Organic and sustainable high-valve vegetable production in greenhouse and high tunnel



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Demand for organic vegetables increasing throughout the United States (U.S.). In the last two decades, a strong positive growth trend was noticed for both the organic market and farmer's market which further promote the expansion of local and direct market sale outlets in the U.S. Thereby, the consumer demand for organic food leads to further opportunities for vegetable growers to participate in high-value markets within the US. The greenhouse and high tunnel growers have more opportunities to get benefits through adopting the production and sales of certified organic vegetables. However, the adoption of organic production practices is highly challenged by nutrient management, which is an important factor to influence the yield and quality of organic vegetable crops. The use of organic fertilizers leads to 20-50% lower crop yields compared to inorganic fertilizer use. The application of commercially available liquid organic fertilizers could be a suitable alternative to limit the challenges in organic farming by providing adequate fertility to the high-value greenhouse and high tunnel grown crops. For that reason, the overall goal of our research was to reduce the yield gaps between organic and inorganic vegetable production in greenhouse and high tunnel conditions using different approaches as follows Project 1: Liquid organic fertilizer effects on growth and biomass of lettuce grown in a soilless production system. Demand for locally produced, organically grown leafy greens is increasing throughout the US. However, due to lack of efficient organic fertilizers (OFs) for soilless substrates, organic greenhouse production of leafy greens may be challenging. Therefore, a greenhouse study was conducted to analyze the effects of six liquid OFs on growth and development of lettuce in a soilless system. Two experiments were conducted using a randomized block design, and treatments included six fish- or plant-based OFs: OF1 (5N–1P–1K), OF2 (2N–5P–1K), OF3 (3N–1P–1K), OF4 (2N–2P–2K), OF5 (4N–1P–1K), and OF6 (3N–3P–2K); one inorganic fertilizer treatment (IF, 24N–8P–16K); and one unfertilized control treatment. Fertilizer solutions were prepared at 2 dS.m-1 and applied at 100 mL/plant. In Expt. 1, fresh biomass for IF-treated plants was 12% to 38% greater than OF treatments, whereas this difference ranged from 25% to 57% in Expt. 2. Similarly, leaf area values of IF-treated plants were 5% to 40% greater than OF treatments in Expt. 1, and the difference ranged from 28% to 90% in Expt. 2. A possible explanation could be greater availability of nutrients in the IF treatment compared with OF treatments. There was no significant difference among fertilized treatments for number of leaves and stem diameter. Based on the index-based ranking, fish-based (OF1) and fish- and plant-based (OF2 and OF6) performed well among different liquid OFs used in the study. Although the yield under OFs was less compared with that under IF, there is potential to reduce this yield gap by optimized fertility management of these fertilizers. Future research is needed to investigate the impact of optimized rate, timing, different placement, and additional nitrogen (N) sources of OFs on the soilless production of lettuce. Project 2: Influence of arbuscular mycorrhizal fungi on physiology and yield of eggplant in organic soilless production system Recent studies suggest that arbuscular mycorrhizal fungi (AMF) have the potential to improve the growth and yield of eggplant (Solanum melongena L.) under soil-based organic production systems. However, the application of AMF in organic soilless vegetable production in a greenhouse has not been well studied, creating an important knowledge gap. Therefore, two greenhouse experiments [Experiment-1 (E1) and Experiment-2 (E2)] were conducted to investigate the effect of AMF (Glomus spp) on the growth, gaseous exchange, and yield of eggplant fertilized with various liquid organic fertilizers (OFs) and inorganic fertilizers (IFs) in a soilless greenhouse production system. The experiment was conducted in a split-plot design with four replications in which liquid OFs [OF1 (5N-1P-1K), OF2 (0N-5P-5K and 3N-3P-3K), OF3 (3N-1P-1K), OF4 (5N-1P-2K), OF5 (3.7N-2.7P-3.7K), and OF6 (3N-3P-5K)] and IFs [IF1 (6N-4P-4K) and IF2 (4N-0P-1K and 1N-3P-5K)] were randomized as main plot factor, and AMF [inoculated and uninoculated (control)] as a subplot factor. Results indicate that AMF inoculation had no significant effect on the growth, gaseous exchange, and yield parameters of eggplant. Among different OFs, the eggplant fertilized with OF6 resulted in a 4.3% and 3% reduction of leaf area compared to top-performing IF1 treatment in E1 and E2, respectively. Further, the OF6 treatment resulted in a 12% and 15% reduction in total yield per plant compared to IF1 in E1 and E2, respectively. The differences in plant gaseous exchange parameters were also non-significant for eggplants fertilized with different OFs and IFs treatments in both E1 and E2. These results conclude that Glomus spp was not associated with a significant increase in the yield of eggplant in the soilless production system. However, OFs were performing similar to IFs in terms of growth and yield, which could be due to a higher nutrient availability of these OFs which are highly useful for the production of eggplant in greenhouse soilless production systems. Project 3: Comparison of organic eggplant yields under open-field and high tunnel production systems in Texas. High tunnel (HT) cultivation provides many production benefits compared to an open field (OF), however, organic cultivation practice inside HT to improve soil health and further crop yields compared to OF is limited. Organic amendments like organic fertilizers may potentially improve soil health by adding more soil organic matter and optimizing higher crop yields in the HT system. For that reason, we compared liquid organic fertilizer (LOF) and inorganic fertilizer (IF) use to assess the growth and yield of eggplant (Solanum melongena L.) cultivars grown under two production systems. The study was conducted in a split-split plot design with a production system (HT and OF) as the main plot, fertilizer treatments (LOF and IF) as the split-plot, and eggplant cultivars (Angela and Jaylo) as split-split plot factors. Fertilizer and cultivar treatments were replicated three times. The daily average temperature and relative humidity were relatively higher by 2 °C to 4 °C and 2% to 4%, respectively under HT than in OF conditions. In contrast, the average daily light integral (DLI) of HT decreased by 18 to 24% compared to OF. Results from pooled growth and yield data of both experiments showed that HT produced 61% taller plants with 62% thicker stem diameter compared to OF, but no difference in eggplant height and stem diameter were observed between plants fertilized with different fertilizer types and between cultivars. Leaf area was 97% higher under HT than OF, 6% higher with inorganic fertilization than LOF, and 4% higher in Angela cv. than Jaylo. The total yield was 90% higher in HT due to a significantly higher fruit count per plant (70%) and average fruit weight (10%) compared to OF. Eggplant fertilized with IF resulted in a 12% higher fruit yield compared to LOF treatment, but no difference in fruit count per plant and average fruit weight were observed between eggplant receiving LOF and IF. The yield parameters were similar between Angela and Jaylo cultivars. Regardless of fertilizer and cultivar, our results indicate that HTs protected eggplant from early crop damage and offered a favorable microclimate which encouraged plant growth and higher fruit yield compared to OF conditions. The tested LOF for HT production may be feasible in the organic HT production system. Both eggplant cultivars were performed equally in terms of growth and yield attributes, which suggests that both cultivars could recommend for organic HT production.

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Organic Vegetables, Liquid Organic Vegetables, Growth Parameters, Total Yield