Phosphorus and Potash
The physiological responses of crops to phosphorus is well known. In potato the requirement of P & K assumes added significance due to the shallow root system of the crop and the high requirement of K for rapid bulking of the tubers. In addition, potato is grown in diverse soil types ranging from acidic hill soils to the neutral to slightly alkaline soils of the northern plains. In contrast to N, phosphorus is fixed in many soils and so is not easily available. Moreover, P does not move much in the soil. In the case of K also fixation does take place, though fixed K is easily available through exchange process. Therefore the application rate, time of application as well as the method of application of these two nutrients would require greater manipulation for making it easily available. Apart from the effect of P&K on the growth, development and yield of the crop K has also been found to impart resistance against frost and also mitigate the effect of moisture stress and biotic stress Thus P&K nutrition has to be given its due importance but is often ignored.