Effect of plant compost, salicylic and ascorbic acids on Mentha piperita L. plants

There are ongoing efforts to use organic fertilizers to minimize nutrient losses and reduce waste accumulation. Salicylic acid (SA) and ascorbic acid (AsA) can affect plant growth and productivity. Mint (Mentha piperita) plants were fertilized with plant compost (PC) or traditional NPK as a control. The plants were foliar-sprayed (FS) using tap water, 150 ppm of SA or AsA and a combination of both. Fertilizers and FS treatment significantly affected plant growth, and essential oil (EO) percentage and yields. Treatment with 48 t ha(-1) PC, SA and AsA yielded fresh and dry weights 43% and 29% higher, respectively, than those from NPK-fertilized plants treated with tap water. There was no difference in EO yield between plants treated with 36 t ha(-1) PC and the NPK-fertilized plants using tap water, AsA or SA + AsA, in all cases. The plants treated with 48 t ha(-1) PC + any FS treatment except tap water had EO yields similar (0.69-0.88ml plant(-1)) to NPK-fertilized plants treated with tap water (0.74ml plant(-1)). Treated plants with 48 t ha(-1) of PC and SA + AsA increased their EO concentration by 87% compared with the NPK-fertilized plants treated with tap water. The effect of fertilization and FS treatment on mint growth and productivity was associated with changes on chlorophyll a and b and carotenoid concentration. The N, P and K concentrations were increased by increasing the PC rates and the SA or AsA treatments. PC, SA and AsA effectively improved mint productivity, and can reduce the use of chemical fertilizers and conserve natural resources.