LETHBRIDGE – Crops effectively mine the soil for nitrogen, but two agriculture researchers say phosphorus uptake is another matter.
Studies conducted since 2001 have shown that excessive application of manure causes phosphorus to accumulate and pose environmental risks, particularly to water.
“After five years of annual application of manure and compost based on the nitrogen requirements of the crops, we got about a nine to 10 times increase in that phosphorus in the top 15 centimetres of the soil,” Barry Olson of Alberta Agriculture told a manure management seminar in Lethbridge Jan. 15.
Read Also
Malting barley exporters target Mexican market
Canada’s barley sector is setting its sights on the Mexican market to help mop up some of the lost demand from China
Alberta’s Agriculture Operations Practices Act sets the standards for manure applications to soil based on how much nitrogen is required to support crops on a given soil type.
Five years of data on cereal silage crops with soil samples taken as deep as 1.5 metres showed there was little change in the nitrogen content from fields receiving compost, manure or commercial fertilizer.
Olson said producers have several options when dealing with phosphorus:
- Acquire more land to manage the phosphorus.
- Haul manure greater distances to phosphorus deficient land.
- Apply manure at lower rates to balance the minerals.
“If we have to apply manure at lower rates, that certainly is going to be a challenge,” Olsen said.
Composting is one way to deal with high volumes of manure. Frank Larney of Agriculture Canada’s Lethbridge Research Centre said the process removes most of the water from the manure, making it easier to transport greater distances.
However, less than 10 percent of manure is composted.
The process converts manure into a different product in which nutrients are released more slowly over several years as opposed to a single season.
About 25 percent of nitrogen is available to plants from raw manure while five percent is available in compost.
