Plant growth responses to the application of liquid organic fertiliser: A dissertation submitted in partial fulfilment of the requirement for the degree of Bachelor of Horticultural Science with Honours

Abstract

Whether or not liquid organic fertilisers (LOF's) are effective in enhancing aspects of plant production has been an ongoing topic of scientific debate and research for many years. Some of the debate may hinge upon the nutritional (irrigation) versus non - nutritional effects of LOF as few experiments have removed all confounding factors. Many scientists suggest LOF's have no influence on plant growth. Nevertheless, some scientists and manufacturers of LOF continue to produce evidence suggesting LOF's enhance seed germination, plant growth and yield, and suppress pathogens. However, mechanisms of action and the active constituents have not been confirmed. Four LOF's (Aunty Jane's Super Seaweed®, Bio Gold!M, Biotrina® and Maxicrop®) were screened for their effects on plant growth. Perennial ryegrass (Lolium perenne cv 'Grasslands Nui') was sown at a rate of 150 seeds per 800 ml pot containing perlite. The plants were grown in a glasshouse (27°C day, 10°C night) from March to May 1999 under natural light. Fifty mls of standard nutrient solution (providing sufficient nutrients to remove any nutrient effect between LOF's) was applied per pot three times per week. Pots were maintained above 75% saturation capacity by weight with tap water. At 21 days after sowing (DAS), plants were trimmed to 1.5 cm. Twenty eight and 35 days after sowing, 25 ml of water (control), or Aunty Jane's Super Seaweed® (0.005%), Bio Gold™ (0.01 %), Biotrina® (0.01 %) and Maxicrop® (0.005%) were applied, diluted with water, to concentrations (in brackets) as per manufacturers instruction. There were eight replicates of each treatment. Seven days· after the second LOF application the chlorophyll concentration (SP AD) was measured and plants cut at 1.5 cm above the perlite to determine fresh and dry weight per plant. A second harvest occurred a further 21 days after the first, and plant weight measurements were repeated.