Nitrogen
The importance of nitrogen for potato and for that matter all crops is well recognized. The amount, time of application and source of nitrogen are the critical decisions in this case. This is because, in the northern Indo Gangetic plains the duration is short and nitrogen stress would slow down the growth. On the contrary over fertilisation of this nutrient delays the onset of tuberisation and the completion of the growth cycle within the available growing period. N also affects the quality. To high as well as low nitrogen impairs tuber quality. Therefore the amount of N for each variety, growing condition has to be critically worked. Since N is highly mobile, time of application becomes very critical since if it is applied and not taken up by the crop, it would be lost thus creating pollution problems in addition to economic and yield loss. Hence, decisions such as whether it has to be applied full at planting or in splits,or use of slow release N sources or through foliar feeding needs to be taken. In many cases the residual effect of N applied to potato is made use of by proper choice of the succeeding crop so that the problem of left over N in soil is minimised.