Paper presented at the 52nd CFCS Annual Meeting, Guadeloupe, July 10-16, 2016
HYDROPONIC PRODUCTION SYSTEMS FOR WATERCRESS (NASTURTIUM OFFICINALE R. BR.,) Shahinaz Mohammed1, Kimberly Singh2 and Puran Bridgemohan3 Laboratory Technician1, Research Assistant2 , Associate Professor – Crop Science3 Centre for Biosciences, Agriculture and Food Technology, The University of Trinidad and Tobago puran.bridgemohan@utt.edu.tt Keywords: hydroponic, recirculating, aeration , shade growth analysis, photosynthetic rate Abstract Watercress is produced by small farmers who divert water from rivers into paddies to ensure a continuous flow. The objective of this study was to evaluate novel systems of production for optimal growth and yield. The two new hydroponic production systems : recirculating and continuous aeration under two levels of shade using four different planting media were evaluated in both open and green house conditions. The crop were treated to Blaukorn fertilizer (12:12:17) at three rates, and a growth analysis and photosynthetic rate conducted . After 2 weeks of growth, watercress stalks that were at and above 10cm were harvested. The watercress re-circulating system in shaded conditions has produced consistently higher average results versus the watercress in full sunlight, in terms of fresh weight- 11.89 g vs 4.94 g; dry weight- 0.83 g vs 0.49 g; stem length- 17.60 cm vs 10.68 cm and number of leaves- 17 vs 15. Also the visual appearance and texture of the watercress grown in shaded conditions in the re-circulating system is better than that of the watercress grown in full sunlight and resembles the watercress produced in large scale systems more closely. Introduction Watercress, Nasturtium officinale R. Br., is used in salads and are a source of vitamins A and C, niacin, ascorbic acid, thiamine, riboflavin, and iron (Stephens, 2015). Watercress needs to be grown in areas with ¼ to 2 inches of cool flowing water (McHugh et al., 1987); farmers in Trinidad usually plant watercress near a river, where the water can be diverted to create a stream throughout their plantation and then exit back into the river; thereby creating a continuous flow system. Water temperature also influences the growth of watercress; temperatures above 25.5o C cause poor or stunted growth. Nitrate content is another important factor for watercress growth; optimum growth is at about 4 ppm (McHugh et al., 1987). The discouraging factors highlighted by farmers into watercress production is the need for continuously flowing water and the danger of being bitten by poisonous coral water snakes that comes from the river. Materials and methods Recirculating system design Three containers each 91 x 22 cm was connected via 2’’ PVC pipe at the middle. Gravel was filled 15 cm away from the top of the containers. A pump was immersed into a 55 gallon barrel with a pipeline connection from the base to the top of the barrel and extended to the furthest container. An average of 42 pieces (498.54 g) of watercress stalks were placed in each container. This design was repeated twice, one in full sunlight and one in shaded conditions. Each week, Blaukorn fertilizer (12:12:17) was applied in accordance with the farmer’s rate, at 13.6 g for each 91 x 22 cm container. After 2 weeks of growth, watercress stalks that were above 10cm (4 inches) were harvested and records were taken for stem length, number of leaves, fresh and dry weights. pH, temperature and electrical conductivity were also monitored. Nitrate and phosphate content were monitored at intervals before and hours after application of fertilizer.
Figure 1. Photo and diagram illustrating the recirculating system for watercress production
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