Effect of rates and methods of phosphorus application on herb and oil yields and nutrient concentrations in Japanese mint (Mentha arvensis L.)

Abstract

Japanese mint (Mentha arvensis L.), one of the important essential-oil-bearing crops of India, is a potential source of natural menthol which is widely used in various pharmaceutical and cosmetic preparations. Generally under intensive cultivation, the application (broadcast with incorporation) of phosphorus leads to enhanced herb and oil yields of different mint species (Rao, Rao & Singh, 1983; Singh et al. 1983; Vadivel & Sampath, 1981), but the knowledge that P-adsorption to soil surface reduces plant availability suggests that a P application method limiting soil-P contact may improve P availability and use efficiency (Phillips & Webb, 1971). Therefore, the placement depth and method may be an important factor in the proper use of applied phosphorus. Since uptake of P is reduced in dry soils (Reichman & Grunes, 1966; Simpson, 1960), P placed deeper in the soil would remain more available because of increased soil moisture. Another factor involved is the positional availability of the P source (Cooke, 1954). If placed too close to the surface, the roots may not come in contact with the fertilizer or too few would contact the band to maximize uptake.