Cotton Gin By-Products (CGB)/Dairy Manure
Composting for Desert Farming
FW11-018
Project Type:
Farmer/Rancher Project
Projected End Date: 2012
Funds Awarded: $13,336
Region: Western
State: New Mexico
Coordinators:
Dr. Robert Woody
Email
915-203-2966(Office)
671 Tumbleweed
Chaparral, NM 88081
Participants:
Dr. Robert Flynn
Extension Agronomist
NMSU
Final Report
Summary
Dairy manure was composted with cotton gin byproduct (CGB) at a ratio of three parts dairy manure to two
parts CGB using standard composting procedures. At six months the matured compost was sent to an
analytical laboratory for standard analysis. Prior to compost application on bermudagrass, the grass leaves
were analyzed for nutrient content. In August 2011 the grass was cut and bales were counted and weighed.
Later in August 2011 the compost was applied at three different rates. The bermudagrass was sampled again
six weeks later for nutrient content. Bales once again were weighed and counted.
Unfortunate limiting impacts of the 2011-2012 drought and a resulting drop in the well's static level created an
unavoidable limiting factor which prevented a fully successful outcome.
Due to water limitations, overall grass production decreased 16% in the composted fields compared to precompost production. Nitrogen content of the compost alone was insufficient to grow the bermudagrass;
however, the compost did appear to positively impact zinc, iron, manganese and possibly copper within
bermudagrass tissue.
Over the period of the study, another impact of the drought became apparent. Whereas the cost of CGB in
early 2011 was $17/ton, by the beginning of 2012 the cost had increased to $64/ton, since the CGB was now
being avidly bought by the dairies to feed dry cows in place of other more expensive feeds.
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The increased cost of CGB made its use in composting economically impractical. Despite this, CGB might yet
provide a useful carbon and nutrient source for compounding in the future. It cannot adequately supply
nitrogen, however.
Introduction
My farm is located in the Chihuahua Desert, about 15 miles across the Franklin Mountains from large dairy
and cotton producers in the lower Rio Grande Valley of Dona Ana County, New Mexico. Because the major
soil deficiency I encounter is the lack of organic material, I proposed to transport dairy manure and CGB to
my farm, compost it to maturity and apply it at three different rates to my bermudagrass pastures. I would use
identical and uniform nitrogen and water applications, varying only the rates of compost. Compost nutrient
content and baseline bermudagrass tissue content would be determined and baseline weights and bale number
measured before compost application. The same values would be repeated after compost application. The
goals were to determine if this compost improved bermudagrass production and was economically feasible.
Objectives/Performance Targets
1. Determine if compost from dairy manure and CGB can provide adequate nitrogen for bermudagrass
production
2. Determine if the compost can provide sufficient other nutrients for bermudagrass production
3. Compare the production and nutrient content of bermudagrass before and after compost application at three
different rates.
compost analysis
bermudagrass tissue analysis
Methods
Dairy manure was composted with CGB at a ratio of three parts manure to two parts CGB. Piles were
monitored for temperature and moisture and brought to maturation at six months. Compost samples were sent
for analysis, including organic-N, inorganic-N, phosporous, potassium, sulfur, calcium, magnesium, sodium,
zinc, iron, manganese, copper, soluble salts, pH and dry matter content (Table 1). Prior to application of
compost to a bermudagrass hay field, the leaves were sampled for nutrient content. Bermudagrass was mowed
August 19, 2011. The bales of grass were weighed and counted from each of four passes where the compost
would be applied. The compost was applied in late August 2011 at three rates (8.2, 17.4 and 24.7 T/ac). Plots
were identically fertilized with urea (92 lb N/ac.) and irrigated. Severe drought occurred, and a concomitant
drop of the water table caused the well to run dry, thus limiting potential grass growth and optimal results of
this project.
Outcomes and Impacts
Prior to composting, the grass averaged 12 bales (+/- 4) per pass, weighing 52 (+/- 2) lb/bale. Total average
grass collected from treated areas averaged 631 (+/- 248) lb/ac. Grass yield was 16% less (530 lb/pass) across
all treatment in 2012. This was likely the result of the ongoing drought and failure of the irrigating well. This
illustrates the Law of the Minimum where water became the most limiting factor of crop production in 2012
and would have masked any benefits from the application of compost. Compost application did not change N
conc. six weeks after application. It did seem to affect Zn, Fe, Mg and Cu conc. six weeks after application,
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especially at the high compost application rate. The Fe conc. in the composted CGB was over 6000 ppm. This
may have implications towards mineral supplements depending on livestock and feeding rates.
Accomplishments
The project contributed to two major accomplishments:
1. Improved metric skills for assessing productivity and quality
Through many communications with the Technical Advisory, Dr. Robert Flynn, NMSU Ag Extension
Service, my workers and I acquired skills in qualitatively assessing crop productivity. We learned a systematic
approach to compare pre- and post-application results.
We dealt with the interference created by unexpected variables (the 2011-12 drought) which factored into, but
did not, defeat the study's design and ultimate outcome.
We also gained great skills in composting, building upon the framework we had initially acquired through an
earlier Western SARE-funded project.
2. Improved soil and crop quality
Although overall bermudagrass production decreased 16% because of severe water restrictions created by the
drought, we have objective evidence that future years' productivity may be enhanced because of residual
nutrients supplied by the compost. The soil also gained valuable organic material from the heavy composting
of 2011.
Potential Contributions
It remains to be seen if CGB compost is economically feasible. Although in 2011 it appeared to be so, by
2012, it did not because of the dramatically higher cost of CGB. That may change over time. I certainly would
be keeping my eyes open for another chance to buy CGB at a low price to use as a carbon source for
composting.
The soil salts delivered through composting remain low, and it would be possible to re-compost the same
fields in the future. Since the bermudagras pastures are used in the winter for sheep grazing, composted CGB
without dairy manure (and its inevitable salt-related problems) might be even more applicable.
Publications/Outreach
Although the project originally proposed a field day, no opportunity arose for such a day. Given the drought,
escalated price of CGB and scarcity of farming in the 15 miles around my farm, I concluded that such a field
day would be poorly attended.
The decreased overall productivity of bermudagrass (down 16% from 2011), and the somewhat marginally
increased nutrient improvements, suggested to me that factsheets and posters would be of little interest.
Future Recommendations
The study's results were powerfully, but not fatally, affected by the drought of 2011-12. The benefits of
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rainfall on cation nutrient root absorption from highly alkaline soils probably prevented fully beneficial effects
of the compost. More seriously, the exceptional/extreme drought conditions lowered the static water level in
the well used to irrigate the bermudagrass, reducing production by 16% from the baseline. Another
unexpected result of the drought was the inflated cost of CGB, since it was now avidly sought by the dairies as
a foodstuff for cows. While unfortunate, these drought-related effects suggest that in non-drought years CGB
compost might provide a useful non-nitrogen nutrient and soil organic material source for desert farming in
the Chihuahua Desert.
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author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.
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