Sustainable Irrigation Methods for Alternative Crop Production
Recent changes in commodity programs and competition from imported commodities have increased the income risk to farmers. As a result, many farmers are considering a transition to an alternative, high-value crop production as a way to sustain their income. One crop of significant interest is rabbiteye blueberry. Recent demand for this fruit has increased dramatically and so have prices received for the product by producers. Over 270 acres of blueberries have been planted in southeastern Alabama in the past three years. Sites selected for blueberry establishment generally followed row crops land, where soils were marginally suited for blueberry production, featuring low soil organic matter content, and high soil pH. Supplemental irrigation water sources in the southeastern part of the state are carbonate aquifers. In events where the supplemental irrigation is the predominant water source, particularly in drought years, alkaline irrigation water will create alkaline soil conditions that will not favor successful blueberry establishment and production. The purpose of this on-farm study was to generate an enhanced knowledge of the benefits of using different approaches to improve the soil organic matter content, to correct soil pH, and to manage irrigation water alkalinity for sustainable blueberry production.
The main objectives of our study were to:
1) Assess the effect of sulfuric acid treatment injected through the irrigation system on soil pH and blueberry growth and development;
2) Evaluate the effect of plug-in emitter and micro-jet irrigation systems on soil pH and blueberry performance;
3) Determine the effect of different rates of pine bark and peanut hull treatments on soil organic matter content and blueberry establishment and plant growth.
Two on-farm experimental plots were selected in 2008 to apply a set of soil organic amendments and various irrigation systems. Soil amendments consisted of various rates of pine bark and peanut hulls, applied at 134 yd3, 269 yd3, and 403 yd3 of organic matter per acre respectively. The experimental plots were replicated three times, and planted to ‘Climax’. Irrigation treatments consisted of: Client-installed drip tape (Control), Client-installed drip tape with soil moisture/feedback (treatment 1); Plug-in drip emitters (treatment 2), and Micro-Jet Spray emitters (treatment 3). In all treatments a timer was installed with soil moisture feedback for irrigation scheduling. The irrigation treatments were applied to Austin and Climax blueberry cultivars.
In 2009, drip tape with soil moisture control/feedback reduced the system operation time by 12% when compared with grower-installed drip tape with timer. Fertigation with nitrogen was started in early April and the cooperator noticed a problem of no fertilizer being injected into treatments 2 and 3. Large system flow differences between Control/treatment 1 and treatments 2 and 3 required injector adjustment for proper operation. For whatever reason, there was no assurance that these adjustments were routinely made. We, therefore, have little confidence that either nitrogen fertilizer or sulfuric acid pH was successful on treatments 2 and 3. Also, operation time for treatments 2 and 3 was only 17% of the control treatment, which is a concern relative to adequate irrigation water application to these treatments. We are not aware of the 2009 start irrigation date and stop irrigation date, which presents a limitation in calculating the 2009 average hours per day or average gallons/plant/day applied.
Our results revealed the irrigation treatment had no effect on Austin blueberry leaf area in both years of this study. Climax blueberry produced bushes with a similar leaf area in response to the plug-in emitters and drip tape irrigation systems, while plants with a smaller leaf area were evident for the micro-jet treatment applied.
During 2009, the greatest vegetative growth was observed for Climax plants receiving drip tape irrigation, whereas the micro-jet treated Climax plants showed the smallest increase in bush growth. In both experimental years, Austin blueberries had similar vegetative growth across the irrigation systems in our test.
More than likely, pH injection problems caused by inadequate injector adjustments for much lower water flow to the spray-jets and plug-in emitters prevented application of adequate amounts of pH-corrected water and injected fertilizer, which could tend to explain poor bush growth and yield performance of these two treatments during the 2009 season. No apparent injector problems occurred with the higher water flows to Control and treatment 1 valves.
In 2009 fruit samples were analyzed to determine the average berry size and other important berry characteristics. The plug-in emitter treatment resulted in largest mean berry size when compared to the micro-jet and the control treatments. Between the two blueberry cultivars tested Austin had larger berries (2.1 g on average) than Climax (1.2 g on average). Plug-in emitter treatment resulted in sweetest berries (12.9 % soluble solids content), followed by the control treatment (12.6% soluble solids), while the soluble solids content for micro-jet irrigated berries was 10.8%.
Results on the effect of the three mulching treatments tested on Climax leaf area suggest that the 12” pine bark and 4” pine bark plus 4” peanut hulls treatments resulted in greater blueberry leaf area in the second year of our study, when compared to the control treatment. We also observed that the 12” pine bark treatment produced the greatest plant growth and the largest average berry size in the second year of this experiment based on the calculated plant growth index. This treatment corresponded to the largest amount of organic matter incorporated into the soil.
Overall, a significant improvement in plant development was observed in the experimental plots following acid injection implementation/adoption and soil amendment enrichment by participating growers. We also observed a considerable improvement of blueberry plant growth and development in cases where the growers implemented irrigation water acidification for their blueberry operation.
Impacts and Contributions/Outcomes
On May 28, 2009, we conducted a commercial blueberry production workshop at the Wiregrass Research and Extension Center in Headland. Invited speakers included extension specialists from Alabama Cooperative Extension System, the Department of Agricultural Economics and Rural Sociology, Department of Agronomy and Soils, Biosystems Engineering Department, and the Department of Horticulture, Auburn University. Educational program included outdoor demonstrations and indoor discussions on the following topics: irrigation system maintenance, fertigation practices for blueberries, and fire ant bait demonstrations in commercially grown blueberries. An update on the project findings and emerging problems in blueberry production for the Wiregrass region were provided.
Summary of our experience was presented at the Annual Meeting of the Southern Region ASHS in Orlando, Florida in February 2010.
This study was designed to facilitate developing alternative crops that help a producer’s operation to become more economically sustainable and investigates practices and systems that increase the viability of an existing farming practice. Other contribution of this research is the promotion of low-volume systems that can apply precise and uniform water volumes while conserving natural resources, and make the most efficient use of on-farm resources. The integration of natural biological cycles will contribute to improving soil physical properties and soil health.