The second most limiting nutrient to plant growth in terrestrialecosystems is _______.
Phosphorus is usually the most limiting nutrient in _______ ________ _______.
Phosphorus has just one basic chemical form in soil, what is it?
Plants use about ___ as much Phosphorus as Nitrogen
Plants use the phosphate ions H2PO4? and HPO42? Distribution between the two forms is controlled by pH, which form is found in high pH and which is found in lower pH?
High pH: HPO42-Low pH: H2PO4-
Many acidic tropical soils (oxisols) are depleted of Phosphorusbecause of P fixation by:
Al and Fe oxides
Soon after addition to soils, much P fertilizer becomes unavailable because of several mechanisms:
– In acid soils, P ions are adsorbed to Fe and Al oxides, orprecipitate with Fe and Al to form insoluble minerals.– In neutral to alkaline soils, P ions are adsorbed to CaCO3, orprecipitate with Ca to form insoluble Ca phosphates.
Only P in _____ ______ to a plant root is absorbed.
close proximity (~ 2 mm)
Usually no more than 30% of applied P is taken up by plants, why?
because of the reactions with soil
What can be done to maximize P availability?
• Maintain pH at 6 to 7• Add organic material to soils – this ‘plugs’ up P fixation sitesand reduces soil P?fixing capacity• Apply P fertilizers in concentrated bands near plant roots(minimize contact with soil)
Factors Affecting P Availability
• Soil Temperature– Lower P availability in colder soils (slower P ion movement)• Soil Moisture– Higher P availability in flooded soils (more P minerals dissolve
apatite is mined.
It is treated with acids to:
form various fertilizers:– triple superphosphate– single superphosphate– ammonium phosphates
Animal manures have __________________ relative to other nutrients
high P concentrations
Phosphorus contamination can cause eutrophication. What is the process of eutrophication?
1. Accelerated growth of algae and water plants2.
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