Tuesday, July 15, 2014
Carbon Dioxide or Oxygen?
Soil CO2 respiration should be center-stage in the emerging Soil Health discussion, according to Brinton who addressed the recent Soil Renaissance gathering in Oklahoma City. He showed early data from the Swedish soil ecologist Lundegårdh who quantified plant CO2 demand due to photosynthesis and contrasted it with soil CO2 respiration. A biologically active soil was able to cover the plant’s carbon budget but depleted soils did not come close. Air CO2 must make up the deficit. Calculations show that wheat at full growth would need to filter 10 cubic acres of air (and corn 38 cubic acres) to support an acre of carbon yield. This means CO2 could be a temporarily limiting nutrient like nitrogen or phosphorus,- but nobody thinks of it that way.
While many assume carbon is simply coming from the air Brinton stressed that “we’re overlooking the role that healthy soil respiration plays in directly sustaining plants with sufficient CO2 for photosynthesis – and right where plants need it”. Lundegårdh complained in a 1926 Soil Science article that “unfortunately mineral nutrients are getting all the attention”- still true today. During intense plant canopy development it is possible that biologically depleted soils do not furnish sufficient CO2 from soil efflux for the full crop potential. Combine this with recent evidence that plant nutrient uptake – especially nitrate – comes at a biological CO2 cost, and soil-plant respiration emerges as a vital indicator of a truly productive soil crop system.
In this way Brinton thinks CO2 respiration may be of central significance in plant productivity, “separate and above” other soil biology or soil health parameters that are being proposed. Brinton developed Solvita as a means to enable more cost-effective measuring of soil CO2. “Now, if we can grow yields by healthier soil-plant CO2 exchanges, that’s a huge benefit all by itself,- but we won’t do it overnight”.
On July 1, 2014 Brinton presented this topic in a SSSA hosted Webinar on Soil CO2 Respiration. Lots of talk about the greenhouse conditions across the Midwest this summer, but some soils have more oxygen than others. I am not talking about tile lowering the water table, I am talking about soil containing 50% atmospheric air. That does not happen near enough.
Take a look at gypsum to increase your air and water movement. I've written a lot about it and I can see it's advantages. Here, it is the cheapest two nutrients a farmer can buy, calcium and sulfur.
Six dollars a ton picked up at the plant, what a deal!
The straw is so heavy in today's picture, we are going to have to discuss how to break this straw down.