Agriculture Reference
In-Depth Information
Dried blood, fish meal, shrimp waste, and oyster shell products
also provide
phosphorus, but usually at low rates of available phosphate. The downside of
commercial organic phosphorus fertilizers is their cost, which can be prohib-
itive for large orchards.
PHOSPHATES AND MANURE
Another effective use of colloidal phosphate and rock phosphate is
to include them with animal manures during the composting process.
Acids in the manures dissolve the available phosphate, which then
helps to stabilize the nitrogen in the manures.
Applying Phosphorus
Phosphorus is relatively immobile in soils under most conditions and is best
applied before planting your trees. Unfortunately, phosphorus can react with
other minerals in the soil and become unavailable to plants. On moderately
to strongly acidic soils, phosphorus combines with aluminum and iron. Under
alkaline conditions, phosphorus reacts with calcium to become unavailable.
For instance, when applied directly to the orchard floor, rock phosphates are
most available and effective on acidic soils and remain generally unavailable
on neutral to alkaline soils. A key way to effectively manage phosphorus is
to keep your soil pH between 6.0 and 7.0 and, ideally, 6.5 to 7.0.
Base your phosphorus applications on “available phosphate” or P O
5
2
Many materials contain high concentrations of phosphorus, but they are in
forms that plants cannot use. The given amount of phosphorus in all fertil-
izers refers to the amount of available phosphate that is released from fer-
tilizer materials in a weakly acidic solution. This solution mimics chemicals
that are released by roots to make certain mineral nutrients more available
and assist in their uptake.
