Variations in the growth and yield of lettuce [Lactuca sativa L.] with organic and inorganic fertilizer combinations during two cropping cycles in an ultisol of Southeastern Nigeria

Abstract

Lettuce production is constrained by poor soil fertility among other factors. Thus, organic (poultry manure – PM) and inorganic fertilizers (NPK) were evaluated singly or in combinations on the growth and yield of the crop. Fertilizer treatments were: Control, 300 kg NPK 20-10-10, 300 kg NPK 15-15-15, 300 kg NPK 20-10-10 + 5t/ha PM, 300 kg NPK 15-15-15 + 5t/ha PM, 150 kg NPK 20-10-10 + 10t/ha PM, 150 kg NPK 15-15-15 + 10t/ha PM and 20t/ha PM. A second cycle experiment utilized 50% of the initial fertilizer dosage. Growth and yield data measured were subjected to analysis of variance and significant treatment means were separated using Fisher’s Least Significant Difference (F-LSD) at 5% probability level. Data on number of leaves, leaf area and vigor index measured during six weeks after treatment application were significantly (P < 0.05%) influenced by the fertilizer treatments during the two cropping cycles. Survival count varied significantly only in the second cycle planting. Similarly, whole plant biomass yield, and below and above ground biomass yields distinctly varied with fertilizer treatments in the two cropping cycles. In all cases, 20 t/ha PM or 150 kg/ha NPK 20:10:10 + 10 t/ha PM outperformed all other treatments in the first cropping cycle. The second cropping cycle revealed that the highest biomass yield was obtained in plots that received 10 t/ha PM, and 75 kg/ha NPK 20:10:10 + 5 t/ha PM. Under the growing conditions in Nsukka, application of 20 t/ha PM or 150 kg/ha NPK 20:10:10 + 10 t/ha PM is recommendable for production of lettuce.