Comparisons of composts with low or high nutrient status for growth of plants in containers

Composts may be incorporated into container mixes for several purposes, including to supply nutrients, add organic matter, or suppress plant diseases. The objective of this research was to assess the nutritional benefits of two composts derived in common from composted chicken manure and used in formulation of container media for growth of tomato (Lycopersicon esculentum Mill.). The composts differed in extractable and total plant nutrients so that one of the composts was considered a nutrient-rich material and the other a nutrient-poor material. Media were formulated from soil or peat with the composts added in a progressive array of concentrations from a medium with no compost addition to a medium that was all compost. Half of the media were treated with a water-soluble, complete fertilizer and half were left unfertilized. Optimum growth occurred in media in which compost did not exceed 25% of the volume. The beneficial effects of the composts on plant growth were associated with increased supply of nutrients for the plants. The suppressive effects were attributed to restricted accumulation of nutrients with the nutrient-poor compost and to excessive potassium supply and accumulation with the nutrient-rich compost. Fertilization was beneficial in increasing plant growth with the nutrient-rich compost and was essential for plant growth with the nutrient-poor compost. The research demonstrated that composts can be used in formulation of media for container growth of plants.