with the seed, is usually adequate to produce optimum yields.

Phosphate for organic production can be added to the soil by applying rock phosphate.  However, rock phosphate has a very low solubility so is very slowly available. Therefore, it should be used as a part of a long term program. This may also include using buckwheat as a plow-down crop.  Buckwheat has been shown to have the ability to accumulate phosphate and make it available following a plow-down. Livestock manure is also a very good source of phosphate.

Potassium (K2O)
Potassium helps in the building of protein, photosynthesis, grain quality and reduction of diseases. It also may increase straw strength.  Oat response to potassium usually occurs when soil test levels are below 250 kg/ha (280 lbs/acre).  Potassium deficient soils tend to be light textured (sand to sandy-loam), alkaline, carbonated and imperfectly to poorly drained in their natural state. Organic soils are also frequently deficient in potassium.

An application of 17 kg/ha (15 lbs/acre) seedrow applied potassium chloride (0-0-60) may offer benefits in cold, wet soils – even when soil test levels are sufficient, may result in a crop response.  Applications made at levels higher that 20 kg/ha (18 lbs/acre) should be side-banded or broadcasted to avoid damage to seedling plants.

Potassium for organic production can be added from a number of sources including some sources of potassium sulphate.  This will also add sulphur to the soil.  Other sources include wood ash and greensand (glauconite).  Livestock manure is also a very good source of potassium.

Sulphur (S)
Sulphur is essential for production of protein and oil. It promotes activity and development of enzymes and vitamins as well as helping in chlorophyll formation.  Oats require sulphur in a fairly high level in comparison to other crops.  It is required at lower levels that canola but about the same per acre levels as wheat.  Deficiencies appear similar to nitrogen deficiencies as pale, stunted plants.  Often sulphur deficiencies appear as isolated spots in a field due to extreme variability across a field.  This may also result in misleading results from soil tests if a high-sulphate area is inadvertently sampled.

An application of 10-18 kg/ha (9–15 lbs/acre) of a sulphate fertilizer will be sufficient in most soils, especially if a part of a well balanced sulphur program.  Applications of elemental sulphur may not provide adequate levels of sulphur, especially if applied in the seed-row.

Sulphur for organic production can be added from a number of sources including some sources of potassium sulphate.  This will also add potassium to the soil.  Other sources include gypsum (calcium sulphate)and some sources of elemental sulphur.  Livestock manure may be a good source of sulphur.

Micronutrients
There are a number of nutrients classified as micro-nutrients that are essential to plant growth.  Where deficient, these may cause a reduction in crop production.  Normally, these will not be deficient in western Canadian soils.

Of these, oats is most susceptible to a deficiency of Manganese.  Manganese deficiencies mainly occur on organic soils, high-pH soils or sandy soils low in organic matter.  A manganese deficiency in oats results in a disorder known as Grey Speck. 

Oats show manganese deficiency as a general yellowing and stunting, occasionally with grey specks on the leaves.  A foliar application of manganese will cure a manganese deficiency where it occurs.

 

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