Evaluating functional diversity in an organic intercropping system

Evaluating functional diversity in an organic intercropping system

Summary

Water demand and weed, pest, and disease control are major challenges facing organic farmers in Texas and the southern United States. Inputs in the form of pesticides, fertilizers, irrigation and manual labor increase the potential for surface water contamination, further deplete potable water sources and reduce producer profit margin. Additionally, producers are limited to only a few select crops that can withstand summer temperatures in the region. We are investigating the utilization of single crop and various intercropping combinations of watermelon, peanut, okra, cowpea and pepper. An incremental increase in functional crop diversity in an organic intercropping system may enhance ecosystem functioning and crop resource-use efficiency while improving or sustaining crop yields and fruit quality. Preliminary data suggests that intercropping combinations utilizing watermelon reduce soil temperatures by between 2 and 3°C on average and promote short-term soil moisture retention by 25% VWC. Okra benefited most from intercropping when compared to its monocrop with an increase in soil moisture content of 46% VWC. Weed dry biomass was significantly reduced by 73% in intercropping treatments containing watermelon. Utilizing all 5 component crops in combination resulted in a significant increase in soil organic matter content and a land equivalent ratio (LER) comparable to monocrops. The results from this data suggest that intercropping has the potential for alleviating heat and soil moisture stress on crops during the peak of the summer heat in Texas and the South, for suppressing weed competition as well as potentially yielding soil fertility and total crop productivity benefits.

Objectives/Performance Targets

1. To examine the relationship between functional diversity and soil chemical (organic matter content, total and organic soil C and N) and physical properties (soil moisture, soil temperature)
2. To examine the relationship between architectural complexity and nutrient-, radiation, and water-use efficiency
3. To determine how incremental increases in functional diversity affect weed suppression and disease incidence and severity
4. To evaluate the effectiveness of intercropping systems on sustaining or enhancing crop yield and quality
5. To incorporate this research into the student-led Aggie Green Fund Organic Farm which is geared toward education and research

Accomplishments/Milestones

Objective 1: Soil sampling and measurements from year one of the study have concluded. Soil C and N analyses are still currently being conducted; however, organic matter content, temperature and moisture data have been completed. Intercropping utilizing all 5 component crops has potential soil fertility and moisture retention benefits. Preliminary results were presented at Texas A&M University’s annual student research week held in March.

Objective 2: Photosynthesis and other plant-response measurements were taken throughout the growing season, 2011. Plant tissue analysis of C and N are currently being done to determine nutrient-use efficiency. Irrigation inputs were closely monitored and recorded and, along with yield data, are being used to calculate water-use efficiency.

Objective 3: In 2011, Texas experienced record-setting temperatures and one of the worst droughts in history. The dry conditions resulted in no detectable disease incidence, therefore could not be measured. Weed biomass was collected toward the end of the study in 2011. Intercropping with watermelon resulted in very effective weed suppression.

Objective 4: Yield measurements concluded at the end of the growing season in 2011. Data have been analyzed and presented, along with other results, at regional conferences.

Objective 5: The student-led on campus organic farm, Howdy Farm, was incorporated into the study by exchanging labor for marketable produce. Students involved in the farm assisted with harvesting and the produce sold from harvest was worth well over $1,000. This year, students will be given a tour of the study site and the opportunity to assist with scientific measurements.

Impacts and Contributions/Outcomes

The initial findings of this study indicate that utilizing a functionally diverse cropping system has the potential for alleviating heat and moisture stress on crops during the peak of the summer heat in Texas and the southern region. Furthermore, soil fertility can potentially be sustained without excessive amounts of additional inputs while at least sustaining total crop yield per unit area of land. For small-scale organic producers in Texas and the southern region, this translates to a reduction in manual labor and input costs and provides a viable alternative for sustainable organic vegetable production.

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