Cropping fertilizers vary significantly in their phosphorus (P) content. Summit’s AllRich for example contains 8.7% P, compared to 22.8% for MAP. It follows that different fertilizers need to be applied at different rates in order to achieve the same desired target P rate. Granule output from seeding machinery will also differ and the space between granules (distribution) will vary between product.

This has clear implications from a logistical standpoint. Using low analysis products results in greater loading, freight and storage requirements, plus greater downtime from more frequent fills at seeding, compared to higher analysis products.

Relative distribution of compound granules and seed along rows at 10-inch tine spacing.

What is less clear however is how granule distribution can impact P availability to the growing seedling. To investigate this, Summit’s Field Research team collected data on the number of granules in a unit mass of 3 fertilizers – AllRich, MAP and MAPSZC. Calculations and models were then made to determine granule distribution patterns.

Key conclusions from this study:

  • High analysis products contain 50% (MAPSZC) and 90% (MAP) more P per granule than AllRich.
  • At reasonable seed rates (using Scepter Wheat) with appropriate target P rates, each seed will have access to P from more than one fertilizer granule regardless of the product (AllRich, MAP or MAPSZC) used.

For further information, see our technote.