Pole Beans as a Sustainable Alternative to Enhance Farm Productivity and Soil Health

Commodities

• Vegetables: beans, eggplant, peppers, sweet potatoes

Practices

• Crop Production: crop improvement and selection, cropping systems, crop rotation, foliar feeding, nutrient cycling, nutrient management, organic fertilizers
• Education and Training: on-farm/ranch research, participatory research, workshop
• Soil Management: composting, green manures, organic matter, soil analysis, soil microbiology, soil quality/health

To address the challenges of producing beans sustainably for small-scale production, this on-farm research will take place on a farm located in southeastern Puerto Rico. The project focuses on integrating a strategic crop rotation with a locally produced biostimulant-based soil nutrient management system. It is designed to evaluate best practices to enhance soil health, reduce the gap between yield goals and achievable yields, and establish a resilient farming model tailored to the tropical, hot, and humid conditions of the region. By combining innovative cropping strategies, efficient labor practices, and sustainable soil nutrient management, the research aims to evaluate  the best practices as a replicable model for small-scale tropical farms.

The research will be conducted within a crop rotation designed to optimize productivity, maintain soil fertility, and reduce disease pressure (Aslam et al., 2024; Shan et al., 2021; Nadeem et al., 2019). The rotation begins with a Solanaceae family crop (either eggplant or sweet peppers) planted in April 2025, followed by sweet potatoes during the hurricane-prone wet season (September 2025 to January 2026), pole beans during the cooler dry months (January to April 2026), and a return to peppers from April to September 2026. This rotation leverages seasonal patterns in the region, aligning crop cycles with optimal growing conditions, mitigating pest and disease cycles, and promoting efficient resource use (Wessel-Beaver et al., 2022; Jordan et al., 2014; Guertal et al., 1997). Sweet potatoes provide critical ground cover during the wet season, reducing soil erosion and replenishing organic matter (Oshunsanya, 2016). Pole beans, as legumes with N₂-fixation capacity, reduce the demand for soil nitrogen  (Karavidas et al., 2022).

Pole beans will be cultivated using a trellis system, offering significant benefits over bush beans, particularly in areas where agricultural intensification is needed such as small scale productions. Unlike bush beans, which are typically intercropped with maize and other crops, climbing beans like pole beans exhibit prolific vertical growth and are better suited for sole cropping systems (Katungi et al., 2018). Although trellis systems require additional labor and upfront capital for installation, they provide long-term advantages by positioning the beans at an accessible height, reducing physical strain during harvesting, and improving efficiency (Musoni et al., 2014; Ruganzu et al., 2014). Furthermore, the vertical structure enhances airflow around the plants, mitigating humidity and reducing the risk of fungal diseases common in the humid climate of southeast Puerto Rico. While initial adoption may be challenging due to higher resource demands, the benefits include extended and consistent harvest periods, reliable yields, and healthier plants, as demonstrated in on-farm evaluations outside Puerto Rico (Franke et al., 2016; Ronner et al., 2018). Integrating this system into the crop rotation not only optimizes labor use and plant health but also ensures stable production and supports sustainable farming practices.

Pole beans will be cultivated using a trellis system, offering significant benefits over bush beans, particularly in areas where agricultural intensification is needed such as small scale productions. Unlike bush beans, which are typically intercropped with maize and other crops, climbing beans like pole beans exhibit prolific vertical growth and are better suited for sole cropping systems (Katungi et al., 2018). Although trellis systems require additional labor and upfront capital for installation, they provide long-term advantages by positioning the beans at an accessible height, reducing physical strain during harvesting, and improving efficiency (Musoni et al., 2014; Ruganzu et al., 2014). Furthermore, the vertical structure enhances airflow around the plants, mitigating humidity and reducing the risk of fungal diseases common in the humid climate of southeast Puerto Rico. While initial adoption may be challenging due to higher resource demands, the benefits include extended and consistent harvest periods, reliable yields, and healthier plants, as demonstrated in on-farm evaluations outside Puerto Rico (Franke et al., 2016; Ronner et al., 2018). Integrating this system into the crop rotation not only optimizes labor use and plant health but also ensures stable production and supports sustainable farming practices.

The application of biostimulants also aligns with regenerative agricultural practices by contributing to carbon sequestration, mitigating climate change, and reducing environmental impacts (Rengalaskshmi et al., 2018). The project will also investigate the benefits of increasing the microbial community in soil, which is expected to improve carbon use efficiency, nitrogen fixation, and soil carbon storage while reducing nitrogen external input requirements (Soares and Rousk, 2019; Malik et al., 2016). Collectively, these practices aim to establish a sustainable, cost-effective strategy for improving bean crop productivity, building soil health, and mitigating climate change through enhanced carbon sequestration.

Throughout a two-year trial, regular soil testing will be conducted to assess changes in soil nutrient levels, soil microbial activity, and soil structure, providing a comprehensive evaluation of soil health dynamics and the effectiveness of the implemented strategies with the application of biostimulants. These data will guide iterative refinements to the biostimulant production and application processes, ensuring that the approach remains adaptable and responsive to on-farm conditions (Darhhofer et al., 2010). By integrating crop rotation, a trellising system, and locally produced biostimulant this project proposes an innovative, self-sustaining solution tailored to the unique challenges of agriculture in Puerto Rico, furthermore to the southeast coastal region. These strategies are designed to meet immediate productivity needs while fostering long-term soil health and ecosystem sustainability.

The anticipated outcomes of this research include increased crop productivity, reduced labor demands, enhanced nutrient cycling, and improved soil fertility, directly addressing the critical challenges faced by small-scale farmers in Puerto Rico (Zougmore et al., 2005). By integrating these results, the project offers a replicable and adaptable framework for fostering resilient agroecological systems that bolster food security and promote agricultural self-sufficiency. To maximize impact, findings will be shared widely through targeted field days, hands-on workshops, and strategic partnerships with agricultural organizations, ensuring effective knowledge transfer and adoption by farmers across Puerto Rico and USVI. This initiative seeks to establish a scalable and sustainable model that harmonizes ecological stewardship with economic viability, equipping farmers with the tools and strategies needed to build more resilient, productive, and independent agricultural systems while contributing to long-term environmental sustainability.

Materials and Methods

Study site

The on-farm trial will be conducted in Yabucoa, located in the southeast region of Puerto Rico, and will focus on pole beans as the primary crop, integrated within a crop rotation system involving Solanaceae crops (sweet peppers or eggplant), sweet potatoes, and beans. The trial site features soils from the Pandura series, classified as Loamy, mixed, active, isohyperthermic, shallow Dystric Eutrudepts. The experiment will span two years and will account for field variability by implementing treatment plots arranged in blocks. This design ensures the reliability of results and addresses potential differences in soil properties across the experimental area.

Experimental Design

The experimental design for this study will follow a Randomized Complete Block Design with four replicate blocks to ensure statistical rigor and account for field variability. Each block will consist of six experimental plots, each measuring 8 m x 4.5 m, with 2-meter buffer zones between adjacent plots to prevent cross-contamination. The plots will be assigned one of six nutrient management treatments: (1) a control using commercial compost; (2) BA, which includes commercial compost combined with an organic fertilizer to meet the nutrient requirements of each crop in the rotation; (3) BA+Biostimulant, applying the same treatment as BA but supplemented with a biostimulant produced using the Johnson-Su method; (4) BIO, which uses only the biostimulant; (5) BIO+LH, a combination of the biostimulant and liquid humus; and (6) BIO+LH+Ca, which builds on BIO+LH by adding a calcium extract based on preliminary soil analysis showing low calcium levels. This design allows for the systematic evaluation of different nutrient management strategies and their effects on soil health and crop productivity while maintaining robust experimental controls. Compost and biostimulant analysis will be conducted, with samples sent to the Analytical Lab for detailed nutrient and quality assessment. 

Soil sampling

To accomplish the soil analysis related to the objectives of this study, soil samples will
be collected on three sampling dates per year: baseline (before transplanting the first crop of the rotation), establishment (before planting beans, the main cash crop) and late (after harvesting beans). Taking into consideration the microbial characterization, soil sampling will be conducted following an aseptic protocol, rinsing tools with isopropyl alcohol (70%) and let dry before making another sampling. From each plot, 12 soil sub-samples (cores of 0-20 cm depth) will be collected from random locations and combined into a single composited soil sample. Soil samples will be placed in plastic bags and will be stored in a compartment with ice packs to transport to the Environmental Chemistry Laboratory at the Agricultural Experimental Station (ECL-AES) in Río Piedras. Each composite sample will be sieved through a 2-mm diameter mesh sieve to remove coarse material and roots and divided in three parts: (1) the sub- sample (air dried) used for a standard soil fertility test, texture, SOM, total C and total N, (2) a sub-sample that will sent to Cornell lab for a Soil Health Analysis Package (NRCS-216), and (3) a subsample stored at 4 °C, freeze-dried and sent to Ag Regen Lab for microbial characterization with PLFA method. 

Plant Analysis

In this study, crop growth for peppers and beans will be evaluated using a modified functional approach to growth analysis, as described by Hunt (1990). Plants will be randomly selected from each plot, avoiding the plot borders, with three plants harvested per plot by cutting them 1 cm above the soil level. Plants will be separated into leaf lamina and stems for detailed analysis. The leaf lamina will be measured using an electronic planimeter (model LICOR LI3001) to determine the leaf area, while all samples will be stored in paper bags, dried at 70 ± 1°C for 48 hours, and weighed. The average of the three subsamples per plot will be used in growth analysis calculations. Key growth parameters, including Leaf Area Index (LAI), Crop Growth Rate (CGR), Relative Growth Rate (RGR), and Net Assimilation Rate (NAR), will be calculated using standard equations. This analysis will provide insight into the growth dynamics of peppers and beans under the influence of different nutrient management treatments. These evaluations will not only allow us to monitor the development of these crops throughout the growing season but will also help identify the most effective treatments for promoting sustainable productivity in the unique climatic and soil conditions of southeastern Puerto Rico.

In addition to the growth analysis, NDVI (Normalized Difference Vegetation Index) assessments will be conducted to evaluate crop health and canopy vigor, providing a non-destructive measure of photosynthetic activity and overall plant condition. Furthermore, Brix evaluations will be performed on both foliar samples and fruit for peppers to assess sugar content and nutrient status, offering insights into crop quality and potential market value. These complementary assessments will provide a comprehensive understanding of crop performance, integrating physiological, biochemical, and remote sensing approaches to support data-driven recommendations for sustainable management practices.

Statistical Analysis 

Data will be analyzed using RStudio and SAS statistical software to ensure robust and comprehensive statistical evaluation. A Generalized Linear Mixed Model (GLMM) will be applied to analyze the data within the randomized complete block design framework, incorporating fixed effects of nutrient management levels, sampling dates, year, and their interactions, along with random effects of block and the interaction between block and nutrient management levels. This approach allows for the assessment of treatment effects while accounting for variability within the experimental design.

Least-square means will be compared using Fisher's Least Significant Difference (LSD) method at a significance level of α = 0.05 to identify meaningful differences among treatments. Additionally, advanced statistical approaches such as regression analysis and unconstrained and canonical ordination analyses will be employed. These analyses will facilitate a deeper understanding of microbial community dynamics in relation to soil properties, and the influence of nutrient management practices. The results will also be used to examine the correlation between these factors and observed yield responses in pole beans and second cash crops.