Optimization of cultivation and production conditions for multiple harvests of Salicornia neei, Apium graveolens and Paspalum vaginatum in an aquaponic saline system
Author: Kennia Brum Doncato (Currículo Lattes)
Supervisor: Dr César Serra Bonifácio Costa
Abstract
The cultivation of vascular plants in aquaponic integrated systems to marine animal production is growing in the food sector. Thereby, the establishment of best propagation techniques, the attendance of nutritional requirements and appropriate use of cutting frequencies for the halophytes Salicornia neei Lag., Apium graveolens L. and Paspalum vaginatum Sw. will contribute to the increment of vegetative production of these marketable species. This thesis aimed to optimize the production of the Brazilian halophytes S. neei, A. graveolens and P. vaginatum in saline aquaponics with clarified water from the production of Litopenaeus vannamei B. in Biofloc Technology (BFT) system. In order to establish a protocol of germination for the wild variety of A. graveolens, trials with distinct temperatures, concentration and types of chemical disinfectants were tested, resulting in production of seedling of wild celery (90-100%) by the disinfection of the seeds with 5–10% sodium hypochlorite and incubating them under a 20/30 ºC thermoperiod (12h:12h) (Chapter 1). In Chapter 2, it was verified if the three studied halophytes can uptake both nitrogen forms supplied (ammonium or nitrate), and highlighted that nitrate is the preferred nitrogen form absorbed by S. neei and A. graveolens. Nitrogen level higher than 10 mg L-1 improved growth and biomass production, even in combination of mixed nitrogen forms. High supply of ammonium as sole nitrogen form affect negatively S. neei and A. graveolens, due to rhizosphere acidification, but this stress can be relieved by increasing water pH. Paspalum vaginatum was not sensitive to the high ammonium concentration. Phosphorus level was not an issue for all species, but may limit S. neei and A. graveolensproduction under a high nitrate concentration in the cultivation water, unusual phosphorus condition in current aquaculture systems. Micronutritional requirements of the S. neei growth and biomass production are attended by the use of the clarified water from BFT system of L. vannamei. However, micronutrient supplementation in the water (particularly iron, manganese and molybdenum) was necessary to increase P. vaginatum growth. Poor development of A. graveolens plants under the experimental conditions did not allow evaluation of their responses to micronutrient additions. Foliar fertilization of micronutrient was not effective to improve halophytes’ growth (Chapter 3). Plants were submitted to consecutive cuttings of their aerial structures at every 14 and 28 days (Chapter 4), and P. vaginatum and S. neei showed ability to regrowth in all treatments applied. One cutting treatment (every 28 days) allowed foliar structures with better marketable value, due to prevent the accumulation of dead matter and have plentiful tillering and leaves of P. vaginatum, as well as to produce S. neei with large amount of branches with marketable size and not lignified. Cutting practice did not modify halophytes capacity of nitrogen assimilation into their biomass from water of the aquaponic systems. Overall, the studied Brazilian halophytes can be easily produced in saline aquaponics with waters from BFT system of L. vannamei with the disclosed practices of best germination, use of minimum nutritional needs and cutting management established in this thesis.