Optimization of Irrigation Practices in Organic and Sustainable Vegetable Production with Soluble Dye as an Educational Tool

View the project final report

Commodities

• Fruits: melons

Practices

• Crop Production: organic fertilizers
• Production Systems: general crop production
• Soil Management: organic matter, soil analysis

The environmental impact of intensive vegetable production may be reduced through the implementation of Best Management Practices (BMPs) that integrate water and nutrient management together. This multi-faceted project used a combination of visualization of water movement in mulched beds, nutrient profile below the plants, diagnosis of plant nutritional status to help eight cooperating growers better understand the relation between fertilization, irrigation, and nutrient leaching. Although growers used sophisticated irrigation schedules (split drip irrigations), the vertical movement of the water front ranged from 0.5 to 2.5 inches/day (and reached 5.3 inch/day on one occasion). Nutrient management in drip-irrigated, plastic mulched organically-grown bell peppers proved particularly challenging. All cooperators increased their understanding and knowledge of nutrient and water management, and they indicated they planned to reduce their preplant fertilizer and irrigation rates. This type of project that involves growers is likely to have a positive impact on water quality.

Tables and Figures mentioned in this report
are on file in the Southern SARE office.
Contact Sue Blum at 770-229-3350 or
sueblum@southernsare.org for a hard copy.

Introduction

Most vegetable growers in the Suwannee Basin region of North Florida are small growers who have adopted drip irrigation and plastic mulch over the past twenty years to produce vegetable such as tomato, bell pepper, eggplant and watermelon. More recently, the availability of short-vined tropical pumpkin varieties (‘La Estrella’ and ‘El Dorado’) and increased demand for tropical pumpkin, has resulted in the emergence of a small tropical pumpkin industry. The dominant production system currently used for tropical pumpkin is bare ground with drip irrigation. Soils in the area are sandy with low water holding capacity (<10%) and low organic matter content (<1.5%). Hence, vegetable production in North Florida requires intense irrigation and fertilization management. The recommendations of UF/IFAS for irrigation management for vegetable crops include using a combination of target irrigation volume, a measure of soil moisture to adjust this volume based on crop age and weather conditions, a knowledge of how much water the root zone can hold, and an assessment of how rainfall contributes to replenishing soil moisture (Simonne et al., 2005a).

Previous educational efforts in North Florida have focused on plant establishment and fertilizer management (Hochmuth et al., 2003). The recent development and adoption of state-wide Best Management Practices in Florida in rule 5M-8 of the Florida Administrative Code (Florida Department of Agriculture and Consumer Services, 2005) and the increase in production costs, have emphasized the need for improved irrigation practices and a better understanding of water movement in mulched bed. Growers’ understanding of the interdependence between fertilization, irrigation, and nutrient leaching below the root zone was increased through a targeted effort supported by a 2003-2004 SARE on-farm project with three cooperators (Simonne et al., 2005b). While cooperators’ irrigation and fertigation schedule were adequate throughout the season, it appeared that irrigation in excess of crop water use necessary for plant establishment early in the season resulted in early nutrient leaching. Hence, monitoring nutrient in the soil was needed not only at the end of the season, but also at the beginning. Therefore, the goal of the 2005 project was to address the effect of irrigation on nutrient movement early in the season.

More specifically, the objectives of this project were to (1) increase the number and diversity of growers/production systems involved in the “dye” project, (2) optimize our portable dye rig for on-farm dye injections, (3) visualize the movement of irrigation water in the soil (3) determine nitrate and ammonium distribution in the soil profile early in the season, and (4) collect feed-back information on the lessons learned