Weed management alternatives for organic coffee agroforestry systems of Puerto Rico

Weed management alternatives for organic coffee agroforestry systems of Puerto Rico

Summary

A comparison of different organic weed management practices in organic coffee agroforestry systems (CAFS) is providing insight into the effectiveness of organic weed management practices at both suppressing weeds and conserving the natural resources of coffee farms. Although it required more labor time, the use of cover crops was more effective in suppressing weeds than mechanical and natural herbicide treatments. The provision of ecosystem services (i.e. soil conservation, natural pest control and nematode diversity conservation) is also being examined. Farmers’ perceptions of different organic weed management practices are being assessed through visits to experimental sites, surveys, interviews and workshops.

Objectives/Performance Targets

1) Evaluate the effectiveness of different organic weed management practices in established organic coffee agroforestry systems (CAFS) and coffee farms transitioning to organic CAFS.
2) Determine the effect of different organic weed management practices on labor time and coffee production.
3) Determine the effect of different organic weed management practices on the ecosystem service of soil conservation.
4) Determine the effect of different organic weed management practices on the ecosystem service of natural pest control.
5) Determine the effect of different organic weed management practices on the ecosystem service of soil nematode diversity conservation.
6) Evaluate farmers’ perceptions of different organic weed management practices.
7) Develop guidelines for weed management in organic coffee farms.

Accomplishments/Milestones

Project accomplishments for each project objective are presented below.

I. Objective 1. Evaluate the effectiveness of different organic weed management practices in established organic CAFS (Orocovis site) and coffee farms transitioning to organic CAFS (UPR-Utuado site).
A. Activities completed by December 2012
1) Weed management treatment maintenance in UPR-Utuado and Orocovis sites.
2) Finish weed biomass data collection in UPR-Utuado and Orocovis sites.
3) Conduct statistical analyses.
The UPR-Utuado study site is a coffee farm transitioning to become an organic coffee agroforestry system. Shade trees are young (less than two years old) and do not provide substantial shade cover. Weed biomass values were higher at this site, and weed communities were dominated by grasses. At the UPR-Utuado site, treatments had a significant effect on weed biomass (p<0.0001). The two cover crop treatments (Heterotis rotundifolia and Arachis pintoi) had significantly less weed biomass (mean = 6.08g and 7.27g, respectively) than the trimmer (mean = 28.95g), OMRI-listed herbicide (mean = 34.51g), and control treatments (mean = 92.25g) . The OMRI-listed herbicide and trimmer treatments had significantly less weed biomass than the control treatment.
The Orocovis study site is an established organic coffee agroforestry system with mature shade trees. Weed biomass values were lower at this site. Weed communities were dominated by vines and leaf litter was abundant. At the Orocovis site, treatments did not have a significant effect on weed biomass (p=0.44).

B. Activities to be completed after December 2012
1) Continue to conduct statistical analyses.
2) Characterization of Utuado and Orocovis agroforestry systems.
3) Taxonomic identification of weed species present in experimental plots.
4) Presentation of results at local and national congresses.
5) Manuscript preparation of experiment results.
6) Publish results in peer-reviewed journal.

II. Objective 2. Determine the effect of different organic weed management practices on labor time and coffee production.
A. Activities completed by December 2012
1) Conduct statistical analyses.
2) Finish labor time data collection in Utuado and Orocovis sites.
At the UPR-Utuado site, treatment had a significant effect on weed management labor time (p<0.0001). The two cover crop treatments (Heterotis rotundifolia and Arachis pintoi) required significantly more labor time (mean = 11 and 13 minutes, respectively) than the trimmer (mean = 4 minutes), and control treatments (mean = 2 minutes) . Sampling date also had an effect on labor time (p<0.0001). Even though the two cover crop treatments required more labor time during the first three months of the experiment, labor time for these treatments was reduced after cover crop establishment.
At the Orocovis site, treatment had an effect on weed management labor time (p=0.0104). The cover crop treatment (Arachis pintoi) required significantly more labor time (mean = 5 minutes) than the control treatment (mean = 0 minutes). The Heterotis rotundifolia cover crop was not evaluated at the Orocovis site, because the farm owner had concerns over the plant becoming a weed. Sampling date also had an effect on labor time (p=0.0043). Labor time was higher for the cover crop treatment during the first month of the experiment, but after this period, it was similar to the other treatments.

3) Finish coffee leaf sugar content data collection in Utuado and Orocovis sites.
Treatment did not have a significant effect on coffee leaf sugar content at the UPR-Utuado site (p=0.21), or at at the Orocovis site (p=0.95).

III. Objective 3. Determine the effect of different organic weed management practices on the ecosystem service of soil conservation.
A. Activities completed by December 2012
1) Finish runoff, rainfall and soil nutrient data collection at the Orocovis site.
2) Continue eroded soil, runoff and rainfall sample processing from the UPR-Utuado site.
3) Continue erosion measurements at UPR-Utuado and Orocovis sites.
In this report, we present data collected from February 2012 to November 2012. At the UPR-Utuado site, overall soil erosion for the treatments was: 0.034 g/m2/day for the control, 0.016 g/m2/day for the organic herbicide, 0.044 g/m2/day for the mechanical (trimmer), 0.017g/m2/day for the cover crop Arachis pintoi, and 0.061 g/m2/day for the cover crop Heterotis rotundifolia. Repeated measures ANOVA on soil eroded preliminary data showed no treatment effect (p = 0.09) and no time effect (p = 0.25) at the UPR-Utuado site. No consistent pattern was found in soil eroded with time. Our preliminary data showed that A. pintoi and herbicide treatments had lower soil eroded values throughout the period measured, however control, mechanical and H. rotundifolia treatments showed more variability with time.
At the Orocovis site, overall soil erosion for the treatments was:0.020 g/m2/day for the control, 0.019 g/m2/day for the organic herbicide, 0.023 g/m2/day for the manual (machete) and 0.014g/m2/day for the cover crop Arachis pintoi. Repeated measures ANOVA on soil eroded showed no treatment effect (p = 0.38), however there was a time effect (p = 0.005) at the Orocovis site. All treatments showed a consistent increase in soil eroded with time. For February 2012, soil eroded ranged from 0.002 g/m2/day to 0.012g/m2/day while in June 2012 soil eroded values ranged from 0.026g/m2/day to 0.033g/m2/day.

B. Activities to be completed after December 2012
1) Continue rainfall, soil eroded and runoff data collection for UPR-Utuado site until February 2013.
2) Conduct soil sampling at UPR-Utuado site for soil nutrients and basic soil characterization after termination of soil erosion and runoff measurements.
3) Finish statistical data analysis for soil eroded, runoff, rainfall and soil nutrients for the UPR-Utuado and Orocovis sites.

IV. Objective 4. Determine the effect of different organic weed management practices on the ecosystem service of natural pest control.
A. Activities completed by December 2012
1) Finish predatory arthropods sampling.
Treatment did not have a significant effect on arthropod (all species) total abundance at the UPR-Utuado site (p=0.09), or at at the Orocovis site (p=0.83). The effect of treatment on predatory arthropod species, abundance and species richness will be determined when taxonomic identification of arthropod species is completed.

2) Finish coffee berry borer and coffee leaf miner sampling.
Treatment did not have a significant effect on coffee berry borer abundance at the UPR-Utuado site (p=0.19), or at at the Orocovis site (p=0.93). However, there was an effect of sampling date (p<0.0001) and block (p<0.0001) at the UPR-Utuado site.
At the UPR-Utuado site, treatment did not have a significant effect on coffee leaf miner leaf damage (p=0.13), but sampling date did (<0.0001). At the Orocovis site, coffee leaf miner damage was not observed.

B. Activities to be completed after December 2012
1) Taxonomic identification of all predatory arthropods collected.
2) Continue to conduct statistical analyses.

V. Objective 5. Determine the effect of different organic weed management practices on the ecosystem service of soil nematode diversity conservation.
A. Activities completed by December 2012
1) Finish soil nematode data collection at Orocovis site.
2) Taxonomic identification of nematode genera collected.
Taxonomic identification of nematodes in samples from experimental plots continues. A total of 19 soil nematode genera have been identified from UPR-Utuado samples, and a total of 19 genera from Orocovis samples. Preliminary data suggest that plant and bacterial feeders are the most abundant nematodes in both experimental sites. Rotylenchulus appears to be the most abundant plant feeder in the UPR-Utuado site, and Criconemella, in the Orocovis site.

B. Activities to be completed after December 2012
1) Continue taxonomic identification of nematode genera collected.
2) Finish soil nematode data collection at UPR-Utuado site.
3) Conduct statistical analyses.

VI. Objective 6. Evaluate farmers’ perceptions of different organic weed management practices.
A. Activities completed by December 2012
1) Continue to interview organic coffee farmers in Puerto Rico about their current weed management practices.
2) Continue to facilitate farmer and agriculture student workshops on organic coffee farming and organic coffee weed and pest management (including guided visits to experimental areas).
3) Conduct pre and post workshop surveys to workshop participants.
4) Survey preliminary data analyses.
Surveys ask farmers and students to rate: their level of knowledge regarding soil, weed and pest management strategies; their level of agreement on several statements associated with soil, weed and pest management; and the soil, weed and pest management strategies they currently use. Pre and post survey results of agriculture students (n=16) indicate that significant, positive changes took place among them after exposure to workshops. Wilcoxon signed-rank tests show that there were statistically significant increases in:
– Self-reported level of knowledge of cover plants as a weed management technique (p = 0.02). Median item score increased from 1 (little knowledge) to 2 (some knowledge) on a 3 point scale.
– Self-reported level of knowledge of cover plants (p = 0.05) and biological control (p = 0.02) as insect population management techniques. Median scores increased from 1 (little knowledge) to 2 (some knowledge) on a 3 point scale for both items.
– Higher scores on sustainable agriculture values scale where students selected their agreement with values that support sustainable agriculture (p = 0.03). Median scale scores increased from 16.5 to 21, with a maximum possible score of 24.
– Higher scores on a scale measuring self-reported knowledge of soil management techniques (p = 0.04). Median scale scores increased from 4.5 to 5.5, with a maximum possible score of 9.
Information on areas without statistically significant changes will be used to inform upcoming program activities. For example, workshops will include more information on OMRI-listed herbicides, since students did not show statistically significant increases on this subject.

B. Activities to be completed after December 2012
1) Continue to facilitate farmer and student workshops on organic coffee farming and organic coffee weed and pest management (including guided visits to experimental areas).
2) Continue to provide surveys to workshop participants.
3) Continue to interview organic coffee farmers in Puerto Rico about their current weed management practices.
4) Facilitate two project results workshops (The workshops will include SWOT Analyses of the weed management practices evaluated).
5) Continue to conduct statistical analyses.

VII. Objective 7. Develop guidelines for weed management in organic coffee farms.
A. Activities to be completed after December 2012
1) Development of organic weed management manual.
2) Distribution of manual to workshop participants and interest groups.
3) Visit to farms of farmers who received the manual, and evaluation of weed management practices used by these farmers.
4) Final project evaluation.

Impacts and Contributions/Outcomes

The project has benefited producers/consumers in the Southern Region through changes in knowledge, actions and conditions.

A. Changes in knowledge
1) Increased knowledge of ecosystem services and practices that conserve them in farms.
2) Increased knowledge of organic weed (and pest) management practices.
3) Increased knowledge of organic coffee farming.
4) Increased knowledge of organic agriculture in general.

B. Changes in actions
1) Farmers consider several factors (e.g. ecological and financial) when deciding which weed (and pest) management practices to use.
2) Coffee farmers consider organic production as a viable alternative.
3) Organic and transitioning coffee farmers have more weed management alternatives to choose from.

C. Changes in conditions
1) Organic coffee farms provide more ecosystem services.
2) A higher number of farmers start producing organic coffee.

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