Fertility management in soilless growth media for vegetable and ornamental crop production

Greenhouse production is growing rapidly, with a focus on sustainability and efficient resource use, particularly in potted plant cultivation using soilless growth media. The objective of this research was to assess the effects of varying rates of nitrogen (N), phosphorus (P), and potassium (K) on the productivity and growth of several crops including beet, petunia, spinach, lettuce, radish, cucumber, tomato, and geranium. Treatments included 0 to 200 mg L⁻¹ of N, P, and K in spinach, lettuce, radish, and beet, while concentrations of 0 to 500 mg L⁻¹ were applied to geranium and petunia. Tomato plants received 0 to 400 mg L⁻¹ N, 0 to 200 mg L⁻¹ P, and 0 to 500 mg L⁻¹ K; while cucumber plants received 0 to 250 mg L⁻¹ N, 0 to 100 mg L⁻¹ P, and 0 to 200 mg L⁻¹ K. Growth parameters such as shoot dry weight, SPAD values, and leaf number increased with greater N and K rates. When N and K levels were equivalent to, or greater than P, beet, radish, and spinach growth increased, while lettuce had greater growth with greater P levels at 150 to 200 mg L⁻¹. Greater N and K levels were associated with increased growth and yield in cucumber and tomato tests (up to 150 mg L⁻¹ and 300 mg L⁻¹, respectively). In all crops, greater N and K rates increased leaf number, root and shoot weights, and SPAD values; however, the optimum fertilizer combinations varied depending on the species. Tomato plants had greater growth when given 200 mg L⁻¹ N, 100 mg L⁻¹ P, and 300 mg L⁻¹ K, but cucumber had greater when given 150 mg L⁻¹ N, 50 mg L⁻¹ P, and 100 mg L⁻¹ K. Beet produced greatest yields when given fertilizer rates of 100 mg L⁻¹ N, 100 mg L⁻¹ P, and 150 mg L⁻¹ K. Radish plants grew greater when given 100 mg L⁻¹ N, 150 mg L⁻¹ P, and 100 mg L⁻¹ K. Lettuce plants had greatest yield with a fertilizer rate of 100 mg L⁻¹ N, 150 mg L⁻¹ P, and 100 mg L⁻¹ K. Spinach, showed optimal growth when given 200 mg L⁻¹ N, 100 mg L⁻¹ P, and 100 mg L⁻¹ K. For petunia plants, the ideal fertilizer rate was 200 mg L⁻¹ N, 200 mg L⁻¹ P, and 300 mg L⁻¹ K. Geranium plants performed greatest with greatest levels of 400 mg L⁻¹ N, 200 mg L⁻¹ P, and 200 mg L⁻¹ K.