The influence of nitrogen deficiency and excess in potato plants on biomass accumulation and distribution

Nitrogen nutrition index (NNI), harvest index (HI), dry matter accumulated by different organs were estimated several times during the vegetation period of potato plants grown in the both field and pot experiments at the Experimental Station in Jadwisin, Poland. Nitrogen fertilizer as NH4NO3 was applied at three doses (40, 120, and 200 kg·ha=-1 N) in the field experiment and 2,7 g N in 1996 and 4g N in 1997 and 1998 per each plant in the pot experiment. Results showed that the values of NNI both in field and pot experiments increased from emergence till the about closing rows and then they gradually decreased. The NNI values were dependent on N rates. The higher were N doses, the higher were values of NNI. These differences were especially present during the first half of vegetation periods. The excess of N in potato plants (NNI values above 1,O) was recorded in the greater part of vegetation periods in plants grown at the dose 200 kg·ha-1 N and for short length of time at the rate 120 kg·ha-1 N. The excess of nitrogen was associated with the highest values of total biomass accumulation and with decreasing ofthe harvest index; (average NNI=0,53). Unsuffieient level of nitrogen nutrition (NNI values below 1,0) was found for the whole vegetation periods in all plants grown in pots and in the field at the dose 40 kg·ha-1 N. These plants produced less total biomass but more of it was distributed to the tubers with average values of HI: 0,68 in field and 0,78 in pot experiments. Plants grown in the field under warmer weather conditions had better nitrogen nutrition status than those grown under cooler and wetter ones