2021 rice carbon uptake data

Hard numbers may positively affect compensation in the carbon market.

⋅ By Ronnie Helms, Jim Grove and Trey Helms ⋅

Jim Grove with G&H Associates, a contract research company in Stuttgart, Arkansas, uses schedule 40, 6-inch PVC pipe to sample rice roots.

Climate-smart farming, sustainable farming practices, green house mitigation and carbon sequestration are terms that are now in many agricultural publications.

Depending on the farming practices, several carbon marketing companies will pay farmers to adopt such practices as no-till and cover crops. The adoption and payment for these practices is based on the fact that these practices reduce greenhouse gasses and are part of the attempt to reduce global warming. On our farm, we use conventional minimum-till and no-till planting methods, as well as many other sustainable farming practices when we grow rice, soybeans, corn, millet, oats or wheat. 

Evaluating measured parameters

In our contract research business, we were asked by an environmental, forward-thinking sustainable company to evaluate five rice varieties or hybrids for yield, biomass and percent carbon of rice roots, straw, whole grains and brokens and bran and rice hulls for total carbon uptake during the growing season to develop baseline information on these measured parameters.

I, Ronnie Helms, have worked in rice research for more than 42 years and have never conducted a really straight-forward simple rice study of this type. The rice varieties or hybrids on which we evaluated grain yields were: RT7321 (9,038 pounds/acre), Delta Grow 263 (7,191 pounds/acre), Titan (5,898 pounds/acre), Diamond (6,007 pounds/acre) and CLL16 (6,549 pounds/acre). The average percent carbon for hybrid in rice varieties was rice roots 0.34%, rice straw 0.401%, whole grain and brokens 0.405%, rice brand 0.44% and rice hulls 0.41%.

The total carbon uptake for the measured rice components is presented in Table 1. The carbon uptake was calculated by multiplying the biomass for each component by the percent carbon in each component.

Rice roots evaluation

Rice root measurements was an interesting part of this study. We used schedule 40, 6-inch PVC pipe to sample the rice roots. Our sampling depth was 12 inches, and we used a front-end loader on a tractor to push the PVC pipe into the soil. We used two sieves to remove the soil from the roots, then washed the soil from the roots. There were rocks, glass and previous crop residue among the roots. 

This soil core was collected from PVC pipe. A sieve is used to remove soil and collect rice roots to determine what percent carbon they contain.

There were differences among the rice varieties for carbon uptake, but in general, the highest-yielding rice line in this test (RT7321) had the highest carbon uptake (9,143.7 pounds/acre). There was some variability in total carbon uptake relative to grain yield, but in general, it appears that grain yield might be an indicator of total carbon uptake for rice varieties. 

Now the question is: How is this first-year rice variety carbon data to be potentially utilized? For example, if a carbon marketing company pays a farmer to adopt no-till planting practices, is the amount of carbon uptake and/or sequestered carbon the same if a farmer produces 7,500 pounds per acre of rice compared to a 9,000 pounds per acre rice yield? Another question is: Can this type of rice carbon uptake data be used in conjunction with greenhouse gas and/or carbon sequestration predictive models that currently exist in the scientific community?

Rice hull analysis

The rice hull carbon uptake data is an interesting component in this study. Rice hulls are typically around 20% of the rough rice yields.

When the rice is milled, the hulls are removed from the grain. The rice hulls can be processed and used as an abrasive in various industries. Rice hulls can also be used in manufactured decking lumber materials, water filters, organic fertilizer, concrete bricks and poultry bedding materials just to mention a few uses.

When we have discussed the concept that rice hulls are sequestered carbon, it is obvious that many carbon purchasing companies do not understand how rice is processed. 

I have had the same type of conversation with carbon purchasing companies about cotton lint yields. The carbon in cotton lint, in our opinion, is sequestered carbon. We pointed out to a young lady who worked for a carbon purchasing company that she was wearing sequestered carbon in her cotton shirt and jeans. She had not considered cotton lint that was removed from the field as sequestered carbon.

In reality, agriculture is a relatively small business. We have to stand up and explain our agricultural profession, along with our farming and sustainable farming practices to those we may be interacting with in the carbon markets. Otherwise, we may not be appropriately compensated in our sustainable farming and carbon sequestration practices.  

Dr. Ronnie Helms, Jim Grove and Trey Helms are research agronomists with G&H Associates, Stuttgart, Arkansas. Ronnie Helms may be reached at ronniehelms@centurytel.net.


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