2014 Exploring the potential for using seaweed (Ulva lactuca) as organic fertiliser MS Breure Wageningen UR PPS-80436 0 Exploring the potential for using seaweed (Ulva lactuca) as organic fertiliser MSc Thesis Plant Production Systems PPS-80436 Wageningen University Name: MS Breure Registration nr.: 900224 124020 Program: MSc Plant Sciences Date: September 2014 Supervisors: Peter Leffelaar Willem Brandenburg Examiner: Gerrie van de Ven Acknowledgements I am grateful for the opportunity to work with and learn from Peter Leffelaar during this thesis and I want to thank him for his supervision and support. I want to thank Willem Brandenburg for organising the greenhouse facilities needed to perform my experiments. I would like to thank both Peter and Willem for their feedback, questions, answers, advice and enthusiasm. I also want to thank Hennie Halm for analysing the samples, the availability of his lab and his willingness to help me during the practical work of my thesis. I want to thank Jetze van Zwol for his help in collecting seaweed material in Zeeland and his great support and greenhouse management during one of my experiments. I am thankful that my friends Andrea, Arnold, Hanna, Marga and Nadine helped me with practical work and finally I want to thank my flat mates and friends for the mental support that is indispensable when doing a thesis. Abstract The focus of this project is on P recovery by using seaweed (Ulva lactuca) as organic fertiliser. The possibilities for using seaweeds as fertiliser, depend on two components. First, to determine whether seaweed is suitable as organic fertiliser, it is necessary to analyse the nutrients taken up by the seaweed, to gain insight in the amounts of nutrients that could be applied to the soil. Phosphorus content of Ulva lactuca grown under different initial P concentrations in the water (Pi) was measured. Phosphorus content in relation to Pi concentration showed Michaelis-Menten kinetics with Pmax = 0.46% DW and Km 1.19 µM. N content was also measured and P and N content were found to be related. Second, it was analysed how Ulva lactuca material decomposed over time in an agricultural sandy soil when incorporated in June (2013). The mesh bag method was used to monitor the dry matter decomposition. The relative decomposition rate of Ulva lactuca was found to be 0.0413 d1. In addition, the effects of seaweed fertiliser on two crops, lettuce and mustard, was studied. Mustard plant height and lettuce diameter were measured throughout the course of the experiment. After harvest, shoot and root dry weight were determined and P and N content were measured. Ulva lactuca application increased N content (p<0.05) and P content (p<0.10) of mustard plants, either due to Ulva lactuca application or the reduced dry matter production. Ulva lactuca application had a negative effect on crop appearance in both crops and reduced shoot dry matter in lettuce (p<0.05) and mustard (p<0.10). A delay in crop growth and development was visible under Ulva lactuca treatment, but the exact functioning of Ulva lactuca in crop performance remains unknown. Table of Contents 1 Introduction .................................................................................................................................... 1 1.1 Global food security ................................................................................................................ 1 1.2 Nutrient flows ......................................................................................................................... 1 1.3 Aim of the project ................................................................................................................... 2 2 Literature study ............................................................................................................................... 3 2.1 Agricultural production ........................................................................................................... 3 2.1.1 Introduction .................................................................................................................... 3 2.1.2 Phosphorus and nitrogen ................................................................................................ 3 2.1.3 Decomposition and nutrient availability ......................................................................... 4 2.1.4 Organic fertilisers ............................................................................................................ 5 2.2 Ulva lactuca ............................................................................................................................. 6 2.2.1 Taxonomy, morphology and reproduction ..................................................................... 6 2.2.2 Growth and nutrient uptake characteristics ................................................................... 7 2.2.3 Chemical characteristics ................................................................................................. 8 2.2.4 Applications ..................................................................................................................... 9 2.3 Seaweeds as fertilisers .......................................................................................................... 10 2.3.1 History ........................................................................................................................... 10 2.3.2 Beneficial effects ........................................................................................................... 11 2.3.3 Disadvantages ............................................................................................................... 15 2.3.4 Ulva lactuca as organic manure .................................................................................... 16 2.3.5 Possibilities and opportunities ...................................................................................... 18 3 Materials and Methods ................................................................................................................. 19 3.1 Nutrient uptake experiment ................................................................................................. 19 3.1.1 Materials ....................................................................................................................... 19 3.1.2 Methods ........................................................................................................................ 20 3.1.3 Phosphorus uptake model ............................................................................................ 21 3.2 Decomposition experiment .................................................................................................. 22 3.2.1 Materials ....................................................................................................................... 22 3.2.2 Methods ........................................................................................................................ 22 3.2.3 Climate data .................................................................................................................. 23 3.3 Crop growth experiment ....................................................................................................... 24 3.3.1 Materials ....................................................................................................................... 24 3.3.2 Methods ........................................................................................................................ 24 3.3.3 Climate data .................................................................................................................. 26 4 Results and discussion .................................................................................................................. 27 4.1 Nutrient uptake experiment ................................................................................................. 27 4.1.1 Growth rate ................................................................................................................... 27 4.1.2 Phosphorus content ...................................................................................................... 28 4.1.3 Nitrogen content ........................................................................................................... 30 4.1.4 Relation P and N content .............................................................................................. 31 4.1.5 General discussion ........................................................................................................ 31 4.2 Decomposition experiment .................................................................................................. 34 4.2.1 Decomposition rate ...................................................................................................... 34 4.2.2 General discussion ........................................................................................................ 36 4.3 Crop growth experiment ....................................................................................................... 37 4.3.1 Growth and development ............................................................................................. 37 4.3.2 Crop morphology .......................................................................................................... 38 4.3.3 Dry matter production .................................................................................................