Headline : The Carbon Chronicles – Part 3

Read more from the original article on here at understandingag.com.

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No. of Paragraph 28

The first two parts of this series examined the critical role of carbon in powering plant and soil life (all terrestrial life) and the cyclic outflow from an average corn field. Now let’s look at inflows.

Unsurprisingly, the lack of photosynthesizing plant cover throughout the growing season makes the carbon inflows smaller. Maintaining living cover throughout the growing season is the best and easiest way to increase carbon flow into the soil. Plant photosynthesis is by far our biggest arrow. The corn crop in the diagram emerges and reaches maturity in about 120 days. The remaining growing days are lost opportunity if there is no living cover. Adding a cover crop adds a new inflow, and it’s more likely that a portion of that carbon will stay in the soil if that cover crop is not harvested. Adding a perennial to the crop rotation can also drive a large increase in photosynthesis. Diversity in the cover crops or perennials increases photosynthetic activity even more. Farmers switching from tillage and fallow to a no-till cover crop system or from set stocked to adaptive grazing often see an increase in soil organic matter. Why? Because they have reduced the outflow and increased the inflow of carbon. You can also add carbon via humic products or compost, but the most efficient route is to let plants do the work for us.

Fertilizers and animal manures are a special case, because whether the ultimate result is net positive or negative depends on how they are managed. Animals in a well-managed adaptive grazing system tend to have an overall net positive impact. This can be quite large and drives the most rapid increases in soil organic matter that can be achieved without bringing in a large amount of biomass from somewhere else. On the other hand, poor fertility management can have a detrimental effect. Overapplying fertilizers or manure (especially high N fertilizers or anaerobic pit manure) can create nutrient imbalances, increase salt loads, and disrupt soil function. Adding too much nitrogen has the same result as tillage. It can spike microbial activity and drive the conversion of organic matter to CO2. However, manure does add carbon to the system so the net effect is hard to predict. Excesses of other nutrients can also cause nutritional imbalances in the plant that limit productivity.

There is one more way to increase the inflow of carbon that is almost always overlooked. Can you guess what it is? Many researchers believe that it is not possible to increase soil organic matter much beyond 0.1% per year. They prove this using the exact same math that you see in the diagram. But what if one of the underlying assumptions is wrong? Photosynthetic efficiency is typically assumed to be constant when these calculations are done. This is the amount of light energy that is converted into chemical energy during photosynthesis.

Read more from the original article on here at understandingag.com.

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