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There is not enough manure (or compost) to sustain agriculture
October 18, 2017
There is not enough manure. Not enough to supply nutrients to our crops, not enough to maintain our soils. Those were the conclusions in my last two posts, but before we see what this means for agriculture, let’s look to other organic amendments. Is there enough of any of them?
Can manure sustain soils?
September 19, 2017
Once you start asking questions, innocence is gone. -Mary Astor

How much manure do you need to spread to maintain your soil’s organic matter? Photo: werktuigendagen via Wikimedia Commons

My first question about manure, “Can Manure Supply Nitrogen and Phosphorus to Agriculture?” was answered here. But manure is more than nutrients. The bulk of manure is organic material, the carbon that the primary-producer feed crop took from the air and built into organic molecules (hence the name “organic”). When added to the soil, some of this manure bulk ends up as soil organic matter.

Organic matter is a small but crucial portion of soil. If we can maintain a soil’s organic matter levels, we have gone a long way in maintaining soil health and function. Can manure do this? Can manure sustain soils?
Can Manure Supply Nitrogen and Phosphorus to Agriculture?
September 7, 2017
Once you start asking questions, innocence is gone. -Mary Astor

Manure, whether fresh, old, or composted, is often declared a key component of sustainable agriculture. From countless trials, researchers have come to similar conclusions (Haynes and Naidu 1998). Manure use is promoted as a solution in discussions of sustainable agriculture topics including: soil fertility, soil health, organic farming, regenerative farming, carbon sequestration, and renewable resources. However, I have questions. Not about the actual spreading of manure, or calculating application rates, but about manure’s role in sustaining agriculture. Is manure a sustainable source of nutrients? Is manure a sustainable organic soil amendment, able to build soil organic matter, store carbon in the soil, and so assist in reducing greenhouse gases? When is manure application a sustainable practice?

In my next few posts, I will answer these questions with the hope of putting manure in its proper role in sustaining agriculture. First, let’s look at the nutrient-supplying potential of manure. It all starts with figuring out where manure comes from.