Organic Fertilizers for Sustainable Production of Marigolds

Consumers’ increased awareness of the environment and sustainability has created new markets for the floriculture industry; hence, a market for organic floriculture is developing.  Floriculture growers are increasingly adopting organic agricultural practices to meet market demands.  Some organic management areas such as organic media and pest control have been investigated, but cultural information about using organic fertilizers in a commercial operation is unavailable.  The objective of this study was to evaluate plant quality and nitrogen (N) leaching with organic fertilization.  Seven fertility regimes (one chemical and six organic) were evaluated for marigold (Tagetes erecta L.) quality and N losses through leaching.  In four treatments, chemical 20-2-20, oilseed extract (3-0.4-0.8), fish hydrolysate (2-1.8-0.8), and alfalfa-pellet (5-0.4-1.7) fertilizers were used alone. In three treatments, fertilizers were combined: oilseed + fish, alfalfa pellets + fish, and oilseed + alfalfa pellets. All liquid treatments received the same amount of N.  Leachate was collected six times at ten-day interval and analyzed for ammonium and nitrate.  Sixty-two days after transplanting, plant growth was measured, and recently matured leaves were sampled and analyzed for nutrient accumulation.  Substrates were analyzed for pH and electrical conductivity (EC).  Among all the fertilizers studied, Oilseed extract fertilizer resulted in the highest substrate pH, smallest plant weight and width, and lowest nutrient accumulation.  Although chemical fertilization produced plants with the greatest weights, alfalfa pellets alone or in combination with oilseed extract or fish fertilizers, produced plants with similar height and flower size as those grown with chemical fertilizer.  The largest N leaching occurred with fish fertilizer.  Alfalfa pellets, alone or combined with oilseed extract or fish resulted in the smallest.  Chemical or fish-fertilized plants accumulated more N in the leaves than those grown in the other treatments.  Leaves of plants fertilized with fish fertilizer contained the highest concentrations of phosphorus, calcium, magnesium, zinc, and manganese.  Results indicate that it is possible to grow high-quality marigold with organic-based fertilizers.  Alfalfa pellets, either alone or combined with fish or oilseed extract fertilizer produced good quality plants with limited N leaching.