Direct seeding practices can result in crop yields as good or better than traditional tillage-based cropping systems. Reducing tillage has proven to be economical as well as environmentally friendly. Direct savings on farm fuel, labor, and machinery-life plus the elimination of soil erosion are real and immediate benefits. Generally, moisture conservation and improvements in soil quality can be expected over time with important implications for nutrient cycling and higher yield potential as soil disturbance is reduced.

 

Biologically, the fertility implications of less tillage are:

There are other specific interactions that begin to occur when tillage stops. A transition period will arise for nitrogen cycling and other nutrient equilibriums. Crop residues return carbon, nitrogen and other essential nutrients in various degrees back to the soil. Soil disturbance interferes with the microbial function of soil in association with plant roots. (ie: mycorrhizae fungi). Climate, soil texture, crop rotation, and fertilizer management are important factors that influence how quickly and to what extent these direct seeding transformations take place.

 

Direct seeding usually improves soil moisture reserves by trapping snow and capturing run-off. High levels of crop residue protect the topsoil from heat and wind while increasing field water holding capacity. An increased yield outcome subsequently impacts removal and availability of soil nutrients. The degree of change in soil fertility tends to be greater for LDS than high disturbance systems because soil displacement and residue incorporation are minimized. Primarily, a direct seeding implement needs only to:

 

 

Direct seeding carries yield advantages overtime because early seeding into a firm moist seedbed stabilizes crop establishment, lowers weed competition, and provides nutrient efficiency. Earlier seeding in dryland prairie normally implies a yield advantage because of a short growing season and limited soil moisture. By eliminating extra field operations otherwise needed for fertilizer application or seedbed preparation, direct seeding allows timely seeding. Nutrient management adjustments for unexpected seedbed conditions (too cold, too wet, or too dry, etc.) can be made while direct seeding. A flexible crop rotation along with residue management and a pre-seed weed control strategy are integral steps.

Experienced direct seeders have discovered the benefits of timely, precision-fertilizer placement. The main factors influencing nutrient placement in a direct seeding system are fertilizer type, rates, and timing.

 

Alberta’s sustainable cropping program, Reduced Tillage LINKAGES (RTL) promotes the adoption of low disturbance direct seeding (LDS) = less than 40% stubble knockdown after seeding[1]. Simultaneous, or one-pass seed and fertilizer placement within an LDS system has further implications for nutrient management. Important terms distinguish fertilizer placement capabilities of a direct seeding implement:

 An SS system implies concern for crop injury due to seed and seedling damage from seed-placed fertilizer. In DS systems, there are various methods that address this concern, in particular for fertilizer-N (nitrogen).[2]

 

Direct seeding requires fertilizer use and placement to be just right to become profitable. In order to maintain optimum yields, it is important to have a good understanding of fertility for P (phosphorus) and K (potassium), as well as meet the high demand for N (nitrogen) sometime into the growing season. Sulfur (S) deficiency and micronutrient management are issues that should also be addressed.

 

 

A common misconception is that seed-placed nutrients are required. In reality, a crop seed doesn’t need anything more to resume its biological heritage than air and moisture (for germination) plus sunlight to warm the soil and foster emergence. Shortly after roots and leaves begin to form however, there should then be a “balanced” nutrient package readily available so the plant can commence and sustain photosynthesis.

 

Cool soil temperatures can impede root development, and the fact that P & K are not very mobile in the soil (unlike fertilizer-N) suggest these nutrients should be placed nearby the seed, according to soil-test recommendations. However, combining so-called starter fertilizer with seed can create unnecessary problems. Solutions for common fertilizer placement troubles in direct seeding include:

 

 

Second only to H2O, nitrogen (N) tends to be the most limiting crop nutrient. Direct seeding has several positive implications for N-cycling. Precision-placement of crop nutrients at the time of seeding can reduce:

 However, N-efficiency can also be reduced due to:

Normally, the higher the soil moisture, the more likely crop response to N will be. LDS systems optimize soil moisture. In simple SS direct seeding, risk of crop injury from seed-placed N decreases as soil moisture increases. Likewise, crops grown in course sandy soil are more at risk than fine textured clay. Although more complex, high rates of N-fertilizer are best managed with a DS system that separates the fertilizer (safety) without compromising the seedbed (moisture).

 

Rotational cropping in a direct seeding system has a unique spin-off for sulfur (S) management, in terms of mobility and crop use.

 

The best fertility management practice is an ongoing soil-testing program that can account for nutrient supply and demand (ie: balance available soil nutrients with crop-use). GPS technology now makes field zoning and variable rate applications possible for advanced nutrient management. New biotechnology for seed treatments and fertilizer coatings is revolutionizing seed and fertilizer use, but still requires more research and development for direct seeding.

The operational diversity of a farm mainly revolves around seeding and harvest.

 

In practice, direct seeding validates all of the above. Early seeding and precision-placed fertilizer, combined with a pre-seed burnoff and timely in-crop spraying for weeds, makes continuous cropping more competitive and profitable compared with crops grown under less intensive tillage-based systems (bare-fallow). Soil remains biologically healthy because of crop rotation and less erosion.

 

The features of a direct seeding implement’s opener width[8] and row spacing[9] have become highly interactive with all aspects of a successful reduced tillage cropping system. They will determine not only the flexibility for nutrient rates and placement, but significantly influence the timing and outcome of fundamental crop rotation, weed control, and residue management strategies.

 

Without incorporation of crop residue (tillage), or in the absence of a diverse crop rotation, stratified nutrient levels or even pH changes may occur overtime. However, this has not been well documented or extensively researched in Alberta and remains a minor concern after more than 20 years of direct seeding.

 

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