Protecting Your Phosphorus Fertilizer Investment

Your investment in phosphorus fertilizer can be substantial, depending on soil P levels and crop needs. A typical application for two-year crop P needs can range from $40 - $80 per acre. While the average losses of P205 (phosphate - the fertilizer form of P) usually average only 1-2 lbs. per acre per year, larger losses can and do occur under certain conditions. These losses can be off-site losses, into a stream or other waterbody, or they can occur within the field, moving from one part of the field to another.

Variable Rate Technology (VRT) and HD Soil Sampling are used extensively for good reasons. It is a precise and cost-efficient method of applying fertilizer. However, if substantial off-site losses or within-field movement occurs, the extra expense of utilizing this technology is wasted.

The question then, is “How do I protect my P fertilizer investment?” There are several answers to that question. We want to help you find some methods that fit your operation that you can effectively use to protect yourself from excessive P losses.

Here is our list - you may have ideas of your own that you would like to discuss.

  • Inject as much P fertilizer as is practical. This may be in the form of starter, or deep placement in combination with strip-till, or with the use of disc-equipped shallow placement rigs.

  • Do not surface apply P fertilizer before a significant rain event (>1 inch of predicted rain in the next 12 hours), or on frozen or snow-covered soil. Losses from these situations can be very large.

  • If surface application is used AND tillage is already planned, perform the tillage before the next rainfall event. This will sharply decrease soluble P losses (which is the main culprit in harmful algal blooms) but may increase sediment-bound P losses due to increased soil erosion. It’s a tradeoff...hence the next recommendation.

  • Begin the transition to more no-till practices and cover crops, starting on your fields with the best drainage. This combination of no-till and cover crops reduces soil erosion and losses of sediment-bound P and improves water infiltration, the water-holding capacity of the soil, and overall soil health.

  • SOIL TEST REGULARLY and apply P fertilizer accordingly. WORKING WITH A 4R-CERTIFIED SERVICE PROVIDER LIKE IAS ENSURES THAT FERTILIZER WILL BE RECOMMENDED AND APPLIED ACCORDING TO SOUND AGRONOMIC RESEARCH.

  • Use geo-referenced HD soil sampling and apply with variable rate technology. This ensures that all areas of the field receive only what is needed.

  • Identify those fields in your operation that are most at risk of elevated P losses. Work with us to help identify these fields (or areas of fields). Some of the characteristics of elevated P loss fields are:

    • Very high soil P levels, especially if over 100 ppm

  1. Adjacent to a stream or road ditch, where surface water flows directly into the stream or ditch.

  2. Tile inlet structures or French drains.

  3. Fields with defined areas of concentrated surface water flow and no grass waterway are present. This could be an eroded swale, a washout, or a gully.

  4. Highly compacted fields.

  5. Fields where both primary and secondary tillage is performed in

  6. the fall, often called “stale seedbed.”