Enhancing Nitrogen Availability in Liquid Fertilizers Derived from Solid Organic Sources for Fertigation

The need for solution fertilizers from local resources is important, especially for growers of long-term food crops from taro and fruit trees. Locally derived nutrient fertilizers for fertigation would help local farmers remain competitive and sustainable. With this goal in mind, we used tankage (meat and bone meal by products) containing about 10% total nitrogen (N) as a N source. Three main factors were manipulated to enhance the release of inorganic N [Nitrate (NO₃-N) and ammonium (NH₄-N)] into solution: 1) time (0 to 48 hours) and temperature (75 °F and 95 °F; 2) cover and aeration; and 3) chemical and biological agents (soil, sugar, baking soda, and vermicompost). Time up to 48 hours and 95 °F significantly increased the NO₃-N concentration in the liquid fertilizer by 65% and 25%, respectively. Cover and brewing the solution increased significantly NO₃-N concentration in the liquid by 20 and 40%, respectively. The addition of a small amount (0.1 gram or less) of vermicompost significantly increased the NO₃-N release by 60, 55, and 35% compared with soil, sugar, and baking soda, respectively. Individual and combined factors were tested in a series of lab trials. Greenhouse and on-farm trials are ongoing to evaluate the quality of the produced liquid fertilizers.