This study compares the soil nutrients from an intensive and semi-intensive and an organic marine shrimp farm located in Guaraíra Lagoon, Rio Grande do Norte State, Brazil. The organic system showed significant lower levels of organic matter and phosphorus when compared to the two conventional systems. The results indicate that the conventional systems release large amount of nutrients into the environment and the organic system is a sink of nutrients from the Guaraira Lagoon ecosystem

Focken, Ulfert

Schober Lima, Juliana

English

Organic Eprints

9. Wissenschaftstagung Ökologischer Landbau. Beitrag archiviert unter http://orgprints.org/view/projects/wissenschaftstagung-2007.html Analysis of Soil Nutrients and Organic Matter in organic and conventional Ma-rine Shrimp ponds at Guaraíra Lagoon, Rio Grande do Norte State, Brazil J. Schober, G. Lima1 and U. Focken 1 Keywords: marine shrimp farm, nutrient management Abstract:  This study compares the soil nutrients from an intensive and semi-intensive and an organic marine shrimp farm located in Guaraíra Lagoon, Rio Grande do Norte State, Brazil.  The  organic  system  showed  significant  lower  levels  of  organic  matter  and phosphorus when compared to the two conventional systems. The results indicate that the conventional systems release large amount of nutrients into the environment and the organic system is a sink of nutrients from the Guaraira Lagoon ecosystem. Introduction and Objectives: Shrimp marine farming is a growing industry in Brazil. Most of the farms are located in Rio Grande do Norte State, which produces 40.6% of the total national production. Guaraíra Lagoon is located at Rio Grande do Norte State and is surrounded by a large number of conventional marine shrimp farms. More recently a former local conven-tional farm was converted into an organic marine shrimp farm.  The local conventional marine shrimp farms use compound feed in order to enhance shrimp growth while in the local organic farm only the natural food is used. Several authors (AVNIMELECH & RITVO  2003,  AVNIMELECH  &  LACHER  1979)  state  that  there  is  an  association between the input of feed in aquaculture ponds and the accumulation of organic mat-ter, phosphorus, and nitrogen in the soil of the pond bottom. This study aims to compare soil characteristics from intensive, semi-intensive, and organic marine shrimp ponds located at Guaraira Lagoon. Methods: Area description: The farms studied were situated at Guaraira Lagoon. The lagoon is located in the South of the eastern coast of Rio Grande do Norte State and has a volume of 2.4*106 m3 and covers approximately 325 km2 (IDEMA 2005). Tab. 1: General characterization of the marine shrimp ponds studied at Guaraíra Lagoon.   Intensive farm  Semi-intensive farm Organic farm Cultured species  Litopenaeus vannamei L. vannamei  L. vannamei Crassostrea gigas Number of cycles/yr  1  1  3.5 Use of aerators  Yes  Yes  No Use of nursery ponds  No  No  Yes Stocking  density/m2  in the grow-out ponds 65 PL10  30 PL10  2.6 shrimps* Final weight (g)  9.8  9.2  9.9 Yield per pond (kg/ha/yr)  2 510  2° 060  650 Source: direct interview.  * Stocking density from the grow-out ponds. In the organic system, the post-larvae are stocked in nursery ponds prior to the transfer to the grow-out ponds with an average weight of 2.2 g.                                                  1Institute for Animal Production in the Tropics and Subtropics. Department of Aquaculture Systems and Animal Nutrition. University of Hohenheim, 70593 Stuttgart, Germany. jschober@uni-hohenheim.de, focken@uni-hohenheim.de 9. Wissenschaftstagung Ökologischer Landbau. Beitrag archiviert unter http://orgprints.org/view/projects/wissenschaftstagung-2007.html Soil analysis: Samples of soil were collected from inside the organic, semi-intensive and intensive grow-out ponds during one rearing cycle at the intensive and semi-intensive pond and two consecutive rearing cycles in the organic pond. The samples were analysed for phosphorus, nitrogen, and organic matter according to the EMBRAPA (1997). The data was analysed in a two way ANOVA with repeated measures on one factor. Dun-can´s multiple range test was used to compare the averages. Results and Discussion: Fig. 1 shows that the soil from the intensive farm has significantly higher average values of organic matter (87.8 g/kg). During the first rearing cycle the organic farm system  had  a  higher  organic  matter  content  (73.1  g/kg)  compared  to  the  semi-intensive system (66.6 g/kg).  The organic system can be comparable to the extensive system, as it does not use artificial feed and large amount of fertilizer to improve the yields. The organic system is a sink of organic matter in the Guaraira Lagoon ecosystem and it uses organic matter from the environment to raise the shrimps. According to BOYD (1992), influent water poses a major source of sediment in extensive systems.    Fig. 2 shows significantly higher concentrations of phosphorus in the soil from the intensive system (282.7 mg/kg) followed by the semi-intensive system (103.9 mg/kg). The organic system showed the lowest concentrations with 33.7 (mg/kg) during the wet season and 25.5 (mg/kg) during the dry season. Fig. 3 shows a significant differ-ence in nitrogen concentration in the soil from the intensive system (400 mg/kg) com-pared to the semi-intensive system (280 mg/kg) and the organic system in the first (240 mg/kg) and second (230 mg/kg) rearing cycle.   Fig. 1: Content of organic matter (g/kg) in the soil of the intensive, semi-intensive and organic marine shrimp pond. Average ±1 SD. Different letters above the columns indicate significant differences at p<0.05 according to Duncan´s test. Intensive systemSemi-intensive systemOrganic system 1st cycleOrganic system 2nd cycle0255075100 acbdOrganic Matter (g /kg)9. Wissenschaftstagung Ökologischer Landbau. Beitrag archiviert unter http://orgprints.org/view/projects/wissenschaftstagung-2007.html Tab.2. Estimated values for organic matter inputs and outputs from an intensive, semi-intensive and organic marine shrimp farm located at Guaraíra Lagoon.   Intensive pond Semi-intensive pond Organic pond 1st cycle- rainy season Organic pond 2nd cycle-dry season Organic  matter  in  the feed input (kg/ha) 5 400  3 632  -  - Organic  matter  in  the fertilization  and  other organic inputs (kg/ha) 30  19  4.8  1.9 Estimate  total  organic matter input (kg/ha) 5 430  3 651  4.8  1.9 Organic matter content in the harvest (kg/ha) 500  441  37.2  42.2 Estimated ratio organic matter  input/organic matter output 10.8  8.3  0.12  0.04 Source: direct sampling and records from the studied farms.     MARTIN et al (1998) showed that up to 38% of the total nitrogen input accumulates in the sediments of a shrimp pond. About 63% of the added phosphorus was reported to accumulate  in the  sediment  of  a  semi-intensive shrimp farm  (PAEZ-OSUNA  et  al. 1997).  Fig. 2: Phosphorus content (mg/kg) in the soil of the intensive, semi-intensive and organic marine shrimp pond. Average ±1 SD. Different letters above the columns indicate significant differences at p<0.05 according to Duncan´s test. 9. Wissenschaftstagung Ökologischer Landbau. Beitrag archiviert unter http://orgprints.org/view/projects/wissenschaftstagung-2007.html   Conclusions: The results of this study report lower concentrations of nutrients (N and P) and organic matter in the organic system. The environment is the main source of organic matter in the soil of the organic pond while in the conventional systems the feed is the main source of the organic matter content. The organic farming system is environmentally friendly but studies are required to evaluate the sustainability of the spread of the organic marine shrimp farms at Guaraira Lagoon.  Acknowledgments: We thank Dr. Hartmut Richter for help with the statistical analysis, the EMPARN staff for help in the soil analysis, the staff from the studied farms, especially Mr. Alexandre Wainberg, M.Sc., for providing important information for this study. A grant by DAAD (German Academic Exchange Service) to JSGL is gratefully acknowledged.   References: Avnimelech Y., Ritvo, G. (2003): Shrimp and fish pond soils: processes and management. Aqua-culture 220: 549 – 567  Avnimelech Y., Lacher M. (1979): A tentative nutrient budget for intensive fish ponds. Bamidgeh, Isr. J Aquac 31: 3-8  Boyd C. E. (1992): Shrimp pond bottom soil and sediment management. In: Wyban, J. Proc. of the Special Session on Shrimp Farming. World Aquatic Society, Baton Rouge, LA , pp166-180  EMBRAPA  (1997):  Manual  de  métodos  de  análise  de  solo.  Centro  Nacional  de  pesquisas  de Solos, Rio de Janeiro: 212 p IDEMA (2005): Projeto de zoneamento ecologico-economico do litoral do Rio Grande do Norte. Governo do Estado do Rio Grande do Norte, Natal, 34 p Martin J. M., Veran Y., Guerlorguet O., Pham D. (1998): Shrimp rearing: stocking density, growth, impact on sediment, waste output and their relationships studied thought the nitrogen budget in rearing ponds. Aquaculture 164: 135-149. Intensive systemSemi-intensive systemOrganic system 1st cycleOrganic system 2nd cycle050100150200250300350400450 abc bcNitrogen (mg /kg)Fig. 3: Nitrogen content (mg/kg) in the soil of the intensive, semi-intensive and organic marine shrimp pond. Average ±1 SD. Different letters above the columns indicate significant differ-ences at p<0.05 according to Duncan´s test. 9. Wissenschaftstagung Ökologischer Landbau. Beitrag archiviert unter http://orgprints.org/view/projects/wissenschaftstagung-2007.html Archived at http://orgprints.org/9911/ 

Analysis of Soil Nutrients and Organic Matter in organic and conventional Marine Shrimp ponds at Guaraíra Lagoon, Rio Grande do Norte State, Brazil

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