Improved nitrogen management for potato crops

The report describes work to evaluate a nitrogen (N) management model.  The model relates crop N uptake and redistribution from haulm to tubers to the amount of solar energy absorbed by the crop.  The model can be used to estimate the yield potential of the crop at final harvest on the basis of crop samples taken 45-50 days after crop emergence.  

In total, crop yield, N uptake and radiation absorption data were collected from 211 experimental or commercial crops in the UK and in the USA.  The purpose of the work in the USA was to test the N model in commercial crops using varieties and environmental conditions that contrasted to those in UK. 

The key findings from the programme were that crop yield potential was closely associated with total N uptake and that the majority of total N uptake occurred within c. seven weeks from crop emergence.  Factors that reduced early N uptake, (e.g. insufficient N, water stress or compaction) reduced N uptake and, in turn, reduced yield potential.  In some crops, yield potential was not realised and this may be attributed to the effects of heat or water stress or disease.  Since the yield potential of crops was set early in the season, where late applications of N were made, these had little effect on N uptake, canopy persistence or yield.

Varietal differences in total N uptake and partitioning between haulm and tubers were consistent with differences in N fertilizer requirement and the N model can be used to rapidly assess the likely N requirement of new varieties.